Thermally Stimulated Luminescence (TSL) and Conductivity (TSC) of synthetic crystalline quartz

A comparative and simultaneous study of TSL and TSC above room temperature (20-400 degrees C) has been performed on ''as-grown'' and ''hydrogen-swept'' synthetic quartz crystals. Following X-irradiations, TSL spectra (heating rate = 1 degrees C/s) feature a number of peaks: at 75 degrees C an intense structure is observed (the well-known ''100 degrees C'' peak of quartz); the analysis of this peak obtained by numerical methods has shown that it follows monomolecular kinetics, giving a value of 0.83 eV for the trap depth. Additional peaks are observed at 110 degrees C and 160 degrees C, followed by weaker and less resolved emissions above 200 degrees C. TSC peaks at 80 degrees C, 120 degrees C and 160 degrees C, particularly evident in as-grown samples when measured with the electric field applied along the x-axis, can be associated to the corresponding TSL peaks. However, spectra performed with the electric field applied along the z-axis evidence different features. In as-grown samples a strong and broad peak at approximately 132 degrees C is observed, while hydrogen-swept samples are characterized by two peaks at 180 degrees C and 275 degrees C. Such an anisotropic character, and the fact that no TSL structures are observed in the same temperature range, support the hypothesis of an ionic nature for the latter peaks. TSC ''pre-dose'' measurements of the 75 degrees C peak show that no current enhancement is observed upon irradiation and heating treatment: this result is in accordance with previous radioluminescence and thermally stimulated exoelectron emission experiments and supports the proposed model of the dynamics of this effect.