Growth and physical properties of epitaxial metastable Hf1 − xAlxN alloys deposited on MgO(001) by ultrahigh vacuum reactive magnetron sputtering
✍ Scribed by B. Howe; J. Bareño; M. Sardela; J.G. Wen; J.E. Greene; L. Hultman; A.A. Voevodin; I. Petrov
- Publisher
- Elsevier Science
- Year
- 2007
- Tongue
- English
- Weight
- 666 KB
- Volume
- 202
- Category
- Article
- ISSN
- 0257-8972
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✦ Synopsis
Epitaxial metastable Hf 1 -x Al x N alloys with 0 ≤x ≤ 0.50 were grown on MgO(001) substrates at 600 °C by ultrahigh vacuum reactive magnetron sputtering from Hf and Al targets in 90% Ar + 10% N 2 discharges at 7 mTorr. X-Ray diffraction and cross-sectional transmission electron microscopy show that Hf 1 -x Al x N alloys are single crystals with the B1-NaCl structure. Rutherford backscattering spectroscopy investigations reveal that all films are slightly overstochiometric with N / (Hf + Al) = 1.05 ± 0.05. The relaxed lattice parameter decreased linearly from 0.4519 nm with x = 0 to 0.4438 nm with x = 0.50, compared to 0.4320 nm expected from the linear Vegard's rule. We find a metastable single phase field that is remarkably broad given the large lattice mismatch (≃9%) between the two alloy components. Alloying HfN with AlN leads to an increase in hardness (≃30% to 32.4 ± 0.7 GPa), as well as nanostructured compositional modulations due to the onset of spinodal decomposition.