@article {43577, title = {Thickness tunable transport in alloyed WSSe field effect transistors}, journal = {Applied Physics Letters}, volume = {109}, year = {2016}, month = {OCT}, pages = {Article Number: 142101}, abstract = {We report the field effect transistor characteristics of exfoliated transition metal dichalcogenide alloy tungsten sulphoselenide. WSSe is a layered material of strongly bonded S-W-Se atoms having weak interlayer van der Waals forces with a significant potential for spintronic and valleytronic applications due to its polar nature. The X-ray photoelectron spectroscopy measurements on crystals grown by the chemical vapor transport method indicate a stoichiometry of the form WSSe. We report flake thickness tunable transport mechanism with n-type behavior in thin flakes (<= 11 nm) and ambipolarity in thicker flakes. The devices with flake thicknesses of 2.4 nm-54.8nm exhibit a maximum electron mobility of similar to 50 cm(2)/V s along with an I-ON/I-OFF ratio > 10(6). The electron Schottky barrier height values of 35 meV and 52meV extracted from low temperature I-V measurements for 3.9 nm and 25.5 nm thick flakes, respectively, indicate that an increase in hole current with thickness is likely due to lowering of the bandgap through an increase in energy of the valence band maximum. Published by AIP Publishing.}, doi = {10.1063/1.4964289}, author = {Karande, Shruti D. and Kaushik, Naveen and Narang, Deepa S. and Late, Dattatray and Lodha, Saurabh} } @article {43686, title = {Synthesis of gamma-WO3 thin films by hot wire-CVD and investigation of its humidity sensing properties}, journal = {Physica Status Solidi A-Applications and Materials Science}, volume = {214}, year = {2017}, month = {MAY}, pages = {Article Number: 1600717}, type = {Article}, abstract = {In this study, monoclinic tungsten oxide (gamma-WO3) have been grown in a single step using HW-CVD method by resistively heating W filaments in a constant O-2 pressure. The formation of gamma-WO3 was confirmed using low angle-XRD and Raman spectroscopy analysis. Low angle-XRD analysis revealed that as-deposited WO3 film are highly crystalline and the crystallites have preferred orientation along the (002) direction. HRTEM analysis and SAED pattern also show the highly crystalline nature of WO3 with d spacing of similar to 0.38 nm, having an orientation along the (002) direction. Surface topography investigated by SEM analysis shows the formation of a uniform and homogeneous cauliflower like morphology throughout the substrate surface without flaws and cracks. A humidity sensing device incorporating WO3 is also fabricated, which shows a maximum humidity sensitivity factor of similar to 3954\% along with a response time of similar to 14 s and a recovery time of similar to 25 s. The obtained results demonstrate that it is possible to synthesize WO3 in a single step by HW-CVD method and to fabricate a humidity sensor by using it. (C) 2017 WILEY-VCH Verlag GmbH \& Co. KGaA, Weinheim}, doi = {10.1002/pssa.201600717}, author = {Jadkar, Vijaya and Pawbake, Amit and Waykar, Ravindra and Jadhavar, Ashok and Date, Abhijit and Late, Dattatray and Pathan, Habib and Gosavi, Suresh and Jadkar, Sandesh} } @article {46183, title = {Fiber optic Fabry-Perot interferometer sensor: an efficient and fast approach for ammonia gas sensing}, journal = {Journal of the Optical Society of America B-Optical Physics}, volume = {36}, year = {2019}, month = {MAR }, pages = {684-689}, type = {Article}, abstract = {

In this work, we propose and demonstrate a Fabry-Perot-interferometer-based polydimethylsiloxane (PDMS) and poly(methyl methacrylate) (PMMA)-composite-coated optical sensor for ammonia and volatile organic compounds (VOCs) detection at room temperature. The principle of sensing is based on change in the cavity length of the FP cavity in the presence of varied concentrations of gases, which results in changes in the total reflectance due to the shift in wavelength of an interference pattern. The sensing composite material was coated on a single-mode optical fiber by using a simple dip-coating technique and explored it for sensing. The ammonia and VOCs measurements were performed for concentrations ranging from 5 to 500 ppm. The corresponding sensitivity and limit of detection of the developed sensor for ammonia gas detection was observed of the order of around 4.16 pm/ppm and 4.8 ppm, respectively. The response and recovery times of the sensor were found to be of the order of 50 s and 10 s, respectively, for the ammonia gas. This sensor provides a simple, cost-effective, highly sensitive, and repeatable approach to measure ammonia gas and other VOCs at room temperature and could fulfill the demands of industrial applications. (C) 2019 Optical Society of America

