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Spin orbit and tetragonal crystalline field interaction in the valence band of CuInSe 2 ‐related ordered vacancy compound CuIn 7 Se 12
Author(s) -
Philip Rachel Reena,
Pradeep B.,
Shripathi T.
Publication year - 2005
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.200402135
Subject(s) - tetragonal crystal system , band gap , x ray photoelectron spectroscopy , vacancy defect , valence (chemistry) , absorption spectroscopy , analytical chemistry (journal) , crystallography , lattice constant , chemistry , spectral line , materials science , diffraction , crystal structure , nuclear magnetic resonance , optics , physics , optoelectronics , organic chemistry , chromatography , astronomy
Thin films of the off‐tie‐line ordered vacancy compound CuIn 7 Se 12 were deposited on optically flat glass substrates by multi‐source co‐evaporation method. The preliminary structural, compositional and morphological characterizations were done using X‐ray diffraction, energy dispersive X‐ray analysis and atomic force microscopy. The X‐ray diffraction data were further analysed applying the Nelson–Riley method and CTB plus η = η experiment rule, respectively, for lattice constants ( a = 5.746 Å and c = 11.78 Å) and bond length estimations ( R Cu–Se = 2.465 Å and R In–Se = 2.554 Å). A detailed analysis of the optical absorption spectra of the compound, which exhibited a three‐fold optical absorption structure in the fundamental gap region, yielded three characteristic direct energy gaps at 1.37, 1.48(7) and 1.72(8) eV indicative of valence band splitting, which were evaluated using Hopfield's quasi‐cubic model. The 0.04 eV increase in spin–orbit splitting parameter of the compound (0.27 eV) compared to that of CuInSe 2 (0.23 eV) is found to be suggestive of the smaller contribution of Cu d orbitals to hybridization (determined by the linear hybridization model) in this Cu‐deficient compound. Spectral response spectra exhibit, in addition to a maximum around 1.34 ± 0.03 eV, two other defect transition peaks near 1.07 and 0.85 eV. The binding energies of Cu, In and Se in the compound were determined using X‐ray photoelectron spectroscopy. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)