Abstract

Cathodoluminescence (CL) spectroscopy in an SEM has been used to investigate the point defect structure of clear natural α-quartz at 295 K. Cathodoluminescence processes and experimental factors that influence the CL spectra from α-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 centres including: interstitial molecular O at 0.968 eV; a charge-compensated substitutional Fe3+ impurity centre at ∼1.65 eV; a non-bridging oxygen hole centre (NBOHC) at 1.9 eV; an NBOHC with OH- precursor at 1.95 eV; an NBOHC with a non-bridging impurity (e.g. Li+, Na+ or K+) precursor at ∼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 E1′ centre in α-quartz at 2.7 eV; a charge-compensated substitutional Al3+ impurity centre 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 SiO2 are likely at ∼2.7 and 4.3 eV.

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