Preparation, characterization and photoelectronic properties of germanium-substituted Fe2O3 single crystals

Abstract

Single crystals of germanium-substituted Fe₂O₃ have been grown using chemical vapour transport with tellurium tetrachloride and their crystallographic, electrical, magnetic and photoelectronic properties have been studied. Germanium-substituted Fe₂O₃ crystallized with the corundum structure and is an extrinsic n-type semiconductor with a room-temperature resistivity of ca. 5 Ω cm and an impurity ionization energy of 0.12 eV. Low-temperature susceptibility measurements suggest that insertion of Ge^IV leads to reduction of Fe^III to Fe^II without spinel-phase inclusion. Photoelectrochemical measurements and determinations of the flatband potential by different techniques suggest that the behaviour of Fe₂O₃ photoanodes may be influenced by energy levels in the bandgap near the conduction band.