The magneto-transport properties of single proton-implanted ZnO and of
Li(7\%)-doped ZnO microwires have been studied. The as-grown microwires were
highly insulating and not magnetic. After proton implantation the Li(7\%) doped
ZnO microwires showed a non monotonous behavior of the negative
magneto-resistance (MR) at temperature above 150 K. This is in contrast to the
monotonous NMR observed below 50 K for proton-implanted ZnO. The observed
difference in the transport properties of the wires is related to the amount of
stable Zn vacancies created at the near surface region by the proton
implantation and Li doping. The magnetic field dependence of the resistance
might be explained by the formation of a magnetic/non magnetic heterostructure
in the wire after proton implantation.Comment: 6 pages with 5 figure