For the measurement of optical constants, the electrodeposited films o
f CdTe were lifted off their opaque substrates and transferred onto gl
ass slides using a transparent liquid adhesive. This technique proved
to give results more reliable than those obtained on samples in which
CdTe is deposited on CdS-coated conducting glass. The measured optical
dispersion in the photon energy range of E<1.5 eV is in excellent agr
eement with that for the single crystal. The optical absorption coeffi
cient was determined in the E<3.5 eV range and was compared with that
for the single crystal. The results revealed two direct allowed transi
tions at 1.50 eV [Gamma(8) valence band(VB)-->Gamma(6) conduction band
(CB)] and 2.43 eV [Gamma(7)(VB)-->Gamma(6)(CB)] and three indirect all
owed transitions at 1.27 eV [L-4,L-5(VB)-->Gamma(d)], 1.83 eV [L-6(VB)
-->Gamma(d)], and 2.84 eV [Gamma(8)(VB)-->L-6(CB)]. The 1.27 and the 1
.83 eV transitions, which have not been reported previously and were n
ot detected in single-crystal data, are attributed to the transitions
to grain-boundary-related defect energy band Gamma(d), 0.65 eV above G
amma(8) (VB). The indirect transitions at 1.83 and 2.84 eV are assiste
d by phonons having energies of 80 and 84 meV, respectively. (C) 1997
American Institute of Physics.