EP-4740714-A1 - SURFACE-WATER-ASSISTED DEPOSITION OF PATTERNED FILMS OF ALIGNED NANOPARTICLES

EP4740714A1EP 4740714 A1EP4740714 A1EP 4740714A1EP-4740714-A1

Abstract

Methods of forming films of aligned elongated nanoparticles, films made using the methods, and electronic devices, such as transistors, that incorporate the films are provided. In the methods, elongated nanoparticles floating at the surface of a liquid film are deposited onto a liquid film-adsorbing surface region of a substrate as the liquid film dissipates from the surface. The alignment and deposition of the elongated nanoparticles occurs along a contact line that is defined by the liquid film, the substrate, and either an immiscible liquid suspension of the elongated nanoparticles or air. As the liquid film dissipates, the contact line recedes across the liquid film-adsorbing surface region and elongated nanoparticles pinned at the contact line are deposited onto the surface in the form of a nanoparticle film.

Inventors

ARNOLD, MICHAEL SCOTT
FORADORI, Sean

Assignees

Wisconsin Alumni Research Foundation

Dates

Publication Date: 20260513
Application Date: 20240619

Claims (20)

1. A method of forming a film of aligned elongated nanoparticles on a substrate, the method comprising: providing a substrate having at least one liquid film-adsorbing surface region bounded by at least one liquid film-repelling surface region; forming a liquid film on the at least one liquid film-adsorbing surface region, wherein the liquid film is bounded by the at least one liquid film-repelling surface region; contacting a suspension that comprises dispersed elongated nanoparticles with the at least one liquid film, wherein the suspension is immiscible with the at least one liquid film, such that the at least one liquid film and the suspension form an interface and elongated nanoparticles are transferred from the suspension to a surface of the at least one liquid film at the interface; and allowing the at least one liquid film to dissipate, whereby the elongated nanoparticles are deposited on the at least one liquid film-adsorbing surface region along a contact line defined by: the liquid film; the substrate; and the suspension or air, as the liquid film dissipates.
2. The method of claim 1, wherein the at least one liquid film-adsorbing surface region is more hydrophilic than the at least one liquid film-repelling surface region.
3. The method of claim 2, wherein the liquid is an aqueous medium.
4. The method of claim 1, wherein the at least one liquid film-adsorbing surface region is less hydrophilic than the at least one liquid film-repelling surface region.
5. The method of claim 1, wherein forming the liquid film on the at least one liquid film-adsorbing surface region comprises flowing a liquid over the at least one liquid film-adsorbing surface region to wet the at least one liquid film-adsorbing surface region, whereby the liquid is retained on the at least one liquid film-adsorbing surface region and not on the at least one liquid film-repelling surface region.
6. The method of claim 1, wherein contacting the suspension with the at least one liquid film comprises flowing the suspension over the at least one liquid film.
7. The method of claim 1, wherein forming the liquid film on the at least one liquid film-adsorbing surface region comprises submerging at least one liquid film-adsorbing surface region in a liquid and withdrawing the at least one liquid film-adsorbing surface region, from the liquid, whereby the liquid film is retained on the at least one liquid filmadsorbing surface region after said at least one liquid film-adsorbing surface region has been withdrawn from the liquid.
8. The method of claim 1, wherein the steps of forming a liquid film on the at least one liquid film-adsorbing surface region and contacting a suspension that comprises dispersed elongated nanoparticles with the at least one liquid film are carried out by forming a layer of the suspension on the liquid, submerging the at least one liquid film-adsorbing surface region in the liquid, and withdrawing the at least one liquid film-adsorbing surface region from the liquid and through the layer of the suspension.
9. The method of claim 8, wherein the layer of the suspension is continuously flowed over the liquid as the at least one liquid film-adsorbing surface region is withdrawn from the liquid and through the layer of the suspension.
10. The method of claim 1, wherein the elongated nanoparticles are carbon nanotubes.
11. The method of claim 10, wherein the elongated nanoparticles are semiconducting single-walled carbon nanotubes.
12. The method of claim 11 , wherein the semiconducting single-walled carbon nanotubes form a liquid crystal on the surface of the aqueous film.
13. The method of claim 11 , wherein the semiconducting single-walled carbon nanotubes have a linear packing density of at least 200 pm' 1 in the film of aligned semiconducting single-walled carbon nanotubes.
14. The method of claim 1, wherein the film of aligned elongated nanoparticles has an area of at least 50 cm 2 .
15. The method of claim 1, wherein the substrate is a silicon substrate.
16. The method of claim 15, wherein the at least one liquid fdm-adsorbing surface region comprises silicon dioxide.
17. The method of claim 16, wherein the at least one liquid film-repelling surface region comprises an organic polymer or organic functional groups.
18. A method of patterning a silicon dioxide surface of a substrate with one or more hydrophilic surface regions bounded by one or more less hydrophilic surface region, the method comprising: forming a layer of a resist on the silicon dioxide surface; patterning the layer of resist to expose one or more regions of the silicon dioxide surface through the layer of resist; depositing a layer of yttrium metal or a layer of scandium metal over the layer of resist and the one or more exposed regions of the silicon dioxide surface to form yttrium metal-coated or scandium metal-coated surface regions on the silicon dioxide surface; removing the patterned layer of resist from the silicon dioxide surface; oxidizing the yttrium metal or scandium metal on the silicon dioxide surface; forming a layer of material having a lower hydrophilicity than the silicon dioxide on the silicon dioxide surface and over the oxidized yttrium or oxidized scandium; and removing the oxidized yttrium or oxidized scandium from the silicon dioxide surface to form one or more hydrophilic silicon dioxide surface region bounded by the material having the lower hydrophilicity than the silicon dioxide.
19. A field effect transistor comprising: a source electrode; a drain electrode; a gate electrode; and a conducting channel in electrical contact with the source electrode and the drain electrode, the conducting channel comprising a film comprising aligned semiconducting single-walled carbon nanotubes, the field effect transistor having a current density of at least 1.8 mA pm' 1 and a transconductance of at least 1. 14 mS pm' 1 , as measured at 0.6 V dram voltage.
20. The field effect transistor of claim 19 having a cunent density in the range from 1.8 mA gm’ 1 to 2.2 mA gm' 1 and a transconductance in the range from 1.14 mS gm' 1 to 1.4 mS gm’ 1 , as measured at 0.6 V drain voltage.

