title: Formation of Cu x Au1- x phases by cold homogenization of Au/Cu nanocrystalline thin films.
abstract: It is shown, by using depth profiling with a secondary neutral mass spectrometer and structure investigations by XRD and TEM, that at low temperatures, at which the bulk diffusion is frozen, a complete homogenization can take place in the Cu/Au thin film system, which leads to formation of intermetallic phases. Different compounds can be formed depending on the initial thickness ratio. The process starts with grain boundary interdiffusion, which is followed by a formation of reaction layers at the grain boundaries that leads to the motion of the newly formed interfaces perpendicular to the grain boundary plane. Finally, the homogenization finishes when all the pure components have been consumed. The process is asymmetric: It is faster in the Au layer. In Au(25nm)/Cu(50nm) samples the final state is the ordered AuCu3 phase. Decrease of the film thicknesses, as expected, results in the acceleration of the process. It is also illustrated that changing the thickness ratio either a mixture of Cu-rich AuCu and AuCu3 phases (in Au(25nm)/Cu(25nm) sample), or a mixture of disordered Cu- as well as Au-rich solid solutions (in Au(25nm)/Cu(12nm) sample) can be produced. By using a simple model the interface velocity in both the Cu and Au layers were estimated from the linear increase of the average composition and its value is about two orders of magnitude larger in Au (ca. 10(-11) m/s) than in Cu (ca. 10(-13) m/s).
authors.affiliation: National Technical University of Ukraine "Kiev Polytechnic Institute", 37 Prospect Peremogy, 03056 Kiev, Ukraine ; Department of Solid State Physics, University of Debrecen, P.O. Box 2, 4010 Debrecen, Hungary.
authors.forename: Alona
authors.initials: A
authors.lastname: Tynkova
authors.affiliation: Department of Solid State Physics, University of Debrecen, P.O. Box 2, 4010 Debrecen, Hungary.
authors.forename: Gabor L
authors.initials: GL
authors.lastname: Katona
authors.affiliation: Department of Solid State Physics, University of Debrecen, P.O. Box 2, 4010 Debrecen, Hungary.
authors.forename: Gabor A
authors.initials: GA
authors.lastname: Langer
authors.affiliation: National Technical University of Ukraine "Kiev Polytechnic Institute", 37 Prospect Peremogy, 03056 Kiev, Ukraine.
authors.forename: Sergey I
authors.initials: SI
authors.lastname: Sidorenko
authors.affiliation: National Technical University of Ukraine "Kiev Polytechnic Institute", 37 Prospect Peremogy, 03056 Kiev, Ukraine.
authors.forename: Svetlana M
authors.initials: SM
authors.lastname: Voloshko
authors.affiliation: Department of Solid State Physics, University of Debrecen, P.O. Box 2, 4010 Debrecen, Hungary.
authors.forename: Dezso L
authors.initials: DL
authors.lastname: Beke
keywords: Cu/Au; grain boundary diffusion; nanofilms of intermetallic compounds; secondary neutral mass spectrometry (SNMS); solid state reaction