Abstract
Inspired by recent studies on MoS2 and MoSi2N4, we propose and investigate Janus MoBXY2 (X = N, P; Y = S, Se, Te) monolayers, which exhibit robust dynamic and thermal stabilities. Our findings reveal that all these monolayers are semiconductors, with MoBNS2 and MoBPTe2 exhibiting direct band gaps at the K/K' points, resulting in degenerate valleys and significant valley spin splitting (VSS) in the valence band. Notably, Berry curvatures at K and K' points, with opposite signs, suggest potential for inducing the valley Hall effect (VHE). Furthermore, MoBNS2 and MoBPTe2 demonstrate pronounced optical absorption in the visible light region and high carrier mobility, especially MoBNS2 with a hole mobility reaching up to 2.0 × 103 cm2 V-1 s-1 along the zig-zag direction. Attributed to their Janus structure, these monolayers exhibit strong in-plane and out-of-plane piezoelectric responses, with d11 values ranging from 1.268 to 4.754 pm V-1 and d31 values ranging from 0.053 to 0.137 pm V-1. Investigation of strain effects highlights possibilities for indirect-to-direct band gap transitions and manipulation of band gaps and VSS. This study not only enriches the understanding of MoBXY2 monolayer properties but also suggests their promising applications in valleytronics, photovoltaics, and piezoelectric devices.
Published Version
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