Transmission electron microscopy studies of the Pd–C films obtained by physical and chemical vapor deposition

Transmission Electron Microscopy (TEM) analysis of carbonaceous films that contain palladium nanoparticles were carried out. These layers will be used in next-generation hydrogen sensors. The investigated films were obtained in Physical Vapor Deposition (PVD) and followed in Chemical Vapor Deposition (CVD) processes. For TEM analysis, cross-sections specimen (lamella) of both samples (i.e. PVD and PVD/CVD) were prepared with the usage of Focus Ion Beam (FIB). TEM analysis of the cross-sections determined the films' thickness, which were ∼200 nm and ∼300 nm for PVD and PVD/CVD films respectively. The greater thickness of the PVD/CVD films was associated with xylene decomposition and consecutive formation of porous structure. Our studies allowed to obtain some information about the distribution of palladium crystallites and porous carbon in the both layers of Pd–C.Furthermore, aggregation of small (∼2 nm) Pd nanocrystallites around the larger ones was observed for PVD and PVD/CVD films. In the PVD/CVD films a polycrystalline palladium have been observed.

► Palladium–carbon films obtained by PVD and CVD method. ► Different thickness of the layers as a result of the formation of a porous layer of carbon in the CVD process. ► The occurrence of palladium in the form of polycrystalline and with graphite shell.