Method of forming a film of aligned elongated nanoparticles on a substrate, method of patterning a silicon dioxide surface of a substrate and field effect transistor

Abstract

This invention provides methods for forming films of arranged elongated nanoparticles, films made using such methods, and electronic devices, such as transistors, having such films. In these methods, elongated nanoparticles floating on the surface of a liquid film are deposited on a liquid film adsorption surface region of a substrate as the liquid film dissipates from the surface. The arrangement and deposition of these elongated nanoparticles occur along a contact line defined by the liquid film, the substrate, and an immiscible liquid suspension or air containing the elongated nanoparticles. As the liquid film dissipates, the contact line recedes on the liquid film adsorption surface region, and the elongated nanoparticles attached to the contact line are deposited on the surface in the form of a nanoparticle film.

Description

Technical Field

[0001] The present application relates to surface water-assisted deposition of patterned films of aligned nanoparticles. CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. non-provisional patent application No. 18 / 366,300, filed on August 7, 2023, the entire contents of which are incorporated herein by reference. Prior Art

[0003] Semiconducting carbon nanotubes (CNTs) are one-dimensional materials with superior electronic properties. Field-effect transistors fabricated with CNT-based channels have demonstrated current densities greater than those of 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, Vol. 2, No. 9). The high current carrying capacity of CNTs and the ability to easily adjust their conductivity due to their small diameter make them a promising material for next-generation communications and logic devices. Maximizing the performance of CNT-based transistors requires that the CNTs in the transistor be arranged and arranged in a densely packed monolayer array.

[0004] High purity semiconducting CNTs are available as suspensions in aqueous and organic solvents, known as inks. Fabrication and deposition of aligned CNT arrays on substrates from inks have been studied using shear, vacuum filtration, directed evaporation, dielectrophoresis, evaporative self-assembly, bubble blowing assembly, airflow self-assembly, spin coating, contact printing assembly, elastic release, dimension-limited self-alignment, DNA directed assembly, and the Langmuir-Blodgett and -Schaefer methods.

[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 these interfaces, and the aligned CNTs can be picked up or deposited onto a substrate. For example, it has been observed that spreading a thin layer of polymer-surrounded CNTs dispersed in an organic solvent such as chloroform on top of a water bath causes the CNTs to self-align at the interface between chloroform and water (Joo, Yongho et al., "Dose-Controlled, Floating Evaporative Self-assembly and Alignment of Semiconducting Carbon Nanotubes from Organic Solvents", Langmuir, 2014, Vol. 30, No. 12, pp. 3460-3466), (Jinkins, Katherine R. et al., "Nanotube Alignment Mechanism in Floating Evaporative Self-Assembly", Langmuir, 2017, Vol. 33, No. 46, pp. 13407-13414). Using this effect, CNT assemblies can be transferred to large-area substrates in a process called tangential flow interfacial self-assembly (TaFISA) by continuously flowing a thin layer of CNT ink over the surface of a subaqueous phase while simultaneously lifting the target substrate through the flowing ink layer at a constant speed. Summary of the invention

[0006] The present invention provides methods for forming films of arranged elongated nanoparticles, films made using these methods, and electronic devices incorporating these films, such as transistors. Also provided is a method for forming a patterned substrate for use in the film forming method.

[0007] One embodiment of a method of forming a film of arranged elongated nanoparticles on a substrate comprises the steps of providing a substrate having at least one liquid film adsorption surface region bounded by at least one liquid film repulsive surface region; forming a liquid film on the at least one liquid film adsorption surface region, wherein the liquid film is bounded by the at least one liquid film repulsive surface region; contacting a suspension containing dispersed elongated nanoparticles with the at least one liquid film, wherein the suspension and the at least one liquid film are immiscible, such that the at least one liquid film and the suspension form an interface and the elongated nanoparticles are transferred from the suspension to a surface of the at least one liquid film at the interface; and dissipating the at least one liquid film, whereby as the liquid film dissipates, the elongated nanoparticles are deposited on the at least one liquid film adsorption surface region along a contact line defined by: the liquid film; the substrate; and the suspension or air.

