Partial epitaxial growth of Ni 2Ge and NiGe on Ge(111)

Abstract

Transmission electron microscopy (TEM), scanning electron microscopy (SEM), Rutherford backscattering (RBS) channeling and Read camera glancing X-ray diffraction analysis have been applied to study the interfacial reactions of nickel thin films on Ge(111) with particular emphasis on the epitaxial growth of Ni 2Ge and NiGe at this surface. Ni 2Ge and NiGe were found to grow epitaxially at 160°C and 250°C respectively. Epitaxial Ni 2Ge regions, 30 nm in average size, were observed to cover about 100% of the surface area. The orientation relationships were analyzed to be Ni 2Ge[0001]Ge[111] and Ni 2Ge( 10 ̄ 10) Ge ̄ 220). The best NiGe epitaxy was obtained in samples annealed at 500°C for 1 h. The orientation relationships were determined to be NiGe[010]Ge[111] and NiGe(002) Ge ̄ 220). The average size of epitaxial regions was measured to be about 4.5 μm. The areal fraction of epitaxial regions for NiGe was found to be about 70%. NiGe was found to agglomerate to form islands after 600°C annealing. The results obtained from Read camera glancing-angle X-ray diffraction and RBS channeling analysis were found to agree with those from TEM and SEM examinations.