Growth, characterization and device fabrication of two dimensional materials

Abstract

In this thesis, a new method to grow large area monolayer MoS2 on sapphire using Chemical Vapour Deposition (CVD) has been devised and demonstrated. An extensive and detailed analysis of growth mechanism was done. Raman, photoluminescence (PL) spectroscopy were used to confirm the monolayers as seen from optical microscope. Top gated field effect transistors (FETs) were fabricated to do the electrical characterization and transport measurements. At first, the conventional method was optimized on the system as a reference point for the proposed growth method. Taking the associated growth parameters as the basis, a new CVD growth method was implemented. Once optimized, the new method produces single layer MoS2 monolayers in the order of hundred microns and continuous MoS2 single layers of centimetre scale. Optical characterization was done using optical microscope, Raman and PL spectroscopy. Raman and PL mapping were also done to check the homogeneity of layers formed. The height profile analysis was done using atomic force microscopy(AFM). X-ray photoelectron spectroscopy (XPS) was used to analyse elemental compositions and to quantize the impurities resulting from the new growth method. In addition, top gated FET was fabricated and the electronic quality of the films was investigated through their associated transfer characteristics.