Influence of Ultra-Violet Radiations on the Etching of Quartz

Abstract

EXPERIMENTS have been carried out to investigate the influence of ultra-violet radiations on the etching of quartz by hydrofluoric acid. The quartz plate under investigation is subjected simultaneously to the actions of the corrosive acid and the ultra-violet radiations. The etching cell used consists of a short pitch-coated glass tube of which the quartz plate under study forms the bottom. The inner surface of the plate is in contact with the acid while the rim of its polished outer surface is covered by a paper ring. In this way, the ultra-violet radiations which penetrate the plate from underneath will irradiate only the central portion of its inner surface. With such a device, the two parts of an etched surface, one subjected to, and the other protected from, the action of ultra-violet radiations, can be conveniently compared. The strong ultra-violet radiations used come from a 'condensed' discharge between two iron electrodes. They are focused on the base of the etching cell by means of a quartz lens. Plates cut in different orientations and plates of amorphous fused silica have been investigated. With a moderately strong acid, the duration of each experiment lasts generally about eight hours.