Defect-induced diverse electronic, magnetic and optical properties in monolayer CaP3

Abstract

Monolayer CaP3 (mCaP3), a semiconductor predicted theoretically with suitable band gap and high electron mobility, shows potential applications in nanoelectronics and optoelectronics. In this work, using first-principles calculations, diverse electronic, magnetic and optical properties of mCaP3 were explored by substituting P atoms by B, C, N, O and F or introducing P and Ca vacancy, respectively. The results show that B and C prefer to substitute P atoms (denoted by P1) bonding with four adjacent P atoms, while N, O and F tend to substitute P (denoted by P2) bonding with two P and two Ca atoms. These two types of systems, expressed by X(P1)-mCaP3 (XB and C) and X(P2)-mCaP3 (XN, O and F), are favorable in energy. The systems of B(P1)-mCaP3, N(P2)-mCaP3 and F(P2)-mCaP3 with four different doping concentrations are found to be spin-non-polarized semiconductors. Notably, in N(P2)-mCaP3 and F(P2)-mCaP3, the band-gap is monotonically tuned by changing doping concentrations. In contrast, in C(P1)-mCaP3 and O(P2)-mCaP3, the spin-polarized semiconducting characters are obtained at the two low doping concentrations, and the transition from semiconducting to metallic states appears at the highest doping concentrations. Besides the tunable band gaps obtained, good optical absorption features in entire visible-light range are kept in all doped systems as the pristine one. In particular, an additional absorption peak in low energy region is induced by Ca vacancy and P substitution by C. These diverse electronic, magnetic and optical properties obtained by selective doping in mCaP3 will expand its potentials in future applications.