On the selective deposition of tin and tin oxide on various glasses using a high power diode laser

The deposition of SnO₂ using a 120-W high power diode laser (HPDL) on both fused silica and soda-lime-silica glass has been successfully demonstrated. Deposition on both glass substrates was carried out with laser power densities of 650-1600 W cm^-2 and at rates of 420-1550 mm min^-1. The thickness of the deposited layers was typically approximately 250 μm. The maximum theoretical coverage rate that it may be possible to achieve using the HPDL was calculated as being 3.72 m² h^-1. Owing to the wettability characteristics of Sn, it proved impossible to deposit the metal on either glass substrate. Evidence of solidified microstructures was observed, with the microstructures differing considerably across the same deposited track. These differences were attributed to variations in the solidification rate, R, and the thermal gradient, G. Adhesion of the SnO₂ with the soda-lime-silica glass was found to be due to mechanical bonding. The adhesion of the SnO₂ with the fused silica was seen to be the result of a chemical bond arising from an interface region between the SnO₂ and the fused silica glass substrate. This interface region was found to be comprised of mainly Si and rich with Sn₃O₄.