Drastic change of phase interference by small diffusion of heavy-mass electrode atoms in carbon nanotubes and phase switching device

We slightly diffuse atoms of electrode materials into one end of multiwalle d carbon nanotubes (MWNTs), grown using nanoporous alumina membranes. Diffu sion of the light-mass materials (carbon and aluminum) lead to weak localiz ation in Altshuler-Aronov-Spivak oscillation, consistent with past reports. In contrast, we find that diffusion of heavy-mass materials (gold and plat inum) at the volume ratio of only about 5% change this weak localization to antilocalization. It is understood by a drastic change of the phase interf erence caused by the injection of spin-flipped electrons due to spin-orbit interaction in the diffusion region, in the entire part of the MWNTs. We al so propose an electron-wave phase switching circuit using this effect. (C) 2001 American Institute of Physics.