Toward Perfect TMDs Surfaces with Ion Bombardment and Annealing Treatment

Wan-Hsin Chen^1*, Naoya Kawakami¹, Jing-Wen Hsueh², Lai-Hsiang Kuo², Jiun-Yu Chen¹, Ting-Wei Liao², Chia-Nung Kuo^3,4, Chin-Shan Lue^3,4,5, Yu-Ling Lai⁶, Yao-Jane Hsu⁶, Der-Hsien Lien⁷, Chenming Hu⁸, Jyh-Pin Chou⁹, Meng-Fan Luo², Chun-Liang Lin¹

¹Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, Taiwan
²Department of Physics, National Central University, Jhongli, Taiwan
³Department of Physics, National Cheng Kung University, Tainan, Taiwan
⁴Taiwan Consortium of Emergent Crystalline Materials, National Science and Technology Council, Taipei, Taiwan
⁵Program on Key Materials, Academy of Innovative Semiconductor and Sustainable Manufacturing, National Cheng Kung University, Tainan, Taiwan
⁶Nanoscience Group, National Synchrotron Radiation Research Center, Hsinchu, Taiwan
⁷Institute of Electronic Engineering, National Yang Ming Chiao Tung University, Hsinchu, Taiwan
⁸International College of Semiconductor Technology, National Yang Ming Chiao Tung University, Hsinchu, Taiwan
⁹Department of Physics, National Changhua University of Education, Changhua, Taiwan

* Presenter:Wan-Hsin Chen, email:lucychen.ep05g@g2.nctu.edu.tw

Layered transition metal dichalcogenides (TMDs) are two-dimensional materials exhibiting a variety of unique features with great potential for future electronic and optoelectronic applications. Ideally, a defect-free surface is expected in layered TMDs due to their self-terminated nature. In reality, TMDs’ surfaces are imperfect. High defect density is commonly observed despite their preparation methods (either by exfoliation or growth methods). Recent efforts have focused on delicate controls of growth conditions to reduce the defect density, but creating a defect-free surface remains challenging. In this work, we propose a counterintuitive approach to largely remove surface defects in layered TMDs by a two-step process: the surface was firstly bombarded by Ar⁺, followed by a post-annealing process. We show that more defects were created on the as-cleaved PtTe₂ and PdTe₂ surfaces after the Ar⁺ bombardment. Surprisingly, all defects were removed after an annealing process in the vacuum. The self-recovery process of the TMDs’ surface is directly monitored by scanning tunneling microscopy (STM). The recovered surfaces are further characterized by reflection high-energy electron diffraction (RHEED) and X-ray photoelectron spectroscopy (PES). The mechanism of the two-step process is explained by density functional theory (DFT). This work offers a new method to repair the surfaces of layered TMDs and could potentially be used in device-level applications.

Keywords: self-healing, 2D materials, defects, ion bombardment, surface modification