This paper describes the fabrication process and characteristics of ceramic thin-film pressure sensors based on Ta-N strain gauges for harsh environment applications. The Ta-N thin-film strain gauges are sputter-deposited on a thermally oxidized micromachined Si diaphragm with buried cavities for overpressure tolerance. The proposed device takes advantage of the good mechanical properties of single-crystalline Si as a diaphragm fabricated by SDB and electrochemical etch-stop technology, and in order to extend the temperature range, it has relatively higher resistance, stability and gauge factor of Ta-N thin-films more than other gauges. The fabricated pressure sensor presents a low temperature coefficient of resistance, high-sensitivity, low nonlinearity and excellent temperature stability. The sensitivity is 1.21-1.097 mV/V•kgf/cm² in temperature ranges of 25-200°C and a maximum non-linearity is 0.43 %FS.

In this work, TiO₂ thin films were prepared by RF sputtering onto thermally grown oxide layers on Si substrates. Cobalt and iron implantation into the TiO₂ films was performed using a metal vapor vacuum arc ion source. The as-implanted and annealed films were characterized using Rutherford backscattering spectrometry, transmission electron microscopy, x-ray diffractometry, x-ray photoelectron spectroscopy, spectroscopic ellipsometry, and vibrating sample magnetometry. The dependence of the magnetic properties on the implantation and annealing conditions were studied in detail. Clear room temperature ferromagnetic properties (RT FM) were observed. The saturation magnetization (M_s) values per implanted Co or Fe atom exhibit an oscillatory dependence on the implantation dose. The maximum M_s in one Co implanted samples was determined to be 2.3 μ_B/Co, exceeding the bulk Co value. The possible origins of the RT FM properties are discussed.

The possibility of using sputtered metals as mask materials for deep anisotropic chemical etching in silicon was investigated. Sputtered films of chrome, nickel and tungsten were all found to be chemically resistant to potassium hydroxide (KOH) and tetramethyl ammonium hydroxide (TMAOH). However as expected, these metals had poor adhesion to the silicon substrate. By comparison sputtered titanium was found to have excellent adhesion properties, and was chemically resistant to TMAOH but not to KOH. Resistance to KOH was achieved by thermal oxidation of the titanium film, at temperatures between 600 and 900° C. Following oxidation, etch depths more than 200μm were readily achieved in KOH etching. This makes sputtered titanium a potential alternative to the conventional mask material, silicon nitride, for the application of deep anisotropic etching. The reduction in etch rates due to a galvanic effect of conductive metal masks on silicon-on-insulator wafers was also investigated. It was observed that this effect was also overcome by thermal oxidation of the titanium mask.

Patterned Ti-based shape memory alloy films have attracted considerable research effort in recent times owing to their favorable characteristics for potential applications as micro-actuators in microelectromechanical systems. Titanium-Nickel-Palladium (TiNiPd) shape memory alloy film can be used to fabricate micro actuators for high temperature applications. These films are to be patterned to realize the microactuators. We have made an attempt to laser pattern amorphous TiNiPd shape memory alloy films on a silicon substrate, deposited by DC-magnetron sputtering using a Ti₅₄Ni_36.8Pd_9.2 alloy target. These films were micromachined by KrF excimer laser induced ablation at 248nm. Two different mask patterns have been used, one having an array of squares and circular features and the other having lines of varying widths and pitch. Three types of film removal mechanisms were observed i) due to amorphous to crystalline phase transformation, ii) due to solid to liquid transition followed by crystallization and iii) removal of the film along with silicon substrate melting. These mechanisms of TiNiPd film removal from silicon substrate appear to be similar to the mechanisms of TiNi film removal from silicon substrate reported in the literature. This paper presents the dependence of TiNiPd material removal mechanisms and feature quality on laser parameters such as fluence, pulse repetition frequency and number of shots.

This paper will detail investigations into rapid thermal annealing (RTA) treatment of ohmic contacts to reactive ion etch (RIE) damaged p-type GaN. It was found that annealing at moderate temperatures in N₂ atmosphere can improve the ohmic nature of contacts to RIE-damaged p-GaN. After chlorine-based RIE treatment of the p-GaN surface the sheet resistance and contact resistivity of the ohmic contact metallisation scheme increased, and the contacts became extremely non-ohmic. After RTA treatment in N₂ atmosphere at 550°C, linearity of the I-V curves was substantially improved, and the contact resistivity decreased. This improvement is most likely related to improvements in the metal-GaN interface and/or improvements in the bulk material when protected by the contact metal. Unprotected surfaces were further damaged (manifested as higher sheet resistance) by the annealing procedure.

Various types of micro-motion devices have been developed in the past decade for applications including the manipulation of cells in micro-surgery and the assembly of micro-chips in micro-assembly industries. Most of the micro-motion devices are designed using the compliant mechanism concept, where the devices gain their motions through deflections. In addition, closed-loop parallel structures are normally adopted due to better stiffness and accuracy compared to the serial structures. However, the forward kinematics of parallel structures are complex and non-linear; to solve these equations, a numerical iteration technique has to be employed. This iteration process will increase computational time, which is highly undesirable. This paper presents a method of deriving a simple, linear and yet effective kinematic model based on the loop closure theory and the concept of the pseudo-rigid-body model. This method is illustrated with a 3 DOF (degree-of-freedom) micro-motion device. The results of this linear method are compared with a full kinematic model for the same micro-motion system. It is proved that the derived kinematic model in this paper is accurate and the methodology proposed is effective. The static model of the micro-motion device will also be presented. The uncoupling property of the micro-motion systems, based on the static model, will be briefly discussed.

In this paper we consider the dynamic modelling of compliant micropositioning mechanisms using flexure hinges. A simple modelling method is presented that is particularly useful for modelling parallel micropositioning mechanisms. This method is based upon linearisation of the geometric constraint equations of the compliant mechanism. This results in a linear kinematic model, a constant Jacobian and linear dynamic model. To demonstrate the computational simplicity of this methodology it is applied to a four-bar linkage using flexure hinges. Comparisons are made between the simple dynamic model and a complete non-linear model derived using the Lagrangian method. The investigation reveals that this new model is accurate yet computationally efficient and simple to use. The method is then further applied to a parallel 3-degree of freedom (dof) mechanism. It is shown that the method can be simply applied to this more complex parallel mechanism. A dynamic model of this mechanism is desired for use in optimal design and for controller design.

We present a new single-chip diaphragm-type Fabry-Perot microcavity pressure sensor with a novel single deeply corrugated diaphragm. Both analytical and experimental results have shown that some common issues, such as signal-averaging effect and cross-sensitivity to temperature with diaphragm-type Fabry-Perot microcavity pressure sensors, can be substantially alleviated by the proposed technique.

