Surface Characterization of Silicon Nitride and Silicon Carbide Powders

The nature and composition of the surfaces of silicon nitride and silicon carbide powders were investigated using high voltage and high resolution transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and secondary ion mass spectrometry (SIMS). An amorphous oxide (or oxygen-rich) layer, approx. =3-5 nm thick, present on the powder surfaces forms strong bridges between particles. Both XPS and SIMS show that oxygen is the major impurity on the powder surfaces, but minor impurities such as chlorine, fluorine, carbon, iron and sodium are also revealed. The extent of the oxide layer was reduced substantially by washing the powder in anhydrous hydrofluoric acid or by treatment in an argon/hydrogen gas mixture at approx. =1300/sup 0/C. Surface treatment in the gas mixture did not cause further agglomeration of the powder.