Tungsten carbide (WC) has been suggested as a new buffer layer for the GaN-on-Si technology. We have investigated and optimized the sputtering condition of WC layer on the Si-substrate. We confirmed the suppression of the Si melt-back phenomenon. In addition, surface energy of WC/Si layer was measured to confirm the possibility as a buffer layer for GaN growth. We found that the surface energy(γ=82.46 mJ/cm²) of WC layer is very similar to that of sapphire substrate(γ=82.71 mJ/cm²). We grow GaN layer on the WC buffer by using gas-source MBE, and confirm that it is available to grow a single crystalline GaN layer.

In this study, the surface modification of copper foil using an inductively coupled O2 / Ar plasma as O2 gas fraction (0∼100%) was investigated in order to improve the surface characteristics. After plasma treatment, the measurement of the surface roughness, surface contact angle and surface energy were performed for the surface analysis of copper foil. As a result, the surface roughness and the surface energy were increased. And plasma diagnostics was performed by a double Langmuir probe (DLP) and optical emission spectroscopy (OES). Using these results, the plasma surface modification mechanism was investigated.