Authors: Jean-Nicolas Deraspe | Claudia M. Bazán | Delphine Bouilly
Source: ECS Meeting Abstracts (article, 2025-07-11)
Field: Materials Science — Materials Chemistry

High-Yield Assembly of Single-Carbon-Nanotube Field-Effect Transistors from Dispersed CVD Growths for Single-Molecule Biosensing Single-molecule biophysical techniques can provide key insights into the dynamics and heterogeneity of biochemical processes. Among these, carbon nanotube field-effect transistors (CNTFETs) have been shown to be powerful tools for studying isolated biomolecules, offering exceptional sensitivity for probing rapid timescales, such as DNA hybridization and denaturation 1 , as well as heterogeneous dynamical processes like enzymatic catalysis 2 . In such devices, a single biomolecule is tethered to the surface of an isolated nanotube connected with electrodes and immersed in an electrolytic environment. Molecular conformational changes and reaction kinetics are extracted from the analysis of fluctuations in the electrical conductance of the nanotube. Despite their promises, the assembly of CNTFETs presents important challenges, due to their nanoscopic dimensions and the stochastic nature of the carbon nanotube growth that can cause low device yield for each fabrication cycle. In this project, we optimized CNTFET fabrication for single-molecule biomolecular dynamics analysis by enhancing fabrication throughput. Carbon nanotubes were grown via chemical vapor deposition (CVD) using a carefully selected concentration of ferric chloride (FeCl 3 ) catalyst particles dispersed on Si/SiO2 substrates. We obtained a controlled surface density such that between 1 and 3 CNTs are found every 100 microns. We then patterned an array of millimeter-long, few-micron-separated electrode pairs: we will show how this design maximizes the connection of electrode pairs by at least one carbon nanotube, while also enabling the assembly of a flow cell for solution delivery. After mapping all connecting nanotubes with scanning electron microscopy, all but one per electrode pair were etched using a negative photolithography process along with reactive ion etching (RIE). Finally, we will show our characterization of single-point functionalization on CNTFETs, made possible via few-nanometers-wide channels etched in thin resist using an electron beam to expose a short segment of nanotube to coupling reactions in a flow cell 3 . In future work, we aim to minimize noise by testing various electrode and passivation geometries to identify configurations that enhance the signal-to-noise ratio. Hyperspectral imaging tools and scanning electron microscopy controlled by machine learning algorithms will also be investigated to automate nanotube mapping and selection after the electrode patterning. These results will promote a rational design of CNTFET devices which will improve their performance in single-molecule detection and reaction kinetics measurement. (1) Sorgenfrei, S.; Chiu, C.; Gonzalez, R. L.; Yu, Y.-J.; Kim, P.; Nuckolls, C.; Shepard, K. L. Label-Free Single-Molecule Detection of DNA-Hybridization Kinetics with a Carbon Nanotube Field-Effect Transistor. Nature Nanotech 2011 , 6 (2), 126–132. https://doi.org/10.1038/nnano.2010.275. (2) Choi, Y.; Moody, I. S.; Sims, P. C.; Hunt, S. R.; Corso, B. L.; Perez, I.; Weiss, G. A.; Collins, P. G. Single-Molecule Lysozyme Dynamics Monitored by an Electronic Circuit. Science 2012 , 335 (6066), 319–324. https://doi.org/10.1126/science.1214824. (3) Bouilly, D.; Hon, J.; Daly, N. S.; Trocchia, S.; Vernick, S.; Yu, J.; Warren, S.; Wu, Y.; Gonzalez, R. L. Jr.; Shepard, K. L.; Nuckolls, C. Single-Molecule Reaction Chemistry in Patterned Nanowells. Nano Lett. 2016 , 16 (7), 4679–4685. https://doi.org/10.1021/acs.nanolett.6b02149. Carbon nanotube ; Nanotechnology ; Materials science ; Biosensor ; Carbon nanotube field-effect transistor ; Yield (engineering) ; Field-effect transistor ; Transistor ; Optoelectronics ; Electrical engineering ; Engineering ; Composite material ; Voltage Carbon Nanotubes in Composites ; Molecular Junctions and Nanostructures ; Nanotechnology research and applications