Abstract
Planview and cross-sectional transmission electron microscopy (XTEM), Auger electron spectroscopy and X-ray diffraction (XRD) have been applied to study the interfacial reactions of palladium thin films on Ge(111) and Ge(001) with particular emphasis on the epitaxial growth of Pd 2 Ge on Ge(111). Polycrystalline palladium and Pd 2 Ge grains as well as epitaxial Pd 2 Ge regions were observed in as-deposited (111) samples. Epitaxial Pd 2 Ge was found to cover about 60% of the germanium surface area in samples annealed at 160°C. The orientation relationships between epitaxial Pd 2 Ge and the germanium substrate were determined to be Pd 2 Ge[0001]|Ge[111] and Pd 2 Ge( 10 ̄10)| Ge ̄220). The Pd 2 Ge-Ge interface was found to be not very smooth. In samples annealed at 250-500°C, only polycrystalline PdGe was found. Randomly oriented polycrystalline palladium and Pd 2 Ge were found in as-deposited (001) samples. In samples annealed at 160°C, Pd 2 Ge and PdGe grains were found to coexist. Only polycrystalline PdGe grains were observed in samples annealed at 250-500°C. XTEM observations and XRD data revealed the presence of an epitaxial Pd 2 Ge layer, about 20-30 nm in thickness, locally between the palladium metal layer and germanium substrate in as-deposited (111) samples, irrespective of palladium metal layer thickness (30-220 nm) and deposition rate (0.1-0.7 nm s -1 ). The results for Pd 2 Ge and PdGe formation on germanium are compared with those for Pd 2 Si and PdSi formation on silicon. © 1988.