[0008] A specific example of a method for patterning a silicon dioxide surface of a substrate having one or more hydrophilic surface regions bounded by one or more less hydrophilic surface regions comprises the following steps: forming a resist layer on the silicon dioxide surface; patterning the resist layer to penetrate through the resist layer to expose one or more regions of the silicon dioxide surface; depositing a yttrium metal layer or a scandium metal layer over the resist layer and the one or more exposed regions of the silicon dioxide surface to expose one or more regions of the silicon dioxide surface; and A yttrium metal-coated or scandium-coated surface region is formed on a silicon surface; a patterned resist layer is removed from the silicon dioxide surface; the yttrium metal or the scandium metal on the silicon dioxide surface is oxidized; a layer of a material having a lower hydrophilicity than silicon dioxide is formed on the silicon dioxide surface and above the yttrium oxide or the scandium oxide; and the yttrium oxide or the scandium oxide is removed from the silicon dioxide surface to form one or more hydrophilic silicon dioxide surface regions bounded by the material having a lower hydrophilicity than silicon dioxide.

[0009] One embodiment of a field effect transistor includes: a source electrode; a drain electrode; a gate electrode; and a conduction channel in electrical contact with the source electrode and the drain electrode, the conduction channel comprising a film containing aligned semiconductor single-walled carbon nanotubes. Some embodiments of the field effect transistor are characterized by a current density of at least 1.8 mA μm-1 and a transconductance of at least 1.14 mS μm-1 measured at a drain voltage of 0.6 V.

[0010] Other key features and advantages of the present invention will become apparent to those having ordinary knowledge in the art when reviewing the following drawings, embodiments and appended claims. Simple diagram description

[0011] Illustrative embodiments of the present invention will be described below with reference to the accompanying drawings, wherein like numerals represent like elements. Panels (a) to (f) of [FIG. 1] illustrate the formation of a high-density film of aligned elongated nanoparticles on the bottom surface of a flow channel using surface water-assisted deposition. [FIG. 2A], panels (a) to (e), illustrate the formation of a high-density film of aligned elongated nanoparticles from the interface between an aqueous medium and an immiscible organic solvent using surface water-assisted deposition. [FIG. 2B] illustrates the formation of a high-density film of aligned elongated nanoparticles using surface water-assisted tangential flow interfacial self-assembly (TaFISA) deposition. [FIG. 2C to 2H] illustrate the layers of nanoparticle film deposition during the surface water-assisted TaFISA method. In FIG. 2A and FIG. 2B, for simplicity, the elongated nanoparticles floating on water are shown as dots as if they are aligned perpendicular to the image. However, the elongated nanotubes in the nanoparticle ink and floating on water can move and can have other orientations. [Figure 3] Insets (a) to (g) show the processing flow for forming patterned hydrophobic and hydrophilic surface areas on a hydrophilic SiO2 surface. Panels (a) to (d) of [FIG. 4] show high-resolution atomic force microscopy (AFM) height images at increasing magnifications of a semiconductor single-walled carbon nanotube film strip of approximately 50 μm wide formed on a hydrophilic region of a substrate using a TaFISA-based method, as described in the Examples. [Figure 5A] to [Figure 5D] show high-resolution AFM height images of semiconductor single-walled carbon nanotube films formed on hydrophilic strips (Figure 5A) and uniformly hydrophobic areas (Figure 5B) using a TaFISA-based method, as well as corresponding histograms of the alignment levels of visible semiconductor single-walled carbon nanotube segments (Figure 5C, Figure 5D). [FIG. 6A] to [FIG. 6C] show high-resolution AFM height images of s-SWCNT films (panel (a)), superimposed manual markings of visible s-SWCNT segments (panel (b)), and histograms of the angular distribution of visible s-SWCNT segments of three s-SWCNT films deposited using surface water-assisted TaFISA (panel (c)). [FIG. 7] shows a high-resolution AFM height image of a semiconductor single-walled carbon nanotube film used as a channel in a field effect transistor (FET) in an embodiment. [FIG. 8A] and [FIG. 8B] show representative transfer curves of FETs made based on the high packing density semiconductor single-walled carbon nanotube film shown in FIG 7. FIG 8C and FIG 8D show plots of maximum current density (FIG. 8C) and maximum transconductance (FIG. 8D). [Figure 9] shows calibration data that correlates the packing density of semiconductor SWNT films measured by AFM imaging with the Raman spectra ratio of the semiconductor SWNT G peak to the Si 520 cm-1 peak measured on a substrate treated with hexamethyldisilazane (HMDS) and a hydrophilic substrate treated with yttria. When using least squares regression fitting, both substrates produce similar calibration results. [Figure 10A] shows the Raman spectra measurement results of semiconductor single-walled carbon nanotube film alignment. [Figure 10B] shows the linear and logarithmic Raman signals of the semiconductor single-walled carbon nanotube G peak and Si 520 cm-1 of the densely packed semiconductor single-walled carbon nanotube film on Si / SiO2 (about 130 nm) sample as a function of the sample rotation. The data were collected using a polarized 532 nm laser and a polarizer in the scattered photon optical path parallel to the Raman laser orientation. The dotted line is the cos 4 (α) curve fitted to the maximum and minimum values ​​of the semiconductor single-walled carbon nanotube G peak, which represents the predicted signal of a perfectly aligned semiconductor single-walled carbon nanotube film under ideal polarization conditions. The solid line is the predicted signal of semiconductor single-walled carbon nanotube films with various disordered alignment levels, which is represented by a surrounding normal distribution with standard deviations of 5°, 10°, 15° and 20°. Also shown is the [sin(α)cos(α)] 2 fitting curve for the predicted Si 520 cm -1 peak height under these polarization and sample rotation conditions. [FIG. 11A] and [FIG. 11B] show cross-polarization optical images of the s-SWCNT film according to Example 2. The images in [FIG. 12A] and [FIG. 12B] are AFM height images showing a representative s-SWCNT film according to Example 2. Implementation

