bcc Phase Formation in Fe, Co, and Ni Thin Films Deposited on GaAs(110) Substrates

Fe, Co, and Ni thin films are deposited on GaAs(110) substrates at room temperature using a radio frequency magnetron sputtering system. The film thickness is varied in a range between 1 and 40 nm. The growth behavior and the detailed resulting film structure are investigated by reflection high-energy electron diffraction and pole-figure X-ray diffraction. The bcc single-crystals nucleate on the substrates for all the film materials, though the bcc structure is metastable for Co and Ni materials. The metastable structure is stabilized through heteroepitaxial growth. The crystallographic orientation relationship is bcc(110)[001]||GaAs(110)[001]. With increasing the thickness beyond 2 nm, the bcc-Co and bcc-Ni crystals start to transform into fcc structure through atomic displacements parallel to the slide planes of bcc(101), bcc(011), bcc(011), and bcc(101) that are 60° inclined from the surface. The Co and Ni films thicker than 2 nm involve fcc crystals. On the contrary, Fe films possess bcc structure for all the thicknesses.