Multiple bonds in hydrogen-free amorphous silicon

The short-range-order structure and electron paramagnetic resonance of amor phous silicon prepared by vacuum sublimation and by ion implantation are in vestigated. It is found that amorphous silicon with atoms in the sp(2) hybr id state is formed in the annealing of evaporated silicon at 500 degrees C or in the irradiation of a silicon single crystal with neon at a dose great er than or of the order of 10(17) cm(-2). In the latter case the amorphous material is depthwise inhomogeneous and contains a layered structure consis ting of silicon atoms with a period of 5.16 Angstrom. In each case an ESR s ignal with a g factor g similar or equal to 2.0048, which corresponds to a dangling bond of a silicon atom in the sp(2) state, is observed. (C) 1999 A merican Institute of Physics. [S1063-7826(99)02408-4].