Surface Functionalization Tailored Electronic Structure and Magnetic Properties of Two-Dimensional CrC2 Monolayers

Spintronics is the promising technology for next-generation information storage due to its low energy consumption, high speed, and high circuit integration density, where the high spin polarization is pursued. The bipolar magnetic semiconductor (BMS) is proposed to easily achieve the reverse spin orientation. Surface chemical modification is a valid method to manipulate the electronic structure of two-dimensional materials. Here, the CrC2 monolayer with single-side and both-side functionalization is investigated by first-principles calculations. The monolayer CrC2 functionalized with O atoms (named 2OX) at both sides shows the bipolar half-metallic characteristics at high symmetry point X, while it is a BMS by being functionalized with H atoms (named 2HX). Under the tensile uniaxial strains along both a (εa) and b (εb) directions, the 2OX model turns into the p-type half-semiconductor, which shows robust characteristics with 100% spin-up polarization against the varied uniaxial strains. Total magnetic anisotropy energy (MAE) of the 2OX model fluctuates with varied uniaxial strain εa and decreases as tensile uniaxial strain εb decreases. The 100% spin-up polarized carriers and 100% spin-down polarized carriers appear in the 2HX model by 0.1 hole doping formula unit (f.u.) and 0.1 electron doping f.u., respectively. The results show that the functionalized CrC2 monolayer has potential applications in two-dimensional spintronics.