[0012] The present invention provides methods for forming films of arranged elongated nanoparticles, films made using these methods, and electronic devices incorporating these films, such as transistors. Also provided is a method for forming a patterned substrate for use in the film forming method.

[0013] In these methods, elongated nanoparticles (such as carbon nanotubes) floating on the surface of a liquid film are deposited on the surface of a substrate as the liquid film dissipates on the surface of the substrate. The arrangement and deposition of the elongated nanoparticles occur along a contact line defined by the liquid film, the substrate and a second liquid immiscible with the liquid film or by the liquid film, the substrate and air. As the liquid film dissipates, the contact line recedes on the substrate surface, and the elongated nanoparticles are deposited from the contact line onto the substrate surface in the form of a nanoparticle film.

[0014] The methods can produce large-area (e.g., wafer-scale) patterned elongated nanoparticle films with extremely high nanoparticle alignment and linear packing density in a continuous and tunable process. The degree of alignment of the elongated nanoparticles in the deposited film refers to the degree of alignment of the nanoparticles along their long axis within the film, which can be quantified using the methods described in the embodiments. In some embodiments, the average degree of alignment of the elongated nanoparticles in the deposited film is ±10° or better (i.e., the average value of the degree of misalignment of the elongated nanoparticles in the deposited film is no greater than 10°). This includes elongated nanoparticles in the elongated nanoparticle film having an average degree of alignment of ±6° or better.

[0015] The density of the elongated nanoparticles in the film can be measured by its linear packing density, which can be quantified in terms of the number of elongated nanoparticles per micron and is measured as described in the Examples. In some embodiments, the methods described herein deposit a film having an elongated nanoparticle linear packing density of at least 30 elongated nanoparticles per micron. This includes embodiments in which the film has an elongated nanoparticle linear packing density of at least 50 elongated nanoparticles per micron, at least 100 elongated nanoparticles per micron, and at least about 200 elongated nanoparticles per micron.

