IDENTIFICATION AND CHARACTERIZATION OF SILICON IN FUSED QUARTZ TUBING

摘要

Type 1 fused quartz tubing melted under a hydrogen/helium atmosphere is known to contain trace concentrations of reduced silica, namely oxygen deficient SiO_(2-x). The ultraviolet absorption band, centered at 242 nm, is characteristic of fused quartz melted under the reducing conditions of a hydrogen melting atmosphere. TEM and electron diffraction measurements show that silicon can also form during the quartz melting process, and crystallize on cooling. These silicon particles were observed during quartz flameworking as "glow bands". The higher emissivity of silicon results in greater incandescence compared with the fused quartz matrix. Silicon was found to increase UV absorption within the range 170 nm - 230 nm, with peaks at about 176 nm and 204 nm The strong oxygen-deficient silica band at 242 nm was unaffected by the fully reduced silicon crystallites. Absorption is due to the generation of additional E' defect centers [6.1 eV], and probably to the formation of silicon clusters [7.1 eV].