Coulomb barrier creation by means of electronic field emission in nanolayer capacitors

The main mechanism of energy loss in capacitors with nanoscale dielectric films is leakage currents. Using the example of Al-Al 2 O 3 -Al, we show that there are two main contributions, namely the cold field emission effect and the hopping conductivity through the dielectric. Our main finding is tha...

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Bibliographic Details
Published in:Nanoscale 2020-09, Vol.12 (36), p.18761-1877
Main Authors: Ilin, Eduard, Burkova, Irina, Draher, Timothy, Colla, Eugene V, Hübler, Alfred, Bezryadin, Alexey
Format: Article
Language:English
Subjects:
Aluminum oxide
Capacitors
Charging
Dielectric strength
Electric fields
Electrons
Energy dissipation
Field emission
Hopping conduction
Insulators
Leakage current
Room temperature
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Summary:The main mechanism of energy loss in capacitors with nanoscale dielectric films is leakage currents. Using the example of Al-Al 2 O 3 -Al, we show that there are two main contributions, namely the cold field emission effect and the hopping conductivity through the dielectric. Our main finding is that an application of a high electric field, ∼0.6-0.7 GV m −1 , causes electrons to penetrate the dielectric. If the temperature is sufficiently low, such electrons become permanently trapped in the dielectric. To achieve a strong charging of the dielectric, the voltage needs to be high enough, so that a field emission occurs from the cathode into the dielectric. Such a strongly charged dielectric layer generates a Coulomb barrier and leads to a suppression of the leakage current. Thus, after the dielectric nanolayer of the capacitor is charged, the field emission and the hopping conductivity are both suppressed, and the hysteresis of the I - V curve disappears. The phenomenon is observed at temperatures up to ∼225 K. It would be advantageous to identify insulators in which the phenomenon of the Coulomb barriers persists even up to the room temperature, but at this time it is not known whether such dielectrics exist and/or can be designed. Electrons tunnel from the cathode into the dielectric, get trapped on defects and build up a volume charge. These immobilized electrons generate an addition barrier, the Coulomb barrier, which reduces the leakage current of the nanocapacitor.
ISSN:2040-3364
2040-3372
DOI:10.1039/d0nr04660d