Computational study of the effects of silicon doping on structural, electronic and the born effective charge properties of monoclinic HfO2 ferroelectric material

Abstract

In this study, the structural, electronic, and born-effective charge properties of silicon (Si) doped were investigated with respect to density functional theory by using the Quantum Espresso Package. The local density approximation (LDA) and the generalized gradient approximation (GGA) were used to compute the exchange correlation energy. The total minimum energy of hafnium oxide is determined as a function of cutoff energy and Monk Horst-Pack grid size. The results show that the total minimum energy per atom is monotonically decreasing with increasing cutoff energy due to the variational principle. The total minimum energy is converged at the 5 X 5 X 5 k-point cutoff 35 Rydberg and Monk horst-pack mesh. Furthermore, the lattice parameter is taken from the literature. Our materials' lattice parameters are a = 5.14Å, b = 5.19Å, and c = 5.32Å. This result is in good agreement with the experimental value. Finally, structural, electronic, and born-effective charge properties are calculated for pure and silicon-doped hafnium oxide. The results show that after silicon dope, the band is changed from indirect band gap to direct band gap, and the value of the band gap is decreased because of lattice distortion after silicon dope. One hafnium atom is substituted by a silicon atom because hafnium is more stable than oxygen. The doped-born effective charge shows a large value when we compare with pure hafnium oxide, and it makes a great contribution to the dielectric response