Characterization of thin crystalline alumina supports prepared by electron irradiation

Thin crystalline alumina supports (substrates) were produced by electron irradiation of amorphous films in an electron microscope. The resulting alumina structures have been characterized by transmission electron microscopy and transmission electron diffraction. The results show that the structure of alumina is dependent on irradiation conditions. A low irradiation energy leads to 2000-A-sized grains consisting of eta- and/or #betta#- and delta-Al2O3 whilst high irradiation energy yields micron-sized [0001]-, [11 anti 2 0]-, and [21 anti 3 2]-oriented α-Al2O43 (sapphire) grains. Thee α-Al2O3 substrates were used to study the structure of Au and Pd particles condensed on (0001) and (11 anti 2 0) areas at a temperature lower than 5000C. When the substrate temperature is between 400 and 5000C, the tetrahedral shape of the particles is influenced by the symmetry of the (0001) substrate but the particles have no azimuthal orientation