The influence of H impurities on the formation of C nano-clusters in C-enriched (>1017/cm3) float-zone Si was studied by means of electron paramagnetic resonance together with uniaxial stress experiments. The H was incorporated by proton implantation at room temperature. Electron paramagnetic resonance was used to study previously unidentified electron paramagnetic resonance defects with S = 1/2 and a C2-symmetry g-tensor. This was observed in fast-neutron irradiated Si. It was found that H implantation of float-zone Si with high contents of C generated, upon subsequent annealing above about 250C, the most prominent electron paramagnetic resonance signal of the defect. Various sets of hyperfine satellites were clearly revealed. Uniaxial stress experiments revealed a very large value (~2.8eV) for the activation energy of atomic reorientation. This was in good agreement with the cluster nature of the defect. It was suggested that the presence of H led to a strongly coordinated formation of nano-clusters which included C and self-interstitial atoms. It was proposed that the electronic structure of this defect corresponded to a double donor in a positive charge state.

Hydrogen-Enhanced Clusterization of Carbon in Crystalline Silicon. V.Gorelkinskii, A.Abdullin, B.N.Mukashev, G.O.Tojibaev: Materials Science and Engineering C, 2003, 23[1-2], 67-70