CuxY compounds as thin films: crystallographic and compositional analyses of yttrium rich phases

The interdiffusion of Y films deposited onto Cu substrate by flash evaporation and sputtering was studied (concentration profiles, X-ray and electron diffraction patterns) in the temperature range 373–553 K. In samples deposited by flash evaporation the first phase to be detected is CuY at 393 K. At higher temperatures an intermediate phase, close to the Cu3Y2 compound, is formed before the Cu2Y stoichiometric phase is produced at 513 K. Crystallographic data confirm the formation of this intermediate Cu3Y2 phase (orthorhombic unit-cell) as resulting from the reaction CuY+Cu2Y→Cu3Y2. The results are identical for sputtered Y films deposited under a cryogenic vacuum (2−5×10−7 Pa). When Y is deposited under a standard vacuum (2−5×10−6 Pa), the influence of a diffusion barrier at the Cu–Y interface is noticed. This influence is characterized in the concentration profiles by an Y concentration hump at the Cu–Y interface and a depletion of Y at the front of the profile. Three main phases are observed. They correspond to the Cu5Y2, Cu2Y and Cu3Y2 compounds.