Interface induced transition from Schottky-to-Ohmic contacts in single-walled carbon nanotube-based van der Waals Schottky heterostructures

The unique advantages of one-dimensional (1D) van der Waals (vdW) Schottky heterostructures in electronic devices have gradually been highlighted with the improvement of experimental technology in recent years. However, it is inevitable that metal and semiconductor contact will be in the 1D nanodevices, leading to many challenges in the formation of low-resistance Ohmic contacts due to the Fermi level pinning (FLP) effect. Herein, we employ density functional theory to explore a series of 1D armchair carbon nanotube (CNT)-based vdW Schottky heterostructures. By comparing three kinds of Schottky barrier heights (SBH) of S2-NT/CNT, S-NT/CNT, and Se-NT/CNT under different interface distances, we find that only S-NT/CNT can form an Ohmic contact when the interface distance is reduced to 3.01 Å. By analyzing the interface charge transfer, band alignment, and flexoelectric effect, we find that flexoelectric polarization can promote more charge transfer at the S-NT/CNT interface when interface distance becomes smaller, and energy band at the interface bends upwards and overlaps the Fermi level, resulting in the interface to change from a depletion region to an inversion layer and leading to the formation of p-type Ohmic contacts. The results achieved in this study provide a new avenue for the design of 1D vdW electronic devices.