Cathodoluminescence microcharacterization of point defects in alpha -quartz

Cathodoluminescence (CL) spectroscopy in an SEM has been used to investigate the point defect structure of clear natural alpha -quartz at 295 K. Cathodoluminescence processes and experimental factors that influence the CL spectra from alpha -quartz are investigated. Electron irradiation may induce changes in the average local crystal microstructure of quartz, locally transforming it to a less dense, amorphized state. The observed CL emissions are identified with a range of native and impurity defect centers including: interstitial molecular O at 0.968 eV; a charge-compensated substitutional Fe (super 3+) impurity center at approximately 1.65 eV; a non-bridging oxygen hole center (NBOHC) at 1.9 eV; an NBOHC with OH (super -) precursor at 1.95 eV; an NBOHC with a non-bridging impurity (e.g. Li (super +) , Na (super +) or K (super +) ) precursor at approximately 1.9 eV; a radiative recombination of the self-trapped exciton (STE) associated with an E' centre in electron-irradiation-amorphized quartz at 2.3 eV; a radiative recombination of the STE associated with the E (sub 1) ' center in alpha -quartz at 2.7 eV; a charge-compensated substitutional Al3+ impurity center at 3.3 eV; and a neutral relaxed O vacancy at 4.3 eV. In addition, unresolved contributions from O-deficient defects in electron-irradiation-amorphized SiO (sub 2) are likely at approximately 2.7 and 4.3 eV.