Studies of ultrafast photocarrier dynamics in spatially heterogeneous transition metal dichalcogenides using time-resolved photoemission electron microscopy

• Main Author: Xu, Ce
• Other Authors: Loh Zhi Heng
• Format: Thesis-Doctor of Philosophy
• Language: English
• Published: Nanyang Technological University 2021
• Subjects: Science::Chemistry::Physical chemistry
• Online Access: https://hdl.handle.net/10356/145896
• Institution: Nanyang Technological University

Transition metal dichalcogenides (TMDs) are among some of the most popular two-dimensional materials. Different from graphene, TMDs have intrinsic bandgaps, which open the door for their application in a variety of ultrathin semiconductor devices. The fabrication of TMDs result in diverse spatial heterogeneities in these materials, which can be either beneficial or detrimental to their properties. Therefore, it is crucial to visualize and analyze the ultrafast dynamics for a further comprehensive investigation of the alternate properties caused by the presence of heterogeneities, which can inspire defect engineering of TMD-based devices. The challenges are to achieve high spatial resolution for the observation of heterogeneities and high temporal resolution for the analysis of ultrafast dynamics at a femtosecond scale. The time-resolved photoemission electron microscopy (TR-PEEM) combines ultrafast pump-probe technique and PEEM, achieving 50-fs temporal resolution and 70-nm spatial resolution. Here, I will describe the effects of heterogeneities on the photocarrier dynamics of TMDs based on our TR-PEEM studies.