Effect of Elastic Strain Fluctuation on Atomic Layer Growth of Epitaxial Silicide in Si Nanowires by Point Contact Reactions

Effects of strain impact a range of applications involving mobility change in field-effect-transistors. We report the effect of strain fluctuation on epitaxial growth of NiSi₂ in a Si nanowire via point contact and atomic layer reactions, and we discuss the thermodynamic, kinetic, and mechanical implications. The generation and relaxation of strain shown by in situ TEM is periodic and in synchronization with the atomic layer reaction. The Si lattice at the epitaxial interface is under tensile strain, which enables a high solubility of supersaturated interstitial Ni atoms for homogeneous nucleation of an epitaxial atomic layer of the disilicide phase. The tensile strain is reduced locally during the incubation period of nucleation by the dissolution of supersaturated Ni atoms in the Si lattice but the strained-Si state returns once the atomic layer epitaxial growth of NiSi₂ occurs by consuming the supersaturated Ni

Gold Catalyzed Nickel Disilicide Formation: A New Solid–Liquid–Solid Phase Growth Mechanism

The vapor–liquid–solid (VLS) mechanism is the predominate growth mechanism for semiconductor nanowires (NWs). We report here a new solid–liquid–solid (SLS) growth mechanism of a silicide phase in Si NWs using in situ transmission electron microcopy (TEM). The new SLS mechanism is analogous to the VLS one in relying on a liquid-mediating growth seed, but it is fundamentally different in terms of nucleation and mass transport. In SLS growth of Ni disilicide, the Ni atoms are supplied from remote Ni particles by interstitial diffusion through a Si NW to the pre-existing Au–Si liquid alloy drop at the tip of the NW. Upon supersaturation of both Ni and Si in Au, an octahedral nucleus of Ni disilicide (NiSi₂) forms at the center of the Au liquid alloy, which thereafter sweeps through the Si NW and transforms Si into NiSi₂. The dissolution of Si by the Au alloy liquid mediating layer proceeds with contact angle oscillation at the triple point where Si, oxide of Si, and the Au alloy meet, whereas NiSi₂ is grown from the liquid mediating layer in an atomic stepwise manner. By using in situ quenching experiments, we are able to measure the solubility of Ni and Si in the Au–Ni–Si ternary alloy. The Au-catalyzed mechanism can lower the formation temperature of NiSi₂ by 100 °C compared with an all solid state reaction

Gold Catalyzed Nickel Disilicide Formation: A New Solid–Liquid–Solid Phase Growth Mechanism

The vapor–liquid–solid (VLS) mechanism is the predominate growth mechanism for semiconductor nanowires (NWs). We report here a new solid–liquid–solid (SLS) growth mechanism of a silicide phase in Si NWs using in situ transmission electron microcopy (TEM). The new SLS mechanism is analogous to the VLS one in relying on a liquid-mediating growth seed, but it is fundamentally different in terms of nucleation and mass transport. In SLS growth of Ni disilicide, the Ni atoms are supplied from remote Ni particles by interstitial diffusion through a Si NW to the pre-existing Au–Si liquid alloy drop at the tip of the NW. Upon supersaturation of both Ni and Si in Au, an octahedral nucleus of Ni disilicide (NiSi₂) forms at the center of the Au liquid alloy, which thereafter sweeps through the Si NW and transforms Si into NiSi₂. The dissolution of Si by the Au alloy liquid mediating layer proceeds with contact angle oscillation at the triple point where Si, oxide of Si, and the Au alloy meet, whereas NiSi₂ is grown from the liquid mediating layer in an atomic stepwise manner. By using in situ quenching experiments, we are able to measure the solubility of Ni and Si in the Au–Ni–Si ternary alloy. The Au-catalyzed mechanism can lower the formation temperature of NiSi₂ by 100 °C compared with an all solid state reaction