LEED Study of the Growth of Aluminum Films on the Ta(110) Surface

Growth of aluminumfilms on clean Ta(110) surfaces has been investigated by LEED techniques. Five phases of aluminum have been found, which are: (1) disordered Al(111), formed by depositing at T <600°C; (2) Al(111) c (2×2) formed by heating film, deposited at T <300°C, to 700°C; (3) Al(100) c (2×2), formed by heating film, deposited 300< T <600°C, to 700°C; (4) Epitaxial Al(111), formed by depositing film with substrate T in range 600< T <670°C; (5) Diffuse phase, formed by heating any of the preceding to 800°C. Two orientations of each structure have been observed; this results from the close match between primitive unit meshes of aluminum (111), (100) and Ta(110). A mechanism for the growth of Al(111) and Al(100) is suggested. Comparisons with some published LEED data on epitaxy are made.