The formation and morphological development of two phase composite films still has a number of open questions. Metal–metal (nano)composites are posing many unsolved growth problems. Especially the basic processes of morphological and texture development in them needs to be further clarified [1,2]. The Cu-Ag system can be a suitable model for the investigation of structure development in metal-metal nanocomposites.
We deposited Cu-Ag films in vacuum of 10-5-10-6 mbar onto freshly cleaned Si wafers. The composition of the films corresponded to Cu, Cu9Ag1, Cu4Ag6 and Ag in connection to the physical and morphological properties of these films [4]. By selecting thickness (40nm – 500nm), deposition temperatures (20 or 400oC) and rates (1 or 30 nm/s) we aimed to map the structure zone diagram [2] of the system and define the main atomic processes in its zones.
The films were investigated by X-ray diffraction, where pole figures of 111 and 200 reflections were recorded. TEM and XTEM were used to determine the morphological properties of the films.
In the 40 nm thick layers (Ts=20oC, v=1nm/s) the pure Cu films have no measurable texture. Texture formation appears when Ag is added. Sharp biaxial <100> texture (epitaxy) is observed in Cu9Ag1 composition films. A strong one axis <111> texture appears in the nanocomposite of the eutectic composition (Cu4Ag6). In films of 400 nm thickness (Ts=20oC, v=1nm/s) biaxial texture is present in Cu and Cu9Ag1 compositions, however, in the eutectic composition again the one axis <111> texture is observed. Ag films both thick and thin have <111> one axis texture.
As we can see from the results, Ag is enhancing the formation of the biaxial <100> texture through the selection processes usually known in thin films [1, 2]. In the eutectic nanocomposite, however, due to the very small grain size, these process play a very limited role in the formation of the <111> texture.
This work was supported by the Hungarian National Science Foundation; OTKA T-043437 and 048699 projects.
1. A. Kovács, P.B. Barna, Solid State Ionics 141–142 (2001) 105.
2. I. Petrov, P.B. Barna, L. Hultman, J.E. Greene, J. Vac. Sci. Technol. A 21(5) (2003) S117.
3. F. Misják, P. B. Barna, A. L. Tóth, T. Ujvári, I. Bertóti and Gy. Radnóczi, to be published.
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