## 1 Introduction  
N-alkane nanofilms supported on solid substrates have been extensively studied both experimentally [1; 2; 3; 4; 5; 6; 7; 8; 9; 10; 11; 12; 13] and theoretically [14; 15] since the last decade. Interesting points for these studies are not only its fundamental importance for n-alkane as a main constituent of many molecules with industrial (e.g., as the principal constituents of commercial lubricants [16]) and biological relevance, as well as constituents in lots of polymers (as prototypes of more complex polymers) used in coatings, adhesives, and electronic devices, but also its interfacial structure at the molecular level, which acted as the desirable temporary masks to protect surfaces owing to the physisorbed and easily removed characteristic [17]. This is because the long-chain hydrocarbon plays an important role in the structure formation process, such as the crystallization of fats and polymers, and the formation of lipid membranes. Most of the past studies focused on the fundamental understanding of the structure formation of hydrocarbons based on a simple long-hydrocarbon-chain molecule, such as n-alkane,and all the studies related to different lengths of the n-alkane molecules and substrates concluded that long-hydrocarbon-chain molecules were arranged in an ordered lamellar structure, in which the molecular long-chain axes were parallel to each other due to the van de Waals interaction among the molecules, and their end groups were on same plane. Two typical preferred molecular orientation states were observed on substrate surfaces, to the highly attractive surface, e.g., metal and HOPG, and very thin n-alkane was found to crystallize with their molecular axes parallel to the substrate [15], while for intermediate-length n-alkane prepared on SiO\({}_{2}\) (Si wafer with native oxides), it was found that the chains were dominantly perpendicular to the substrate, proposed by [PERSON] and co-workers [1; 2; 3; 4]. [PERSON]'s group also proposed that for intermediate-length-chain alkane molecules on SiO\({}_{2}\), there is one or two molecular layers of the parallel chains underneath [5; 6; 7; 8; 9]. Very recently, a Monte Carlo simulation by [PERSON] et al. [15] suggested that the crystalline films consist of thin crystalline lamellae where chains are either parallel or perpendicular to the substrate. The relative number of the lamella types is dependent on film thickness, substrate attraction, and crystallization temperature. They concluded that the thicker films on substrates of higher attraction comprise dominantly parallel lamellae, while thinner films on substrates with weaker attraction prefer perpendicular lamellae. [PERSON] et al. [10] demonstrated very recently that, based on vacuum-evaporation-deposited n-alkane (n = 23-27) thin, using X-ray diffraction (XRD) and atomic force microscopy (AFM) analysis, there is only a perpendicularly orientated state at a high substrate temperature and a low evaporation rate, while the films are composed by the \"co-existence\" of both perpendicular and parallel states at lower temperatures. They concluded that the perpendicular state is the most thermodynamically stable state. The thin films of n-alkane can be prepared both by liquid (wet chemistry, dip coating based on physical absorption, and/or spin casting) and dry (evaporation in vacuum) methods on a Si wafer (with native oxide layer), Ag, In, and HOPG. However, spin casting used for preparing the nanofilms of n-alkane, as a very simple method, still lacks a systematic study, such as a systematic study of n-alkane films with different thicknesses prepared by spin casting. Meanwhile, the preparation and study of the monolayer of n-alkane films prepared by spin casting has barely been reported. Herein, we have designed and prepared the n-alkane films with different thicknesses from a sub-monolayer to multilayer by spin casting systematically and established a method to control the film thickness.