Pulsed laser deposition of single phase n- and p-type Cu2O thin films with low resistivity

Low resistivity (p similar to 3-24 m Omega.cm) with tunable nand p-type single phase Cu2O thin films have been grown by pulsed laser deposition at 25-200 degrees C by varying the background oxygen partial pressure (O-2pp). Capacitance data obtained by electrochemical impedance spectroscopy was used to determine the conductivity (nor p-type), carrier density, and flat band potentials for samples grown on indium tin oxide (ITO) at 25 degrees C. The Hall mobility (mu(H)) of the nand p-type Cu2O was estimated to be-0.85 cm(2)/V.s and 4.78 cm(2)/V.s respectively for samples grown on quartz substrate at 25 degrees C. An elevated substrate temperature 200 degrees C with O-2pp = 2-3 mTorr yielded p-type Cu2O films with six orders of magnitude higher resistivities in the range, rho similar to 9-49 k Omega.cm and mobilities in the range, mu(H) similar to 13.5-22.2 cm(2)/V.s. UV-Vis-NIR diffuse reflectance spectroscopy showed optical bandgaps of Cu2O films in the range of 1.76 to 2.15 eV depending on O-2pp. Thin films grown at oxygen rich conditions O-2pp >= 7 mTorr yielded mixed phase copper oxide irrespective of the substrate temperatures and upon air annealing at 550 degrees C for 1 h completely converted to CuO phase with n-type semiconducting properties (rho similar to 12 Omega.cm, pH-1.50 cm(2)/V.s). The as-grown pand n-type Cu2O showed rectification and a photovoltaic response in solid junctions with n-ZnO and p-Si electrodes respectively. Our findings may create new opportunities for devising Cu2O based junctions requiring low process temperatures. (c) 2020 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).