Structural evolution of a-Si:H/SiO2 multilayers upon step by step thermal annealing

摘要

a-Si:H/SiO2 multilayers were prepared by alternatively changing plasma enhanced chemical vapour deposition of a-Si:H layers and in situ plasma oxidation process. Subsequently, as-grown samples were annealed at temperatures from 350℃ to 1100℃ in N2 ambient with an increment of 100℃. The evolution of bonding configurations and structures with annealing treatments was systematically investigated by Fourier-transform infrared spectroscopy. The peak position of Si-O stretching vibration of SiO2 layers shift to 1087cm-1 after annealing at 1100℃, which demonstrates that the SiO2 films fabricated by plasma oxidation after high temperature annealing can have similar properties to the thermal grown ones. A Si-O vibration from interfacial SiOx was identified: the value x was found to increase as increasing the annealing temperature, which is ascribed to the cooperation of hydrogen effusion and reordering of the oxygen bond in SiOx networks. The H-related bonds were observed in the form of H-Si-O3 and H-Si-Si3-nOn (n=1-2) configurations,which are supposed to be present in SiO2 and interfacial SiOx layers, respectively. The H atoms bonded in different bonding configurations effuse at different temperatures due to their different desorption energies.