In-situ Transmission Electron Microscope Investigation of Atomic-scale Titanium Silicide Monolayer Superlattice.

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]