## 3 Results and Discussion
The evolutions in the ratios of O/Si and N/Si as a function of the gas flow ratio are also depicted in Figure 4b (the dash line indicates the stoichiometric composition of SiO\({}_{2}\) with the ratio of O/Si = 2). The film deposited using the TMS-O\({}_{2}\) gas had an O/Si ratio of about 2.08, implying an oxygen-rich SiO\({}_{2}\) film. When the ammonia gas was introduced into the glow discharge at \(R\) = 0.25, the ratio of the O/Si decreased to 2.01 and a low N content (\(\sim\)0.8%) was detected in the film. For the film synthesized from the gas mixture at a ratio of 0.5, the ratio of the O/Si was a little lower than 2 (\(\sim\)1.98) with the increase in the N content (\(\sim\)1.38%). The O/Si ratio was further decreased to 1.93 as the film was deposited using the TMS-O\({}_{2}\)-NH\({}_{3}\) gas mixture at a flow ratio of 0.75. In agreement with the previous reports, the decrease in the O/Si ratio also led to the shift in the stretching mode of the Si-O bond from 1066 to 1051 cm\({}^{-1}\), as shown in Figure 3b [19; 21; 38]. A sharp reduction in the O/Si ratio (\(\sim\)1.38) and a high N/Si ratio of about 0.16 with a large amount of carbon atoms (\(\sim\)11.2%) were measured from the film using the TMS-NH\({}_{3}\) gas mixture. This oxygen-deficient film, which implied the incomplete decomposition of the TMS monomer under the glow discharge of the TMS-NH\({}_{3}\) gas mixture, was characterized as Si-CH\({}_{2}\)-Si and C-H/C-C bonds, as shown in Figure 3b. Accordingly, although the ammonia gas incorporation into the glow discharge functioned to suppress the oxidation of the TMS monomer, only limited nitrogen atoms were introduced into the deposited film and thus a very weak Si-N absorbance peak was observed in Figure 3b. The surface roughness of these films synthesized from various gas flow ratios are illustrated in Figure 5a-e. Many sharp protrusions with a peak height of about 16.6 \(\pm\) 3.42 nm could be seen from the surface of the film synthesized using the TMS-O\({}_{2}\) gas mixture (i.e., \(R\) = 0), as shown in Figure 5a. An apparent reduction in the amount of the protrusions was observed from the film synthesized using the TMS-O\({}_{2}\)-NH\({}_{3}\) gas mixture at a gas flow ratio of 0.25 (Figure 5b). The decrease in the density of these protrusion structures also led to a low surface roughness of 1.12 nm. As the ammonia gas was introduced to a gas flow ratio of 0.5, the surface of the synthesized film was almost free from protrusions and the lowest surface roughness of about 0.48 nm was achieved. However, when the gas flow ratio increased to 0.75, a few dot-like protrusions appeared on the surface of the deposited film, and therefore the surface roughness was degraded to 0.81 nm. For the film synthesized without oxygen incorporation (i.e., using the TMS-NH\({}_{3}\) gas mixture), a surface roughness of about 1.34 nm was measured as a consequence of large amounts of small dot-like protrusions spread over the film surface with a peak height of about (12.5 \(\pm\) 2.26) nm, as shown in Figure 5d. Figure 6a-c further investigated the surface morphologies of the film synthesized from the TMS-O\({}_{2}\)-NH\({}_{3}\) gas mixture at the gas flow ratios of 0, 0.5, and 1, respectively. The film synthesized from the TMS-O\({}_{2}\) gas mixture which contained sharp protrusions in the AFM image also had many circular patterns with a diameter larger than 200 nm in the SEM photograph, as presented in Figure 6a, whereas the dot-like protrusions distributed over the film deposited using the TMS-NH\({}_{3}\) gas mixture exhibited smaller circles with a diameter of approximately 100 nm (Figure 6c). Moreover, no significant patterns were observed  
Figure 4: **(a)** Atomic concentrations and **(b)** the ratios of O/Si and N/Si for the films synthesized from various gas flow ratios measured by X-ray photoelectron (XPS).