GROWTH AND CHARACTERIZATION OF MONOLAYER TRANSITION METAL DICHALCOGENIDES:

Abstract

Over the last few decades, the silicon-based technology has dominated in the industrial electronics market. However, in the recent decades ago, the advent of graphene, the first true 2D material, marked a historic point for potentially new-generation of electronics. Not long after that, the successive discoveries of different 2D materials including an insulator (hexagonal Boron Nitride), semiconductors (transition metal dichalcogenides TMDCs), metallic (graphene) provide a great chance to achieve extremely thin and light optoelectronic devices. In order to achieve the high performance optoelectronic, yielding 2D materials with remarkable quality is highly desirable. The essence of this work lies on growth technique that produces high quality 2D materials applicable to new-generation of 2D optoelectronic devices. In this dissertation, monolayer TMDCs were chosen as subjects to study. In chapter 1, I will briefly introduce layer-dependent physical and structural properties monolayer TMDCs as well as the current synthesis approaches for growing monolayer TMDCs. I initially grew large-scale, highly optical quality monolayer TMDC using chemical vapor deposition method. Towards practical applications, the continuous monolayers MoS2 were synthesized and its photoresponsibility was also characterized in order to fabricate competitive metal-semiconductor-metal photodetector in chapter 2. An additional part of this dissertation will discuss the nonlinear optical characteristic of monolayer TMDCs towards design a broad and strong second harmonic susceptibility χ(2) materials. Nonlinear properties theory will be mainly discussed in term of second harmonic generation. In chapter 3, nonlinear characteristics of transferred MoS2 on the transparent substrate were studied in comparison with as-grown MoS2 onto SiO2/Si substrate, which could be applied to Fabry-Perót cavity in the laser technology. In chapter 4, another typical member of monolayer TMDC, MoSe2, was also investigated using both intensity dependent SHG and wavelength dependent SHG techniques. The results suggested its potential use of high-powered second-order NLO devices. In chapter 5, the resonant second harmonic generation characteristics were analyzed in ternary monolayer alloy MoS2(1-x)Se2x, showing a feasibility to apply them into tunable second-order NLO devices. Finally, stacked heterostructures needed to be investigated to solve the quest of high NLO material. The final chapter will present our preliminary but rather interesting results on artificially stacked monolayers TMDCs for next-generation of 2D optoelectronic devices.