Epitaxial growth of gamma-Al2O3 on Ti2AlC(0001) by reactive high-power impulse magnetron sputtering

• Al2O3 was deposited by reactive high-power impulse magnetron sputtering at 600 degrees C onto pre-deposited Ti2AlC(0001) thin films on alpha-Al2O3(0001) substrates. The Al2O3 was deposited to a thickness of 65 nm and formed an adherent layer of epitaxial gamma-Al2O3(111) as shown by transmission electron microscopy. The demonstration of epitaxial growth of gamma-Al2O3 on Ti2AlC (0001) open prospects for growth of crystalline alumina as protective coatings on Ti2AlC and related nanolaminated materials. The crystallographic orientation relationships are gamma-Al2O3(111)//Ti2AlC(0001) (out-of-plane) and gamma-Al2O3(2 (2) over bar0)//Ti2AlC(11 (2) over bar0) (in-plane) as determined by electron diffraction. Annealing in vacuum at 900 degrees C resulted in partial decomposition of the Ti2AlC by depletion of Al and diffusion into and through the gamma-Al2O3 layer.

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