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Fabrication of Gas Nanosensor based on 2D Nanostructure Titanium trisulfide/Graphene Heterojunction

Rafiefard, Nasim | 2020

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 53003 (48)
  4. University: Sharif University of Technology
  5. Department: Institute for Nanoscience and Nanotechnology
  6. Advisor(s): Iraji Zad, Azam; Sasanpour, Pezhman; Esfandiar, Ali
  7. Abstract:
  8. Titanium trisulfide (TiS3), a transition metal chalcogenide, bears the potential to replace silicon, when taking the form of nanoflakes, due to its favorable band gap and optical response. In this work, first we investigate the response of TiS3 nanoflakes to gas detection through a careful quantum computational approach and a few succinct measurements. The computations are benchmarked and compared with a relevant experiment at each step, where their results/conclusions are discussed. The most stable surface of TiS3 particles is determined to (001), in agreement with the literature. The adsorption of 5 gas molecules is characterized through formulating and estimating their adsorption intensity, rather than using singled-out values of binding energies. This formulation, which roots in a statistical view of the gas adsorption process, distinguishes H2 and CH4 molecules from H2O, O2 and ethanol explicitly and unambiguously through comparing their adsorption profiles. The difference in the adsorption intensities thus predicts and elucidates the difference in the sensing behaviour of TiS3 particles. This work suggests that computationally obtained profile for the adsorption spectrum of gas molecules serves as a tool/criterion to predict the selectivity of their detection by TiS3. After showing the TiS3 response to ethanol both theoretically and experimentally, in the second step, the room temperature polar vapor sensing behavior of 2D heterojunction Graphene-TiS3 materials and lithographically patterned TiS3 nanoribbons is investigated. TiS3 nanoribbons and graphene (Gr) flakes with high surface to volume ratio were synthesized via chemical vapor transport (CVT) and chemical vapor deposition (CVD). Their structure was investigated by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), energy dispersive X- ray spectroscopy (EDS), X-ray diffraction (XRD), Raman spectroscopy and Fourier transform infrared spectroscopy (FT-IR) analysis. The gas sensing performance of the 2D heterojunction Graphene-TiS3 materials and lithographically patterned TiS3 nanoribbon sensors was assessed through the changes in their electronic behavior. It is observed that TiS3 device has a rather linear I-V behavior while the Gr-TiS3-Gr forms a contact with a higher Schottky barrier (250 meV). I-V responses of the sensors were recorded at room temperature with a relative humidity of 55% and for different ethanol vapor concentrations (varying from 2 to 20 ppm). I-V plots indicated the increase in the resistance of Gr-TiS3-Gr by the adsorption of water and ethanol molecules with relatively high sensing response (~3353% at 2 ppm). Our results indicate that selective and stable responses to a low concentration of ethanol vapor (2 ppm) can be achieved at room temperature with the transient response and recovery times around 6 s and 40 s respectively. Our proposed design paves a new way forward for selective molecular recognition using polar interactions between analyte vapors and heterojunctions of 2D-materials
  9. Keywords:
  10. Graphene ; Gas Sensor ; Ethanol Gas Sensor ; Hetero Structure ; Chemical Vapor Deposition (CVD)Growth of Graphene ; Chemical Vapor Deposition (CVD) ; Dielectrophoresis Technique ; Two Dimentional Materials ; Titanium Trisulfide Nanoribbons

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