6533b851fe1ef96bd12a99be
RESEARCH PRODUCT
Frenkel defect process in amorphous silica
Koichi KajiharaMasahiro HiranoLinards SkujaLinards SkujaHideo Hosonosubject
Materials scienceSiliconbusiness.industryDopingDangling bondchemistry.chemical_elementCrystallographic defectAmorphous solidMolecular geometrychemistryChemical physicsKröger–Vink notationFrenkel defectOptoelectronicsbusinessdescription
Point defects strongly influence optical properties of synthetic amorphous silica (synthetic a-SiO2) used in excimer laser photolithography and their properties are intensively studied. Decomposition of an Si-O-Si bond into a pair of oxygen vacancy and interstitial oxygen species is an intrinsic defect process in a-SiO2. It is similar to the creation of vacancy-interstitial pairs in crystalline materials and is regarded as "Frenkel defect process" in an amorphous material. Oxygens are also known to be emitted from a-SiO2 surfaces under irradiation with vacuumultraviolet (VUV) light or electron beam. However, the anion part of the Frenkel pair in a-SiO2, interstitial oxygen atom, lacks reliable spectroscopic signatures. Therefore, Frenkel process has been studied much less than another intrinsic defect process in a-SiO2, a simple cleavage of an Si-O bond, yielding a pair of silicon and oxygen dangling bonds. Interstitial oxygen molecule (O2), a common form of the interstitial oxygen species in a-SiO2, exhibits characteristic infrared photoluminescence (PL) at 1272 nm. This PL band allows interstitial O2 to be detected selectively with a high sensitivity, and is useful in studying Frenkel defect processes in both a-SiO2 and crystalline SiO2. The Frenkel process is dominant over the formation of the dangling bond pairs in highpurity synthetic a-SiO2. Both these processes are influenced by the degree of the structural disorder of a-SiO2characterized by distribution of Si-O-Si angles. Fluorine doping promotes the structural relaxation and is useful in decreasing the concentration of "strained" Si-O-Si bonds, which have Si-O-Si bond angles widely different from the relaxed angle and are vulnerable to radiation. Moderate fluorine doping is effective in improving both UV-VUV transparency and radiation hardness, whereas heavy fluorine doping tends to enhance defect processes involving the Frenkel mechanism and to degrade the radiation hardness.
| year | journal | country | edition | language |
|---|---|---|---|---|
| 2011-05-05 | Proc. of SPIE |