FABRICATION AND CHARACTERIZATION OF MoS2 BASED DEVICES

Abstract

Transition metal dichalcogenides (TMDs) are highly attractive two dimensional (2D) materials with unique structural, electrical and optical properties that make them very important for different applications. Among TMDs, we have selected molybdenum disulfide (MoS2) as the main semiconducting material. 2D MoS2 thin films have distinct properties like existence of sizable bandgap that make it more appealing for various applications. Monolayer MoS2 is a direct gap (~1.9 eV) semiconductor while multi-layered or bulk MoS2 is an indirect gap (~1.2 eV) semiconductor. In the present work, MoS2 thin films were fabricated on difference substrates using DC magnetron sputtering. For large area and high purity fabrication of MoS2 films, sputtering technique offers very interesting route. The morphology of sputtered MoS2 thin films strongly depends on the thickness. As the thickness of the MoS2 film increases, surface morphology of the films turned from nanoparticles like structures to vertically aligned and highly ordered nanoworm like surface morphology. The nanoworm type surface morphology of sputtered MoS2 films provide great advantages for energy storage, Schottky diode and gas sensing applications. The sputtered MoS2 nanoworm thin films have an open pore structure. Such unique nanostructured MoS2 supercapacitor device exhibits high specific capacitance. Gas response of the sensor is instigated by the response of gas molecules to the top surface of the sensitive material. The adsorption of gas molecules is higher for nanoworm type MoS2 structures. Such nanoworm type structure provides the active sites for gas molecules to adsorb and desorb. MoS2 has emerged as a promising candidate for electronic devices due to its exotic properties. In electronic devices, Schottky devices are suitable for high speed applications due to fast switching. The performance of MoS2 based Schottky devices are also strongly affected by the structure and thickness of MoS2 film. A small change in the thickness of MoS2 may tune the electrical nature of the metal-MoS2 junction from Schottky to Ohmic. The influence of high energy irradiation on different devices is also very useful in the studies of their performance in radiation harsh environment and in space where they are exposed to high stream of energetic particles. Swift heavy ion (SHI) irradiation can modify the device performance by introducing the defects like vacancies, interstitials, dislocations and inhomogeneities at the interface.