Highly infrared-transparent and p-type conductive CuSc1−xSnxO2 thin films and a p-CuScO2:Sn/n-ZnO heterojunction fabricated by the polymer-assisted deposition method

Abstract

We fabricated a series of infrared (IR)-transparent and conductive Sn-doped CuScO₂ thin films using a polymer-assisted deposition (PAD) method. Highly c-axis oriented films were grown on a-plane sapphire substrates, and the orientation relationship with respect to the substrates was confirmed to be CuScO₂:Sn[3R](0001)//a-Al₂O₃(110). The films exhibited good p-type conductive characteristics, and a high conductivity of 17.86 S cm⁻¹ was achieved for CuSc_0.94Sn_0.06O₂ at room temperature, which is 19 times larger than the un-doped film at room temperature. The prepared films retain a transparency of >70% in the near-IR region and >90% in the mid-IR region, which are the best performing p-type IR transparent conductive thin films grown by chemical solution methods to date. As x changes from 0 to 0.06, the hopping activation energy varies within the range of 129–98 meV. As an application of such films, p-CuScO₂:Sn/n-ZnO heterojunction diodes were fabricated using the PAD technique. The measured ∼2 V threshold voltage of the p-CuSc_0.94Sn_0.06O₂/n-ZnO diode is in reasonable agreement with the bandgap energy of CuSc_0.94Sn_0.06O₂. The resulting films can be used in optoelectronic devices over a wide wavelength range from the visible to IR band, due to their high electrical conductivity and optical transparency.