Synthesis and Characterization of 2D Tellurene Flakes for Device Application

Abstract

Tellurene, a single layer of tellurium atoms arranged in a zig-zag chain structure, is a recent addition to the family of 2D materials. It has a trigonal crystal lattice with inherent structural anisotropy. Tellurene has huge potential for nanoelectronic and opto-electronic applications. Tellurene has interesting properties e.g., semiconducting, photoconductive, thermoelectric, piezoelectric, topological, and acousto-optic properties making it suitable for application in electronics, sensors, optoelectronics and energy devices. Additionally, Tellurene exhibits extraordinary carrier mobility, high stretchability, and significant optical absorption. Due to its inherent structural anisotropy, previously reported methods were not very successful in synthesizing 2D sheets. However, the solvothermal technique is a substrate-free solution process that can produce large area, high-quality Tellurene without the need for high growth temperature, delicate control of growth atmosphere, or specific substrate for growth, unlike other methods like CVD, PVD, etc. So far there hasn’t been much in-depth study of electronic or optoelectronic properties of solution grown Tellurene. In this thesis we have synthesized 2D Tellurene using solvothermal technique and studied their properties in detail. After synthesis, the morphology and structure of the samples were characterized by using SEM, TEM, XRD, AFM, STM and Raman spectroscopy. This work mainly involves the study of electrical and opto-electronic properties of Tellurene by fabricating devices using photo-lithography. The electrical properties such as mobility, on/off ratio, current density and opto-electronic properties such as rise time, fall time, on/off ratio were studied in detail. Devices with different contact material were made on the as-grown flakes. The contact resistance between various materials such as Platinum, Palladium, Nickel and Gold were studied. The effect of these contact materials on the properties of Tellurene flakes were also studied in detail. For the first time we herein report the observation of contact induced metallization of Tellurene flakes. The polarization dependent imaging of the samples were also performed.