' J. of Col. of Education No. 6/2000 The Effect of Fast Neutron on the Optical Band Gap Of Cobalt Oxide Thin Film N. F. Habubi K. R. Mishjal A. F. Atwan College Of Education I AI- Mustansyriah Untversity 4.-IJJ u!t.;-11 ,_; 4..!4.) J! t,..r.JI.::o..li Abstract Thin films of cobalt oxide have been prepared using spray pyrolysis rechnitlue. The effect of fast neutron on the optical energy gap was smdied. It was found that fast neutron radiation increases the absorbance and optical band gap. Introduction In recent years much attention has been paid for thin films preparation and technology step by step with its wide scientific applications. The increase interest in solar energy applications in the last decades has lead to the development of spectrally selective surface. with the maximum possible absorptance across the solar spectrUm and the minimun possible emittance for the longer wavelengths relevant to thermal radiation. Other essential- properties of a practical solar selective coating are low cost. ease of mass production, stability at operating temperature and good resistance 41