Water Adsorption in Chemically Vapor‐Deposited Borosilicate Glass Films

Abstract

Infrared absorption measurements have been made of physically adsorbed water and silanol in borosilicate glass films which were chemically vapor‐deposited at 400δC and then exposed at room temperature to moist air of relative humidity . Both the physically adsorbed water and silanol were found to increase with time up to about 105 min and then to decrease. The process of water adsorption was limited by the diffusion of water in CVD glass. The adsorption sites of CVD glass were suggested to decrease with the increase of time. The diffusion coefficient of water in the as‐deposited glass films at room temperature was estimated to be on the order of 10−15–10−14 cm2/sec and was found to decrease with the increase of content of the glass and annealing temperature prior to exposure to moist air. Heats of physical adsorption of water were 1.2 kcal/mol below 120δC and 3.3 kcal/mol above 120δC for as‐deposited borosilicate glass containing 8.7 molar per cent .