[0016] The high nanoparticle packing density and alignment levels that can be achieved using these methods make films made by these methods suitable for a variety of high-performance electronic applications, including as channel layers in FETs. The high density and alignment levels that can be achieved in semiconductor single-walled carbon nanotube (s-SWCNT) films made using the methods of the present invention enable the fabrication of FETs with current densities of at least 1.8 mA μm-1 and transconductances of at least 1.14 mS μm-1 (measured at a 0.6 V drain voltage). This includes FETs with current densities as high as 2.2 mA μm-1 and transconductances as high as 1.4 mS μm-1 or even higher (measured at a 0.6 V drain voltage). More details on the fabrication and characterization of such high-performance FETs are provided in the Examples.

[0017] The methods are performed on a substrate having a surface with at least one liquid film adsorption surface region, the boundary of which is defined by one or more liquid film repellent surface regions. The liquid film adsorption and liquid film repellent surface regions are characterized by their difference in hydrophilicity, so that a liquid applied to the surface adsorbs to the liquid film adsorption region but not to the liquid film repellent region. Depending on the liquid used, the hydrophilicity of the liquid film forming region may be greater than that of the liquid film repellent region, or vice versa. For example, if the liquid film comprises an aqueous medium or comprises a hydrophilic organic solvent, the hydrophilicity of the liquid film adsorption region will be greater than that of the liquid film repellent region. (For the purposes of this disclosure, the term "aqueous medium" refers to pure water, as well as aqueous solutions in which one or more solutes are dissolved in water and aqueous solutions including one or more organic solvents as minor co-solvents. For example, a solute that lowers the melting point of water or an antibacterial agent may be dissolved in water to provide an aqueous medium.) However, if the liquid film comprises a hydrophobic organic solvent, the hydrophilicity of the liquid film adsorption region will be less than that of the liquid film repellent region. It should be noted that the description of the film-adsorbing and film-repelling regions as having a "difference in hydrophilicity" does not imply that both regions are hydrophilic (i.e., have a water contact angle of 0° or greater). Rather, it is possible that both the film-adsorbing and film-repelling regions are hydrophilic, both the film-adsorbing and film-repelling regions are hydrophobic (i.e., have a water contact angle of 0° or greater), the film-adsorbing region is hydrophilic and the film-repelling region is hydrophobic, or the film-adsorbing region is hydrophobic and the film-repelling region is hydrophilic. The key is that the difference in hydrophilicity of the two regions is different enough to allow the film to selectively remain on the film-adsorbing region.

[0018] As used herein, a hydrophilic surface region is a surface region having a water contact angle equal to or less than 90°, and a hydrophobic surface region is a surface region having a water contact angle (WCA) greater than 90°, as measured using a sitting drop method at the temperature at which film formation is performed. For film deposition at room temperature, this temperature would be about 23°C. For illustrative purposes only, in some embodiments of the methods, both the film-adsorbing and film-repelling surface regions are hydrophilic according to the above definition of hydrophilicity, but the film-adsorbing region is more hydrophilic. For example, the film-adsorbing region may have a WCA less than 10°, and the film-repelling region may have a WCA in the range of 25° to 60°, or vice versa.

[0019] One embodiment of a method of forming a film of aligned elongated nanoparticles is schematically depicted in Figure 1. The procedure starts with a substrate 102 having a surface with liquid film adsorption surface regions (here strips) 104. The strips 104 are bounded above and below by two liquid film repelling regions 106.

[0020] By contacting the substrate surface with the liquid, the liquid is adsorbed to the liquid film adsorption surface area to form a liquid film thereon, thereby forming a liquid film 108 on each of the one or more liquid film adsorption surface areas 104. The substrate surface can be contacted with the liquid by flowing the liquid over the substrate surface, immersing the substrate in the liquid, spraying the liquid onto the substrate surface, printing the liquid onto the substrate surface, or by other means. The liquid is selectively retained on one or more liquid film adsorption surface areas, but not on the liquid film repellent area, so that the boundaries of the liquid film adsorption surface area are defined by the liquid film repellent surface area. This is illustrated in the inset (b) of FIG. 1 , which shows the liquid film 108 fixed on the strip 104 and bounded by the liquid film repellent area 106.

