INTERNAL STRUCTURE AND INTERFACE EFFECTS OF OXIDE-COVERED SILICON NANOCRYSTALLITES BY VARIOUS GAS PHASE PROCESSES

摘要

Various gas phase processes have been employed to produce oxide-covered Si nanocrystal-lites. Single crystalline and almost defect-free Si nanoparticles are obtained only by condensation from the gas phase at sufficiently high supersaturation. At low supersaturation, and by thermal decomposition of Si suboxide, respectively, the particles are formed within an amorphous matrix and frequently exhibit planar defects characteristic of growth processes during solid phase crystallization. For Si particles not embedded in a matrix a size dependence of the thickness of the unavoidable surface oxide was observed. Simultaneously, size-dependent changes of the lattice spacings were measured. Accordingly, a negative interface stress was derived that effectively limits the surface oxide formation at very small particle sizes. Photoluminescence emission in the visible region was found for both supported and matrix-embedded Si nanocrystallites.