X-ray diffraction and electron diffraction techniques indicate that Cd
-x Zn1-xSe thin films on glass substrates have a polycrystalline natur
e, with sphalerite structure for x less than or equal to 0.5 and wurtz
ite structure for x greater than or equal to 0.6. The crystalline size
in each composition increases with increasing the film thickness. The
room temperature dark resistivity rho varies from one composition to
another showing a transition at x = 0.55 The temperature dependence of
rho of the deposited films revealed two conduction mechanisms, one be
low 352 K due to shallow levels, surface states, and defects introduce
d during the film growth, and over 352 K due to deep-level ionization
following the ordinary semiconducting behaviour. The thermal activatio
n energy of the free charge carriers decreases linearly with increasin
g the molar fraction x of the CdSe content up to x = 0.55, above which
it increases with increasing x. The optical constants of Cd-x Zn1-xSe
thin films of different compositions were determined in the spectral
range 400-2000 nm. The analysis of the absorption coefficient at and n
ear the absorption edge indicates the existence of allowed direct tran
sition energy gaps decreasing with increasing x.