Synthesis of Pd-Ag Alloy Nano-composite Thin Films at Room Temperature by DC Magnetron Co-Sputtering

The PdAg alloy thin films are of interest for hydrogen sensing and storage applications. The present work reports on the synthesis of PdAg alloy nanocomposite thin films by DC magnetron co-sputtering. We have synthesized the PdAg alloys films at three different compositions of Pd and Ag in the ratio 9:1, 7:3 and 1:1 with nomenclature of Pd90Ag10, Pd70Ag30, and Pd50Ag50 respectively. The relative ratio of Pd and ag was confirmed by Rutherford backscattering using 2 MeV alpha particles. The deposition rates of both Pd and Ag were individually calibrated by sputtering of individual Pd and Ag targets and subsequent film thickness measurement by X-ray reflectivity. The deposition was performed in 99.99% pure Argon environment at a pressure of $2.7\times 10-3$ torr, whereas the base pressure was $1\times 10-7$ torr. The X-ray diffraction of the samples reveals that there is no indication of separate peaks of either Pd or Ag, and the peak position lies in between the expected individual peaks of both Ag and Pd, which implies that a PdAg alloy is formed at ambient temperature by self- assembly process. It was found that the PdAg alloys films have the face-centred cubic (fcc) structure. FESEM images reveals that the Pd90Ag10 film is densely bound whereas the Pd50Ag50 film has higher porosity.