Effect of fast-neutron irradiation on tetrahedrally bonded amorphous thin films

Thin films of RF sputtered amorphous germanium, silicon and silicon carbide have been irradiated in a reactor with fast-neutron fluence of up to 3.6 x 1013 n/cm2 at a temperature not exceeding 50 deg C. The irradiation induced changes in electrical and structural properties have been studied. The effect of irradiation on dark conductivity is appreciable though the activation energy gap and phonon spectra do not seem to undergo much change. The results could be explained as a combined effect of two processes (i) the rearrangement of the atoms of the amorphous medium in the presence of neutron fluence to produce a more complete amorphous network, and (ii) the production of defect clusters in certain regions of the amorphous medium, giving rise to isolated zones with high concentration of dangling bonds. Our results, however, indicate that in the amorphous thin films studied, the first process is predominant throughout the volume. (author)