Stability, Electronic, Elastic, and Mechanical Properties of Graphene/TiO2 Heterostructure — Theoretical Study Using DFT

Abstract

In this study, we conduct an in-depth exploration of the stability, mechanical, elastic, and electronic properties of a two-dimensional graphene/titanium dioxide (GR/TiO₂) heterostructure using density functional theory calculations. After geometry optimization, we confirm that the individual structures are stable, with respective lattice parameters of a = b = 12.33 Å and vacuum parameter of c = 13.60 Å for graphene, a = b =11.86 AA and c=29.83 Å for TiO₂, and a = b = 12.19 Å and c = 15.83 Å for GR/TiO₂. This stability is further confirmed by formation energy calculations and phonon spectral analyses, which ensure the absence of imaginary modes. It is demonstrated that a strong Ti–O–C type chemical bond is established between the two components, leading to strong electronic coupling and a notable enhancement of optical response in the visible range, thus reinforcing the capabilities of TiO₂ for photovoltaic and photocatalysis applications. Regarding mechanical properties, we determine Young's modulus, shear modulus, and Poisson's ratio based on elastic constants, thus confirming the mechanical stability and strength of the hybrid material under deformation. Band structure analysis reveals that the GR/TiO₂ heterostructures exhibit indirect bandgap semiconductor behavior, with a reduced gap of 0.88 eV. This, in fact, is in a sharp contrast with the intrinsic gap of 2.932 eV for pure TiO₂. The reduction in the energy gap is corroborated by the density of electronic state calculations, which indicate significant hybridization of states at the interfaces, favorable for efficient charge transport. These results highlight the remarkable potential of the GR/TiO₂ system for next-generation electronic, optoelectronic, and photovoltaic devices, particularly in the context of optimal exploitation of the solar spectrum.