In this work, thin films of pure Cu, and Cu with 0.02 or 2.98 wt % Ti were deposited on SiO 2 covered Si substrates. The samples were annealed at 500-800°C in vacuum to investigate their morphological evolution, interfacial reaction, and diffusion. X-ray diffraction reveals Cu͑111͒ and Cu͑200͒ peaks for pure Cu and Cu͑0.02 wt % Ti͒ films. However, the Cu͑2.98 wt % Ti͒ film exhibits a very weak Cu͑200͒ peak, indicating that this film is textured in ͗111͘ orientation. Concurrently, scanning electron microscopy shows that the grain size of the Cu͑2.98 wt % Ti͒ film is significantly smaller than those of pure Cu and Cu͑0.02 wt % Ti͒ films. In addition, Cu͑2.98 wt % Ti͒ film remains smooth after annealing up to 800°C, while the other two films become discontinuous. X-ray photoelectron spectroscopy indicates that a TiO x layer has formed at the Cu(0.02 wt % Ti)/SiO 2 and Cu(2.98 wt % Ti)/SiO 2 interfaces after 700°C annealing. Nevertheless, the TiO x layer is thicker in the Cu͑2.98 wt % Ti͒ system than in the Cu͑0.02 wt % Ti͒ system. Consequently, the Cu͑2.98 wt % Ti͒ film shows no diffusion of Cu into SiO 2 at temperatures up to 700°C. Connections between the segregation of Ti addition and the morphological/interfacial characteristics are discussed.

We report experimental studies on the formation of Type 2 micropipe defects in 4H-SiC crystals grown by a physical vapor transport method. Compared with Type 1 micropipes, Type 2 micropipes exhibit new features allowing them to lie at an oblique angle about 12u to the [0001] crystal axis and are smaller in size than Type 1 micropipes. By changing the growth conditions, we find that a smaller axial temperature gradient and a larger grain size in the SiC source are beneficial to eliminate the Type 2 micropipes. We think that the liquid silicon is responsible for the formation of Type 2 micropipes. A possible formation mechanism for Type 2 micropipes is put forward.