Radiation damage in silicon studied in situ by nanocalorimetry

In situ observations of thermal processes involving nJ energies are impractical, if not impossible, with conventional differential scanning calorimetry (DSC), but the nanometric scale of recently developed nanocalorimetry systems should make such observations possible. Nanocalorimetry is based on membrane calorimeters made using nanofabrication technologies. Here we present initial results of an in situ investigation of damage dynamics in amorphous silicon (a-Si). A thin film of a-Si was deposited on the calorimeter membrane and implanted with low-energy Si ions. One-time heat releases were measured for doses ranging from 10¹² to 10¹⁴ion cm ^-2. Subsequent calorimetry scans showed no difference with the baselines, indicating that the damage remaining is stable over the temperature of operation. The measurements were taken immediately after ion implantation in the same environment and were repeated. For doses of 10¹²ion cm ^-2 and less, the signal intensity was below the sensitivity limit. A saturation of the total heat released was observed. This saturation was correlated with previous DSC measurements and attributed to the relaxation of ion beam implanted a-Si.