Doping and segregation of impurity atoms in silicon nanowires

Raman peaks were observed at about 618 and 643 cm-1 for SiNWs synthesized by using a Si target with B. The peak frequencies are in good agreement with those of a local vibrational mode of B in Si crystal. The Fano broadening due to a coupling between the discrete optical phonon and a continuum of interband hole excitations was also observed in the optical phonon peak, which indicates heavily B doping. These results prove that B atoms were doped in substitutional sites of the crystalline Si core of SiNWs. ESR measurements were also performed to investigate defects and P donor/conduction electrons in P-doped SiNWs. The observation of ESR signal due to conduction electrons clearly showed that P atoms were doped in substitutional sites of the crystalline Si core of SiNWs. The segregation behaviors of B and P were investigated by using B local vibrational peaks and Fano broadening for B-doped SiNWs, while an ESR signal of conduction electrons was used for P-doped SiNWs.