In situ infrared and visible-light ellipsometric investigations of boron nitride thin films at elevated temperatures

In situ infrared and visible-light ellipsometric investigations of boron nitride thin films at elevated temperatures situ infrared and visible-light ellipsometric investigations of boron nitride thin films at elevated temperatures" (1998). Faculty Publications from the Department of Electrical and Computer Engineering. 14. In situ infrared ͑IR͒ spectroscopy and visible-light ͑VIS͒ spectroscopic ellipsometry over the spectral range from 700 to 2000 cm Ϫ1 and 1.5–3.5 eV, respectively, were used to investigate the optical behavior of boron nitride ͑BN͒ thin films at temperatures from room temperature ͑RT͒ to 600 °C. The polycrystalline hexagonal ͑h͒ and mixed-phase hand cubic (c)-BN thin films were deposited by magnetron sputtering on ͓001͔ silicon. We observe a reversible moisture incorporation process in as-grown h-BN samples. When stored in normal ambient, the h-BN thin films absorb water into thin-film micropores. When annealed in ultrahigh vacuum or a dry nitrogen atmosphere, the samples expel moisture but retain their microstructure. This is observable by reduction of the thin-film refractive indices in accordance with changes in the IR lattice resonance behavior. The optical properties of high c-BN content thin films remain unchanged during annealing. And both intrinsic hand c-BN thin-film VIS refractive indices are nearly temperature independent, at least up to 600 °C. Therefore, RT BN optical constants can be used for feedback loop control in in situ thin-film growth at temperatures up to 600 °C. ͓S0021-8979͑98͒07613-0͔