}, issn = {0740-3224}, doi = {10.1364/JOSAB.36.000684}, author = {Kanawade, Rajesh and Kumar, Ajay and Pawar, Dnyandeo and Late, Dattatray and Mondal, Samir and Sinha, Ravindra K.} } @article {46173, title = {Negative axicon tip-based fiber optic interferometer cavity sensor for volatile gas sensing}, journal = {Optics Express}, volume = {27}, year = {2019}, month = {MAR }, pages = {7277-7290}, type = {Article}, abstract = {

In this research work we demonstrated negative axicon optical fiber tip filled with Polydimethylsiloxane (PDMS) as a sensor platform for volatile organic gases detection at room temperature. The response of the sensor was measured with various Volatile Organic Compounds (VOCs) such as Chloroform, Hexane, Isopropanol, Acetone, Toluene and Methanol in the concentration ranging from 5 to 200 ppm. The corresponding sensitivity and limit of detection (LOD) of the developed sensor for the measured VOCs were observed between the order of around 23.7 to 3.2 pm/ppm and 0.84 to 6.10 ppm, respectively. The response and recovery time of sensor were found between the order of 30 to 57 seconds and 8 to 25 seconds respectively for the measured VOCs. Thermal stability of the developed sensor was also studied at 30-70 degrees C with intervals of 10 degrees C. The principle of sensing is based on change in the length of the Fabry-Perot Interferometric (FPI) cavity in the presence of varied concentrations of VOCs, which results in changes in the shift in wavelength of an interference pattern attributed to the change in PDMS filling the cavity length (swelling). The experimentally observed trends in the relative swelling of PDMS with VOCs are found in agreement with the theoretically calculated values obtained from the Hansen solubility parameter (HSP). The developed gas sensor has the potential to fulfill the demands of industrial applications.

}, issn = {1094-4087}, doi = {10.1364/OE.27.007277}, author = {Kanavvade, Rajesh and Kumar, Ajay and Pawar, Dnyandeo and Vairagi, Kaushal and Late, Dattatray and Sarkar, Sudipta and Sinha, Ravindra K. and Mondal, Samir} } @article {46097, title = {Solvothermal growth of PbBi2Se4 nano-flowers: a material for humidity sensor and photodetector applications}, journal = {Physica Status Solidi A-Applications and Materials Science}, volume = {216}, year = {2019}, month = {JUN}, pages = {1900065}, type = {Article}, abstract = {

In the present work, lead bismuth selenide (PbBi2Se4) nano-flowers are synthesized by using a simple solvothermal method. Humidity sensor and photodetector based on PbBi2Se4 nano-flowers are fabricated on indium tin oxide (ITO) substrates and their sensing properties are investigated. Formation of PbBi2Se4 is confirmed by XRD, EDS, and XPS whereas formation of nano-flowers is confirmed by SEM and TEM analysis. XRD analysis reveals the hexagonal crystal structure of PbBi2Se4 phase with a = b = 4.22 angstrom, and c= 17.42 angstrom. The surface morphology of PbBi2Se4 clearly shows the formation of well-organized flower-like nanostructures which closely resembles the shape of Dahlia. The elemental mapping of chemical constituents obtained from SEM-EDS analysis shows uniform distribution of chemical constituents for the Pb, Bi, and Se in PbBi2Se4 nano-flowers. The PbBi2Se4 nano-flowers based humidity sensor has a typical response time of approximate to 65s and recovery time of approximate to 75 s. In case of PbBi2Se4 nano-flowers-based photodetector, the response and recovery time are observed approximate to 121 and approximate to 123 s, respectively, under visible light illumination with photoresponsivity (5 x 10(-6)), photosensitivity (2.16\%), and quantum efficiency (1.5 x 10(4)). The obtained results demonstrate the potential applications of solvothermally grown PbBi2Se4 nano-flowers-based devices for humidity sensors and photodetectors. The ease of the present work is to develop novel material to obtain device quality humidity sensors and photodetectors.

}, keywords = {humidity sensor, PbBi2Se4, photodetector, XPS, XRD}, issn = {1862-6300}, doi = {10.1002/pssa.201900065}, author = {Aher, Rahul and Bhorde, Ajinkya and Nair, Shruthi and Borate, Haribhau and Pandharkar, Subhash and Naik, Dhirsing and Vairale, Priti and Karpe, Smita and Late, Dattatray and Prasad, Mohit and Jadkar, Sandesh} }