Paper Title
A DFT-based studies on Electronic and Optical Properties of Tetragonal Hafnium Dioxide (t-HfO2) and the Effect of Silicon (Si) Doping

Abstract
The electronic and optical properties of silicon-doped tetragonal hafnium dioxide (t-HfO2) have been investigated by using the meta-generalized gradient approximation (MGGA-TB09+c) approach within the framework of density functional theory (DFT). Silicon (Si) is identified to promote the t-HfO2 phase most effectively among the investigated dopants. Si doping is an important approach to improve the desired properties of high-k gate dielectric oxides. The unique characteristics of this material are closely associated with the inclusion of dopants within the unit cell. The primary objective of this study is to examine and contrast various systems distinguished by their doping percentages of Si as 0%, 6.25%, 12.50%, and 18.75% respectively. The use of on-site Coulomb interaction is utilized to investigate the Hf 5d, O 2p, and Si 3p orbitals. The ground state properties such as lattice parameters and volume are calculated and compared to the available experimental data and previous theoretical works. A comprehensive theoretical investigation of bandgap, and dielectric properties is done. This analysis not only yielded the experimental bandgap of the material of 5.83 eV but also revealed a notable reduction in the bandgap of the doped structures. Subsequently, the optical properties are computed, revealing a discernible isotropic spectrum phenomenon, which is attributed to the inherent electronic configuration of the dopant. A significant increase in the static dielectric constant is seen for the doped systems, accompanied by a shift in the absorption spectra at a specific wavelength, hence enabling optical absorption within the visible range. The experimental results demonstrated a simultaneous rise in the real component of the refractive index and a significant enhancement in optical conductivity. These findings indicate the promising suitability of the proposed materials for applications in negative capacitance field effect transistors and future-generation memory devices. Keywords - DFT, t-HfO2, Si Doping, Electronic Properties, Optical Properties