Effect of sputtering parameters on surface morphology and catalytic efficiency of thin platinum films

Abstract

This paper presents a research on the influence of sputtering parameters (dc power, argon pressure) and film thickness/metal loading on the surface structure and morphology of platinum thin films and their catalytic activity toward the oxygen reduction in acid aqueous solutions. The properties of the sputtered films were studied using scanning electron microscopy (SEM), X-ray diffraction (XRD), and the electrochemical methods of cyclic voltammetry and steady state polarisation. It was found that low sputtering power and high sputtering pressure lead to deposition of mechanically stable crystalline Pt films with extended surface area. Optimal sputtering parameters of 68 mTorr argon pressure and 100 W dc power were determined. The films deposited at these conditions possess homogeneous, highly developed surface with columnar structure. The increase in thickness results in essential epitaxial growth of the platinum particles with distinct [1 1 1] orientation. The best utilization of the catalyst (1.10 −3 A cm −2 nm Pt −1 mass activity determined from the polarisation curves at 0.4 V) was achieved at 120–130 nm film thickness.