Growth of Al2O3 films on chemically strengthened glass substrates by different deposition techniques

The exchange of small sodium ions in silicate glass by larger potassium ions from a molten salt bath below Tg produces a compressive stress on the glass surface region, which results in glass strengthening. The effects of thin film nucleation and initial growth on high stress and potassium-rich property of chemically strengthened glass substrates were investigated. Al2O3 thin films were prepared on chemically strengthened glass substrates by electron beam evaporation with ion beam assisted deposition and magnetron sputtering, respectively. The crystalline structure and morphology of Al2O3 thin films were studied by grazing incident X-ray diffraction and field emission scanning electron microscopy. The concentration distributions of potassium, aluminum and oxygen elements near the Al2O3 film/chemically strengthened glass interface were analyzed by electron probe micro-analyser. It is shown that Al2O3 films deposited on chemically strengthened glass substrates by different deposition techniques have an amorphous structure. Potassium ions outward diffusion from the chemically strengthened glass substrates are accompanied by aluminum and oxygen ions inward diffusion from the Al2O3 thin films into glass during deposition. Diffusion rates of potassium, aluminum and oxygen ions are very different using different deposition techniques. Compared with the chemically strengthened glasses, the surface compressive stress and the depth of the compressive layer in the chemically strengthened glasses deposited Al2O3 films decrease variously. The results show that the change of chemical composition throughout glass surface region in the Al2O3 thin films deposition process can cause a change in physico-chemical and mechanical properties of chemically strengthened glasses.