## 3 Results  
The Cu 20 and Cu 50 composite targets showed no electrical conductivity, while the Cu 80 targets showed a good sheet resistance of 2.1 \(\times\) 10\({}^{-3}\)\(\Omega\)/sq. Therefore, first, the nanocomposite thin film was fabricated using an RF power source, and the change in the physical properties of the thin film according to the Cu composition in the composite target was investigated. Figure 2a shows a cross-sectional TEM image of the Cu 80 MF thin film. The inserted element mapping image displays homogenous distribution of copper and fluorine atoms in the thin film. Cu metal nanoclusters were distributed in a spherical shape with a size of 10-20 nm. Figure 2b shows a lattice of nanocluster Cu in PPFC thin film matrix. The central Cu nanocluster domain, which is marked yellow, shows (111) plane orientation with a lattice distance of 0.208 nm. In this TEM image, we confirmed that Cu nanoclusters were well formed as a crystalline phase in the plasma polymer fluorocarbon matrix. Figure 3 shows the optical properties for a 100 nm thick Cu/PPFC nanocomposite thin film. Figure 3a shows the optical transmittance graph of the Cu/PPFC nanocomposite thin film deposited by RF sputtering. For comparison, the results for the thin films deposited using a pure PTFE target devoid of Cu are also shown. The optical properties of the Cu 20 RF and Cu 50 RF nanocomposite thin films were very similar to those of PTFE RF thin films. They exhibited a high transmittance of 90% or more in the visible light region and showed excellent transmission characteristics even in the infrared (IR) region. For the Cu 80 RF thin film, visible light transmittance was drastically decreased, and the transmittance was about 70% at a wavelength of 500 nm. As the Cu content increased, the characteristics of Cu in the nanocomposite thin film became more remarkable. Figure 3b shows the optical transmittance characteristics of the nanocomposite thin films deposited by RF, MF, and DC sputtering with a Cu 80 target, which has a low electrical resistance. The Cu 80 MF thin film exhibited a transmittance of less than 20% in the visible light region, whereas the Cu 80 DC thin film had a transmittance of less than 10%, which was similar to that of the Cu thin film. Thus, the transmittance is high in the order of Cu 80 RF \(>\) Cu 80 MF \(>\) Cu 80 DC, confirming that the physical properties of the films differ depending on the power source even when a composite target of the same composition is used. Remarkably, the Cu 80 MF nanocomposite thin film showed an electrical conductivity of 2 \(\times\) 10\({}^{4}\)\(\Omega\)/sq, whereas the electrical resistance of the Cu 80 DC thin film was as low as 34.55 \(\Omega\)/sq. Thus, the content and role of Cu in the nanocomposite thin films fabricated using the MF and DC power sources are greater than that in those obtained using RF. All other samples showed no electrical  
Figure 2: (a) Cross-sectional TEM image of the Cu 80 MF thin film and element mapping images, (b) nanocluster Cu in PPFC thin film matrix. conductivity. Figure 3c plots the optical absorption of the Cu/PPFC nanocomposite thin films as a function of the target composition and power source. The Cu 80 MF nanocomposite thin film exhibited an absorption peak at 618 nm, whereas that for the Cu 80 DC thin film was at 678 nm. This is attributed to the surface plasmon resonance phenomenon of the metal nanoclusters [1; 2] and confirms that the Cu nanoclusters are well formed in the PPFC matrix. It is expected that the size of the agglomeration of Cu nanoclusters in Cu 80 DC is larger than that in Cu 80 MF because the peak position is red shifted. The large size of the Cu nanoclusters also affects the conductivity of the nanocomposite thin films. Figure 3d compares the transmittance and color of each sample. The PTFE RF, Cu 20 RF, and Cu 50 RF nanocomposite thin films are quite transparent and colorless. However, the Cu 80 RF sample is slightly yellow, and the Cu 80 MF and Cu 80 DC samples are red in color and exhibit low transmittance.