Dependence of the structural relaxation of amorphous silicon on implantation temperature

The structural relaxation of amorphous silicon, created by ion implantation, was investigated by in situ differential scanning nanocalorimetry. Nanocalorimetry provided the possibility to measure the heat released by relaxation during annealing, for a wide range of implantation fluences and beginning at cryogenic temperatures. Ion implantation was first carried out for fluences between 10(-5) and 0.8 displacements per atom (DPA) at 133 K and 297 K, and then for temperatures ranging from 118 K to 463 K for fluences of 0.0185 and 0.37 DPA. A heat release saturation occurred above 0.1 DPA, and was found to depend on implantation temperature. The saturation level was extrapolated to 0 K, leading to an estimate of 28 +/- 3 kJ/mol for the maximum enthalpy that can be stored in a-Si, relative to crystalline Si.