The SU-8 negative photo resist has been recognised as an unique resist, equally useful for UV lithography and deep x-ray lithography (DXRL) applications; but it is in DXRL where SU-8 has shown a significant advantage over other resists. When compared with the common DXRL resist poly-methyl methacrylate (PMMA), SU-8 has been found to significantly reduce x-ray exposure time, processing time and cost, thus making SU-8 a strong candidate for commercial DXRL applications. Despite these advantages, several factors associated with SU-8 processing are not well understood. Resist-substrate adhesion, which is the key for successful lithography, is one such example. This paper examines the effect of substrate (silicon and graphite), seed layer (Ti/Cu/Ti, Ti/Cu, Cr/Au and Cr/Au/Cr), and the use of adhesion promoters (OmniCoat and MPTS) on the adhesion of SU-8 structures. In addition, parameters such as SU-8 thickness (450 μm, 650 μm, 900 μm) and substrate roughness values (silicon, Ra < 10 nm and Ra = 0.5 μm) have also been investigated. The results of our work highlight the importance of material selection for a given process and the relationship between the different parameters investigated. Increased stress for thicker films (> 850 μm) has lead to the delamination of SU-8 on some substrates. The adhesion has also proven to be a function of process parameters such as pre-bake (time and temperature), exposure dose, development time and post exposure bake (time and temperature). We have found that a <100> silicon wafer (Ra = 0.5 μm) containing a titanium-copper-titanium (Ti/Cu/Ti) seed layer, provided an adequately adhered resist for DXRL, while a chromium-gold (Cr/Au) seed layer on silicon (Ra = 0.5 μm) showed poor adhesion. A detailed correlation of the effect of these parameters on SU-8 adhesion will be discussed in this paper.

Excimer laser ablation is widely used to create a variety of 3D structures and shapes in polymeric materials. The ablated features may be used directly, as moulds that can be electroplated to form tooling, or from which replicas may be cast in elastomeric materials such as PDMS. Irrespective of how the ablated structure will be used, a common set of difficulties is often encountered, namely the redeposition of ablation debris, the non-uniform nature of the bottom of the ablated site, and limits to the aspect ratio. This paper gives experimental descriptions of these phenomena and suggests that the dynamics of the plasma plume created by laser ablation is important in understanding their behavior. Qualitative observations are presented that show that these effects can be modified depending upon the shape of the feature being ablated.

Monodisperse micro-drops have been created successfully in T-shaped microchannels fabricated with the 'modified’ excimer laser-LIGA technique. This technique eliminates the surface wetting problems and the occurrence of a deeper ablation path which happened during the joining of different section of the microchannel with the dynamic laser ablation mode. The experimental study on the shear-induced drop formation from T-shaped microchannels shows that the drop size decreases with increasing shear and that a maximum drop productivity was observed depending on the value of the dispersed phase flowrate used.

A gas sensor system using the assembled molecular layer of poly amino acid derivative, poly-L-proline has been developed. The thin layer was prepared using self assembly technique which was deposited onto a quartz crystal microbalance (QCM) substrate. The QCM coated self-assembly monolayer (SAM) was used to detect the presence of two vapor samples; saturated vapor of acetone and 2-propanol. The sensing sensitivity was based on the change in the fundamental frequency of the QCM upon exposure towards gas sample. It was found that the SAM-coated QCM sensor system was sensitive towards the vapor samples by reducing its fundamental frequency. It was also found that the SAM exhibited a good stability and reproducibility behaviors.

Piezoelectric polymers are a class of materials with great potential and promise for many applications. Because of their ideally suitable characteristics, they make good candidates for actuators. However, the difficulty of forming structures and shapes has limited the range of mechanical design. In this work, the design and fabrication of a unimorph piezoelectric cantilever actuator using piezoelectric polymer PVDF with an electroplated layer of nickel alloy has been described. The modeling and simulation of the composite cantilever with planar and microstructured surfaces has been performed by CoventorWare to optimize the design parameters in order to achieve large tip deflections. These simulation results indicated that a microstructured cantilever could produce 25 percent higher deflection compared to a simple planar cantilever surface. The tip deflection of the composite cantilever with a length of 6mm and a width of 1mm can reach up to 100μm. A PVDF polymer with a specifically designed shape was punched out along the elongation direction on the embossing machine at room temperature. The nickel alloy layer was electroplated on one side of the PVDF to form a composite cantilever. The tip deflection of the cantilever was observed and measured under an optical microscope. The experimental result is in agreement with the theoretical analysis.

This article describes a novel low temperature full wafer adhesive bonding process to fabricate three-dimensional (3-D) embedded microchannels using SU-8 photoresist as structural material. The technology development includes an improvement of the SU-8 photolithography process in order to produce high uniformity films using Taguchi methodology. After that, 3-D embedded microchannels are fabricated by a low temperature adhesive bonding of the the SU-8 thick-films. The process parameters have been chosen in order to achieve a strong and void-free bond. Different examples using this new technology are shown, including bonding between Silicon, Pyrex and combinations of them, in order to obtain 3-D interconnected microchannels between the wafers. Microchannels with vertical smooth walls and aspect ratios up to five have been obtained. Channels depth from 40 to 60 μm and 10 to 250 μm width have been achieved. Liquid has been introduced into the channels verifying a good sealing of the 3-D microchannels. The fabrication procedure described in this article is fast, reproducible, CMOS compatible and easily implemented using standard photolithography and bonding equipment.

Boron nitride thin film has a very unique characteristic of extremely high chemical inertness. Thus, it is a better hard mask than silicon nitride for aggressive etching solutions, such as the isotropic HF/HNO₃/CH₃COOH (or HNA) etchant for silicon. However, because of its high chemical inertness, it is also difficult to remove it. Plasma etching with Freon gases can etch the boron nitride film, but it is unselective to silicon, silicon dioxide or silicon nitride. Cleaning up the boron nitride film with plasma etching will usually leave a damaged or foggy surface. A special wet chemical solution has been developed for etching or cleaning boron nitride film selectively. It can etch boron nitride, but not the coatings or substrates of silicon, silicon nitride and silicon dioxide. It is a very strong oxidizing agent consisting of concentrated sulfuric acid (H₂SO₄) and hydrogen peroxide (H₂O₂), but different from the common Piranha Etch. It may be even more interesting to understand the logic or secret behind of how to formulate a new selective etching solution. Various chemical and chemical engineering aspects were considered carefully in our development process. These included creating the right electrochemical potential for the etchant, ensuring large differences in chemical kinetics to make the reactions selective, providing proper mass transfer for removing the by products, etc.

The use of magnetic actuators at the microscale has so far been limited when compared with the alternative electrostatic approach. This is mainly due to the fabrication difficulties encountered when producing magnetic components at the microscale. However, the force available from a magnetic actuator far exceeds that of its electrostatic counterpart for a given footprint area, as the magnetic devices have a greater potential to be fabricated into the third dimension. The ability to create multiple layer microcoils, easily and reproducibly, would greatly exploit this fact, enabling devices to be constructed that can produce actuation forces/distances far in excess of any other currently available microtechnology. To this end, the fabrication of two types of multiple layer coil has been investigated, both based around the ultra-thick negative photoresist, SU-8. Single, double and quadruple layer coils have been fabricated in electroplated copper and a commercially available silver colloidal paint. The fabrication times and processing steps have been assessed for each, together with the respective conductivities and the maximum current densities, before burnout of the conductors. The thermal implications of stacked multi layered coils have also been assessed. The coils fabricated have a diameter of 0.93mm.

