Novel valleytronic and piezoelectric properties coexisting in Janus MoAZ₃H (A = Si, or Ge; Z = N, P, or As) monolayers

Abstract

In this paper, for the newly proposed two-dimensional (2D) Janus MoAZ3H (A=Si, Ge; Z=N, P, As) monolayer (ML) materials, we theoretically explore the valleytronic and piezoelectric properties using first-principles calculations....

Large piezoelectric responses and ultra-high carrier mobility in Janus HfGeZ3H (Z = N, P, As) monolayers: a first-principles study

“…Specifically, the values of e 31 are 0.32 × 10 −10 , 0.14 × 10 −10 , and 0.02 × 10 −10 C m −1 for the HfGeN 3 H, HfGeP 3 H, and HfGeAs 3 H monolayers, respectively. These results reflect that the HfGeN 3 H monolayer has the highest e 31 among the studied monolayers, which is comparable to that of similar Janus structures such as MoGeZ 3 H 55 and WSiZ 3 H. 56 In addition, the out-of-plane piezoelectricity d 31 of HfGeZ 3 H monolayers has a value ranging from 0.01 to 0.09 pm V −1 . The obtained values of d 31 are close to that in the Janus WSiZ 3 H monolayer.…”

“…The piezoelectric coefficient e 11 is the largest in the Janus HfGeN 3 H monolayer (2.77 × 10 −10 C m −1 ), while the magnitude of d 11 is the largest in the HfGeAs 3 H monolayer (−1.78 pm V −1 ). These values are smaller than the corresponding piezoelectric coefficients in structurally similar compounds such as MoGeZ 3 H 55 and WSiZ 3 H. 56 More importantly, the out-of-plane piezoelectric coefficients in Janus structures are non-zero, resulting from the breaking of mirror symmetry due to different atoms at the two surfaces of the material. Specifically, the values of e 31 are 0.32 × 10 −10 , 0.14 × 10 −10 , and 0.02 × 10 −10 C m −1 for the HfGeN 3 H, HfGeP 3 H, and HfGeAs 3 H monolayers, respectively.…”

Piezoelectric, Thermoelectric, and Photocatalytic Water Splitting Properties of Janus Arsenic Chalcohalide Monolayers

“…x r y y x (31) where ṙis the velocity of the nuclei. NACs are calculated by electron−phonon coupling elements (⟨ψ x |∇ r H|ψ y ⟩), energy gap (ε y − ε x ), and velocity (r).…”

“…The piezoelectric properties of 2D monolayers are specified by in-plane ( d 11 ) and out-of-plane ( d 31 ) piezoelectric coefficients. Janus TiXY (XY = SCl and SeBr), group IV(A) Janus dichalcogenides, YBrI, MoAZ 3 H (A = Si and Ge: Z = N, P, and As), BiXY (X = S, Se, and Te; Y = F, Cl, Br, and I), PtXO (X = S and Se), MoSSiX 2 (X = N, P, and As), BMX 2 (M = Ga and In; X = S and Se), M 2 AB (M = Si, Ge, and Sn; A/B = N, P, and As), and γ-Ge 2 XX’ (X, X’ = S, Se, and Te) show a very high out-of-plane piezoelectric behavior, which is beneficial for piezoelectric devices. Furthermore, the corrected solar-to-hydrogen conversion efficiencies of Janus monolayer-based photocatalysts such as WSSe, MoSSe, PtSSe, WSeTe, AsTeX (X= Cl and Br), AsXY (X= Se and Te; Y = Br and I), and AlXY (X= S and Se; Y= Cl, Br, and I) exceed the 10% criteria for commercial use of photocatalysts.…”