Abstract
Co thin films are prepared on GaAs(111) substrates at temperatures ranging from room temperature to 600 oC by radio-frequency magnetron sputtering. The growth behavior and the detailed resulting film structure are investigated by in-situ reflection high-energy electron diffraction and X-ray diffraction. In early stages of film growth at temperatures lower than 200 oC, Co crystals with metastable A 2 (bcc) structure are formed, where the crystal structure is stabilized through hetero-epitaxial growth. With increasing the film thickness beyond 2 nm, the metastable structure starts to transform into more stable A 1 (fcc) structure through atomic displacements parallel to the A 2{110} close-packed planes. The crystallographic orientation relationship between the A 2 and the transformed A 1 crystals is A 1{111} || A 2{110} . When the substrate temperature is higher than 400 oC, Ga atoms of substrate diffuse into the Co films and a Co-Ga alloy with bcc-based ordered structure of B 2 is formed.
Highlights
Cobalt (Co) is a 3d ferromagnetic transition metal which has two stable crystallographic phases, A3 and A1
A Co single-crystal film with metastable A2 structure is obtained in an early stage of film growth on GaAs(111) substrate, similar to the cases of films deposited on GaAs(100) [4,5,6,7] and GaAs(110) [4, 8, 9] substrates
Co thin films are prepared on GaAs(111) substrates by varying the thickness from 1 to 40 nm and the substrate temperature from room temperature (RT) to 600 °C
Summary
Cobalt (Co) is a 3d ferromagnetic transition metal which has two stable crystallographic phases, A3 (hcp) and A1 (fcc). Application of Co thin film with A2 structure is providing a new possibility a new possibility in the development of magnetic devices. Understanding of the formation conditions is important in order to apply the A2-Co film for practical applications. Formation of A2 phase has been recognized for Co films of a few nm thicknesses grown on GaAs substrates of (100) [4,5,6,7] and (110) [4, 8, 9] orientations by molecular beam epitaxy. There are very few reports on preparation of Co films on GaAs(111) substrates. Co films are deposited on GaAs(111) substrates by magnetron sputtering, which is suitable for practical applications. The growth process and the detailed resulting film structure are investigated
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