Amorphous CuAg Films with High Stability

Films produced by quenching CuAg vapour onto cooled substrates at liquid nitrogen temperature are investigated using electron microscopy, electron diffraction, and electrical resistivity measurements. In the composition range from 30 to 70 at% Cu the as-quenched films are amorphous, and within the range of 35 to 63 at% Cu the amorphous phase is stable above room temperature with a maximum crystallization temperature Tc = 381 K at 47.5 at% Cu. Crystallization results in the formation of a supersaturated f.c.c. solid solution which decomposes in a second crystallization step. The effect of deposition rate, film thickness, temperature, and surface of the substrate, and most importantly of the composition on the transition temperatures is investigated. A comparative study of the formation of amorphous phases in a wide variety of Cu-based alloys is presented.