LOW-TEMPERATURE THERMAL-PROPERTIES AND INTRINSIC DEFECTS IN VITREOUS SILICA

Measurements of the low temperature specific heat Cp (0.04K≦T≦2.4K) and thermal conductivity k (0.5K≦T≦20K) of high purity vitreous silica (Suprasil W) in the as-received and electron-irradiated states are reported. In the temperature range where the localized excitations inherent in glasses dominate Cp (T≲0.5K) no change is observed upon electron irradiation of up to 1019e- (total dose). An anomaly δC around 1.8K is observed in Cp which is reduced by 40% upon irradiation. However, as k is not affected by electron irradiation, localized excitations as origin for δC can be ruled out. The density of paramagnetic centers in the most heavily irradiated sample is 5{dot operator}1017cm-3 as obtained from the ESR signal. It has been suggested that these centers have diamagnetic precursors" in the unirradiated glass. Our measurements indicate that those defects are not associated with the localized excitations. © 1979 Springer-Verlag."