sp2 to sp3 hybridization transformation in 2D metal-semiconductor contact interface suppresses tunneling barrier and Fermi level pinning simultaneously
Wenchao Shan, Anqi Shi, Zhuorong Zhong, Xiuyun Zhang, Bing Wang, Yongtao Li, Xianghong Niu
Abstract
Van der Waals (vdWs) stacking of two-dimensional (2D) materials can effectively weaken the Fermi level pinning (FLP) effect in metal/semiconductor contacts due to dangling-bond-free surfaces. However, the inherent vdWs gap always induces a considerable tunneling barrier, significantly limiting carrier injection. Herein, by inducing a sp 2 to sp 3 hybridization transformation in 2D carbon-based metal via surface defect engineering, the large orbital overlap can form an efficient carrier channel, overcoming the tunneling barrier. Specifically, by selecting the 2D carbon-based X 3 C 2 (X = Cd, Hg, and Zn) metal and the 2D MSi 2 N 4 (M = Cr, Hf, Mo, Ti, V, and Zr) semiconductor, we constructed 36 metal/semiconductor contacts. For vdWs contacts, although Ohmic contacts can be formed at the interface, the highest tunneling probability ( P TB ) is only 3.11%. As expected, the P TB can be significantly improved, as high as 48.73%, when MSi 2 N 4 , accompanied by surface nitrogen vacancies, forms an interface covalent bond with X 3 C 2 . Simultaneously, weak FLP and Ohmic contact remain at the covalent-bond-based surface, attributing to the protection of the MSi 2 N 4 band-edge electronic states by the outlying Si-N sublayer. Our work provides a promising path for advancing the progress of 2D electronic and photoelectronic devices.