PHYSICAL-PROPERTIES OF CVD-GROWN SE-CARBON FILMS

A novel chemical vapor deposition (CVD) approach based on the thermal decomposition of an aromatic hydrocarbon in the presence of Se vapor i s used to grow films of layered Se-carbon compounds. In principle, thi s technique can produce a wide variety of new carbon-based materials, for example, graphite intercalation compounds (GICs) which, for kineti c reasons, cannot be made if the intercalant vapor has to diffuse larg e distances into a pre-existing graphitic host. In particular, homogen eous oriented submicron films of either pure stage-3 (Se24C) or mixed- stage Se-carbon layer compounds have been successfully grown on Ni sub strates in evacuated sealed quartz tubes. X-ray diffraction, X-ray pho toelectron spectroscopy, Raman scattering and the c-axis electrical tr ansport measurements are discussed in terms of both covalent Se-carbon bonding and an ionic model assuming the formation of an acceptor-type Se-GIG with electron transfer from carbon to Se. Our CVD-grown Se-car bon films exhibit the largest thermoelectric power reported in the ope n literature among carbon-based compounds. However, the value is at le ast a factor of 10 less than reported for these materials in patents b y Sharp Corp.