Giant Conductivity Modulation of Aluminum Oxide Using Focused Ion Beam

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 In 2 O 3, a reliable method for increasing the conductivity of highly insulating, wide bandgap dielectrics, such as aluminum oxide (Al 2 O 3 ), has not been reported yet. Al 2 O 3 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 Al 2 O 3 . Our approach greatly exceeds the magnitude of the best previously reported change of conductivity in an oxide (In 2 O 3 ). With an increase in conductivity of ∼14 orders of magnitude, our method presents ∼10 orders of magnitude higher change in conductivity than the best previously reported result. Our method can use focused ion beam to produce conductive zones with nanoscale resolution within the insulating Al 2 O 3 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. The 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 biocompatible matrix, which could find broad applications in electronics, optoelectronics, and medical implants.