Single step deposition method for nearly stoichiometric CuInSe2 thin films
Abstract This paper reports the production of high quality copper indium diselenide thin films using pulsed DC magnetron sputtering from a powder target. As-grown thin films consisted of pin-hole free, densely packed grains. X-ray diffraction showed that films were highly orientated in the (112) and/or (204)/(220) direction with no secondary phases present. The most surprising and exciting outcome of this study was that the as-grown films were of near stoichiometric composition, almost independent of the composition of the starting material. No additional steps or substrate heating were necessary to incorporate selenium and create single phase CuInSe2. Electrical properties obtained by hot point probe and four point probe gave values of low resistivity and showed that the films were all p-type. The physical and structural properties of these films were analyzed using X-ray diffraction, scanning electron microscopy and atomic force microscopy. Resistivity measurements were carried out using the four point probe and hot probe methods. The single step deposition process can cut down the cost of the complex multi step processes involved in the traditional vacuum based deposition techniques.
Se-loss-induced CIS Thin Films in RTA Process after Co-sputtering Using CuSe2 and InSe2 Targets
Chalcopyrite CuInSe2 (CIS) thin films were prepared without Se- / S-containing gas by co-sputtering using CuSe2 and InSe2 selenide-targets and rapid thermal annealing. The grain size increased to a maximum of 54.68 nm with a predominant (112) plane. The tetragonal distortion parameter η decreased and the inter-planar spacing d(112) increased in the RTA-treated CIS thin films annealed at a 400°C, which indicates better crystal quality. The increased carrier concentration of RTA-treated p-type CIS thin films led to a decrease in resistivity due to an increase in Cu composition at annealing temperatures ≥ 350°C. The optical band gap energy (Eg) of CIS thin films decreased to 1.127 eV in RTA-treated CIS thin films annealed at 400°C due to the improved crystallinity, elevated carrier concentration and decreased In composition.
Intrinsic defect states in CuInSe2 single crystals
Abstract High-resolution photoluminescence measurements at 10 K were performed on samples cut from n- and p-type single crystals of (CuInSe2), before and after annealing in air (at 220 and 400 °C, respectively), and in excess of selenium vapor (at 450 and 650 °C). These data provided the basis of the presented energy band diagram which correlates the intrinsic defect levels, their origins and relative concentration with the material electrical behavior and composition. A summary of the variation in the type and relative concentration of the dominant defect states and their electrical role induced by various heat treatments is also given.