3dtransition metals on InP(110): A comparative study of reactive interface evolution

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Abstract
Room-temperature formation of reactive M/InP(110) interfaces (where M denotes the 3d transition metals Ti, Cr, Fe, and Co) have been studied using high-resolution synchrotron radiation photoemission. Detailed line-shape analysis shows that these metals disrupt the substrate to form phosphides and release In atoms to the free surface. For Ti and Cr depositions, there are also ultrathin transition regions or precursors to reaction, which are not observed for Fe and Co, but these precursors do not correlate clearly with Schottky barrier development or final height. Critical coverages of ∼7 Å for Ti, ∼4 Å for Cr, ∼2.7 Å for Fe, and ∼1.6 Å for Co are found which reflect morphology changes in the disrupted overlayer, namely, growth of metal-phosphide nuclei and expulsion of In from the region where compound formation dominates. For depositions greater than ∼22 Å for Ti, ∼12 Å for Cr, and ∼7 Å for Fe and Co, the interface reactions become diffusion limited and the phosphide-rich regions are buried by metallic overlayers. At the same time, In atoms released during earlier stages continue to segregate because of their low solubility in these metals. Comparisons are made to GaAs-based interfaces where epitaxial growth of Fe and Co was observed.