## 3 Results  
### Surface Morphology of the C\({}_{32}\)H\({}_{66}\) Thin Films by AFM  
Although [PERSON]'s group had extensively studied [8; 18] the surface morphology of C\({}_{32}\)H\({}_{66}\) by contact and noncontact AFM using two different thicknesses, 6.5 nm and 9.5 nm, by the dipping coating physical absorption process, their studies were not concentrated on monolayers or sub-monolayers and a series of films with different thicknesses. Here, we prepared a series of samples with different average thicknesses from 2.4 nm (sub-monolayer) to 10.5 nm by changing the C\({}_{32}\)H\({}_{66}\) concentration at a given spin-coating speed. Though the thickness of the films was estimated by XPS, AFM topographic images provided useful information on the thickness and coverage of the alkane film. Typical AFM images and a couple of profiles isolated from the images are shown in Figure 1, as well as in Figures S1 and S2 (Supporting Information). They showed that the topographies were composed of dendrites (relatively low C\({}_{32}\)H\({}_{66}\) concentration) or island-like structures, which is consistent with [PERSON]'s AFM results [8; 18] and [PERSON]'s AFM data [10]. These surface features could be attributed to perpendicularly oriented C\({}_{32}\)H\({}_{66}\) molecules. Our AFM measurement noise on the Si wafer (without coating anything) was about \(\pm\)0.1 nm (see Figure S3). Figure 1: AFM images and two representative profiles isolated from the images of C\({}_{32}\)H\({}_{66}\) thin films deposited with different concentrations on the substrate. (**a**) 0.05% w/v, (**b**) 0.13% w/v, (**c**) 0.3% w/v, and (**d**) 0.5% w/v. Shown in Figure 1a,b are two AFM images for samples made with lower C\({}_{32}\)H\({}_{66}\) concentrations (0.05 and 0.13 w/v, respectively). Self-assembled monolayers (SAMs) of C\({}_{32}\)H\({}_{66}\) were observed. AFM images were flattened line by line along the fast scan direction (x-axis), allowing accurate measurements of the thickness of the monolayers from 10 profiles isolated from the image. The thickness of the monolayers estimated by using this approach for both images was 3.9 \(\pm\) 0.2 nm. Also shown in these two figures are two representative profiles isolated from each of the two images. The thickness and coverage of the monolayers could also be estimated from the histogram and bearing ratio, respectively. For example, the histogram and bearing ratio of Figure 1b are shown in Figure S4. The height rises seen in Figure 1b were excluded for calculations of the histogram and bearing ratio. The histogram suggested that the thickness of the monolayers was 3.9 nm and the bearing ratio indicated that the coverage of the monolayers was approximately 68%. Our AFM results showed that the long-chain alkane molecules self-assembled on the substrate, even though there were no interactions between the methyl groups and the hydrophilic silicon substrate. This suggested that the van der Waals forces between the long methylene chains dictated the assembly of the alkane molecules. Due to the lack of interactions between the molecules in this type of SAM and the substrate, they were susceptible to solvent, which would be discussed later. With an increased concentration, as shown in Figure 1c (0.3% w/v), the formation of multiplayers was observed. The thickness of the top monolayers in the multilayer structure was 4.3 \(\pm\) 0.1 nm, which was slightly thicker than that (3.9 \(\pm\) 0.2 nm) of the monolayers over the substrate seen in Figure 1a,b. This indicated that the molecules in the monolayers on the Si substrate (Figure 1a,b) tilted more than those in the top monolayers of the multilayers (Figure 1c). It was intriguing that the first monolayer contacting the substrate in Figure 1c (the groove-like features located at lower left and upper right) had a lower thickness of 3.4 \(\pm\) 0.1 nm (Figures 1c and S1). When the C\({}_{32}\)H\({}_{66}\) concentration was increased to 0.5% w/v, as shown in Figure 1d, multilayers were seen.