First-Principles Calculations of Angular and Strain Dependence on Effective Masses of Two-Dimensional Phosphorene Analogues (Monolayer <i>α</i>-Phase Group-IV Monochalcogenides <i>MX</i>)

• Main Authors: Yuanfeng Xu, Ke Xu, Hao Zhang
• Format: Article
• Language: English
• Published: MDPI AG 2019-02-01
• Series: Molecules
• Subjects: first-principles calculations; phosphorene analogues; effective mass; anisotropic property
• Online Access: https://www.mdpi.com/1420-3049/24/3/639

Group IV monochalcogenides <inline-formula> <math display="inline"> <semantics> <mrow> <mi>M</mi> <mi>X</mi> </mrow> </semantics> </math> </inline-formula> (<i>M</i> = Ge, Sn; <i>X</i> = S, Se)-semiconductor isostructure to black phosphorene-have recently emerged as promising two-dimensional materials for ultrathin-film photovoltaic applications owing to the fascinating electronic and optical properties. Herein, using first-principles calculations, we systematically investigate the orbital contribution electronic properties, angular and strain dependence on the carrier effective masses of monolayer <inline-formula> <math display="inline"> <semantics> <mrow> <mi>M</mi> <mi>X</mi> </mrow> </semantics> </math> </inline-formula>. Based on analysis on the orbital-projected band structure, the VBMs are found to be dominantly contributed from the <inline-formula> <math display="inline"> <semantics> <msub> <mi>p</mi> <mi>z</mi> </msub> </semantics> </math> </inline-formula> orbital of <i>X</i> atom, while the CBM is mainly dominated by <inline-formula> <math display="inline"> <semantics> <msub> <mi>p</mi> <mi>x</mi> </msub> </semantics> </math> </inline-formula> or <inline-formula> <math display="inline"> <semantics> <msub> <mi>p</mi> <mi>y</mi> </msub> </semantics> </math> </inline-formula> orbital of <i>M</i> atom. 2D SnS has the largest anisotropy ratio due to the lacking of <i>s</i> orbital contribution which increases the anisotropy. Moreover, the electron/hole effective masses along the <i>x</i> direction have the steeper tendency of increase under the uniaxial tensile strain compared to those along <i>y</i> direction.