Cubic-on-cubic growth of a MgO(001) thin film prepared on Si(001) substrate at low ambient pressure by the sputtering method

Magnesium oxide (MgO) films were prepared on a Si(001) substrate by the rf sputtering method at low ambient pressure using a metal target. The X-ray diffraction verified the epitaxial growth of MgO(001) with a cubic-on-cubic arrangement despite the large lattice mismatch between MgO(100) and Si(100), and contractions of the unit cell along both the out-of-plane and in-plane directions. Epitaxial growth is described as a domain epitaxial relation with a domain mismatch consisting of ( k × ℓ) lattice units of the Si substrate and ( m × n ) ones of the MgO film. To visualize the domain mismatch with combinations of k , ℓ, m and n , coherent strains were depicted on polar coordinates. The domain mismatch was estimated as a small value, which was further decreased by the contraction of the unit cell in the epitaxial MgO film.