[0021] A suspension 109 of elongated nanoparticles 111 in a second liquid (referred to herein as "nanoparticle ink") is then brought into contact with the liquid film 108, the suspension being immiscible with the liquid of the liquid film 108. The suspension may be brought into contact with the liquid film by flowing the suspension over the liquid film, forming a layer of the suspension over the liquid film, spraying the suspension onto the liquid film, inkjet printing the suspension onto the liquid film, or by other means. When the immiscible suspension 109 is brought into contact with the liquid film 108, an interface is formed between the suspension and the liquid film, and some of the elongated nanoparticles 111 from the suspension 109 are transferred to the liquid film 108, where the elongated nanoparticles "float" on top of the liquid film 108 (inset (c) of FIG. 1). These floating elongated nanoparticles move freely on the liquid film 108 until they contact and become attached to a contact line formed by the liquid film 108, the substrate 102, and the suspension 109 or air. As the liquid film 108 dissipates and the contact line recedes on the liquid film adsorption region 104, the elongated nanoparticles 111 attached at the contact line become fixed on the liquid film adsorption region 104 and automatically align along the contact line. Subsequently, as the liquid film 108 continues to dissipate, the deposited elongated nanoparticles automatically align according to the previously deposited elongated nanoparticles, thereby causing a densely packed film 112 of highly aligned elongated nanoparticles to be deposited on the substrate 102. Some of the elongated nanoparticles 111 may also be deposited on the liquid film repellent surface region 106. However, the nanoparticle films formed on these regions will generally have a lower nanoparticle packing density and alignment than the nanoparticle films deposited on the liquid film adsorption region 104.

[0022] The elongated nanoparticles may be deposited onto a substrate in the presence of an immiscible suspension (i.e., in the case where the suspension is in contact with a liquid film), in which case the dissipation of the liquid film formed on the liquid film adsorption surface region may be attributed to the dissolution of the liquid into the immiscible liquid of the nanoparticle suspension. In this scenario, the elongated nanoparticles are deposited along the contact line formed by the liquid film, the substrate, and the suspension. Alternatively, the elongated nanoparticles may be deposited onto the substrate after the nanoparticle suspension is no longer in contact with the liquid film formed on the liquid film adsorption surface region (e.g., after the flow of the suspension over the liquid film has ceased, or after the liquid film has left the suspension), in which case the dissipation of the liquid film is attributed to the evaporation of the liquid from the film, and the elongated nanoparticles are deposited along the contact line formed by the liquid film, the substrate, and the air. In some embodiments of the methods, the deposition of the elongated nanoparticles may occur both in the presence of the nanoparticle suspension (panel (d) of FIG. 1 ) and subsequently when the liquid film evaporates in the air (panel (e) of FIG. 1 ). The film 112 of aligned elongated nanoparticles deposited along the receding contact line is characterized by high linear packing density and high elongated nanoparticle alignment (Fig. 1, panel (f)).

[0023] It should be noted that the immiscible suspending liquids used in these methods need not be completely immiscible, as the liquid of the liquid film may be allowed to dissolve to some extent in the suspending liquid. Thus, the immiscible degree of the immiscible suspending liquid need only be sufficient to allow the formation of the nanoparticle film based on the principles and time scales of the nanoparticle film deposition process described herein.

[0024] The embodiment of the method shown in FIG. 1 illustrates how the methods may be performed in a flow channel, wherein one or more interior surfaces of the channel are patterned with liquid film adsorption areas. The flow channel may be a closed channel or an open channel (i.e., a groove). In such methods, a liquid forming a liquid film flows through the channel. After the flow of the liquid stops, the liquid film selectively remains on the liquid film adsorption surface areas. A suspension containing elongated nanoparticles is then flowed through the channel, flowing over the adsorbed liquid film, and deposition of the elongated nanoparticles onto the surface occurs as described above. In such embodiments of the methods, the arranged nanoparticle film will typically be deposited on the bottom surface of the flow channel, but may also be deposited on other channel surfaces (such as walls).