Description

SURFACE-WATER-ASSISTED DEPOSITION OF PATTERNED FILMS OF ALIGNED NANOPARTICLES CROSS-REFERENCE TO RELATED APPLICATIONS [0001] The present application claims priority to U.S. non-provisional patent application number 18/366,300 that was filed August 7, 2023, the entire contents of which are incorporated herein by reference. REFERENCE TO GOVERNMENT RIGHTS [0002] This invention was made with government support under 1727523 awarded by the National Science Foundation. The government has certain rights in the invention. BACKGROUND [0003] Semiconducting carbon nanotubes (CNTs) are one-dimensional materials with exceptional electronic properties. Field effect transistors fabricated with CNT-based channels have been shown to exhibit current density greater than silicon and gallium arsenide transistors. (Brady, Gerald J., et al., “Quasi-ballistic carbon nanotube array transistors with current density exceeding Si and GaAs”, Science Advances, 2017, Volume 2, Issue 9) CNTs’ high current carrying capacity and the ability to easily modulate their conductivity due to their small diameter make them promising materials for next generation communication and logic devices. Maximizing the performance of CNT-based transistors requires that the CNTs in the transistors are aligned and arranged into densely packed monolayer arrays. [0004] High purity semiconducting CNTs are available as suspensions in aqueous and organic solvents, referred to as inks. The fabrication and deposition of aligned arrays of CNTs onto substrates from inks has been investigated using shear, vacuum filtration, directed evaporation, dielectrophoresis, evaporative self-assembly, blown-bubble assembly, gas flow self-assembly, spin-coating, contact-printing assembly, elastomeric release, dimensionlimited self-alignment, DNA directed assembly, and Langmuir-Blodgett and -Schaefer methods, among others. [0005] Some alignment methods accumulate CNTs at the interface between two immiscible liquids or between a liquid and a gas. CNTs can self-align at such interfaces, and the aligned CNTs can be picked up or deposited onto substrates. For example, it has been observed that spreading thin layers of polymer wrapped CNTs dispersed in organic solvents, like chloroform, on top of a water bath results in the self-alignment of the CNTs at the interface between the chloroform and water (Joo, Yongho, et al., “Dose-Controlled, Floating Evaporative Self-assembly and Alignment of Semiconducting Carbon Nanotubes from Organic Solvents,” Langmuir, 2014, Volume 30, Issue 12, pages 3460-3466), (Jinkins, Katherine R., et al., “Nanotube Alignment Mechanism in Floating Evaporative SelfAssembly, Langmuir, 2017, Volume 33, Issue 46, pages 13407-13414.). Using this effect, CNT assemblies can be transferred to large-area substrates by continuously flowing thin layers of the CNT ink over the surface of an aqueous subphase and simultaneously lifting a target substrate through the flowing ink layer at constant velocity - in a process termed tangential flow mterfacial self-assembly (TaFISA). SUMMARY [0006] Methods of forming films of aligned elongated nanoparticles, films made using the methods, and electronic devices, such as transistors, that incorporate the films are provided. Also provided are methods of forming a patterned substrate for use in the filmforming methods. [0007] One embodiment of a method of forming a film of aligned elongated nanoparticles on a substrate includes the steps of: providing a substrate having at least one liquid filmadsorbing surface region bounded by at least one liquid film-repelling surface region; forming a liquid film on the at least one liquid film-adsorbing surface region, wherein the liquid film is bounded by the at least one liquid film-repelling surface region; contacting a suspension that comprises dispersed elongated nanoparticles with the at least one liquid film, wherein the suspension is immiscible with the at least one liquid film, such that the at least one liquid film and the suspension form an interface and elongated nanoparticles are transferred from the suspension to a surface of the at least one liquid film at the interface; and allowing the at least one liquid film to dissipate, whereby the elongated nanoparticles are deposited on the at least one liquid film-adsorbing surface region along a contact line defined by: the liquid film; the substrate; and the suspension or air, as the liquid film dissipates. [0008] One embodiment of a method of patterning a silicon dioxide surface of a substrate with one or more hydrophilic surface regions bounded by one or more less hydrophilic surface regions includes the steps of: forming a layer of a resist on the silicon dioxide surface; patterning the layer of resist to expose one or more regions of the silicon dioxide surface through the layer of resist; depositing a layer of yttrium metal or a layer of scandium metal over the layer of resist and the one or more exposed regions of the silicon dioxi