WAVELENGTH RESOLVED THERMALLY STIMULATED LUMINESCENCE OF SIO2-FILMS

A wavelength resolved thermally stimulated luminescence (TSL) study has been carried out for the first time on X-irradiated chemical vapor deposition SiO2 films deposited on a silicon substrate, from room temperature, to 400 degrees C. Upon irradiation, the TSL glow curve features a prominent structure at a maximum temperature, T-max, of approximately 62 degrees C (heating rate = 1 degrees C/s); the analysis of the emission wavelength shows a peak at 457 nm (2.71 eV). The shape of the TSL peak is complex, and cannot be described in the frame of classical first- or second-order kinetics. Moreover, T-max has a strong and monotonic shift to higher temperatures after partial pre-heating treatments while the spectral emission is not modified: a similar phenomenon has already been observed in bulk fused silica of various types, different from crystalline quartz which does not present any shift of T-max as a function of pre-heating. These results suggest that the TSL peak is characterized by a distribution of trap parameters: specifically, a continuous distribution of trap energy or of the frequency factor can be taken into account. Considerations on the characteristics of the trap parameter distribution are made.