Carbon Tetraflouride (CF₄) plasma etching condition for SU-8 negative photoresist is characterized for its potential applications in photonics and bioMEMS. The effects of main plasma etching parameters such as rf power, gas flow rate, chamber pressure and time were systematically studied and the parameters were optimized by a three-level, L9 orthogonal array of the Taguchi method. By optimization, the optimal parameter range and the weighted percent of each parameter on the final results i.e. depth, surface roughness and wall angle were determined. Photoresist & metal were used and compared as masks for plasma etching. The minimum feature size was 1µm in both cases. Results indicated that with the increase of rf power, etch rate and roughness increases almost linearly. With increase in gas flow rate, etch rate increases while roughness decreases non-linearly. Etch rate is linear with time but roughness is significantly dependent on time initially. The side-wall angle of the samples with metal mask was found to be nearly 90° whereas samples with photoresist as the mask showed poor side-wall angle and surface roughness mainly due to poor mask-resist selectivity. Optimized values of rf power, gas flow rate, time and pressure were found to be 200W, 240sccm, 20minutes and 1Torr respectively, which yielded high etch rate (80nm/min), low surface roughness (5nm) and nearly vertical side-walls (89°).

Nano-electro-mechanical devices are now rapidly approaching the point where it will be possible to observe quantum mechanical behavior. However, for such behavior to be visible it is necessary to reduce the thermal motion of these devices down to temperatures in the millikelvin range. Here we consider the use of feedback control for this purpose. We analyze an experimentally realizable situation in which the position of the resonator is continuously monitored by a Single-Electron Transistor. Because the resonator is harmonic, it is possible to use a classical description of the measurement process, and we discuss both the quantum and classical descriptions. Because of this the optimal feedback algorithm can be calculated using classical control theory. We examine the quantum state of the controlled oscillator, and the achievable effective temperature. Our estimates indicate that with current experimental technology, feedback cooling is likely to bring the required milliKelvin temperatures within reach.

Atomic layer deposition (ALD) is a versatile technique for producing a wide variety of thin films. It provides a method for precisely controlling film thickness and composition. In addition films produced by ALD are highly conformal and are therefore excellent for the generation of MEMS devices. In the present study, single and multi layer films of TiO₂ and Al₂O₃ have been deposited on silicon substrates at 200 and 300°C. These films have been characterised by a number of surface analytical techniques including dynamic secondary ion mass spectrometry (SIMS), ion beam analysis, electron microscopy and spectroscopic ellipsometry. These methods have enabled the optical, chemical and structural properties of the films to be accurately assessed. The results obtained to date demonstrate that ALD produces highly uniform single and multi layer films with minimal impurities. These high quality films are being applied to new opportunities for the development of future MEMS devices.

We give a quantum description of a Quantum Electro-Mechanical System (QEMS) comprising a single quantum dot harmonically bound between two electrodes and facilitating a tunnelling current between them. An example of such a system is a fullerene molecule between two metal electrodes. The description is based on a quantum master equation for the density operator of the electronic and vibrational degrees of freedom and thus incorporates the dynamics of both diagonal (population) and off diagonal (coherence) terms. We derive coupled equations of motion for the electron occupation number of the dot and the vibrational degrees of freedom, including damping of the vibration and thermo-mechanical noise, and give a semiclassical description of the dynamics under a variety of bias conditions. This dynamical description is related to observable features of the system including the stationary conductance as a function of bias voltage.

Solid state lighting devices that utilize semiconducting nanoparticles (quantum dots) as the sole source of visible light emission have recently been fabricated. The quantum dots in these devices have been demonstrated to have quantum efficiencies similar to those of conventional phosphors. The dispersion and concentration of the nanoparticles within a suitable polymeric matrix was found to be critical to device performance. Yet achieving suitable concentrations and adequate dispersion implies chemical compatibility between the nanoparticles and the matrix, which must be achieved without detrimental effect on either the physical/optical properties of the matrix or the stability/surface state of the quantum dots. A number of encapsulation strategies have been identified and are discussed with regard to their effect on nanoparticle dispersion and concentration within silicone and epoxy matrices.

Titanium Nitride (TiN) is a wear resistant and complementary metal oxide silicon (CMOS) compatible material that is increasingly being investigated for MEMS applications. Incorporating any new material into a MEMS device requires the development of a processing strategy. This paper discusses a wet-etching strategy for patterning and releasing TiN features on Cr sacrificial layers. Filtered arc TiN films were deposited onto Cr coated Si (100) substrate. A Cr contact mask was sputtered over the TiN and patterned using UV photolithography. Patterned TiN features were examined using scanning electron microscopy (SEM). Rutherford Backscattering Spectroscopy (RBS) was carried out to investigate the selective etching of TiN and Cr in their respective etchants, which consisted of SC-1 for etching the TiN and a commercial chromic acid solution for etching the Cr. The results showed that Cr was not etched by SC-1 and that TiN was not etched by the Cr etchant.

This paper reports for the first time that a novel MEMS-based micromirror switch has successfully demonstrated for optical switching in a multi-channel fiber optics spectrophotometer system. The conventional optomechanical fiber optic switches for multi-channel spectrophotometers available in market are bulky, slow, low numbers of channels and expensive. Our foundry MEMS-based micromirror switch designed for integrating with commercially available spectrophotometers offers more compact devices, increased number of probing channels, higher performance and cheaper. Our MEMS-based micromirror switch is a surface micromachined mirror fabricated through MUMPs foundry. The 280 μm x 280 μm gold coated mirror is suspended by the double-gimbal structure for X and Y axis scanning. Self-assembly by solders is used to elevate the torsion mirror 30 μm over the substrate to achieve large scan angle. The solder self-assembly approach dramatically reduces the time to assembly the switch. The scan mirror is electrostatically controlled by applying voltages. The individual probing signal from each probing head is guided by fibers with collimated lenses and incidents on the center of the mirror. The operating scan angle is in the range of 3.5 degrees with driving voltage of 0-100 V. The fastest switching time of 4 millisecond (1 ms rise time and 3 ms fall time) is measured corresponding to the maximum speed of the mirror of 0.25 kHz when the mirror is scanning at ± 1.5 degrees. The micromirror switch is packaged with a multi-mode fiber bundle using active alignment technique. A centered fiber is the output fiber that is connected to spectrophotometer. Maximum insertion loss of 5 dB has been obtained. The accuracy of measured spectral data is equivalent to the single channel spectrophotometer with a small degradation on probing signal due to fiber coupling.

