Density measurement of thin glass layers for gas barrier films

In the food packaging industry, transparent gas barrier films consisting of a 10-100 nm thick glass layer deposited on a polymer substrate are being d eveloped. The accurate densitymeasurement. of the thin glass layers with th ickness ranging from 10 to 100 nm was important to characterize nanostructu res, hence the gas permeation property of the films. First, densities of Si Ox layers which were deposited by vacuum evaporation on silicon wafer surfa ces(100) were measured with a weight-volumetric method. The densities were 2.15+/-0.01 andi 2.16+/-0.03 g/cm(3) for layers with slightly different dep osition conditions. Next, a novel method was invented for the density measu rement of thin SiOx layers deposited by vacuum evaporation on polymer subst rates. The method made use of the fact that parallel multiple cracks were i nduced in the SiOx layer when the film was' stretched. The thickness of the SiOx layer was estimated by measuring the depths of crack openings. The de nsity was found to be larger: 2.32+/-0.09 g/cm(3). (C) 1999 American Vacuum Society.