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Point contact reactions between a Si nanowire and a Ni nanowire are reported in which the Si nanowire is transformed into a single crystal NiSi with an epitaxial interface which has no misfit dislocation. The reactions were carried out in situ in an ultrahigh vacuum transmission electron microscope. The growth of the NiSi occurs by the dissolution of Ni into the Si nanowire and by interstitial diffusion from the point of contact to the epitaxial interface. The point contact reactions have enabled the authors to fabricate single crystal NiSi/Si/NiSi heterostructures of atomically sharp interfaces for nanoscale devices. [ABSTRACT FROM AUTHOR]

In this work, the titanium germanosilicide (TiSiGe x) superlattice (SL) has been successfully fabricated. A monolayer of silicon atoms and bilayer of inversed titanium silicide constructed this novel superlattice periodically. A localized strain field has been found as a crucial factor via high resolution Annular Dark Field Scanning Transmission Electron Microscope (ADF-STEM) images, being generated by gradual segregation of germanium atoms. Germanium atoms would be excluded during the formation of the transition silicide. This phenomenon could be interpreted by thermodynamic preference. There was a substitution reaction between silicon and germanium, resulting from similar atomic volumes of both. In other words, germanium segregation pathway was based on where substitution occurred. Eventually, the excluded germanium atoms tended to accumulate at the boundary of TiSiGe x -SL, contributing to a discontinuous thin film layer. A novel titanium disilicide superlattice structure has been observed under in-situ transmission electron microscope at 750 °C. The preferred reaction pathway occurred from the titanium layer to the silicon germanium substrate, eventually forming the island-like superlattice. Additionally, germanium played a significant role in the emergence of the superlattice structure. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The atomic scale Silicidation of Ni-Si System by In-situ TEM Investigation could be divide into three steps. At the first step (250 °C), Ni would diffuse into Si substrate to synthesize triangular Ni 2 Si. Afterwards, continuous NiSi thin films would be synthesized at 400 °C. At last, trapezoid NiSi would react with Si to form NiSi 2 at third step (600 °C). Furthermore, the electric electrical properties of Ni-Si system were identified by four-point probe measurements; the resistivities of NiSi, Ni 2 Si and NiSi 2 were 14.13 µΩ∙cm, 22.80 µΩ∙cm and 37.77 µΩ∙cm, respectively. • The diffusion behaviour of Ni-Si system was investigated through in situ HRTEM. • Ni 2 Si and NiSi were diffusion controlled and NiSi 2 was nucleation controlled. • The resistivities of NiSi, Ni 2 Si and NiSi 2 were 14.1, 22.8, and 37.7 µΩ∙cm, respectively. • The diffusion rate could be calculated by in-situ TEM observation. • This work provides a novel method to obtain low resistivity silicide for IC devices. Nickel silicide has many advantages, such as low resistivity and low formation temperature; therefore, it has been widely used in the fields of solar cells, transistors and complementary metal-oxidesemiconductor (CMOS) devices. To obtain high-quality nickel-silicide thin film, solid-state reaction is a convenient and efficient fabrication method. For better understanding of the dynamic formation mechanism, we used in-situ transmission electron microscopy (TEM) to record the diffusion behavior during the heating process. In this work, three-steps annealing process to synthesize different nickel silicides corresponding to the various formation temperatures were investigated systematically. At 250 °C, the product of the first-step annealing was inverted-triangle Ni 2 Si, embedded in the Si substrate. Then, well-distributed NiSi thin film was synthesized, having the lowest resistivity among Ni-Si system at 400 °C. Finally, NiSi 2 , a Si-rich product, would form during the third-step annealing at 600 °C. NiSi 2 product and Si substrate have small lattice mismatch; thus, the epitaxial relationship would be observed. We provide the evidence of diffusion behaviors and structural identification of Ni-Si system. Furthermore, these results are beneficial for the formation of specific nickel silicides, which is expected to optimize the fabrication of microelectronics. [ABSTRACT FROM AUTHOR]