This paper describes the structure and operation of a new differential phase angular rate sensor and analyses it's response to input rotation. It employs a vibrating beam mass structure that is forced into an elliptical path when subject to rotation due to the Coriolis effect. Two sensing elements are strategically located to sense a combination of drive and Coriolis force on each to create a phase differential representative of the input rotation rate. A general model is developed describing the device operation. The main advantages of the phase detection scheme are shown, including removing the need to maintain constant drive amplitude, independence of sensing element gain factor and novel response shapes. A ratio of device parameters is defined and shown to determine the device response shape. This ratio can be varied to give a high sensitivity around zero input rate or a response shape not seen before, that can give maximum sensitivity around an offset from the zero-rate input. This may be exploited in an array configuration for a highly accurate device over a wide input range. A worked example shows how the developed equations can be used as design tools to achieve a desired response.

The flow produced by a synthetic jet actuator located in one wall of a microchannel is investigated using computational fluid dynamics (CFD) simulations. In the case of no cross-flow, the ejected vortices travel to the opposite wall and replenish the remains of the vortex left behind from the previous cycle. When cross-flow is added, the vortex penetration increases with both stroke length and frequency. The flow in the cavity appears to be nearly symmetrical, with the greatest effect seen near the orifice. In the orifice itself, three-dimensional effects are more noticeable with decreasing jet-to-cross-flow momentum ratio. The microchannel cross-flow causes the vortices to tumble about their transverse axis, the effect of which also increases with decreasing jet-to-cross-flow momentum ratio.

We present herein a new out-of-plane MEMS actuator array. Previously, we developed out-of-plane MEMS actuators having a 180-μm stroke in the out-of-plane direction. However, the maximum output force, scale of integration and density of integration were limited to 0.087 mN, four actuators and 4 mm²/actuator, respectively. In the present paper, we propose a new calculation method by which to estimate the maximum output force and driving voltage according to conventional mechanics of materials. The improved shape of the actuator was derived using this method, and the maximum output force was increased up to 0.83 mN, which is approximately 10 times larger than that of the previous actuator. The scale and density of integration were improved via multilayer interconnection up to 100 actuators (25 times) and 1 mm²/actuator (a four-fold increase), respectively. In addition, we examined the driving behavior of the actuator array.

Single-spin measurement is an extremely important challenge, and necessary for the future successful development of several recent spin-based proposals for quantum information processing. Magnetic resonance force microscopy (MRFM) has been suggested as a promising technique for single-spin detection. We discuss how to read out the quantum state of a single spin using the MRFM technique based on cyclic adiabatic inversion (CAI). We include, in our analysis, a measurement device (an optical interferometer) to monitor the position of the cantilever, which then provides us with information of the spin state. We consider various relevant sources of noise and taken into account the effect of spin relaxation on the single-spin detection scheme. We also present a realistic continuous measurement model, and discuss the approximations and conditions to achieve a quantum non-demolition measurement of a single spin by MRFM. Finally we will present some simulation results for the single-spin measurement process.

This paper describes anodic bonding characteristics of MLCA to Si-wafer using evaporated Pyres #7740 glass thin-films for MEMS applications. Pyrex #7740 glass thin-films with the same properties that were deposited on MLCA under optimum RF magneto conditions (Ar 100%, input power 1 W/cm2). After annealing in 450°C for 1 hr, the anodic bonding of MLCA and Si-wafer was successfully performed at 600 V, 400°C in - 760 mmHg. Then, the MLCA/Si bonded interface and fabricated Si diaphragm deflection characteristics were analyzed through the actuation and simulation test. It is possible to control with accurate deflection of Si diaphragm according to its geometries and its maximum non-linearity being 0.05-0.08 %FS. Moreover, any damages or separation of MLCA/Si bonded interfaces did not occur during actuation test. Therefore, it is expected that the anodic bonding technology of MLCA/Si wafers could be usefully applied for the fabrication process of high-performance piezoelectric MEMS devices.

Numerous studies have been done in studying the etching rates of the isotropic HF/HNO₃/CH₃COOH (or HNA) etchant for silicon in terms of the compositions of the solution. It is well known that the HNA etchant is an autocatalytic solution. Controlling its reaction rate is more complicated than just fixing the ratios of the reagent components - HF, HNO₃, H₃COOH. Sometimes, researchers may experience a runaway reaction, surprisingly even with the same composition used before. Researchers should also look into some chemical engineering aspects - such as etch-area or etchant-volume that can affect the dissipation of the heat generated and the self generated catalyst - HNO₂. All these are very important in terms of the chemical safety inside a MEMS research laboratory. In this study, HNA solutions with similar compositions were used to demonstrate how the runaway reaction could start as a function of etch area, etchant volume, or etch-area:etchant-volume ratio. A larger area would make the reaction go faster, and might increase the chance of running into an uncontrollable manner easily. Usually, using less amount of HNA solution might be a good practice for waste minimization. However, by over doing it, the heat and the HNO₂ generated from the reaction could be accumulated too fast and they might be able to make the reaction out of control. HNA is an autocatalytic etchant and the HNO₂ generated is usually required to keep the reaction going. Thus it is desirable to keep the mass transfer low at the beginning of the etching, in order to keep the HNO₂. Small amount of heat can also help to accelerate the reaction. However, the mass transfer and the heat transfer need to be controlled properly as reaction proceeds. In the case without mechanical setup for controlling the mass transfer and the heat transfer, the volume of the solution will become the major to carry out these tasks through natural convection and diffusion. In our study, we have demonstrated in simple ways on how to control and safe guard the etching reaction from runaway.

In optical communications and optical interconnects, high coupling efficiency between a laser diode and a single mode fiber is indispensable, while the coupling loss mainly originates from the mismatch of their numerical apertures. In order to improve the coupling efficiency, it is a practical scheme to introduce a refractive microlens between them. Nevertheless, the fabrication of refractive microlens array (MLA) often required complicated lithographic and etching process. Moreover, structural homogeneity and dimensional uniformity of fabricated MLA were difficult to sustain. In this paper, we extend the application of low-cost inorganic-organic SiO₂/ZrO₂ sol-gel glass with a simple reflow technique for fabrication of refractive MLA. The intrinsic advantages of hybrid sol-gel material lay not only as an etch-free single-step fabrication material, but also, its uniformity and other excellent optical properties. The adoption of reflow technique in the fabrication of refractive MLA is much more economical and suitable to mass production as expensive high-energy beam-sensitive gray-scale mask, or etching processes is not required. The fabricated refractive MLA have excellent surface smoothness and dimension uniformity, which can provide high coupling efficiency of a laser diode to a single mode fiber. The proposed microlens coupling scheme has the advantages of low coupling loss, low cost and small package volume.

