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Papers by Michael McConnell
The authors report the use of plasma-enhanced atomic layer deposition (PEALD) to fabricate single... more The authors report the use of plasma-enhanced atomic layer deposition (PEALD) to fabricate
single-electron transistors (SETs) featuring ultrathin (1 nm) tunnel-transparent SiO2 in Ni-SiO2-
Ni tunnel junctions. They show that, as a result of the O2 plasma steps in PEALD of SiO2, the top
surface of the underlying Ni electrode is oxidized. Additionally, the bottom surface of the upper Ni
layer is also oxidized where it is in contact with the deposited SiO2, most likely as a result of
oxygen-containing species on the surface of the SiO2. Due to the presence of these surface parasitic
layers of NiO, which exhibit features typical of thermally activated transport, the resistance of Ni-
SiO2-Ni tunnel junctions is drastically increased. Moreover, the transport mechanism is changed
from quantum tunneling through the dielectric barrier to one consistent with thermally activated
resistors in series with tunnel junctions. The reduction of NiO to Ni is therefore required to restore
the metal-insulator-metal (MIM) structure of the junctions. Rapid thermal annealing in a forming
gas ambient at elevated temperatures is presented as a technique to reduce both parasitic oxide
layers. This method is of great interest for devices that rely on MIM tunnel junctions with ultrathin
barriers. Using this technique, the authors successfully fabricated MIM SETs with minimal trace of
parasitic NiO component. They demonstrate that the properties of the tunnel barrier in nanoscale
tunnel junctions (with <1015 m2 in area) can be evaluated by electrical characterization of SETs.
The authors report the use of plasma-enhanced atomic layer deposition (PEALD) to fabricate single... more The authors report the use of plasma-enhanced atomic layer deposition (PEALD) to fabricate
single-electron transistors (SETs) featuring ultrathin (1 nm) tunnel-transparent SiO2 in Ni-SiO2-
Ni tunnel junctions. They show that, as a result of the O2 plasma steps in PEALD of SiO2, the top
surface of the underlying Ni electrode is oxidized. Additionally, the bottom surface of the upper Ni
layer is also oxidized where it is in contact with the deposited SiO2, most likely as a result of
oxygen-containing species on the surface of the SiO2. Due to the presence of these surface parasitic
layers of NiO, which exhibit features typical of thermally activated transport, the resistance of Ni-
SiO2-Ni tunnel junctions is drastically increased. Moreover, the transport mechanism is changed
from quantum tunneling through the dielectric barrier to one consistent with thermally activated
resistors in series with tunnel junctions. The reduction of NiO to Ni is therefore required to restore
the metal-insulator-metal (MIM) structure of the junctions. Rapid thermal annealing in a forming
gas ambient at elevated temperatures is presented as a technique to reduce both parasitic oxide
layers. This method is of great interest for devices that rely on MIM tunnel junctions with ultrathin
barriers. Using this technique, the authors successfully fabricated MIM SETs with minimal trace of
parasitic NiO component. They demonstrate that the properties of the tunnel barrier in nanoscale
tunnel junctions (with <1015 m2 in area) can be evaluated by electrical characterization of SETs.