OPTICAL REFLECTIVITY STUDIES OF RADIATION-INDUCED TRACE DISORDER IN SILICON

For the first time, the effect of randomly distributed volume defects, induced by fast neutrons, on the reflectivity spectrum of crystalline Si has been studied. Reflectivity (R) measurements were performed at 300 K in the range 3.7-11 eV. The influence of surface preparation on the quality of an R spectrum was checked. Proper surface treatment all owed additional features to be revealed of the reflectivity spectrum. It has been found that neutron irradiation tends to reduce the reflect ivity of Si similarly as ion implantation does. Analysis of the reflec tivity drop (DELTAR), considering the defect structure of neutron-irra diated Si, allowed a correlation between DELTAR and the concentration of the main defect species to be found. Precise measurements of the Si lattice constant have shown no changes of the single-crystal structur e after neutron irradiation. The paper proves a very high sensitivity of optical reflection spectroscopy to the trace perturbation of the si ngle crystalline lattice of silicon.