Crystallization, metastable phases, and demixing in a hafnia-titania nanolaminate annealed at high temperature

Journal Article · Wed Sep 15 00:00:00 EDT 2010 · Journal of Vacuum Science and Technology. A, International Journal Devoted to Vacuum, Surfaces, and Films

DOI:https://doi.org/10.1116/1.3474973· OSTI ID:22053993

Cisneros-Morales, Massiel Cristina; Rubin Aita, Carolyn ^[1]

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1. Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, P.O. Box 413, Milwaukee, Wisconsin 53201 (United States)

Nanolaminate films with a nominal 5 nm HfO{sub 2}-4 nm TiO{sub 2} bilayer architecture are sputter deposited on unheated fused silica and Au-coated glass substrates. Films on fused silica are postdeposition annealed from 573 to 1273 K and characterized by x-ray diffraction, scanning electron microscopy, Raman microscopy, and UV-visible-near IR spectrophotometry. The films show weak but progressive crystallization into orthorhombic (o) HfTiO{sub 4} when annealed up to 973 K. o-HfTiO{sub 4} is expected to form under bulk thermodynamic equilibrium conditions in the case of complete mixing of the bilayer components. Annealing above 973 K produces a crystallization sequence that is not predicted by bulk thermodynamics, ultimately involving o-HfTiO{sub 4} demixing to form monoclinic HfO{sub 2} doped with Ti and rutile TiO{sub 2} doped with Hf. These phases have a higher atomic density than o-HfTiO{sub 4} and segregate into discrete mesoscopic features. The authors propose that o-HfTiO{sub 4} demixing into higher density phases is a mechanism for thermal stress relief at high temperature. Demixing results in a major loss of optical transparency in the visible and ultraviolet spectral regions.

• OSTI ID: 22053993
• Journal Information: Journal of Vacuum Science and Technology. A, International Journal Devoted to Vacuum, Surfaces, and Films, Vol. 28, Issue 5; Other Information: (c) 2010 American Vacuum Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1553-1813
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
77 NANOSCIENCE AND NANOTECHNOLOGY
CRYSTAL GROWTH
CRYSTALLIZATION
DOPED MATERIALS
HAFNIUM OXIDES
MONOCLINIC LATTICES
NANOSTRUCTURES
NEAR INFRARED RADIATION
OPACITY
ORTHORHOMBIC LATTICES
RUTILE
SCANNING ELECTRON MICROSCOPY
SILICA
SPUTTERING
THERMAL STRESSES
THERMODYNAMICS
THIN FILMS
TITANIUM OXIDES
ULTRAVIOLET RADIATION
ULTRAVIOLET SPECTROMETERS
X-RAY DIFFRACTION