Interdiffusion and compound formation in Ta–Au thin-film couples

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Abstract
An investigation of the interdiffusion between sputter‐deposited bilevel films of bcc Ta–Au, β‐Ta–Au, and Ta2N–Au has been carried out by using x‐ray diffraction, electron microscopy, and electrical resistance measurements. In all three systems only the TaAu phase was observed to form. The temperature range of formation of the TaAu phase for the systems considered increased in the order β‐Ta, bcc Ta, and Ta2N. The resistance change for a given temperature increased in the order Ta2N, bcc Ta, and β‐Ta. It was concluded that the change of resistance occurred by three mechanisms: (1) diffusion of Ta into the Au grain boundaries, (2) diffusion of Ta into the Au bulk, and (3) transformation of the Au into a high‐resistivity TaAu phase. From the resistance measurements the kinetics of the formation of the TaAu phase were found to be diffusion controlled with the diffusion species moving through the TaAu phase grain boundaries.