Studies on structural and optical gap tunability in α-(GaxCr(1-x))2O3 solid solutions

Abstract

We report the structural and optical properties of ternary α-(GaxCr(1-x))2O3 with 0 ≤ x ≤ 0.45 which is synthesized by solid state reaction method. Single phase with space group R-3c is obtained for the gallium composition range of 0 ≤ x ≤ 0.45 and further increase in Ga concentration results in appearance of secondary C2/m phase corresponds to Ga2O3. Variations in the in-plane ’a’ and out of plane ’c’ lattice parameters shows a clear daviation from the Vegard's law with the bowing parameters of −0.0510 Å and 0.0305 Å respectively. Extended X-ray absorption fine structure (EXAFS) spectroscopy shows larger values of Ga-O bond lengths, which elucidate the deviation in lattice parameters from the Vegard's law and immisibility of Ga in Cr2O3 lattice. Diffuse reflectance spectroscopy (DRS) confirms a blue shift of 0.5 eV in the band gap of α-(GaxCr(1-x))2O3. It has also observed that Cr 3d level shifted towards the O 2p level in the valence band which has been reconfirmed by photo electron spectroscopy. The observed shift indicates enhancement of mixing between these levels which can leads to further delocalization of hole states in the valence band responsible for p-type conduction in the α-Cr2O3. These results suggest that ternary α-(GaxCr(1-x))2O3 (0 ≤ x ≤ 0.45) can be useful in the field of UV transperant electronics and photodetectors. © 2018 Elsevier B.V.