First-principles study of LiNbxM1-x O3, M= V, W, Ta, Mo for holographic memory applications

TL;DR

This study uses first-principles calculations to evaluate how doping LiNbO3 with various transition metals affects its suitability for holographic memory, focusing on band-gap, absorption, and birefringence properties.

Contribution

It provides a comparative analysis of transition metal doping in LiNbO3 for UV photorefraction, identifying V, W, Ta, and Mo as promising elements based on electronic and optical properties.

Findings

W doping yields the minimum band-gap.

V and W show favorable birefringence properties.

V, W, Ta, Mo have low absorption at 351 nm.

Abstract

For holographic memory applications, the photorefraction of well-known ferroelectric such as lithium niobate doped with different transition metals is very important. First principles study assumes special significance in this context, as to why certain transition metal atoms are better than the other. In this work, Nb atom in LiNbO3 was substituted with transition elements having valency greater than/equal to +5 for UV photorefraction applications, and atomistic first-principles calculations were done using HSE06 functionals. The d-states of the transitional elements were found to decrease the band-gap of the host material having implications for a suitable material design. Minimum band-gap was obtained for W, while Ta showed a maximum value. Absorption coefficients were estimated for each material and based on their low values at 351 nm (i.e. for holographic applications) that is the usual UV photorefraction wavelength, the elements found suitable were V, W, Ta, Mo. Then birefringence properties for these crystals were also studied to predict that V and W were good candidates.