XPS, TEM and SAD investigations of nanosized CoxByHz particles obtained by two different borohydride methods

The nanosized CoxByHz particles synthesised by the 'tea' and 'antigravity' methods using a borohydride reduction process have been subjected to structure and composition studies by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and selected area diffraction (SAD). The amounts of the elements Co, B, O-2, H-2 and C as mean volume values, and surface values for the as-prepared particles, as well as after Ar+ etching to a depth of about 15 nm and 30 nm from the initial particle surface, are determined. About 1.5 atoms of cobalt per atom of boron correspond to samples obtained by the 'antigravity' method. The binding energy (BE) of Is electrons of boron atoms has only one value. These particles are angular and are in the typical nanocrystalline state. In the case of samples prepared by the 'tea' method, two atoms of cobalt per atom of boron are found. The presence of two kinds of BE (B-I and B-II) of 1s electrons of boron atoms in the particles obtained by the 'tea' method is observed and almost equal amounts of these two states are established in the spectrum. The particles' shape and structure are typical of the amorphous state. The fact that there is one peak when the 'antigravity' method is applied, in contrast to the two peaks with the 'tea' method indicates the presence of a metal amorphous state in the latter case.