Crystallographic analysis and observation of surface micro-areas using microprobe reflection high-energy electron diffraction

Abstract

A microprobe reflection high-energy electron diffraction (RHEED) technique and its applications to crystallographic analyses and observations of surface micro-areas are reported. Microprobe RHEED is a kind of scanning electron microscopy which uses reflection diffraction spot intensities as an image signal. It was used to analyze crystalline states of lateral epitaxial Si films on SiO₂ substrates (silicon on insulator: SOI). It was found that laser-induced lateral epitaxial regrowth was initiated near the SiO₂ edges. The technique was also used to observe atomic layer structures on crystalline material surfaces. The changes in surface topography of metal-deposited Si(111), and of Si(111) and Si(001) substrates during Si molecular beam epitaxial (MBE) growth, were observed. Growth of ultrathin metal films on Si(111) surfaces was found to be strongly affected by atomic steps on the substrate. Observation of Si MBE growth provided the first known direct evidence that RHEED intensity oscillations occur as a result of layer-by-layer two-dimensional nucleation growth. These results show that microprobe RHEED analysis is a powerful method for characterizing crystalline material surfaces and for studying surface reaction processes with atomic-layer depth resolution.