Epitaxial layers of nickel fluoride on Si(111): Growth and stabilization of the orthorhombic phase

Abstract

The growth and crystal structure of NiF₂ layers on CaF₂/Si(111) heteroepitaxial substrates have been investigated. It has been shown that molecular beam epitaxy at temperatures of 350–450°C provides a stable epitaxial growth of the metastable orthorhombic NiF₂ phase (structural type CaCl₂) with a nickel fluoride layer thickness up to 1 μm in the metastable phase. According to X-ray diffraction, the unit cell parameters in layers of orthorhombic nickel fluoride are a = 4.5680(1) Å, b = 4.7566(3) Å, and c = 3.0505(2) Å, which are very close to the known values for this phase. It has been established that the condition $(100)_{NiF_2 } \left\| {(111)_{CaNiF_2 } } \right.$ holds over a wide range of growth parameters, which agrees with the results of the qualitative crystallographic analysis of the elements of similarity of the structures under consideration. The formation of a domain texture, the character of which depends on the growth temperature and nickel fluoride layer thickness, has been observed in the heterojunction plane.