Two-Dimensional Few-Layered Janus Diamond Nanofilms With Boron-Terminated Surfaces: First-Principles Calculation

In this work, the structural and electronic properties of two-dimensional (111) diamond nanofilms with a layer number of n = 3-6 are investigated by first-principles calculation. Two kinds of Janus models (both-side boron-termination model, one-side hydrogenation and another-side boron termination model) are dynamically and thermally stable. The nanofilms have direct bandgap characteristic, and their bandgaps are tunable in a region of 2.0 - 2.7 eV. The reduced bandgaps are mainly related to the surface termination of boron atoms. Interestingly, the electron mobilities (1500 cm(2).V-1.s(-1)) are higher than their hole mobilities (<660 cm(2).V-1.s(-1)) for both models under various film thickness. The Janus structures are favorable to realize high-performance photocatalysis devices in the visible region.