Transition metal dichalcogenides (TMDCs) have received a great deal of attention from the scientific community since the advent of graphene. Tungsten diselenide (2H-WSe2) has particularly drawn-out attention of researchers because of its broadband spectral detection range. In this work, we have reported a halide assisted chemical vapor deposition (HA-LPCVD) technique for synthesis of large crystallites of 2H-WSe2 with high crystalline perfection. The average crystallite size of synthesized 2H-WSe2 was in the order of ~20 μm. We have reported device 2H-WSe2 device fabrication using poly (methyl methacrylate) and electron beam lithography process to define titanium (Ti) metal contacts. A temperature (T) dependent analysis of the electronic transport reported here reveals a T-dependent conduction process existing at the interface of Ti and 2H-WSe2 and an interfacial barrier height of ~ 0.35 eV was calculated at the thermionic emission regime. From the reported optoelectronic characterization, an on-off ratio (Ion/Ioff) of ~9 was calculated. Furthermore, a responsivity (ℜ) of ~ 242 A/W was calculated for our 2H-WSe2 based photodetector under broadband light excitation. The reported photodetector figures of merit will open avenues for use of monolayer 2H-WSe2 with Ti metal contacts for high performance photodetection.
Tungsten diselenide (WSe2) is an interesting two dimensional (2D) transitional metal dichalcogenide (TMDC) with a high quantum yield in photoluminescence (PL), a strong spin-orbit coupling and tunable transport properties. One way to increase photon absorption in WSe2 is to combine WSe2 with other excitonic nanomaterials such as Quantum dots (QDs) from which photogenerated excitons can be transferred onto the TMDCs via non-radiative energy transfer. Such characteristics prove highly effective in the utilization of QDs toward enhancing the optical responsivity of 2D material-based photo-FET devices. In this study, we fabricated WSe2 based photodetector and showed that its photoconduction property was improved by incorporation of Au-QDs. Monolayer WSe2 was synthesized on SiO2/Si by low pressure chemical vapor deposition method at a growth temperature of ~ 850°C. Thereafter, Au-QDs (~15 nm) were drop casted onto WSe2 followed by vacuum annealing. PL spectroscopy showed enhancement in excitonic A-peak intensity by an order of 2-fold in the region where Au QD was incorporated. E-beam lithography was used to fabricate the back gated photo transistor followed by Au/Ti deposition by E-beam evaporation. The device was illuminated with a red laser source (660 nm) to study its optoelectronic properties. The photoresponsivity was found to improve by a factor of ~102 with the incorporation of Au QDs in 1L WSe2. Our results demonstrate the viability of this hybrid structure for commercial photodetector and light harvesting applications.
Broadband photodetection is crucial for various defense and scientific applications such as biomedical imaging, communications, and environmental and spectral monitoring. In recent years, transition metal dichalcogenide semiconductors, from the two-dimensional layered materials family, have attracted special attention for their application in photodetection due to their outstanding optoelectronic properties and large optical absorbance for their atomically thin thicknesses. Here, we present a CVD-synthesized MoS2 phototransistor with Au/Ti contacts enhanced by Au nanoparticles via surface nanoplasmonics. From electronic and optoelectronic characterizations, intrinsic device parameters were extracted and analyzed including the field-effect mobility of 37.4 cm2V-1s-1, a high ON/OFF ratio of 106. Next, the optoelectronic characterization was carried out before and after Au nanoparticles using a tunable laser with a wavelength absorption range from 400 nm to 1100 nm under vacuum conditions. The spectral photoresponse was improved from a cutoff wavelength of ~ 975 nm before the Au nanoparticles to a broadband spectral detection with a minimum standard deviation of 0.56 μA at from near-ultraviolet to near-infrared and a maximum photocurrent of 7.61 μA at an incident optical power density of ~ 2 μWcm-2. In addition, the photocurrent has been increased 5-fold after decorating the MoS2 photodetector with Au nanoparticles. The improvement of the light-matter interaction of MoS2 nanosheet, described before, is attributed to the localized surface plasmon in gold nanoparticles.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.