Real-time control of AlN incorporation in epitaxial Hf1-xAlxN using high-flux, low-energy (10-40 eV) ion bombardment during reactive magnetron sputter deposition from a Hf0.7Al0.3 alloy target

• Published in: Acta materialia 2011, Vol.59 (2), p.421-428
• Main Authors: HOWE, B. M, SAMMANN, E, WEN, J. G, SPILA, T, GREENE, J. E, HULTMAN, L, PETROV, I
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; HfAlN; Ion bombardment; Metals. Metallurgy; Nanolayers; Production techniques; Sputter deposition; Surface treatment; TECHNOLOGY; TEKNIKVETENSKAP; Transition metal nitrides
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2010.08.023

The AlN incorporation probability in single crystal Hf-1 (-) xAlxN(0 0 1) layers is controllably adjusted between similar to 0% and 100% by varying the ion energy (E-i) incident at the growing film over a narrow range, 10-40 eV. The layers are grown on MgO(0 0 1) at 450 degrees C using ultrahigh vacuum magnetically unbalanced reactive magnetron sputtering from a Hf0.7Al0.3 alloy target in a 5%-N-2/Ar atmosphere at a total pressure of 20 mTorr (2.67 Pa). The ion to metal flux ratio incident at the growing film is constant at 8. Epitaxial film compositions vary from x = 0.30 with E-i = 10 eV, to 0.27 with E-i = 20 eV, 0.17 with E-i = 30 eV, and andlt;= 0.002 with E-i andgt;= 40 eV. Thus, the AlN incorporation probability decreases by greater than two orders of magnitude. This extraordinary range in real-time manipulation of film chemistry during deposition is due to the efficient resputtering of deposited Al atoms (27 amu) by Ar+ ions (40 amu) neutralized and backscattered from heavy Hf atoms (178.5 amu) in the film. This provides a new reaction pathway to synthesize, at high deposition rates, compositionally complex heterostructures, multilayers, and superlattices with abrupt interfaces from a single alloy target by controllably switching E-i. For multilayer and superlattice structures, the choice of E-i value determines the layer composition and the switching periods control the individual layer thickness.