Structural properties of epitaxial γ-Al2O3(111) thin films on 4H-SiC(0001)

Al2O3 thin films were grown on 4H-SiC (0001) by thermal atomic layer deposition and were crystallized to the gamma-Al2O3 phase by rapid thermal annealing in N-2 at 1100 degrees C. The films were found to be chemically stable during processing based on x-ray photoelectron spectroscopy. The change in film structure was initially confirmed by reflection high-energy electron diffraction. As shown by high-resolution transmission electron microscopy images, the abrupt interface of the as-deposited films with the 4H-SiC substrate was preserved during crystallization, indicating no interfacial reaction. Selected area electron diffraction and synchrotron-based x-ray diffraction established an epitaxial relationship of gamma-Al2O3 (111) parallel to 4H-SiC (0001) and in-plane orientation of gamma-Al2O3 (1 (1) over bar0) parallel to 4H-SiC (11 (2) over bar0). No other alumina phases or orientations were observed and no in-plane misorientation was observed in the 27 angstrom Al2O3 films. The full width at half maximum of the gamma-Al2O3 (222) rocking curve is 0.056 degrees, indicating a lack of mosaic spread and a high-quality crystalline film. Twinning around the gamma-Al2O3 [111] axis was the only defect observed in these films. (c) 2007 American Institute of Physics.