Aj. Nelson et al., PHOTOEMISSION INVESTIGATION OF THE ELECTRONIC-STRUCTURE AT POLYCRYSTALLINE CUINSE2 THIN-FILM INTERFACES, Journal of applied physics, 74(9), 1993, pp. 5757-5760
The surface versus bulk composition and electronic structure of polycr
ystalline CuInSe2 thin-film interfaces were studied by synchrotron rad
iation soft-x-ray photoemission spectroscopy. An n-type In2Se3/CuIn3Se
5 surface layer forms on enhanced-grain polycrystalline thin-film p-ty
pe CuInSe2 during fabrication. Enhanced-grain CuInSe2 films were sputt
er etched (500 V Ar) and analyzed in situ to determine core-level bind
ing energies and Fermi-level positions for the n-type surface and the
p-type CuInSe2 bulk within +/- 0.1 eV. The transition between the n-ty
pe surface and the p-type bulk was experimentally observed by noting t
he change in the position of the valence-band maximum relative to the
Fermi level E(F). From these measurements, the valence-band offset DEL
TAE(v) between the layers was determined to be 0.50 eV. Measurement of
the work functions phi was also completed and reveals phi = 4.75 eV f
or the In2Se3 (CuIn3Se5) surface layer and phi = 4.04 eV for the bulk
CuInSe2. Combining these results allows construction of a surface band
diagram for this device configuration as well as determination of the
relationship between composition, electronic structure, and device pe
rformance.