## 5 Results and Discussion
The electron density fluctuations due to the standing wave effect were prominent in the quasi-coaxial TEM mode, and the effect decreased along the X-axis. When comparing the electron density according to the wave mode, in both cases, the electron density near the substrate was measured to be approximately 1.5-2 times higher in the circular TE\({}_{11}\) mode than that in the quasi-coaxial line TEM mode. In the experiment, the rate of increase in density was 2, which was more than the simulation value of 1.5. This is because the electron loss from the quartz window surface along the direction of the electric field was not considered in detail in this simulation model. Figure 14: (**a**) Electron density at the substrate (Experiment) and (**b**) electron density at the substrate (Simulation). In the experiment, the energy distribution function of electrons of radial distance \(\geq\)20 mm followed the Maxwell distribution function. The electron temperature profile shown in Figure 15a is consistent with the simulation results in Figure 15b, which shows that when the radial distances \(>\)20 mm from the quartz window surface, the electron temperature is weakly dependent on the radial distance. To consider each source and the plasma characteristics more deeply, it was necessary to consider the effects by resolving the electric field into the radial and axial direction electric field components. The material properties of plasma act like a lossy medium, which cause not only the transverse field components but also the axial field components to exist [16; 17]. The presence of an axial component of the wave electric field in the quasi-coaxial line source was detailed by [PERSON] et al. [61]. In the presence of the axial component of the wave field, in the high electron density region (ne \(>\) 10\({}^{18}\)), internal wave was represented by a wave that propagated near the window surfaces along the axial direction. Power dissipation in the plasma chamber is concentrated near the dielectric window surface region, so the presence of an internal wave is important as a component that affects the electron heating in the axial direction. In Figure 12, a normalized norm \(|E|\) of the inner conductor (green line) and the window surface (purple line) in the quasi-coaxial TEM source are set to compare with the electron density distribution along the axial direction (Z-axis) in the XZ plane. Normalized norm \(|E|\) was expressed as the RSS (Root Sum Square: \(\sqrt{\frac{\sum\limits_{i=1}^{n}\sigma_{i}^{2}}{\sigma_{i}^{2}}}\)) of the axial and radial components of the electric field. Figure 12 shows that the electron density distribution along the axial direction in the XZ plane follows the norm \(|E|\) profile in the window surface rather than the profile of the norm \(|E|\) in the inner conductor surface. This result is due to the axial field formed near the window surface region, and it can be observed in more detail in Figure 16. Figure 16 shows the distribution of the power dissipation, and the electron density distributions according to the electric field components in the axial and radial directions. Figure 8:0 (**a**) Electron temperature at the substrate (Experiment) and (**b**) electron temperature at the substrate (Simulation). In the TEM wave mode, because the radially radiated electric field was directed in all directions with the same value, \(E_{x}\) (= \(E_{y}\)) represented the component of the radial field, and \(E_{z}\) represented the component of the axial field. In the case of the axial electric field \(E_{z}\), the field strength is the highest at 4 \(\times\) 10\({}^{3}\) V/m for the window surface, and for the radial electric field \(E_{x}\), the field strength is the highest at 3 \(\times\) 10\({}^{4}\) V/m for the inner conductor surface. In Figure 16a,c, it is possible to compare the spatial distribution of the electron density according to each electric field component.