Observation and Formation of Si Nanostructures by Scanning Reflection Electron Microscopy

摘要

We have observed the oxidation process on clean Si surfaces using high-resolution scanning reflection electron microscopy (SREM) and formed nanostructures on them using focused electron beam (EB)-induced surface reactions. Si thermal oxidation occurs layer by layer, and the interface between the oxide film (<1 nm thickness) and Si substrate becomes atomically abrupt. When the sample is heated to 700-800°C after being irradiated by the focused EB on the surface at room temperature, SiO_2 film is selectively decomposed from the EB-irradiated area, resulting in the exposure of a clean Si substrate. The typical width of the clean Si 'open windows' is about 10 nm. Using selective reactions during heating after the deposition of Si and Ge films on the patterned samples, 10-20-nm-wide wires of Si and Ge crystals are formed on Si surfaces. Nanoscale grooves are also formed by selective etching of Si in the window area by supplying oxygen molecules during heating.