The structure of carbonic layer in three samples composed of 4H polytype of silicon carbide and the following sequence of layers: carbon/nickel/silicon/nickel/silicon was investigated with Raman spectroscopy. Different thermal treatment of the samples led to differences in the structure of carbonic layer. Raman measurements were performed with visible excitation focused on two interfaces: silicon carbide/carbon and carbon/silicide. The results showed differences in the structure across carbon film although its thickness corresponds to 8/10 graphene layers. 1. Introduction Silicon carbide (SiC) is known as an excellent material for fabrication high-power, high-frequency, and high-temperature electronic devices due to its properties like: good thermal conductivity, high critical electric field, and simple method of dielectric layer fabrication [1, 2]. Formation of ohmic contacts with low specific resistance is an important aspect in application of silicon carbide [3]. This fabrication is realized by deposition of metallic layer on the substrate surface followed by thermal treatment at high temperature [4, 5]. Nickel is probably the most popular metal used in technology of ohmic contact formation, because the contacts formed with its application have specific contact resistance equal to ~10？6？Ω？cm2 [4]. The interaction of carbonic structures with the SiC substrate was investigated with X-ray photoelectron spectroscopy and Raman scattering [6]. The properties of the ohmic contact are determined by concentration of graphitic nanoflakes formed during the annealing procedure. The initial structure of carbon film has no impact on properties of the formed contact [6, 7]. In previous work, structural and electrical properties of different Ni- and Ni/Si-based contacts to silicon carbide were investigated [8]. Reported structural data obtained by various experimental techniques like X-ray diffraction (XRD), Rutherford Backscattering Spectrometry (RBS), and Secondary Ion Mass Spectrometry (SIMS) showed that optimal metallization sequence for manufacturing ohmic contacts is Ni/Si/Ni/Si. The thicknesses of each layer should provide optimal conditions for creation of Ni2Si silicides. This paper focuses the attention on structural properties on different sides of thin carbon film introduced between SiC substrate and nickel/silicon/nickel/silicon sequence of layer. Since thermal treatment at high temperature results in SiC decomposition, new carbon atoms appear at the interface between silicon carbide substrate and deposited carbonic layer. Decomposition of silicon
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