Strain tunability of the properties of Fe- doped lithium niobate for optoelectronic applications: Theoretical insights

This work elucidates the impact of strain on the optical and electronic properties of Fe-doped lithium niobate using density functional theory. The Fe-doped lithium niobate is applied with the tensile and compressive strain (10% and 20%) and optical properties are analyzed. Lithium niobate, a large bandgap material (bandgap 3.56 eV), has absorption limited to the UV region of the optical spectrum only. For the Fe-doped lithium niobate, the bandgap is 1.38 eV, with low absorption in the visible region. The computed results show that the tensile and compressive strains have significantly narrowed down the bandgap of Fe-doped lithium niobate in compression to the unstrained structures. The decrease in the bandgap is largest for the tensile strain of 20% among all the applied strains. Further, visible light absorption is also improved due to the application of strain. The improvement in visible light absorption is highest for the tensile strain of 20% with absorption completely shifted in the desired visible region. The improved visible absorption due to the applied strain makes Fe-doped lithium niobate a potential candidate for optoelectronics and solar applications.