Multiple bonds in hydrogen-free amorphous silicon

The short-range-order structure and electron paramagnetic resonance of amorphous silicon prepared by vacuum sublimation and by ion implantation are investigated. It is found that amorphous silicon with atoms in the sp2 hybrid state is formed in the annealing of evaporated silicon at 500 °C or in the irradiation of a silicon single crystal with neon at a dose greater than or of the order of 1017 cm−2. In the latter case the amorphous material is depthwise inhomogeneous and contains a layered structure consisting of silicon atoms with a period of 5.16 Å. In each case an ESR signal with a g factor g⋍2.0048, which corresponds to a dangling bond of a silicon atom in the sp2 state, is observed.