Growth, microstructure and sintering behavior of nanosized silicon powders

The growth and properties of nanosized silicon particles produced by gas-phase reaction in a low-pressure silane plasma has been studied. In situ ion-mass spectroscopy and Mie scattering measurements were used to monitor the formation of powders. High resolution transmission electron microscopic (HREM) studies confirmed the observations made by Raman spectroscopy that the nanoparticles grow from medium range ordered clusters. Onset of crystallization was similar to 700 degrees C when structures ranging from very small crystalline ordered regions of 2.5-3.5 nm in size to fast-grown multiply twinned crystallites were formed. Size and surface roughness of the as-prepared powders were widely preserved throughout all stages of heating. It was observed that the powder morphology influences the sintering behavior. Silicon clusters which are formed during the powder synthesis acted as seeds for the crystallization process which led to the formation of polycrystalline particles. Classical sintering models offer inadequate explanation of sintering behavior, but hard-core/sinterable coating or particle sliding models can explain the sintering rate of this powder satisfactorily. (C) 1997 Elsevier Science B.V.