The optical constants of vacuum deposited SbxSe1-x amorphous thin film
s (x = 0.075, 0.15 and 0.20 at%) of different thicknesses (90-150nm) w
ere studied in the wavelength range 550-800 nm. It was found that both
the refractive index n and the absorption index k are independent of
the film thickness, whilst there is a distinct dependence of n and k o
n the Sb content. The allowed optical transition was found to be non-d
irect, the corresponding optical gaps E(g)(opt) are determined. The wi
dth of the band tail E(e) is also determined. As a result, E(g)(opt) d
ecreases while E(e) increases with increasing Sb contents. The variati
on of E(g)(opt) with x for SbxSe1-x agrees with the optical gap E(0) p
redicted theoretically in terms of random bond network proposed by Shi
makawa. The relationship between the optical gap and chemical composit
ion in SbxSe1-x amorphous system is discussed in terms of the average
heat of atomization H-s and the average coordination number m. The res
ults of these calculations can be used to rationalize the observed opt
ical properties of these materials. (C) 1997 Elsevier Science Ltd.