Preparation and characterization of lithium doped indium sesqui-oxide

Abstract

Doping of lithium into indium sesqui-oxide (In 2O 3) brought about an increase in the lattice constant of cubic cell from 10.116 to 10.163 Å and a decrease in the optical absorption energy from 2.72 to 2.68 eV with increasing the nominal molar ratio x (=[Li]/[In 2O 3])<0.5. Enlargement of the lattice constant obeying the Vegard’s law suggests that the doped Li atoms occupied interstitial sites of In 2O 3 crystal. Tight-binding (TB) band-structure calculations with two Li atoms at 8 a sites and those at 16 c sites of the crystal showed decrements in energy splitting between the valence and conduction bands by 0.2 and 0.1 eV, respectively, and supported the observed decrements of the optical absorption energy in In 2O 3:Li x . First-principles molecular-orbital (MO) calculations with clusters for Li atoms at 8 a sites showed similar result to the TB calculation. Changes in the X-ray photoelectron valence band spectra of the In 2O 3:Li x ( x=0, 0.2, and 0.5) agreed with those in the density of states expected from the TB and MO calculations. Non-linear current–voltage characteristics were due to the surface states and surface band bending observed in the valence band spectra.