NOVEL APPROACHES FOR THE SYNTHESIS OF LARGE-AREA 2D THIN FILMS BY MAGNETRON SPUTTERING

Author

Hassana Samassekou, Southern Illinois University CarbondaleFollow

Date of Award

12-1-2018

Degree Name

Doctor of Philosophy

Department

Physics

First Advisor

Mazumdar, Dipanjan

Abstract

This past decade, 2D materials beyond graphene, and most specifically transition metal dichalcogenides (TMDCs) have gained remarkable attention due to their novel applications in electronics and optoelectronics applications. This work reports large-area growth and structural, optical, and electronic transport properties of few-layer MoS2 thin films fabricated using a hybrid approach based on the magnetron sputtering method. In the first part of this dissertation, properties of optimally annealed MoS2 on different substrates such as amorphous BN, SiO2, Si, Al2O3 are discussed using diffraction, spectroscopic, and transport techniques. Later, we show that the physical properties of large-area sputtered MoS2 thin films can be dramatically improved by an ex-situ high-temperature sulfurization process as it leads to the formation of defect-free MoS2 by removing sulfur vacancies. Sharp film-substrate interface along with high bulk structural order is demonstrated as inferred from diffraction and spectroscopic methods. We show that sulfur vacancies can obscure the MoS2 A-B exciton peaks along with a sharp increase in dc conductivity of MoS2. In the last part of my dissertation, we outline the growth of a novel thermoelectric material (SnSe) and new magnetic inverse-Heuslers (of nominal composition MnxFeSi) using the co-sputtering method. These are some of the first attempts, to our knowledge, to grow such materials in thin-film form. Detailed structure-property relations are thoroughly discussed.