## 1 Introduction
In the last decade, several papers [7, 8, 9] have been published discussing the direct carbonization of Si substrates using carbon oxides based on theoretical and experimental studies of the pathways for these reactions, including studies of some intermediate products. It should be noted that [PERSON] et al. [7, 9, 10] studied the problems of the carbonization of Si(111) by CO and concluded that carbon oxide can interact with silicon, forming SiC on the surface, and managed to develop the method to a practical application, namely the synthesis of intermediate SiC nanofilm on Si substrates for the further deposition of AlInGaN heterostructures for LED devices [11]. It should be noted that researchers generally assume that the natural SiO\({}_{2}\) covering Si substrates is extremely harmful and is chemically eliminated according to established protools prior to or during the pretreatment of the substrates at high temperature, especially when chlorine gas is used. To prevent the formation of small amounts of oxides, some researchers deposit a thin film of carbon before the carbonization process [6]. The deposition of only an intermediate film of SiC was thoroughly analyzed in two publications [12; 13], where the thin films were characterized only by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and due to the complexity of these methods, the characterization results appear incomplete. Over the past few years, research has been conducted in two main directions: the development of the CVD methods for the synthesis of SiC coatings for specific purposes and the synthesis of SiC in low-dimensional allotropic forms--1D or 2D by CVD methods. For example, [PERSON] et al. [14], for the synthesis of SiC on graphite, use only polysilaethylene instead of two different gases providing Si and C in the reaction space, but the reaction is carried out at a high temperature (1200-1500) \({}^{\circ}\)C, while [PERSON] et al. [15] propose synthesis at temperatures around 1120 \({}^{\circ}\)C (i.e., compatible with silicon technologies for microelectronics) from silane and propane on different substrates: Al\({}_{2}\)O\({}_{3}\), Si/SiO\({}_{2}\), etc. Different studies are carried out also for obtaining gas-tight SiC coatings to protect carbon fibers/nanotubes from oxidation, ceramic parts from harmful gas effects, etc.--see Refs. [16; 17]. In principle, these methods are associated with reactions at very high temperatures--above (1400-1800) \({}^{\circ}\)C--with the latter method [17], for example, being associated with thermal evaporation of Si from a crucible at a temperature above that of Si melting, with C being provided by the reduction of hydrocarbon gas (e.g., methane). Another major area of interest for researchers in the past few years is the synthesis of low-dimensional forms of SiC--e.g., 1D (see e.g., [18; 19; 20] and 2D/quasi 2D (see e.g., [21])). In a recent study, we successfully simulated the synthesis of SiC with methane on a Si(111) substrate at a temperature of 1423 K [22]. The investigation of the mechanism included all intermediate products and transition states. It was concluded that native oxide does not suppress the process and that the carbon atoms are incorporated in the Si wafer only after the complete hydrogen loss. At high temperatures, the crystal surface is in continuous reconstruction, and no substitution reaction is necessary for carbon incorporation in the silicon structure. Two mechanisms of native oxide reduction were also proposed. In this work, we experimentally investigate the formation of the intermediate SiC thin films by the direct carbonization of Si substrates at about (1130-1140) \({}^{\circ}\)C, i.e., at temperatures at which standard quartz equipment can be used, focusing on the influence of the native oxide on the results.