Interaction between binary alloy thin films and silicon substrate: the conditions of bilayer formation and the effect of additional component

Abstract.

From a physical chemistry point of view the conditions of B/ASi bilayer structure occurrence as a result of silicon interaction with films of various binary alloys A–B (where A = for example Pt, Pd, Co, Ni; B = W, V, Ti, Zr, Hf, Ta) are analyzed. It is shown that the bilayer formation is observed when either the primary dissolution of extremely small amount of A in Si in comparison to the dissolution of Si in A occurs that is estimated by the enthalpies of mixing in extremely indefinitely diluted solutions of A in Si, and Si in A, or the higher surface activity of component A in the couple with silicon in comparison to the B-Si couple occurs that is estimated by the heats of sublimation. The possible segregation of A on the grain boundaries of alloy is taken into account. If in system A–B the intermetallic compounds A_xB_y have been formed, the driving force of alloy depletion process by component A is reduced. It is reasonable that at the appropriate choice of a additional component C (where C = boron,carbon, nitrogen) it is possible to increase the driving force of this process and to form the bilayer structure BC+A_xB_y/ASi. The analysis results are compared to some experimental data.