We report the observation of sample behaviors using the confocal laser scanning microscopy (CLSM) in on-chip microcapillary. Sample loading by pinched valve injection is observed in a new cross injector shape, which has the structure added conventional cross injector to circle shape. In sample loading, because this structure causes a different electric field compared with that in conventional cross injector, high efficient sample plug injection was performed. It is important to investigate further the detailed sample profiles using the CLSM in sample loading for development of the on-chip microcapillary. We attempt the simulation of sample loading in the cross injector using the semiconductor device simulator MEDICI in order to investigate it in further detail. The sample movements in the channel turn along the Z-direction are observed using the CLSM. In order to miniaturize the microfluidic channel, it is necessarily needed to fold the channel, but then it is inevitable that sample dispersion occurs in the turn. We present sample flow profiles along the Z-direction in the turn using the CLSM and the influence on the electrophoretic separation. Also, we improve that fabrication of duct channel for exhaustion the vaporized xylene to outside the chip and the adhesion process

The essential features of the ALD process involve sequentially saturating a surface with a (sub)monolayer of reactive species, such as a metal halide, then reacting it with a second species to form the required phase in-situ. Repetition of the reaction sequence allows the desired thickness to be deposited. The self-limiting nature of the reactions ensures excellent conformality, and sequential processing results in exquisite control over film thickness, albeit at rather slow deposition rates, typically <200nm/hr. We have been developing our capability with ALD deposition, to understand the influence of deposition parameters on the nature of TiO₂ and Al₂O₃ films (high and low refractive index respectively), and multilayer stacks thereof. These stacks have potential applications as anti-reflection coatings and optical filters. This paper will explore the evolution of structure in our films as a function of deposition parameters including temperature and substrate surface chemistry. A broad range of techniques have been applied to the study of these films, including cross sectional transmission electron microscopy, spectroscopic ellipsometry, secondary ion mass spectrometry etc. These have enabled a wealth of microstructural and compositional information on the films to be acquired, such as accurate film thickness, composition, crystallization sequence and orientation with respect to the substrate. The ALD method is shown to produce single layer films and multilayer stacks with exceptional uniformity and flatness, and in the case of stacks, chemically abrupt interfaces. We are currently extending this technology to the coating of polymeric substrates.

Boomerang is a 3GeV synchrotron radiation accelerator, currently being constructed in the State of Victoria, Australia. The outline design of two beamlines, suitable for the fabrication of MEMS devices using the LIGA process, is presented, along with an estimate of the exposure doses throughout the resist. The most commonly used resist is PMMA, which requires a minimum dose of about 4500 J/cm³ for accurate microstructure definition. Exposure with such a dose, in resist thicknesses of several hundred microns, can take hours. Fortunately, SU-8 resist is becoming more widely used as the minimum dosage required is about 35 J/cm³, leading to exposure times of only a few minutes. Although Boomerang will shorten exposure times due to its higher irradiance at the substrate, the full benefits may not be realizable due to excessive resist heating. Heating effects have been simulated and suggest that helium cooling will be essential if the glass transition temperature of the resist (100°C for PMMA, 50°C for SU-8) and thermal distortion of the mask are to be avoided. The parameters chosen in this study of the future performance of Boomerang have been inserted into a cost model. The model shows that Boomerang exposure can become competitive with other exposure methods, particularly where large quantities of devices with deep structures are required.

A scanning electron microscope (SEM) has been modified to enable it to be used as an electron beam lithography instrument for fabricating optically variable devices (OVDs). The pattern data which describes the OVDs is divided into a number of fields which are tiled together. The pattern data for each field is decoded by a dedicated pattern generator which is interfaced to the electron optics of the SEM to control the electron beam deflection and beam blanking in order to expose the fields. The sample stage of the SEM is used to position each of the fields prior to exposure. An automatic focus compensation system has been developed to ensure that the beam is optimally focused for each stage position. The SEM controls are used to optimise the electron optics and to set the beam energy and beam current required for the exposure. One type of OVD comprises a series of diffraction gratings tiled to form a two dimensional array. The orientation and spacing of the lines in the grating pattern on each tile is chosen to produce optical effects that depend on the viewing angle. This method allows different images to be mixed in the same area, with each image revealed at specific viewing angles. Another OVD consists of stochastic arrays of pixels to reproduce a grayscale image. In this device the polarity of the image varies with the viewing angle. One application of these devices is to provide masters for the replication of OVDs for security and anti-counterfeiting purposes.

Polycrystalline Bi-Ti-O thin films were prepared by multilayer deposition method using electron beam evaporation. The thin films were obtained by sequentially evaporating Bi₂O₃ / TiO₂ layers on Si / SiO₂ substrate followed by a heat treatment for 2 hours in air at 900 °C. The piezoelectric response of the sample was measured by pneumatic loading method. A pressure sensor was fabricated by annealed the deposited multilayer thin films on Si / SiO₂ /Au substrate and Al was then deposited as top electrode. When an air pressure was applied and imparted on the sensor, electrical voltage was generated and measured using an electrometer. The sensor’s response was measured at three response cycles. It was found that the sensor has good voltage sensitivity and repeatability. The study shows the possibility to obtain Bi-Ti-O thin film pressure sensor by electron beam multilayer deposition.

This study analyses the two-way actuation of a bi-layer cantilever of nickel titanium (NiTi) and silicon nitride thin films. The cantilever will curl on low temperature and uncurl on high temperature. the curling mechanism results from the stress relaxation of the NiTi film and the uncurling from the shape memory effect. A NiTi film with thickness of about 3 μm was deposited on a silicon substrate coated with a low-stress silicon nitride film with thickness of about 0.6 μm. the NiTi film was heat treated to recrystallise and memorise a flat shape. Over the heat treatment, residual stress built up in the NiTi film. The residual stress was measured to be around 400-800 MPa tensile by the wafer curvature method (Stoney's equation). The transformation temperatures of the NiTi film were measured to be about 36.3°C (A_p) and 32.6°C (R_p) by differential scanning calorimeter. The bi-layer cantilever was released from the silicon substrate by anisotropic wet etching (TMAH). Below R-phase finish temperature (<30°C) the shape memory effect was inactive and the NiTi film relaxed from the residual stress, which caused the cantilever to curl up. Above the austenite finish temperature (>50°C), the NiTi film uncurled toward its memorised shape because of the shape memory effect. Therefore, by cycling the temperature high and low, the cantilever uncurled and curled.

A series of study of trench dislocation occurred in 0.13/0.18um CMOS technologies have been done. First, it is demonstrated for the first time that trench crystal dislocations can be detected successfully using current mapping atomic force microscopy (C-AFM). Different from conventional voltage contrast technique, which uses SEM image brightness for the comparison of leaky contacts/junctions and normal ones, C-AFM probes the surface of samples by contacting them directly and can provide I-V curve mapping data for each contact/junction where the needle passes. Thus a quantified contact/junction leakage current data is acquired and can be used to find out minor trench dislocation (located beneath the leaky contact), which works as a leakage source negligible before but crucial in 0.13um low power devices. Besides, a model concerning about the FEOL overall thermal budget is proposed to explain the formation of trench dislocations.

Liquid crystal spatial light modulators (LC-SLM) provide a viable alternative for all-optical switching. This paper investigates the design and performance of an optical layout for a N×N free space optical switch. The optical switch utilizes liquid crystal spatial light modulators for beam steering.

