Fabrication of nanopores with embedded annular electrodes and transverse carbon nanotube electrodes

Abstract

Nanopores with one or two embedded nanoelectrodes can be fabricated by high resolution, milling-based methods. We first demonstrate how a focused ion beam, whose sputtering mechanism is well understood, can create a nanopore containing an annular electrode of an arbitrary metal, and with a regular perimeter. The inner surface of the nanopore can be insulated, and its diameter can be reduced with nanometer precision, by conformally coating a dielectric material by atomic layer deposition. We then investigate the mechanism of pore formation using a transmission electron microscope (TEM) through studies of the milling rate, and its dependence on the flux of electrons and on the atomic number of different target metals. Sputtering from the surface is identified as the dominant mechanism. Accordingly, light element conductors should be chosen to enhance the rate and resolution of TEM milling, which we demonstrate by articulating a nanopore with transverse carbon nanotube electrodes. Finally, we electrochemically verify that TEM milling preserves the quality of an annular gold electrode through cyclic voltammetry measurements performed at various stages of the fabrication.

Fabricating nanopores with diameters of sub-1 nm to 3 nm using multilevel pulse-voltage injection

“…Recently, “nanopore” technology has been attracting great attention and has become an important subject for study because of its potential to achieve label-free single-molecule DNA sequencing (i.e., direct DNA sequencing) with very high throughput at low cost123456789101112131415161718192021222324252627. In addition to this advantage, another advantage, specifically, the potential to read long DNA sequences (i.e., long-read DNA sequencing), is given by direct DNA sequencing utilising nanopores.…”

“…One is “biological”, i.e., nanopores that are formed with biological molecules (“bio-nanopores”)1234567. The other is “solid-state”, i.e., nanopores that are formed with semiconductor-related materials (“solid-state nanopores”)1789101112131415161718192021222324252627. The most well-known concept of DNA sequencing, common to both bio-nanopores and solid-state nanopores, detects changes in the ionic current through the nanopore during DNA translocation and identifies the four types of nucleotides from the changes in ionic current1234567121314151617181920212223242627.…”

“…To date, focused-electron beam etching via TEM has been used to fabricate nanopores in solid-state membranes. A TEM beam can be condensed to a diameter of less than 1 nm and can thereby be used to successfully fabricate a small nanopore with a diameter of less than 2 nm12142425. For mass production, however, TEM-beam etching is not suitable because of its high cost, low throughput, and complexity.…”

Charge regulation in nanopore ionic field-effect transistors

“…1) were fabricated following a procedure described elsewhere in detail [14]. Briefly, a 20 nm-thick, free-standing membrane of silicon nitride was formed on top of an 800 nm-thick supporting stack of silicon dioxide and silicon nitride, which was in turn supported on a silicon substrate.…”

First-principles study of high-conductance DNA sequencing with carbon nanotube electrodes

“…[11][12][13][14][15] These have been realized experimentally by high-resolution milling-based methods for a number of metal electrodes, but it has been speculated that similar techniques could be used for CNTs with possibly higher resolution. 13 On the theoretical front, the transverse tunneling conductance across nucleobases placed between two gold electrodes has been actively investigated and debated. 4,7,[16][17][18][19][20][21] Interestingly, recently some special attention has been dedicated to exploring graphene nanopore, graphene nanoribbon and carbon nanotubes (CNT) as potential electrodes materials.…”