Changes in Gd2O3 films grown on Si(100) as a function of nitridation temperature and Zr incorporation

We investigated Gd₂O₃ and Zr-incorporated Gd₂O₃ films grown on Si (100) as a function of nitridation temperature under an NH₃ ambient and the incorporation of Zr into the film. The formation of a silicide layer at the interfacial region was suppressed in cases of Zr-incorporated or NH₃-nitried Gd₂O₃ films. The crystalline structure was affected when zirconium, with a relatively small ionic radius, was substituted with gadolinium. When the concentration of Zr atoms in a Gd₂O₃ film reaches a specific level (Gd_0.6Zr_1.9O_4.3), phase transition occurred from cubic Gd₂O₃ to monoclinic ZrO₂. However, the monoclinic phase disappeared after nitridation at 900 °C in an NH₃ ambient. The majority of the nitrogen atoms accumulated near the interface in the films and the concentration of incorporated N increased with increasing Zr content and NH₃ annealing temperature. Moreover, nitrogen atoms bonded to Zr-silicate at the interface, in preference to ZrO₂ in the film. These incorporation characteristics of nitrogen into Zr-incorporated Gd₂O₃ film have an effect on the thermal stability and crystalline structure of a film.     

Transmission electron microscopy study of the initial growth stage of GaSb grown on Si (001) substrate by molecular beam epitaxy method

The microstructural properties at the initial growth stage of the GaSb heteroepitaxial growth on a silicon (Si) substrate were investigated using transmission electron microscopy. Well-separated and tall GaSb islands were observed when GaSb was directly grown on a Si substrate (sample A). On the other hand, GaSb was grown to the coalesced and flat islands when a low-temperature AlSb buffer (sample B) was introduced. The different morphologies of the GaSb islands were related to the microstructural properties of the interface between the GaSb and the Si substrate. The GaSb/Si interface was rough, and disordered atomic arrangements were observed at the interface in sample A. On the other hand, the GaSb/Si interface was flat, and well-ordered atomic arrangements appeared at the interface in sample B. Entirely different mechanisms for the relaxation of a misfit strain were demonstrated from a microstructural viewpoint.