Layer-number and strain effects on the structural and electronic properties of PtSe₂ material

Bandgap engineering of low-dimensional materials forms a robust basis for advancements in optoelectronic technologies. Platinum diselenide (PtSe₂) material exhibits a transition from semi-metal to semiconductor (SM-SC) when going from bulk to monolayer. In this work, density functional theory (DFT) with various van der Waals (vdW) corrections has been tested to study the effect of the layer-number on the structural and electronic properties of the PtSe₂material. The considered vdW corrections gave different results regarding the number of layers at which the SM-SC transition occurs. This variation is due to the different interlayer distances found for each correction, revealing the sensitivity of the bandgap to this distance in addition to the layer number. In fact, the bandgap increases with the increasing of the interlayer distance, due to the energy shift of conduction and valence bands dominated by Se-<i>p_z</i>orbitals. According to the comparison with the available experimental data, the vdW corrections vdW-DF and rVV10 gave the most accurate results. Moreover, the control of the interlayer distance via vertical compressive strain led to the bandgap tuning of semiconductor PtSe₂BL. Indeed, a semi-metal character of PtSe₂BL can be obtained under 17% vertical strain. Our work shows a deep understanding of the correlation between the structural and electronic properties, and thus a possibility to tune the bandgap by strain means.