Surface electrical resistivity and wettability study of fused silica

✍ Scribed by Senn, B. C.; Pigram, P. J.; Liesegang, J.

• Book ID: 101223522
• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 87 KB
• Volume: 27
• Category: Article
• ISSN: 0142-2421
• DOI: 10.1002/(sici)1096-9918(199909)27:9<835::aid-sia642>3.0.co;2-t

✦ Synopsis

The effect of heat treatment on the room-temperature surface electrical conductivity of a fused silica plate has been investigated. Water-drop contact-angle measurements were used to assess the area ratio of SiOH (silanol) to Si-O-Si (siloxane) groups generated on the surface. Electrical resistivity values ranging from 10 12 to 10 16 Z.m were also measured as a function of the generated surface hydration. Three conduction regimes were identified corresponding to the following states of a fused silica surface: strongly hydrated, fully hydroxylated and increasingly dehydroxylated. The conductivity behaviour is interpreted consistently with previously proposed charge conduction mechanisms involving combinations of protonic and ionic conduction. A surface region dielectric constant variation of 3.8-3.2 is also determined for 20-250 °C heat treatments. Resistivity measurements for samples treated above 430 °C are interpreted in terms of the presence of Na Y ions and indicate a surface activation energy of ~0.21 eV for labile Na Y ions to be oxidized and surface pinned.