This work presents a novel method to transfer thin-film transistors from a Si wafer to another flexible plastic substrate. First, high-performance poly-Si TFTs were fabricated on 1-μm thick SiO₂ of a Si wafer and then adhered to a flexible plastic substrate by the optical adhesive. Next, the spin-etching process was utilized to remove the backside Si with SiO₂ as a stopping layer. We have established a qualitative model to explain the relation between the chemical flow rate/rotation speed to the etching rate and the uniformity of Si removal. The Si etching rate is higher than 200 μm/min while maintaining Si to SiO₂ selectivity of 250 under optimized spin-etching parameters. Compared to that before transference, no degradation or yield loss was found due to substrate bonding and Si spin-etching steps. Additionally, extrinsic stress shows little effect to the properties of poly-Si resistors on the flexible plastic substrate.

We specifically studied the influence of a setback-layer thickness on the device performances so as to optimize the required value. Theoretical analysis shows that an optimized setback-layer thickness is available to effectively reduce the barrier height while maintain good device performances. In this work, the effects of a setback-layer thickness on the DC and RF performances of an InGaP/GaAs heterojunction bipolar transistor (HBT) are investigated. Based on the theoretical analysis, the optimized setback-layer thickness WSB is about of 10~30Å for analog amplification. On the other hand, for digital saturated logic application, i.e., a small offset voltage with an acceptable current gain, the optimized W_SB could be up to 50 Å. Therefore, this analysis and predication may cause the considerable promise for practical circuit applications.

A very important aspect in the next stage of genomic research will be the study of genetic diversity originating from an individual, for example, a single nucleotide polymorphism (SNP),. For this, the base-pair sequence needs to be determined quickly and easily; along with effectively gathering the proteins that are produced from the cell and depend on each genetic design. To meet these demands, the use of a miniaturized experimental apparatus formed on a chip is suitable as it gives a very small and well-controlled space to undertake precise analyses. This type of chip device needs to be disposable, inexpensive and of uniform quality, therefore many chips should be fabricated at the same time from a low cost chip material such as plastic. A mass production fabrication process for such plastic chips was determined as follows. A thick coating type photoresist was spin-coated onto a 4-inch size Si wafer to 20 μm thickness and patterned by UV-lithography. Thick Au structures were embedded into the resist mold by microelectropolating. After removal of the resist, Au fine structures remained and were used as a metal mold for plastic casting. Plastic, polymethylmethacrylate (PMMA), beads were dissolved in acetone and the polymer solution was cast into the metal mold under vacuum heating environment producing many identical plastic chips at a thickness of 1 mm. The size of the chemical reaction channel, one of the device’s components, was 50 μm in width and 20 μm in depth.

This paper reports on the formation of a new layered film structure and the highly improved photovoltaic output of the lead lanthanum zirconate titanate (PLZT) employed. PLZT film was deposited onto a Pt/Ti/SiO₂/Si substrate and sandwiched vertically between electrodes. The new structure design is described using a top transparent indium tin oxide (ITO) electrode. Inspection by X-ray diffraction revealed that the PLZT film had a perovskite structure. The PLZT film structure exhibited V and μA output. This means that the photovoltaic current of the PLZT film per unit width was more than 10² times larger than that of bulk PLZT, while the photovoltaic voltage per unit thickness in the layered film structure was almost the same as that in bulk ceramics. These differences are due to the characteristics of the film structure and configuration of the electrode. In addition to the photovoltaic output the PLZT film also has the advantage of its easily controllable parameters: film thickness, illuminated area and illumination intensity. A simple model is used for the phenomenological explanation of the improved photovoltaic effect of the PLZT film.

We have measured the I-V characteristics of the Resonant tunneling diode (RTD) fabricated by ourselves. Basing on the measured results, several questions have been analyzed and discussed: (1) Temperature effects on I-V characteristics; (2) “The Apparent positive resistance phenomena” in negative resistance region. The analysis and discussion on above questions are very useful and helpful for design and fabrication of RTD.

Pb(Zr_0.52Ti_0.48)O₃ thin films were prepared on Pt/Ti/SiO₂/Si substrates by hybrid processing: sol-gel method and pulsed laser deposition. The temperature of postdeposition annealing in hybrid processing is 650°C, and is lower than that in the case of direct film deposition by pulsed laser deposition on a Pt/Ti/SiO₂/Si substrate. The preferred orientation of the PZT films obtained by hybrid processing can be controlled using the seed layer obtained by the sol-gel process. The TEM image showed that the PZT films have a polycrystalline columnar microstructure extending throughout the thickness of the film and no shape interface was observed between the layers obtained by the sol-gel method and the pulsed laser deposition process. Electrical properties of the films were evaluated by measuring their P-E hysteresis loops and dielectric constants. The 1-μm-thick PZT films fabricated by hybrid processing consist of mainly the perovskite phase with a (111)-preferred orientation and have good ferroelectric properties. The ferroelectric parameters were remanent polarization P_r = 23.6 μC/cm², and coercive field E_c = 54.8 kV/cm.

The electrochromic materials change their optical properties under the action of an electric field and can be change back to the initial state by a field reversal. This paper reports the use of two metalloporphyrins derivatives of; 5, 10, 15, 20-tetraphenyl 21H, 23H-porphine cobalt (II)(CoTPP) and 5, 10, 15, 20-tetraphenyl 21H, 23H-porphine manganese (III) chloride (MnTPPCl), Langmuir-Blodgett thin films as an electrochromic materials to detect the presence of chloride in water. It was found that the both thin films were sensitive towards the presence of chloride by presenting the change in their optical absorption spectrum under a bias potential of 3.0 V. However, the CoTPP thin film was not fully reproducibility under the electrochromic process. Meanwhile, the electrochromic property of the MnTPPCl thin film was stable and reproducible. This thin film is potentially be used as an electrochromic material to detect the presence of chloride ion in water.

In micro fabricated gas turbine engine, a micro journal air bearing is used to offer high speed and low wear operations. Fabrication of such a journal bearing is a critical challenge since the clearance of the bearing is only several micrometers with aspect ratio of more than 20. This paper reports on the fabrication of ultra-high aspect ratio micro journal air bearing using ICP DRIE (inductively coupled plasma deep reactive ion etching) process. The process parameters that resulted in bowed and tpaered journal bearing were investigated to improve the profile of the etched journal bearing. Micro journal bearings with sidewall verticality of almost 90° were obtained.

The infrared transmission (400-4000cm^-1) was measured for a series of approximately 0.5μm thick NH₃/SiH₄ and plasma deposited silicon nitride thin film alloys prepared at temperatures between 80 and 300°C using fixed process parameters. It is demonstrated from a detailed analysis of the infrared spectra that the 'condensation' mechanism is not thermally activated as previously reported, but is an entropic process required to stabilise the film structure. Modelling of the various absorption bands in the infrared transmission spectrum using a multiple Lorentzian oscillator parametric model leads to the proposition that thermally activated 'condensation' (networking) is really the formation of N(-Si≡)₃ bonds from the reaction between amine branches. Evidence that the absorption feature around 640cm^-1, usually attributed to Si-H (bending), is N-H related is also discussed.