[0025] In other embodiments of the methods, one or more films of aligned elongated nanoparticles are deposited from a two-dimensional (2D) liquid / suspension interface formed between an adsorbed liquid film and an overlying water-immiscible suspension of elongated nanoparticles. In these embodiments, as a substrate patterned with one or more liquid film adsorption surface regions translates across the liquid / suspension interface, some liquid remains on the liquid film adsorption surface regions as the regions move from the liquid layer into the suspension layer and then into the air. This method is schematically illustrated in FIG. 2A , which shows a cross-sectional view of a substrate 202 having a liquid film adsorption strip (shown as having a water contact angle (WCA) = 0°) 204 bounded by upper and lower liquid film repelling surface regions 206 (shown as having a water contact angle (WCA) = 40°). Initially, strip 204 is immersed in liquid 205, thereby forming interface 207 (inset (a) of FIG. 2A ) with overlying suspension 209 of elongated nanoparticles 211. Liquid 205 and suspension 209 are sufficiently immiscible so that suspension 209 spreads over liquid 205 to form interface 207. Additional suspension 209 may be continuously or intermittently supplied to maintain interface 207 as suspension 209 evaporates during the nanoparticle deposition process. In some embodiments of the methods, suspension 209 continuously flows over liquid 205 throughout the nanoparticle film deposition process, as discussed below in conjunction with FIG. 2B .

[0026] As the substrate 202 is removed from the liquid 205 and passes through the suspension 209, the liquid film 208 remains and is fixed on the liquid film adsorption strip 204 (panels (b) and (c) of FIG. 2A ), and some of the elongated nanoparticles 211 from the suspension 209 are transferred to the interface 207, where they "float" on the surface of the liquid film 208. These floating elongated nanoparticles 211 are attached and arranged at the contact line formed by the liquid film 208, the substrate 202, and the suspension 209 or the air. Then, as the liquid film 208 dissipates, the attached elongated nanoparticles are deposited on the substrate 202 as an arranged nanoparticle film, so that the contact line recedes on the liquid film adsorption surface area 204.

[0027] The elongated nanoparticles may be deposited on the substrate while the liquid film is still immersed in the suspension, in which case the dissipation of the liquid film may be attributed to the dissolution of the liquid in the suspension, and the elongated nanoparticles are deposited along the contact line formed by the liquid, the substrate, and the suspension. Alternatively, as shown in FIG. 2A , the elongated nanoparticles 211 may be deposited on the substrate 202 after the liquid film 208 has completely left the suspension 209, in which case the dissipation of the liquid film is attributed to the evaporation of the liquid into the air, and the elongated nanoparticles are deposited along the contact line formed by the liquid film 208, the substrate 202, and the air (inset (d) of FIG. 2A ). In some embodiments of the methods, the deposition of the elongated nanoparticles onto the substrate may occur when the liquid film dissipates due to the dissolution of the liquid film while it is still immersed in the suspension, and when the liquid film dissipates by evaporation after the liquid film has completely left the suspension. The film of aligned elongated nanoparticles deposited along the receding contact line is characterized by high linear packing density and high elongated nanoparticle alignment (Figure 2A, inset (e)).

[0028] FIG. 2B illustrates an embodiment of the method depicted in FIG. 2A , wherein an immiscible suspension 209 is continuously flowed over a liquid 205 while an elongated nanoparticle film 212 is deposited onto a liquid film adsorption surface region 204 of a substrate 202. Within the flow channel, an interface 207 is formed by flowing the suspension 209 tangentially over the surface of the liquid 205. Because these methods use tangential flow and nanoparticle self-assembly at the contact line, these methods are referred to as tangential flow interface self-assembly (“TaFISA”). The width of the flow channel is defined by a substrate 202 and a surrounding wall 213, which is disposed opposite to the substrate 202 and separated from the substrate 202 by a gap. The substrate 202 and the surrounding wall 213 are immersed in the liquid 205. During deposition of the elongated nanoparticle film 212 onto the substrate 202, the suspension 209 flows between the substrate 202 and the barrier 213 and over the liquid 205 as the substrate 202 translates across the interface 207. The arrows in the pattern indicate the direction of flow of the suspension 209. Translation of the substrate 202 across the interface 207 can be achieved by moving the substrate 202 relative to the interface 207 (i.e., by removing the substrate 202 from the liquid 205 and the suspension 209) or by changing the position of the interface 207 relative to the substrate 202 (i.e., by raising and lowering the level of the liquid 205 in the flow channel). In the embodiment of the method shown in FIG. 2B, the substrate 202 and the barrier 213 are oriented vertically and in parallel. However, the substrate 202 and the barrier 213 need not be arranged in a parallel orientation, and one or both of the substrate 202 and the barrier 213 may be tilted away from a vertical axis.

