Formation and characterization of p-type semiconductor CuCrO2 thin films prepared by a sol–gel method

Abstract

This study adopted the sol–gel method to synthesize p-type semiconductor CuCrO2 films and analyzed the effects of an annealing treatment, under a controlled argon atmosphere by changing the temperature and time, on the phase transformation, micro- and nano-structure, composition, and semiconductor properties of thin films. In the Cu–Cr–O phase transformation system, CuO, Cr2O3, and CuCr2O4 were the intermediate phases of the reaction for forming CuCrO2: in the metastable state reaction process, the composite phases changed into a single phase, CuCrO2; in the stable-state reaction process of CuCrO2, carbon elements of precursors were released and eliminated; and finally the optoelectronic properties of the CuCrO2 thin film were adjusted and changed. The CuCrO2 thin film possessed cell- and polygon-like shaped microstructures. The carbon content in the CuCrO2 film decreased, so the copper, chromium, and oxygen contents increased accordingly. The optical band gap of CuCrO2 thin film increased from 2.81eV to 3.05eV, while the resistivity decreased. The nanoscale crystal was identified which also of the delafossite CuCrO2 structure. Using the sol–gel method to prepare the CuCrO2 thin films, an appropriate annealing temperature and time were helpful in forming the single-phase CuCrO2; the decrease of precursor elements in the thin film could enhance the band gap and the conductivity of the material.