Recent advances in two-dimensional (2D) crystals make it possible to realize an ideal interface structure that is required for device applications. Specifically, a p-n junction made of 2D crystals is predicted to exhibit an atomically well-defined interface that will lead to high device performance. Using angle-resolved photoemission spectroscopy, a simple surface treatment was shown to allow the possible formation of such an interface. Ta adsorption on the surface of a p-doped SnSe shifts the valence band maximum towards higher binding energy due to the charge transfer from Ta to SnSe that is highly localized at the surface due to the layered structure of SnSe. As a result, the charge carriers of the surface are changed from holes of its bulk characteristics to electrons, while the bulk remains as a p-type semiconductor. This observation suggests that the well-defined interface of a p-n junction with an atomically thin {\it n}-region is formed between Ta-adsorbed surface and bulk.
@article{arxiv.2007.09393,
title = {A plausible method of preparing the ideal p-n junction interface of a thermoelectric material by surface doping},
author = {Ji-Eun Lee and Jinwoong Hwang and Minhee Kang and Hyun-Jeong Joo and Hyejin Ryu and Kyoo Kim and Yongsam Kim and Namdong Kim and Anh Tuan Duong and Sunglae Cho and Sung-Kwan Mo and Choongyu Hwang and Imjeong Ho-Soon Yang},
journal= {arXiv preprint arXiv:2007.09393},
year = {2020}
}