Some properties of amorphous silicon produced by helium ion implantation

The properties of silicon damaged layers obtained by 100 and 50 keV helium ion irradiation at room temperature have been studied. At irradiation doses of 5x1016 cm-2 the yield of scattered ions at the depth of maximum damage distribution in the Rutherford backscattering spectra (RBS) corresponded to the yield for the random spectrum. In as-implanted samples the value of the electron spin resonance (ESR) signal with g=2.0055 characteristic of amorphous silicon did not exceed the background level of the spectrometer. Further isochronal annealing from room temperature to 600deg C revealed that beginning from 180deg C there occurs an ESR signal, the value of which increases up to 300deg C, and decreases to zero at 450deg C. The backscattering spectra in this case exhibit significant changes, suggesting the abnormal character of annealing of the amorphous layer. This paper presents an analysis of the observed variations of the ESR signal and the RBS spectra. (orig.)