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single cry
stal
s with the
c axi
s either perpendicular or parallel to the broad face were implanted with Mg ion
s. The concentration
s of defect
s induced by implantation were monitored by optical ab
sorption mea
surement
s. In the Mg-implanted region, direct current electrical mea
surement
s were made between 296 and 445 K. At room temperature, an increa
se in the electrical conductivity of about 15 order
s of magnitude relative to the unimplanted region wa
s ob
served only in cry
stal
s with the
c axi
s perpendicular to the broad face of the
sample
s. The
I–
V characteri
stic
s reveal an ohmic behavior of the electrical contact on the implanted area. Mea
surement
s at different temperature
s sugge
st that the electrical conductivity i
s thermally activated with an activation energy of about 0.02 eV. We relate the enhancement in conductivity ob
served in the implanted region
s to intrin
sic defect
s created by the implantation, rather than with the implanted Mg ion
s.