Meaning
Physical process allows electrons to pass through a thin insulating layer between conductive surfaces. This metal oxide quantum tunneling typically occurs at thicknesses below five nanometers where the wave-like nature of electrons enables them to cross the energy gap. In electrical contacts, this mechanism provides a conduction path even when a thin layer of natural oxidation exists on the surface.
The resulting current-voltage relationship is nonlinear and depends heavily on the barrier height and width.
Barrier Dimension
Electron flow decreases exponentially as the oxide thickness increases. Layers thicker than ten nanometers generally act as insulators.
Conduction Mechanism
Conduction through the interface relies on the probability of an electron appearing on the opposite side of the dielectric. This metal oxide quantum tunneling is sensitive to the work function of the metals involved and the dielectric constant of the oxide. When a voltage is applied, the potential barrier deforms and increases the tunneling probability.
This behavior is often observed in zero-force connectors or lightly loaded probes where mechanical pressure is insufficient to break the oxide. Environmental aging increases the oxide thickness and eventually blocks the tunneling current. Measurement of this phenomenon requires specialized low-voltage equipment to avoid damaging the delicate interface.
Reliable Interface
Reliable connections in smart devices often rely on maximizing the metallic contact area to minimize the reliance on tunneling. Gold or other noble metals are preferred because they do not form these thick insulating layers. If an oxide is present, the contact must be designed to withstand the resulting signal distortion.
