A Diamond ATR Study of Thin 225 nm Films on Glass

Coatings on glass are used in a variety of industries, including automotive, packaging, architectural and decorative. These coatings serve to protect from UV damage and from weathering under hot and humid conditions; increase material strength; facilitate cleaning; and save energy. These coatings are generally very thin and can be a challenge to be measured by infrared spectroscopy. This application note demonstrates the utility of using a high-throughput single-reflection diamond ATR to study these thin coatings on glass.

Experimental

Infrared spectra were collected on an FT-IR spectrometer equipped with the Harrick DiaMaxATR™ single-reflection high-throughput diamond ATR accessory. The system was purged to remove water vapor and CO₂. Spectra were collected at 8 cm^-1resolution and signal averaged over 32 scans. A background spectrum was collected. The glass samples were placed with the coated side against the crystal with optimum force applied to achieve close contact with the diamond ATR element. Five samples were measured all soda lime silica glasses: one untreated, one showing corrosion and three with ~225 nm thick SiO_xN_y coatings having differing oxygen and nitrogen content.

Results and Discussion

Figure 2 shows the resulting spectra. The spectrum of the corroded glass shows the formation of hydroxyl groups, with the broad band at 3400 cm^-1. This band has at least two shoulders, indicating that there are –OH bands bound to the surface somewhat differently. The band at 1402 cm^-1 is likely due to an –OH bend. The structure in the 920-761 cm^-1 region also shows changes due to corrosion, which is probably some combination of shifts in the Si-O-Si stretch due to the presence of the hydroxyl groups and possibly due to the formation of –SiH. The coated glass also shows hydroxyl groups in around 3400 cm^-1. Additional structure in this region is more pronounced for the samples having higher Si and N content as is the intensity of the band near 761 cm^-1.

Conclusion

The Harrick DiaMaxATR, high throughput, single reflection ATR is an effective tool for examining thin films on glass. In this particular case, closer examination of the spectra in the fingerprint region of the coated samples would further elucidate the structures formed by the coatings having slightly different chemical composition.

Harrick Scientific Products, Inc.
141 Tompkins Ave., Box 277, Pleasantville, NY 10570
tel. (914) 747-7202, fax (914) 747-7409
Website: www.harricksci.com