Effect of Substrate Temperature on the Ordered Phase Formation in Sm–Ni Thin Film Deposited on Cu(111) Underlayer

Sm₁₇Ni₈₃ (at.%) alloy thin films are prepared on Cu underlayers hetero-epitaxially grown on MgO(111) single-crystal substrates by employing an ultra-high vacuum molecular beam epitaxy system. The substrate temperature is varied from 100 ^°C to 500 ^°C. The film growth behavior and the detailed resulting film structure are respectively investigated by in situ reflection high-energy electron diffraction and by a combination of out-of-plane and in-plane X-ray diffractions. With increasing the temperature up to 300 ^°C, formation of ordered SmNi₅ phase is recognized. The films deposited above 400 ^°C consist of only epitaxial SmNi₅ (0001) crystal, whereas the films deposited below the temperature include amorphous phase and/or a hexagonal ordered phase other than SmNi₅. When the temperature is increased from 300 ^°C to 500 ^°C, the long-range order degree of SmNi₅ film increases from 0.60 to 0.97. SmNi₅ phase formation is enhanced with increasing the temperature.