새소식

Department of Physics & Astronomy

[김재근 박사/조경준 박사/강기훈 교수(연세대)/이탁희 교수] 분자 도핑이 이차원 반도체의 전하수송에 주는 영향 규명 (Advanced Materials 게재)

2021-09-27l 조회수 359

Molecular Dopant-dependent Charge Transport in Surface-charge-transfer-doped WSe2 Field Effect Transistors

이차원 반도체 물질을 전자소자로 사용하기 위해 이차원 물질을 도핑하고, 도핑으로 인해 전하수송 특성이 어떻게 변하는지, 전하수송에서 도펀트의 역할을 이해하는 것이 중요하다본 연구에서는 이차원 반도체 물질 WSe2에 세가지 다른 종류의 분자로 분자표면도핑(surface charge transfer doping)을 하였을 때 WSe이차원 물질의 전하 수송현상이 어떻게 영향을 받는지에 대해 연구하였다. 이차원 물질과의 전하 교환을 통해 대전된 분자는 쿨롱 산란(Coulomb scattering)을 일으키고, 산란의 정도는 분자의 대전 양에 비례한다는 것을 밝혀내었다. 또한 이차원 물질과 분자사이의 전하교환은 기존에 알려져 있던 두 물질의 에너지 준위 뿐만 아니라 두 물질의 유전 상수, 상태 밀도(density of state) 등 다양한 요인들로 인해 결정 된다는 것을 보였다. 본 연구에서 밝혀낸 결과는 이차원 물질을 도핑하는데 적절한 분자 제시하여 이차원 물질의 전기 전도도 조절을 효과적으로 하는데 도움이 될 것으로 기대된다.  

The controllability of carrier density and major carrier type of transition metal chalcogenides (TMDCs) is critical for electronic and optoelectronic device applications. To utilize doping in TMDC devices, it is important to understand the role of dopants in charge transport properties of TMDCs. Here, we investigate the effects of molecular doping on the charge transport properties of tungsten diselenide (WSe2) using three p-type molecular dopants, 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ), Tris(4-bromophenyl)ammoniumyl hexachloroantimonate (magic blue), and molybdenum tris (1,2-bis (trifluoromethyl) ethane-1,2-dithiolene) (Mo(tfd-COCF3)3).
The temperaturedependent transport measurements show that the dopant counterions on WSe2 surface can induce Coulomb scattering in WSe2 channel and the degree of scattering is significantly dependent on the dopant. Furthermore, our quantitative analysis revealed that the amount of charge transfer between WSe2 and dopants is related to not only doping density, but also the contribution of each dopant ion towards Coulomb scattering. The first-principles density functional theory calculations show that the amount of charge transfer is mainly determined by intrinsic properties of the dopant molecules such as relative frontier orbital positions and their spin configurations. Our systematic investigation of the charge transport of doped TMDCs will be directly relevant for pursuing molecular routes for efficient and controllable doping in TMDC nanoelectronic devices.

Authors: Jae-Keun Kim, Kyungjune Cho, Juntae Jang, Kyeong-Yoon Baek, Jehyun Kim, Junseok Seo, Minwoo Song, Jiwon Shin, Jaeyoung Kim, Stuart S. P. Parkin, Jung-Hoon Lee*, Keehoon Kang*, and Takhee Lee*

DOI: https://doi.org/10.1002/adma.202101598

Published online: September 17, 2021

Link: https://onlinelibrary.wiley.com/doi/10.1002/adma.202101598