Structure of amorphous boron

The short range order structure of amorphous boron is studied. Three sample materials of different appearances, film, whisker and fibre, are prepared by chemical vapour deposition by the reduction of BCl₃ with hydrogen. The reduced radial distribution functions (reduced RDFs) derived from their X-ray or electron diffraction patterns are found to be almost identical among the three samples. The reduced RDFs are compared with those calculated for the four crystalline modifications of boron, i.e.a-rhombohedral,a-tetragonal,ß-tetragonal andß-rhombohedral boron. The reduced RDFs of amorphous boron are found to be similar to those of theß-tetragonal andß-rhombohedral boron. From the similarity of physical and chemical properties and co-existence in deposition, the short range order structure of amorphous boron is shown to be closer to that of theß-rhombohedral modification.