Solid state amorphization at the room temperature deposited Ni∕Si(100) interface

The amorphous Ni–Si layer at the room temperature deposited Ni∕Si(100)-2×1 interface has been characterized by synchrotron ultraviolet photoemission. The growth kinetics of the amorphous Ni–Si layer strongly depends on the interaction between Ni and Si(100)-2×1 at the initial stage of Ni deposition. Three amorphous NixSiy alloys, a-NiSi2, a-Ni2Si, and a-NiSi, are evolved from three different Ni–Si bonding sites on Si(001)-2×1 at 1 ML Ni coverage. The a-NiSi2 bonding environment ceases to grow at 2 ML Ni coverage, which corresponds to the penetration of Ni atoms into the tetrahedral sites around the subsurface of Si(100)-2×1. While a-Ni2Si, and a-NiSi correspond to two different bonding sites above the Si dimers on Si(100)-2×1. A critical coverage of ∼4 ML exists, beyond which a-Ni2Si becomes the dominant phase as predicted by the “first phase rule” at a metal/Si interface. The growth mode of the amorphous Ni–Si layer was proposed to be layer-by-layer-like at Ni coverage less than 6 ML.