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

Al2O3 was deposited by reactive high-power impulse magnetron sputtering at 600 °C onto pre-deposited Ti2AlC(0001) thin films on α-Al2O3(0001) substrates. The Al2O3 was deposited to a thickness of 65 nm and formed an adherent layer of epitaxial γ-Al2O3(111) as shown by transmission electron microscopy. The demonstration of epitaxial growth of γ-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 γ-Al2O3(111)//Ti2AlC(0001) (out-of-plane) and ${{\rm\gamma {\hbox{-}} \rm Al}₂ \rm{O}₃ {(2\bar 20)\text{//}Ti}₂ {{\rm AlC}(11\bar 20)}}$γ- Al 2O3(22¯0)// Ti 2 AlC (112¯0) (in-plane) as determined by electron diffraction. Annealing in vacuum at 900 °C resulted in partial decomposition of the Ti2AlC by depletion of Al and diffusion into and through the γ-Al2O3 layer.