Physical properties of CVD-grown Se—carbon films

Abstract

A novel chemical vapor deposition (CVD) approach based on the thermal decomposition of an aromatic hydrocarbon in the presence of Se vapor is used to grow films of layered Se—carbon compounds. In principle, this technique can produce a wide variety of new carbon-based materials, for example, graphite intercalation compounds (GICs) which, for kinetic reasons, cannot be made if the intercalant vapor has to diffuse large distances into a pre-existing graphitic host. In particular, homogeneous oriented submicron films of either pure stage-3 (Se 24C) or mixed-stage Se—carbon layer compounds have been successfully grown on Ni substrates in evacuated sealed quartz tubes. X-ray diffraction, X-ray photoelectron spectroscopy, Raman scattering and the c-axis electrical transport measurements are discussed in terms of both covalent Se—carbon bonding and an ionic model assuming the formation of an acceptor-type Se—GIC with electron transfer from carbon to Se. Our CVD-grown Se—carbon films exhibit the largest thermoelectric power reported in the open literature among carbon-based compounds. However, the value is at least a factor of 10 less than reported for these materials in patents by Sharp Corp.