When synthetic jet actuators are used to control flow separation in practical situations, it is anticipated that the orifices will be distributed in the form of an array. Wind tunnel experiments were conducted to investigate the effect of the location and number of these actuators on boundary layer separation. Three synthetic jets were located upstream of the separation point in undisturbed flow, and the mean and root mean-square (RMS) velocity profiles were measured at several axial locations within the separated flow region. This paper reports the effect of actuator placement and the integrated effectiveness of two and three synthetic jets with different forcing voltages and frequencies.

In this paper , the importance of boundary conditions for two- way bistable thermal snapping action is analysed by Ansys simulations. Several designs are developed and modified into a novel bistable actuator for out of plane deflection. It consists of 4 long epi-silicon single layered legs , a 1200um x 40um x 3um microbeam and 4 spring-supports in which both are polysilicon/oxide/episilicon layered. Buckling of the released structure is achieved by the compressive residual stress remaining in the oxide layer as a result of the processing. The structure switches between two stable equilibrium states by heating the legs and then heating one of the polysilicon layers to produce the thermal moment needed for snapping to occur, hence achieving two-way bistable operation.

Two experimental techniques have been investigated to examine residual stress in low temperature plasma enhanced chemical vapour deposited (PECVD) SiN_x thin films: one that measures the stress induced substrate curvature, and the other that takes advantage of the stress induced deformation of freestanding diagnostic microstructures. A general linear dependence of residual stress on deposition temperature is observed, with the magnitude of stress changing linearly from circa 300MPa tensile stress to circa 600MPa compressive stress as the deposition temperature is decreased from 300°C to 100°C. However, the results deviate from the linear dependence by a different degree for both measurement techniques at successively lower deposition temperatures. The stress values obtained via the substrate curvature method deviate from the linear dependence for deposition temperatures below 200°C, whereas the values obtained via the diagnostic microstructures method deviate from the linear dependence for deposition temperatures below 100°C. Stress uniformity over the deposition area is also investigated.

Optical crossconnects (OXCs) are critical core for provisioning and restoration in mesh wavelength-division-multiplexing (WDM) networks. An increasingly urgent need for large-port-count OXCs severely challenges the current existing OXC technologies. To reduce the crosspoint complexity, we propose an architecture based on 2×2 switching fabrics by integrating the general symmetric (GS) architecture with Clos and Benes switching architectures together. Rearrangeably and strictly nonblocking structures are examined as well as the control algorithm of the rearrangeably nonblocking structure is studied. Then, we present two basic switching fabrics of the simples 2×2 bidirectional OXC utilizing 2D optical MEMS, one of which is used as the basic building block in our proposed architecture is studied. The resulted switch requires (N/2)×[log₂(N/2)]×(log₂N-1/2) micromirrors, while the switch based on GS architecture needs 2(N/2)² micromirrors. It is very clear that our proposed architecture reduces the number of micromirrors greatly, especially when N is large. Moreover, theoretical analyses have shown that the resulted switch has the same insertion loss, lower power consumption, and better performance of port-to-port repeatability, comparing to the conventional crossbar switch.

This paper presents a new image-processing approach to estimating a pointing error of the electron probe of a scanning electron microscope. An environmental disturbance causes a pointing error of the probe that is reflected upon a specimen image in a microscope. The new approach uses the deteriorated specimen image to estimate the pointing errors of the probe. The microscale is used as a specimen in this experiment, and a simple mathematical model is used to simulate a microscale image. The mathematical model is obtained by using the surfcace tilt and shadowing contrast of the microscale and by approximating the delta and step functions to differentiable functions. Simulated microscale images are identified by a least-squares procedure with measured images to estimate the pointing error of the probe. The estimated pointing errors are used to design a controller for vibration isolation of a scanning electron microscope. The designed controller is based on a transfer function from acceleration sensor outputs to the pointing errors. An acceleration sensor is situated close to the specimen stage in the microscope chamber to detect the stage motion. Sinusoidal excitation tests are performed to determine the transfer function. The sensor outputs are passed through the designed controller to compute the inputs into the image-shifting coils, and the coils move the electron probe to cancel the pointing errors. The performance of the designed controller is verified by comparing specimen images with and without control when the microscope vibrates. The comparison shows the pointing errors are significantly reduced in a region of lower frequencies.

This paper presents an area-changed capacitive accelerometer using a 3-mask fabrication process. The accelerometer is designed as finger structures connected in parallel that have a differential capacitor arrangement. The movable electrodes are mounted on a proof mass of silicon and a pair of stationary electrodes of polysilicon is formed under the mass with a 3 μm air gap. The fabrication process utilizes silicon/glass anodic bonding and deep reactive ion etching (DRIE) for high aspect ratio etching. The simulated mass displacement change rate is 0.076 μm/g and the overall sensitivity is -0.04/μm. This type of accelerometer will be characterized for low-g as well as for medium-g applications.

Silicon crystal planes that can be potentially used as optical mirrors for deflecting light beams from/to optical fibres aligned in grooves were investigated. Aligning grooves and passive mirror-like planes were formed by wet micromachining in KOH and TMAH etchants with addition of additives such as IPA and Triton surfactant. On (100) silicon, {111}, {110}, {311} mirror planes were realized, while on (110) silicon, {010} and {111} mirror planes were demonstrated for the chosen mask orientation. Characterization of passive mirrors with 632nm incident light was performed by measuring angles and specific shape patterns of reflected light beams and by determination of light scattering due to mirror microroughness. Results show that {111} planes exhibit better surface quality compared to {110} mirrors and lowest scattering, however the reflected angle is 54,74° on (100) silicon. On (110) silicon the 45° reflection angle with {010} crystal planes is obtained by proper mask alignment with very small scattering angle below 3°. For reflecting the beam with 1,33 μm wavelength, sputtered layer of aluminum is used as reflecting coating on silicon mirrors, increasing the reflectivity by 24%.

Microfluidic connectors play a key role in the microfluidic packaging systems. This paper presents the results of a development of a new design of polymeric surface connector for single channel connection between tube and microfluidic chip. The design was evaluated using finite element analysis, which takes into account assembly forces and stresses on components. The design offers an easy and simple connection process and is compatible with most polymeric microfluidic systems using different diameter tubes. Prototype PMMA and polycarbonate connectors have been produced for 1.6 mm diameter PEEK (polyethylethylene ketone) tube. These connectors can be connected and disconnected many times and will be suitable for many cases with special requirements. A series of performance tests, which include leakage, connection and disconnection force test, and reliability, have been conducted and to demonstrate the functionality of sealing and reached excess 1.37 MPa (200 psi.) without leakage and pulling force reached 40 N (9 lbf).

