Carbon Nanotube Arrays: 2D Interfacial Assembly, Microstructure, Properties
Abstract
Overview & research problem*This project will focus on the materials science of densely packed, uniformly spaced, pristine arrays o,f semiconducting carbon nanotubes. Carbon nanotube arrays are poised to significantly disrupt the microelectronics industry and beco,me the channel material of choice in many mainstream semiconductor technologies because of their exceptional charge transport proper,ties and solution-based integrability. However, it is not yet possible to create nanotube arrays with the precision required to full,y exploit their properties; and, the electrical behaviors of nanotubes in dense arrays and how they are perturbed by inter-nanotube,interactions and solution-processing residues are poorly understood. *Foundational results*Our team has recently made a breakthrough, by discovering a powerful mechanism for driving the self-assembly of nanotubes into aligned arrays, by coaxing them to form two-dim,ensional liquid-crystals (2D-LCs). We have discovered that when nanotubes are functionalized with polymer wrappers and segregated to, liquid-liquid interfaces, mesogenic interactions cause them to self-align (within +/-5.7 degrees so far) and self-assemble into den,se arrays (> 100 per micron) like those needed for microelectronics. The assembled nanotubes can be easily transferred to substrates, and integrated into high-performance devices.The self-assembly is not yet entirely precise (the nanotubes bunch, bundle, and occasi,onally cross with non-uniform spacing), and the nanotubes do not yet obey all the behaviors expected of nematic LCs (such as increas,ing order parameter with increasing concentration). However, research into 2D-LCs of 1D nanostructures such as nanotubes is in its i,nfancy. There are many opportunities to learn and exploit 2D-LCs to achieve the needed precision.*Objectives, technical approaches &, outcomes*This project will have three thrusts. (A) We will build a fundamental understanding of 2D-LCs of nanotubes and leverage th,e knowledge gained to realize precise arrays. ,., length, concentration, surface functionalization) affect 2D-LC phase behaviors and order parameter. We will length-sort nanotubes, and fundamentally vary the nanotube mesogens by making substantial changes to the polymer wrappers on their surfaces, that we predi,ct will allow superior ordering. (B) We will learn how, why, and under what scenarios inter-nanotube interactions and solution-proce,ssing residues perturb their electrical behaviors. The electrical characteristics of nanotubes in imperfectly organized arrays diffe,r from isolated nanotubes, but we do not know why. We will uncover the nanotube misconfigurations and physics responsible and elucid,ate the effects of assembly-residues (wrappers, solvents) by using surface-sensitive spectroscopies to detect them and shape strateg,ies to remove them. The project will culminate with (C) the benchmarking of nanotube field-effect transistors that exploit the gains, realized above. Novel aspects throughout will include polymer wrapper design and synthesis; molecular dynamics simulations of repul,ctroscopy; 3D finite element electrostatics modeling; & interfacial trap density spectroscopy.*Impact*Nanotube arrays with well-orga,P); (ii) provide a pathway to monolithic 3D integrated circuits with 100-1000x gains in EDP over single layer Si; (iii) outperform t,he speed, linearity, and data-throughput of GaAs in RF (e.g., low-noise linear amplifiers) while allowing the system-on-a-chip integ,ration of RF + logic; and (iv) significantly boost the performance of thin film, flexible, and stretchable electronics. Approved for
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Oct 07, 2022
- Source ID
- N000142212843
Entities
People
- Michael S Arnold
Organizations
- Office of Naval Research
- United States Navy
- University of Wisconsin System