  Precise control of the conductivity of semiconductors through doping has
enabled the creation of advanced electronic devices, similarly, the ability to
control the conductivity in oxides can enable novel advanced electronic and
optoelectronic functionalities. While this was successfully shown for
moderately insulating oxides, such as In2O3, a reliable method for increasing
the conductivity of highly insulating, wide bandgap dielectrics, such as
aluminum oxide (Al2O3), has not been reported yet. Al2O3 is a material of
significant technological interest, permeating diverse fields of application,
thanks to its exceptional mechanical strength and dielectric properties. Here
we present a versatile method for precisely changing the conductivity of Al2O3
. Our approach greatly exceeds the magnitude of the best previously reported
change of conductivity in an oxide. Our method uses focused ion beam to produce
conductive zones with nanoscale resolution within the insulating Al2O3 matrix.
We investigated the source of conductivity modulation and identified
trap-assisted conduction in the ion damage-induced defects as the main charge
transport mechanism. Temperature-dependency of the conductivity and optical
characterization of the patterned areas offer further insight into the nature
of the conduction mechanism. We also show that the process is extremely
reproducible and robust against moderate annealing temperatures and chemical
environment. The record conductivity modulation, combined with the nanoscale
patterning precision allows the creation of conductive zones within a highly
insulating, mechanically hard, chemically inert, and bio-compatible matrix,
which could find broad applications in electronics, optoelectronics, and
medical implants
