In Situ Electron Diffraction and Resistivity Characterization of Solid State Reaction Process in Cu/Al Bilayer Thin Films

Solid state reaction processes in Cu/Al thin films have been studied using the methods of in situ electron diffraction and electrical resistivity measurements. The solid state reaction in the Cu/Al thin films has been found to begin already at 88 degrees C with the formation of the Al2Cu phase in the process of thermal heating in vacuum. The phase sequence at the solid state reaction in the films under study has been determined to be the following: Al2Cu -> AlCu -> Al4Cu9. A model has been suggested for describing the initial formation stage of intermetallic compounds at the solid state reaction in Cu/Al thin films. According to this model, at the initial stage, the intermetallic compounds are formed as separate crystallites at the interface in the Cu/Al thin films. The suggested model can be applied both to the formation of the first phase, Al2Cu, and to the subsequent phases: AlCu and Al4Cu9. For the Al4Cu9 phase the temperature coefficient of the electrical resistivity has been determined to be equal to alpha Al4Cu9}= 1.1 x 10(-3) K-1.