Abstract
Glassy carbon nanofibers (GCNFs) are considered promising candidates for the fabrication of nanosensors for biosensing applications. Importantly, in part due to their great stability, carbon electrodes with sub-10 nm nanogaps represent an attractive platform for probing the electrical characteristics of molecules. The fabrication of sub-10 nm nanogap electrodes in these GCNFs, which is achieved by electrically stimulating the fibers until they break, was previously found to require fibers shorter than 2 µm; however, this process is generally hampered by the limitations inherent to photolithographic methods. In this work, to obtain nanogaps on the order of 10 nm without the need for sub-2 µm GCNFs, we employed a fabrication strategy in which the fibers were gradually thinned down by continuously monitoring the changes in the electrical resistance of the fiber and adjusting the applied voltage accordingly. To further reduce the nanogap size, we studied the mechanism behind the thinning and eventual breakdown of the suspended GCNFs by controlling the environmental conditions and pressure during the experiment. Following this approach, which includes performing the experiments in a high-vacuum chamber after a series of carbon dioxide (CO2) purging cycles, nanogaps on the order of 10 nm were produced in suspended GCNFs 52 µm in length, much longer than the ~2 µm GCNFs needed to produce such small gaps without the procedure employed in this work. Furthermore, the electrodes showed no apparent change in their shape or nanogap width after being stored at room temperature for approximately 6 months.
Highlights
One of the many challenges toward the development of molecular-scale sensing devices is the issue of how to connect molecules or similar sized nanostructures to the outside world
No direct temperature measurements were performed on the Glassy carbon nanofibers (GCNFs), an indication of the effects caused by heating of the GCNF can be inferred from this ΔR value when the fiber is electrically stimulated
We found that a positive electrical resistance change larger than ΔR = 0.05% is suitable to allow the system to reach the activation temperature needed to form a constriction, while preventing the breakdown process from taking place in an uncontrolled manner
Summary
One of the many challenges toward the development of molecular-scale sensing devices is the issue of how to connect molecules or similar sized nanostructures to the outside world To this end, electrodes separated by a few nanometers, known as nanogap electrodes, are commonly used to probe the electrical properties of these nanoscale objects. Photolithography which can be used for the fabrication of larg rectangular nanogap electrodes whose surface area is increased to improve their performance in electrochemical sensing applications[4]. In all of these fabrication methods, the most frequently used material has been gold[6,7,8]. Some drawbacks from the use of this metal for the construction of nanogaps have
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