Temperature dependence of radiation induced defect creation in a a-SIo2

The efficiency of oxygen vacancy defect creation in samples of amorphous SiO2 subjected to ultraviolet laser or ionizing particle radiation (energetic H+ ions) has been measured as a function of sample temperature during irradiation. For the case of laser radiation (Ephoton 5 eV) we find that vacancy centers are only created when the irradiation temperature is above 150 K. The efficiency of peroxy radical defect creation observed after post irradiation annealing is consistent with the behaviour of the oxygen vacancy creation efficiency. In samples with energetic protons, the opposite behaviour is observed and one finds that defect creation is enhanced as the implantation temperature is lowered. Possible physical mechanisms controlling the defect creation efficiency as a function of sample temperature and radiation are discussed.