Near-edge optical absorption behavior of sputter deposited hafnium dioxide

The absorption behavior at the onset of the ultraviolet optical edge of sputter deposited hafnium dioxide is reported. X-ray diffraction showed that films grown at room temperature on fused silica were nanocrystalline monoclinic, and that after air annealing at 1273 K for 24 h, they were well-crysta...

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Veröffentlicht in:Journal of applied physics 2007-06, Vol.101 (12)
Hauptverfasser: Hoppe, E. E., Sorbello, R. S., Aita, C. R.
Format: Artikel
Sprache:eng
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Zusammenfassung:The absorption behavior at the onset of the ultraviolet optical edge of sputter deposited hafnium dioxide is reported. X-ray diffraction showed that films grown at room temperature on fused silica were nanocrystalline monoclinic, and that after air annealing at 1273 K for 24 h, they were well-crystallized monoclinic with a strong (11–1) texture. Spectrophotometry was used to measure transmission and reflection in the 190–1100 nm wavelength range. The absorption coefficient, α(E), as a function of energy, E, was determined from spectrophotometric data. Two persistent features were identified. Feature I is the rapid rise in α(E) above 6.24 eV that is unchanged upon annealing. A linear α(E)1/2 vs E dependence associates this feature with indirect interband transitions. Feature II initiates at ∼5.65 eV and saturates at 5.94 eV. It appears as a low energy shoulder on the absorption edge of the as-grown films and develops into a discrete and more intense band in the annealed films, in which the coordination of Hf with seven O is satisfied. Its annealing behavior explicitly shows that feature II is not caused by an O defect, but is intrinsic to monoclinic HfO2.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.2750406