We give an overview of the design of a metrological scanning probe microscope (mSPM) currently under development at the National Measurement Institute Australia (NMIA) and report on preliminary results on the implementation of key components. The mSPM is being developed as part of the nanometrology program at NMIA and will provide the link in the traceability chain between dimensional measurements made at the nanometer scale and the realization of the International System of Units (SI) meter at NMIA. The instrument is based on a quartz tuning fork (QTF) detector and will provide a measurement volume of 100 μm×100 μm×25 μm with a target uncertainty of 1 nm for the position measurement. Characterization results of the nanopositioning stage and the QTF detector are presented along with an outline of the method for tip mounting on the QTFs. Initial imaging results are also presented.
We give an overview of the design of a metrological Scanning Probe Microscope (mSPM) currently under development
at the National Measurement Institute Australia (NMIA) and report on preliminary results on the implementation of key
components. The mSPM is being developed as part of the nanometrology program at NMIA and will provide the link in
the traceability chain between dimensional measurements made at the nanometre scale and the realization of the SI metre
at NMIA. The instrument is based on a quartz tuning fork (QTF) detector and will provide a measurement volume of
100 μm × 100 μm × 25 μm with a target uncertainty of 1 nm for the position measurement. Characterization results of the
nanopositioning stage and the QTF detector are presented along with an outline of the method for tip mounting on the
QTFs. Initial imaging results are also presented.
We give an overview of the design and planned operation of the metrological Scanning Probe Microscope (mSPM)
currently under development at the National Measurement Institute Australia (NMIA) and highlight the metrological
principles guiding the design of the instrument. The mSPM facility is being established as part of the nanometrology
program at NMIA and will provide the link in the traceability chain between dimensional measurements made at the
nanometer scale and the realization of the SI meter at NMIA. The instrument will provide a measurement volume of
100 μm × 100 μm × 25 μm with a target uncertainty of 1 nm for the position measurement.
The wavefronts reflected by and transmitted through a coated substrate will be influenced by the non-uniformities of the coatings and distortion of the substrate produced as a result of coating stress. In this paper we describe the characterization procedure and results of a coated substrate for the Laser Interferometer Gravitational wave Observatory (LIGO) project. The fused silica substrate is 250 mm in diameter, 40 mm thick and on one side a multilayer anti- reflection coating is deposited and a 50% reflectivity multilayer coating on the other. To characterize the coatings, reflected and transmitted wavefront measurements were carried out with a 300 mm aperture phase-shifting Fizeau interferometer in combination with ellipsometric measurements of the coated surfaces. The interferometric measurements allowed the deformation of the substrate by the coatings to be assessed while the ellipsometric measurements allowed the coatings' thickness variation to be measured and the resulting phase variation in the reflected and transmitted wavefronts to be estimated. The measurements revealed substrate deformation of about 45 nm with a coating relief non-uniformity of about 5 nm over a working aperture of 200 mm.
Fizeau interferometers are traditionally used to determine the surface figure of uncoated optics. Since the reflectances from the uncoated reference and test surfaces are usually equal, the intensity of the interference fringe minimum is zero, so the fringe contrast is unity. If the same reference surface is used to measure the figure of a higher reflecting surface, the fringe minimum intensity is no longer zero and the fringe contrast decreases, eventually reaching zero for 100 percent reflecting optics. The problem can be overcome if the reference surface is coated with a lossy reflecting surface. We describe a coating to measure the figure of optical components having reflectance from 100 percent to 3.5 percent at 1064 nm. The spatial variations across the 150 mm working aperture in physical thickness of the two materials used to coat the reference surface were determined to an accuracy better than 1 nm using a single wavelength ellipsometer operating at 633 nm. Variations across the aperture of the phase changes on reflection from both sides of the reference flat substrate and on transmission were estimated. These results are presented together with calculations designed to determine the relative positions of the outside of the coating with respect to substrate surface as well as the position as seen optically. Substrate distortion due to stress in the coatings has also been measured.
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