Rapid Thermal Synthesis of Molybdenum Disulfide Thin Films for Infrared Detectors

Abstract

Automation and modernization of gadgets in automobiles, safety, remote sensing, defence, agriculture, environmental pollution, imaging in nuclear medicine rely on the use of infrared (IR) detectors. In the current era of IR detectors, the quest for advanced materials turned the research towards transition metal dichalcogenides. Molybdenum disulfide (MoS2) is found to be a suitable candidate for IR detectors as it outperforms over a broad range of IR spectrum. In order to obtain a superior quality of MoS2 films, chemical vapor deposition has been explored which involves sulfurization of various Mo based compounds using inert carrier gases over a prolonged period of time at high process temperature. In this research, a short period growth of MoS2 films is implemented by face to face arrangement of pre-deposited S/Mo films on silicon substrates using rapid thermal process (RTP). In this work, an attempt has been made to explore the dependence of the RTP parameters such as growth duration, process time and gas flow rate on the morphological, microstructural and electronic properties of MoS2 thin films. Morphological properties of RTP grown MoS2 thin films have been investigated by Field Emission Scanning Electron Microscope and Atomic Force Microscope technique, whereas microstructural properties have been studied by X-Ray Diffraction and Raman technique. The electronic properties of the MoS2 films are estimated by current-voltage and capacitance-voltage technique. A correlation between the morphological and electronic properties of RTP grown MoS2 thin film has been systematically established in this research. The MoS2 films with improved morphological and electronic properties have been obtained at 800 °C for the growth duration of 5 min with the Ar:H2 flow rate of 10:1. The n-type and p-type MoS2 thin films are fabricated using benzyl viologen (BV) and gold chloride (AuCl3) solution, respectively by spin coating technique. The modulation of morphological and electronic properties of MoS2/Si samples was studied with the variation in concentration of BV and AuCl3 solution, number of spin coats and temperature of post-treatment annealing. The MoS2 based photoconductive detector, heterojunction, homojunction and Schottky junction are fabricated to investigate IR detection behavior at the wavelength of 850 nm, 940 nm and 1060 nm. MoS2 based Schottky junction has shown a higher current On/Off ratio, whereas fast rise and fall time has been observed for photoconductive devices. MoS2 thin films, synthesized by RTP have shown comparatively better IR detection behavior for 940 nm IR illumination. The above observations will pave a suitable platform for the next generation of IR detectors.