Two-dimensional Janus α-Au2XY (X, Y = S/Se/Te) semiconductors with favourable band gaps and high carrier mobilities predicted by first-principles investigations.

In this work, two-dimensional Janus α-Au2XY (X, Y = S/Se/Te) monolayers are designed and their structural stabilities and fundamental properties are investigated using first-principle calculations. We find that the three α-Au2SSe, α-Au2STe, and α-Au2SeTe structures have high energetic, thermodynamic and mechanical stabilities, indicating that experimental fabrication is feasible. In addition, the proposed systems have anisotropic Young's modulus and Poisson's ratio values. According to the electronic structure calculations, the α-Au2XY monolayers are indirect semiconductors with appropriate band gaps for sunlight absorption of 1.06 to 1.33 eV at the Perdew-Burke-Ernzerhof level. The calculation results from the Heyd-Scuseria-Ernzerhof method for the α-Au2XY monolayers also show indirect band gap semiconductor behavior. Moreover, we utilize the deformation potential technique to analyze the electron and hole mobilities of the α-Au2XY materials to determine their transport properties. Interestingly, α-Au2SSe shows an impressive hole carrier mobility of 6258.42 cm2 V-1 s-1 along the y-axis. α-Au2STe and α-Au2SeTe also have high electron mobilities (μ e) of 642.21/584.96 cm2 V-1 s-1 and 676.56/760.39 cm2 V-1 s-1 in the x/y directions, respectively. In view of the remarkable electronic and transport properties, the α-Au2XY materials are expected to be promising Janus materials for next-generation optical, electronic, and photovoltaic devices.