Formation and annihilation of intrinsic defects induced by electronic excitation in high-purity crystalline SiO2

Abstract

Formation and thermal annihilation of intrinsic defects in α-quartz were examined using high-purity samples, while minimizing the contributions of reactions involving metallic impurities. Electronic excitation with 60Co γ-rays was employed to avoid radiation-induced amorphization. The results clearly show that formation of oxygen vacancies (SiSi bonds) as a result of decomposition of regular SiOSi bonds (Frenkel process) is the dominant intrinsic defect process. Compared with amorphous SiO2, in α-quartz, the formation yield of SiSi bonds is an order of magnitude smaller, the 7.6 eV optical absorption band is less broadened, and their thermal annihilation is complete at a lower temperature, around the α–β quartz transition. In contrast, radiation-induced interstitial oxygen atoms practically do not form interstitial oxygen molecules.

Creation of glass-characteristic point defects in crystalline SiO2 by 2.5 MeV electrons and by fast neutrons

“…However, the presence of interstitial O2 in undamaged α-quartz has never been experimentally demonstrated, while there is ample Raman [19][20][21]23], PL [17,18,22,24], EPR [9] or diffusion-based evidence for O2 in silica and silica-based glasses. The present data further confirm the results of the previous study [3], performed at ≈140× lower dose (0.051 GGy γ-rays), that the POL configuration rather than interstitial O2 may be the preferable way of incorporation of excess oxygen in undamaged α-quartz lattice, and that creation of larger voids than available in an intact α-quartz structure is required for interstitial O2 configuration to exist.…”

“…An exception from this rule is the simplest Frenkel defect, the oxygen vacancy, which is observed both in crystalline and glassy SiO2 with nearly similar optical absorption (OA) bands at 7.6 eV [3]. In contrast, the dangling bond type defects, characteristic to glassy SiO2, are completely absent in γirradiated non-amorphized α-quartz [3][4][5][6] and thus cannot be studied in a strictly crystalline environment. This is unfortunate, since these defects are the most important ones in optical applications of glassy SiO2.…”

“…The third intrinsic defect, inherent exclusively to the glassy form of SiO2, is interstitial O2 molecule, formed by dimerization of radiation-displaced oxygen atoms. It is created by irradiation both in silica [3,4,9,17,18] and in many multicomponent oxide glasses [19,20]. Apart from nuclear particle [18,21] or ionizing [17,18,22] radiation, interstitial O2 is efficiently created in glassy SiO2 as well by fs laser irradiation [23].…”

“…Apart from nuclear particle [18,21] or ionizing [17,18,22] radiation, interstitial O2 is efficiently created in glassy SiO2 as well by fs laser irradiation [23]. In contrast to silica, the interstitial O2 in α-quartz is undetectable after γ-irradiation [3]. However it is found in quartz after particle irradiation [18], or after focused e − irradiation in electron microscope beyond the amorphization fluence [22].…”

Structural and Optical Properties of α-Quartz Cluster with Oxygen-Deficiency Centers

“…This mechanism has been verified in amorphous SiO 2 [23][24][25][26][27][28], where its disordered structure influences both the defect creation and migration. Furthermore, clear experimental evidence for (1) in the ordered lattice of crystalline SiO 2 has been given [29]. However, the remaining main unsolved question about ODC(II) is to explain the observed close relationships between ODC(II) and ODC(I).…”