Optical Properties of CuInSe2 Thin Films Prepared by R.F. Sputtering

The optical absorption of r.f. sputtered CuInSe₂ thin films was studied in the photon energy range from 1 to 3 eV. The gap energy and the spin-orbit splitting are found to be (1.01 ± 0.01) eV and (0.24 ± 0.02) eV, respectively. From the photon energy dependence of the absorption coefficient it is concluded that the heavy and light hole bands are parabolic whilst the split-off band contains terms linear in the wavevector. The optical transition probability for valence band- to- conduction band transitions is estimated to be (10.8 ± 1.0) eV which yields an admixture of copper d states to the valence band of (30 ± 8) %.     

ONE-WAY MULTIVARIATE REPEATED MEASUREMENTS ANALYSIS OF VARIANCE MODEL

The one-way multivariate repeated measurements analysis of variance (1-way MRM ANOVA) model for complete data and the sphericity test are studied.     

Electrical properties of r.f. sputtered thin films of CuInSe2(I)

Thin films of CuInSe₂ are deposited by r.f. sputtering onto glass substrates at different r.f. voltages and substrate temperatures using pressed and powder targets. The films are polycrystalline and p-type conducting. The temperature dependence of the conductivity and the chemical composition of the films are measured as a function of the deposition conditions.     

Electrical properties of r. f. sputtered thin films of CuInSe2(II). Conduction mechanism and intrinsic doping effects

An analysis of the conduction mechanism in p-type polycrystalline films of CuInSe₂ is given. It is shown that in the r.f. sputtered films the hole mobility is limited by tunneling through the grain boundary potential barrier. It is suggested that the charge carrier transport is governed by conduction through valence band states at high temperatures and by impurity band conduction at low temperatures. On the basis of the chemical composition data for the r.f. sputtered films no conclusions can be made regarding the type of the acceptor-like intrinsic defect responsible for the p-type conductivity of the films.     

Optical properties of amorphous CuInSe2

Optical absorption spectra of polycrystalline and amorphous CuInSe₂ thin films were measured at room temperature in the photon energy range from 0.8 to 2.1 eV. In amorphous CuInSe₂ the absorption coefficient follows the relation α(hv) = A(hv?E₀)/hv characteristic of optical transitions between extended states in both the valence and conduction band. The optical gap of E₀ = 1.38 ± 0.01 eV is larger than the fundamental gap energy of E_g = 1.01 ± 0.01 eV in crystalline CuInSe₂. A comparison of the results for CuInSe₂ with those for ZnSe is given.