Tunable electronic and optical properties of GeC/PtO2 vdW hetero-bilayer using first-principles study

The detailed optical and electronic characteristics of 2D GeC and 2D PtO2 under biaxial strains and electric fields across the plane are studied systematically using the density functional theory (DFT) based first-principles framework. The six different stacking patterns of the stacked van der Waals (vdW) GeC/PtO2 hetero-bilayers were DFT screened, and HBL 4 and HBL 5 are found both dynamically stable and energetically favorable, evident from the non-zero phonon frequency and negative binding energy from phonon dispersion and binding energy calculations, respectively. The bandgap of 2D GeC and 2D PtO2 is found to be ∼2.08 eV (direct) and ∼1.63 eV (indirect), while the bandgaps in vdW HBL 4 (HBL 5) are found to be 0.51 eV (0.49 eV). Biaxial strain lowered the bandgap by ∼11.13 (∼1.81) times at 6% compressive (tensile) biaxial strain in HBL 4 (HBL 5). Semiconductor-to-metal switching is found in both HBLs at ±0.6 V/Å of the cross-plane electric field. All the HBLs show type-II band-alignment, evident from the difference in charge density and projected density of state contour, indicating spatial carrier separation capability. The peak of the optical absorption coefficient is found to be ∼3.1 × 105 cm−1 at 310 nm for both HBL 4 and HBL 5, which is comparable to high-absorbing perovskite material. Moreover, the optical absorption is sensitive to the biaxial strains and electric fields, and increased visible band optical absorption is found for tensile strains in both HBLs. These exceptional findings and engineered bandgap in GeC/PtO2 vdW HBL indicate the promising application of this material in 2D advanced nanoelectronics.