Surface structure and topography of vapour deposited carbon investigated by scanning tunneling microscopy

Abstract

Résumé. 2014 Dans les processus de déposition atomique, la structure et la topographie de Abstract. 2014 In atomistic deposition processes the surface structure, the surface steps and the surface topography strongly influence the growth behaviour and thus the properties of the deposited material. However, the structure, the step density and the topography are at the same time the result of the deposition process itself. Hence surface investigation on the atomic level will reveal characteristics of the deposition process and of the growth mechanisms. Scanning tunneling microscopy (STM) was used to characterize the surface topography and structure of carbon films. The films were deposited by chemical vapour deposition (CVD) from methane or ethene at temperatures ranging from 1030 to 1080 ° C and from 800 to 1050 ° C, respectively. Monocrystalline (012) sapphire wafers were used as substrates. The surface topography increased with deposition time and approached asymptotically a limit value of 100 A, which was independent of the growth temperature as well as of the precursor used. For 500 Å thick films deposition conditions yielding a topography less than 50 Å could be found. The microscope could also be operated close to atomic resolution. Surface areas with both ordered and disordered carbon atoms were then detected. The areas with the ordered atoms were very small (about 10 A). The atomic arrangement within these areas resembled that of graphite.