For improving solar efficiencies, down conversion of high-energy photons to visible lights is discussed. The losses due to thermalization of charge carriers generated by the absorption of high-energy photons, can largely be reduced in a solar cell if more than one electron-hole pair can be generated per incident photon. The solar cell consists of dye-sensitized anatase-based TiO₂, approximately 30 nm particle size, 6 μm thickness, and 6 x 6 mm² active area, Pt counter electrode and T₃/T₂ electrolyte. Down conversion phosphor LiGdF₄:Eu(LGF) located on the front surface of the solar cells. And we measured the photo-current, current-voltage characteristics, and down-characteristics, and down-conversion efficiency of the down conversion system.

The new MEMS technology has made a major impact on design of RF components. The results that were not possible with current IC technology are made possible with MEMS technology. Researchers are working to replace the off-chip components with on-chip components so as to achieve a single chip receiver. The high Q inductors and capacitors required for designing RF components are the bottleneck in achieving the single chip receiver. The main advantage of direct conversion architecture is fewer components are required for implementations, but there are certain design issues that must be taken care for these implementations to be successfully achieved. In this paper, MEMS components used within RF systems is analysed. The VCO is the most difficult block of RF front-end design having large impact on system performance; so stringent requirements are imposed on VCO phase noise performance. A typical range of MEMS component values are used to design and implementation the VCO.

The present study reports the sol-gel deposition of PZT thick films on Pt/Ti/SOI substrate and its application to the micro cantilevers and 2D micro optical scanning mirrors. Crack-free PZT thick films (2.7 µm) have fabricated on Pt/Ti/SOI substrate. Thin SiO₂ layer on the top of the SOI substrate was found to play important role as a burrier layer to avoid breaking the Pt/Ti bottom electrode layer. The micro cantilevers and 2D micro scanning mirrors fabricated by MEMS technologies are flat suggesting the advantage of using SOI substrate instead of Si substrate. The deflection of the tip of the 800 µm-long x 250 µm-width micro cantilever was measured to be 5.9 µm at 5 V. The absolute value of the transverse piezoelectric constant |d₃₁| of the PZT thick film calculated from the deflection is as high as 84 pC/N. The scan angle of the cantilever via resonant actuation at 2387 Hz is as high as 40 degree with only 6 V (peak-to-peak). The response time of micro cantilevers were measured to be within 0.3-1 ms. These data indicate the potential application of the present 2D micro scanning mirrors to wavelength division multiplexing (WDM) systems driven at several voltage.

Nano imprinting or Nano embossing process have been introduced to fabricate semiconductor, optical device and Micro Electro Mechanical Systems (MEMS) and the Nano Electro Mechanical Systems (NEMS) to reduce the fabrication cost. In our previous paper, micro hot embossing of Polycarbonate (PC) and Polyetheretherketone (PEEK) for optical switch with 8x8 mirrors was reported. The PC and PEEK sheets were embossed at elevated temperature with an embossing machine designed for the MEMS. In the application, the mirrors on the optical switch had some defects, such as slump, sticking and step at side of the mirror, due to embossing process and process conditions. These defects are attributed to the poor materials flow of plastics into the e Ni mold cavity of complicate shape with different aspect ratio. Therefore, the micro hot embossing is optimized in this paper with PTFE sheet to enhance the materials flow. In this paper, the PC and the PEEK sheets, thickness of 300um, are embossed at elevated temperature with the hot embossing machine with a Nickel mold. To control material flow of the PC or the PEEK sheets, Polytetrafluoroethylene (PTFE) sheet, the thickness of 100um, is placed on the PC or the PEEK sheets at elevated temperature. Mirror shape was transferred with better fidelity on the PC and PEEK sheet, and the thickness of cantilever became thinner than previous embossed structure without the PTFE. Especially, the mirror height and the thickness of cantilever on the PC have been improved at lower embossing temperature.

A theoretical analysis of initially buckled, and thermally actuated bimorph micro bridge is presented in this paper. The micro bridge is to be buckled by compressive residual stress developed in the beam during fabrication. An analytical model that characterizes the buckling shape is proposed, and used in the analysis. This model considers symmetrical rotational stiffness, and infinite axial stiffness at both ends of the bridge. Deflections versus temperature characteristics for a bimorph micro-bridge of length, 1000µm, thickness, 4µm, with various initial deflections ranging from 5µm to 20µm are obtained, and plotted. The results show that a pin-pin micro bridge (rotational stiffness of zero) exhibits bi-stability at lower snapping temperatures when negative thermal expansion material is used as one of the layers. A snapping temperature of less than 100°C is possible. It is also shown that clamped-clamped (rotational stiffness of infinite) micro bridge does not snap at all, and there is maximum allowable rotational stiffness below which snapping is possible.

This paper addresses the influence of mobility degradation on the SCM measurement via modeling and comparison with experimental SCM data. The rational for looking into mobility effect is that SCM capacitance measurement is carried out at 915 MHz. At this frequency, resistance of semiconductor surface can be comparable to the reactance of the SCM capacitance. In our simulation carrier mobilities at the semiconductor surface are set low compared to their bulk values to reflect surface mobility degradation. Our results show that the simulated SCM dC/dV is significantly reduced in the vicinity of p-n junction reflecting what is observed in experiment. We attribute this to the fact that the capacitance between the inverted surface and the SCM probe is not detected due to the high resistance (compared to the reactance of the SCM capacitance) of the inversion layer below the semiconductor and the oxide interface. Only the capacitance on the accumulation side is extracted thus leading to the lowering of the detected SCM capacitance and dC/dV. The major conclusion is that the effect of high resistance due to mobility degradation has to be treated carefully for accurate extraction of dopant profile from experimental SCM data.

In this paper, the development of an integrated and open-architecture precision motion control system is presented. The control system is generally applicable, but it is developed with a particular focus on direct drive servo systems based on linear motors. The overall control system is comprehensive, comprising of various selected control and instrumentation components, integrated within a configuration of hardware architecture centred around a dSPACE DS1004 DSP processor board. These components include a precision composite controller (comprising of feedforward and feedback control), a disturbance observer, an adaptive notch filter, and a geometrical error compensator. The hardware architecture, software development platform, user interface, and all constituent control components will be elaborated on in the paper.

The optical properties of multi-chromophore systems such as conjugated polymers and dendrimers have attracted great interest because of the possibility of these structures displaying enhanced electronic and optical effects. In this manuscript the optical and electronic properties of novel organic materials for possible applications in optical switching, coherent energy transfer, as well as for enhanced emission from metal nanoparticles are presented. Measurements of the steady state absorption and emission, as well as the time-resolved fluorescence of selected novel organic materials are probed in order to provide a comparison of their use in electronic applications.

A simple, non-equilibrium model is used to evaluate the likely DC performance of carbon nanotube field-effect transistors. It is shown that, by appropriate work function engineering of the source, drain and gate contacts to the device, the following desirable properties should be realizable: a sub-threshold slope close to the thermionic limit; a conductance close to the interfacial limit; an ON/OFF ratio of around 10³; ON current and transconductance close to the low-quantum-capacitance limit.