Thin Solid Films 424 (2003) 93–98 0040-6090/03/$ - see front matter  2002 Elsevier Science B.V. All rights reserved. PII: S0040-6090 Ž 02 . 00924-0 Sputter deposited nanocrystalline Ni-25Al alloy thin films and Ni y Ni Al 3 multilayers R. Banerjee*, G.B. Thompson, P.M. Anderson, H.L. Fraser Department of Materials Science and Engineering, The Ohio State University, 177 Watts Hall 2041 College Road, Columbus OH, USA Abstract Thin films of nominal composition Ni-25at%Al have been sputter deposited from a target of the intermetallic compound Ni Al 3 at different substrate deposition temperatures. The film deposited on an unheated substrate exhibited a strongly textured columnar growth morphology and consisted of a mixture of metastable phases. Nanoindentation studies carried out on this film exhibited a strong strain hardening tendency. In contrast, the film deposited at 200 8C exhibited a recrystallized non-textured microstructure consisting of grains of a partially ordered Ni Al phase. At higher deposition temperatures (;400 8C), larger grains of the bulk 3 equilibrium, long-range ordered, Ll Ni Al phase were observed in the film. Unlike the film deposited on an unheated substrate, 2 3 the films deposited at elevated temperatures did not exhibit any dependence of the hardness on the indentation depth and, consequently no strain hardening. The average hardness of the film deposited at 200 8C was higher than the one deposited at 400 8C. In addition to monolithic Ni-25Al thin films, multilayered NiyNi3Al thin films were also deposited. Multilayers deposited non-epitaxially on unheated substrates exhibited a strong {111} fiber texture while those deposited epitaxially on (001) NaCl exhibited a {001} texture. Free-standing multilayers of both types of preferred orientations as well as of different layer thicknesses were deformed in tension untill fracture. Interestingly, the {111} oriented multilayers failed primarily by a brittle fracture while the {001} multilayers exhibited features of ductile fracture.  2002 Elsevier Science B.V. All rights reserved. Keywords: Ni-25Al; Alloy thin films; NiyNi Al 3 1. Introduction Thin films of alloys and intermetallic compounds have a wide range of applications. These include con- ducting barrier layers and passivation layers in micro- electronic devices such as integrated circuits, active layers in giant magnetoresistive recording heads in magnetic storage devices and structural coatings for high temperature aerospace applications. Formation of meta- stable phases in thin films occurs rather commonly because of the rapid cooling rates involved during the transformation from a vapor to a solid film. Nickel-based superalloys are used extensively in the aerospace industry, due to excellent mechanical proper- ties such as yield strength and creep resistance at elevated temperatures w1x. The metal–intermetallic com- posite alloy consists of a g-Ni(Al) matrix with an *Corresponding author. Tel.: q1-614-292-2553; fax: q1-614-292- 7523. intermetallic g9-Ni Al phase. The latter serves as the 3 primary strengthening phase and often takes the form of cuboidal precipitates with a {001} Ni(Al) yy {001} Ni Al, N100M Ni(Al) yyN100M Ni Al interface orienta- 3 3 tion. In addition to Ni-based superalloys, a large amount of research has been carried out on the intermetallic compound Ni Al. However, most of the studies have 3 been directed towards the thermo-mechanical processing and study of deformation mechanisms in bulk Ni Al 3 based alloys. There have been rather limited studies on the thin film form of this compound, especially from the viewpoint of mechanical properties. Some of the earlier reports include investigations of the metastable phases forming in these thin films. Harris and co-workers w2x deposited chemically disordered Ni- 25Al (all compositions in this paper are in atomic%) thin films on unheated as well as liquid nitrogen cooled polycrystalline copper substrates temperatures using high vacuum evaporation. In a different study, nano- crystalline Ni–Al alloy films were prepared by vacuum