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.
Thermal diffusion of Cu into IN2Se3 : A better approach to SEL technique in the deposition of CuInSe2 thin films
This paper reports the modifications made in the preparation techniques of getting CuInSe2 thin films starting with chemical bath deposited (CBD) selenium films. In the present study, CBD Se film was converted into CuInSe2 by stacked elemental layer (SEL) technique and also by thermal diffusion of Cu into In2Se3. In both the cases CBD Se films were used to avoid toxic Se vapor and H2Se gas. Improvements were made in these techniques through a detailed study, varying the composition of the films over a wide range by changing the Cu/In ratio. Structural, optical and electrical characterizations were performed. On comparing the material properties of CuInSe2 deposited by these two techniques, it was found that photosensitivity was better for samples prepared by thermal diffusion of Cu into In2Se3. So the technique of thermal diffusion of Cu into In2Se3 was found to be better than SEL technique in the preparation of CuInSe2 using CBD Se. Cu-rich, In-rich and nearly stoichiometric samples could be prepared by thermal diffusion of Cu into In2Se3. These samples were analyzed using energy dispersive spectroscopy, Raman spectroscopy and atomic force microscopy also.
Phase evolution in low‐pressure Se vapor selenization of evaporated Cu/In bilayer precursors
Evolution of elemental binaries and single‐phase copper indium diselenide, CuInSe2 (CIS) during Se vapor selenization of evaporated Cu/In bilayer metal precursors at pressures of 0.3–10 mbar and temperatures in the range of 260–400 °C has been investigated. At low pressures, the relative kinetics of selenization of Cu and In are changed resulting in the formation of single‐phase CIS even at very low temperatures (260 °C). Optical, Auger, and x‐ray photoelectron spectroscopy investigations are employed to characterize the chalcopyrite absorber layer. At higher pressures (≊7–10 mbar), simultaneous formation of the equilibrium binaries, CuSe and In2Se3 at low temperatures leads to the formation of CIS through a diffusion limited reaction of the binaries at higher temperatures. The availability of Se reacting species varies significantly in the pressure regime. At low reactor pressures and Se availability, the reaction CuSe+In(l)+Se→CIS, proceeds to completion even at low temperatures. The detailed study of t...