Current–VoltageCharacteristics of SiN Membranesin Solution
2020
Recently,
the dielectric breakdown of insulating membranes in aqueous
solution has been utilized to fabricate nanopore sensors for various
molecular detection applications. Generally, the breakdown phenomenon
of an insulator is thought to be strongly related to the behavior
of the current through it. However, until now, the current through
an insulating membrane in aqueous solution has rarely been measured.
In this study, by using thin SiN membranes with large and precisely
defined areas, we achieved accurate and reproducible measurements
of the current–voltage (I–V) characteristics of SiN membranes in aqueous solution. From the
shape of the I–V curves and
their temperature dependence, the carrier conduction process in the
membrane was found to be mainly governed by the Poole–Frenkel
emission and tunnel conduction of the electrons which are transferred
by the ions in aqueous solution to the membrane. In addition, we investigated
how the I–V characteristics
and breakdown voltage changed in accordance with the changes in the
solution pH, solute type, solute concentration, and solvent type.
The results were categorized into two cases. In one case, both the I–V characteristics and breakdown
voltage changed in accordance with the change in each experimental
parameter. In the other case, only the breakdown voltage changed without
changes in the I–V characteristics.
The most drastic changes in both the I–V characteristics and breakdown voltage were observed when
the solvent was changed from water to dimethyl sulfoxide (DMSO), whereas
the solute was LiCl. This observation was attributed to the differences
in ion species that transfer electrons to and from the membrane. H+, OH–, and Cl– were thought
to exchange electrons with the membrane when the solvent was H2O. On the other hand, Li+ and Cl– may have played a role in the electron exchange reaction when the
solvent was DMSO.
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