Electrical and Optical Characterization of MoS2 with Sulfur Vacancy Passivation by Treatment with Alkanethiol Molecules

본 논문에서 이차원 n-type 반도체 물질 중 하나인 이황화몰리브덴(MoS2)의 전기적, 광학적 특성과 MoS2의 황 공격자(sulfur vacancy)를 alkanethiol 분자를 이용하여 패시베이션(passivation) 하였을 때 이러한 특성들이 어떻게 변화하는지에 관한 연구 결과를 기술하였다. MoS2의 sulfur vacancy 위치에 특정한 분자들이 달라 붙으려고 하는 경향성을 이용하여 passivation하여 sulfur vacancy 의 수를 줄여주면, 전하 밀도와 전류 값과 같은 전기적 특성이 변화(감소)하는 것을 관찰하였다. 온도 변화에 따른 전류-전압 곡선 측정을 통하여 분자가 흡착된 후 전류가 어떤 메커니즘으로 감소하는지 밝혔다. 또한, 분자 처리 후 MoS2의 표면에 분자가 달라 붙음으로써 라만 스펙트럼과 photoluminescence의 peak의 위치가 변화한다는 것을 관찰하였다. MoS2의 두께를 바꾸어가며 같은 실험을 반복하여 두께와 변화율 사이의 통계적인 경향성을 관측하였다.

Abstract: We investigated the physical properties of molybdenum disulfide (MoS2) atomic crystals with a sulfur vacancy passivation after treatment with alkanethiol molecules including their electrical, Raman, and photoluminescence (PL) characteristics. MoS2, one of the transition metal dichalcogenide materials, is a promising two-dimensional semiconductor material with good physical properties. It is known that sulfur vacancies exist in MoS2, resulting in the n-type behavior of MoS2. The sulfur vacancies on the MoS2 surface tend to form covalent bonds with sulfur containing groups. In this study, we deposited alkanethiol molecules on MoS2 field effect transistors (FETs) and then characterized the electrical properties of the devices before and after the alkanethiol treatment. We observed that the electrical characteristics of MoS2 FETs dramatically changed after the alkanethiol treatment. We also observed that the Raman and PL spectra of MoS2 films changed after the alkanethiol treatment. These effects are attributed to the thiol (-SH) end groups in alkanethiols bonding at sulfur vacancy sites, thus altering the physical properties of the MoS2. This study will help us better understand the electrical and optical properties of MoS2 and suggest a way of tailoring the properties of MoS2 by passivating sulfur vacancy with thiol molecules.

Authors: Kyungjune Cho(서울대), Misook Min(서울대), Tae-Young Kim(서울대), Hyunhak Jeong(서울대), Jinsu Pak(서울대), Jae-Keun Kim(서울대), Jingon Jang(서울대), Seok Joon Yun(성균관대), Young Hee Lee(성균관대), Woong-Ki Hong(KBSI), and Takhee Lee(서울대),*
ACS Nano, Just Accepted Manuscript

Publication Date (Web): August 11, 2015
DOI: 10.1021/acsnano.5b04400