We have studied the initial stage of formation of carbon nanotube layers in surface decomposition of SiC substrate by means of spectroscopic ellipsometry. Before heating, the surface of the SiC substrate was covered with an SiO2 layer that had been formed by natural oxidation. By heating up to 1100 degreesC, reduction of SiO2 layer occurs. Between 1150 and 1300 degreesC, the surface of SiC decomposes and a (graphite + void) layer is formed on the surface. Then, by heating at 1300 degreesC for longer time, a carbon nanotube layer is formed. As a result, we have detected the beginning of the surface decomposition at 1150 degreesC and the beginning of the formation of a carbon nanotube layer at 1300 degreesC. (C) 2003 Elsevier B.V. All rights reserved.