The effect of Sc doping on the electrocatalytic and optoelectronic properties of 2D SiAs single crystals

Abstract

SiAs with excellent properties has been widely reported in recent years. However, the stubborn p-type conductivity of SiAs itself poses a significant challenge in achieving n-type conductivity. Furthermore, for the two-dimensional (2D) SiAs photodetector, it is also essential to improve its photoelectric performance. SiAs, as one of the representative layered semiconductors of the IV–V group, is considered to be an exemplary alternative catalyst for the HER. Substitution doping has been proven effective in adjusting its intrinsic properties and improving the device performance. Here, replacing doping is considered an effective method to adjust its intrinsic properties, improve the optoelectronic performance of devices, and enhance the HER performance of catalysts. This article demonstrates the preparation of SiAs and SiAs single crystals with different Sc doping concentrations using the chemical vapor transport (CVT) method. A series of optical characterization techniques are applied to prove that Sc is successfully doped into the SiAs lattice by replacing Si. The effect of Sc doping on the electrocatalytic properties of SiAs in the HER is systematically studied through experimental studies and density functional theory (DFT) calculations. We find that doping the rare earth element Sc into SiAs can adjust its electronic structure and reduce its adsorption-free energy for hydrogen. Compared with undoped SiAs, Sc-doped SiAs has a lower overpotential, Tafel slope, and charge transfer resistance and a larger electrochemically active surface area and turnover frequency, thus exhibiting superior catalytic activity and stability. In particular, when the Sc doping concentration reaches 0.97 at%, SiAs exhibits a low overpotential of 66 mV, a Tafel slope of 99.4 mV, and good durability at a current density of 10 mA cm⁻². In addition, field-effect transistors (FETs) and photodetectors based on 2D SiAs and Sc-SiAs were prepared, and their electrical and optoelectronic properties were investigated. Interestingly, as the Sc doping concentration increases, the FET undergoes regular changes from p-type to bipolar and finally to n-type, and its photoresponse characteristics also significantly improve. This work provides valuable guidance for designing doped IV–V group layered semiconductors and provides the HER with a new and effective catalyst to improve catalytic performance.