Template electrodeposition of single-phase p- and n-type copper indium diselenide (CuInSe₂) nanowire arrays

CuInSe₂ nanowire arrays were fabricated by electrodeposition from aqueous solutions of copper sulfate, indium sulfate, selenium dioxide, and citric acid, using anodic alumina membranes as templates. X-ray diffraction patterns showed that the wires were single phase (chalcopyrite structure) but polycrystalline, and a band gap of ∼1 eV was obtained from optical measurements. TEM and SEM confirmed that the grain size in nanowires annealed at 400 °C was in the range of 40 nm. The composition of the nanowires was uniform along the length of the wires and could be tuned by varying the electrodeposition potential. Analysis by ICP-MS showed that naowires grown at -700 mV were slightly Cu-rich, whereas those grown at -750 mV were slightly In-rich. Mott-Schottky plots were employed to determine the doping type and flat band potential, verifying that the Cu- and In-rich wires were p- and n-type, respectively. Single-wire electrical transport measurements were also performed and showed that both types of wires had resistivities in the range 10 ^-1-10^-3 ω·cm, consistent with carrier concentrations in the range 10¹⁸-10²⁰ cm^-3.