Properties of hydrogen sensitive C-Pd films obtained by PVD/CVD method

Abstract

Structural, topographical and morphological changes of carbonaceous-palladium (C-Pd) films obtained by physical vapor deposition /chemical vapor deposition (PVD/CVD) method were studied. Effect of changes in these properties under the influence of CVD process temperature on the hydrogen sensitivity of these films is discussed. Scanning electron microscopy (SEM) observations were used to investigate the topography and morphology of an initial (PVD) film and the film modified in CVD process (PVD/CVD film) at different temperatures. The changes of film’s morphology after modification performed at various temperatures (500, 550, 600, 650, 700 and 750°C) caused changes in their resistance. The electrical measurements carried out in the presence of gas containing 1vol % of hydrogen showed different sensing characteristics for various films. The highest hydrogen sensitivity and the fastest response were observed for films modified at the temperature of 500°C and 550°C. In SEM images on surface of these films palladium nanograins with different sizes were observed. For films modified at the temperatures higher than 600°C Pd nanograins placed under superficial very thin carbonaceous layer were found.