Electronic structure of molybdenum disulfide on highly oriented pyrolytic graphite

• Main Authors: Liu, Jun-Heng, 劉俊亨
• Other Authors: Hoffmann, Germar
• Format: Others
• Language: en_US
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/57rcvx

碩士 === 國立清華大學 === 物理學系 === 106 === 2D Materials have attracted lots of interests due to their unique physical properties and potential applications in electronics. Layered transition metal dichalcogenides(TMDs) are one of the most popular 2D materials. TMDs are often combined with other 2D materials to make van der Waals heterostructure. These heterostructures need to be optimized to be possibly used as building blocks for many different devices. Our experiments focus on molybdenum disulfide on highly oriented pyrolytic graphite. Our research on MoS2 on HOPG can mainly be divided into two parts. One is the defect influence on the electronic properties of MoS2. We've studied the influence of the grain boundary on the band gap of MoS2. We also investigated different kinds of defects such as point defects, sulfur vacancies, point defects with adsorbates. The other is related to the MoS2 as electrocatalyst of hydrogen evolution reaction (HER). HER can be used to produce elemental hydrogen. The produced hydrogen can serve as fuel for hydrogen oxygen fuel cells. Platinum can be used as a catalyst for HER. However, it is too expensive in practical use. MoS2 has the potential to replace the role of platinum, but the problem is the efficiency of the catalysis. In order to increase the efficiency of catalysis, sulfur vacancies are created by plasma treatment on MoS2. After testing the HER catalysis efficiency, samples are investigated by scaning tunneling microscopy (STM). Our experiment is to identify the existence of sulfur vacancies. As a result, we "observed" many different types of sulfur vacancies. Besides these two parts, we've also done lots of characterization of MoS2 on HOPG such as the thickness dependence of the band gap, large area topography, atomic structure and morie patterns.