[0029] FIG. 2C to FIG. 2H illustrate the step-by-step formation of an elongated nanoparticle film using the flow channel of FIG. 2B . In FIG. 2C to FIG. 2H , the flow direction is from right to left in the plane of the page. The submerged portion of the substrate is indicated by dashed lines, and the locations of the liquid film adsorption and liquid film repulsive surface regions on the substrate at each step are shown in the inset on the right side of the figure. Initially, the liquid film adsorption surface region 204 is completely immersed in the liquid 205 and the flowing suspension 209. At this initial stage of the method, nanoparticles 211 from the interface 207 can be deposited on the upper liquid film repulsive surface region 206 due to hydrophobic-hydrophobic interactions ( FIG. 2C ). As the liquid film adsorption region 204 leaves the liquid 205 and passes through the flowing suspension 209 ( FIG. 2D ), a liquid film 208 remains on the liquid film adsorption surface region 204. The elongated nanoparticles 211 are transferred from the suspension 209 to the liquid film 208 where they float on the surface of the liquid. As the liquid film adsorption surface area 204 moves out of the flowing suspension 209, a contact line is formed at the leading edge of the liquid film adsorption surface area 204, the liquid film 208, and the air. As the liquid film adsorption surface area 204 emerges from the flowing suspension 209, a second contact line is formed at the trailing edge of the liquid film adsorption surface area 204, the liquid 208, and the air, and due to the hydrophobic-hydrophobic interaction, nanoparticles 211 from the interface 207 can be deposited on the lower liquid film adsorption surface area 206 (FIG. 2E). The elongated nanoparticles 211 floating on the liquid film 208 gather and deposit at the contact line on the substrate 202. As the liquid film 208 evaporates, the contact line retreats, and therefore, the contact line moves inward on the liquid film adsorption surface area 204, and a film 212 of aligned elongated nanoparticles is deposited across the substrate 202 (FIG. 2F). Substrate 202 may continue to be removed from aqueous medium 205 and suspension 209 until all hydrophilic surface areas have passed through suspension 209. To stop nanoparticle film deposition, flowing suspension 209 may be replaced with water-immiscible solvent 226 that does not contain nanoparticles. As water film 208 continues to evaporate, film 212 of elongated nanoparticles continues to form (FIG. 2G). In this way, a film of elongated nanoparticles may be formed over a large area in a short period of time. By way of illustration, the liquid film remaining on the liquid film adsorption surface area may be completely evaporated in a few seconds or less (e.g., 10 seconds or less). Film 212 of aligned elongated nanoparticles may cover the entire liquid film adsorption surface area, or may leave bare patches on liquid film adsorption surface area 204 if the concentration of nanoparticles in the suspension is insufficient to provide complete coverage (FIG. 2H).

[0030] The elongated nanoparticle film can be formed from a variety of elongated nanoparticles, wherein the elongated nanoparticles are characterized by a high aspect ratio and a nanoscale diameter. For the purposes of this disclosure, a high aspect ratio is defined as a length to diameter ratio of at least 5, including an aspect ratio of at least 10, and a nanoscale diameter is defined as a diameter of no more than 1000 nm, including a diameter of no more than 100 nm, no more than 10 nm, and no more than 1 nm. The elongated nanoparticles include carbon nanoparticles, metal nanoparticles and semiconductor nanoparticles, such as single-walled carbon nanotubes (SWCNTs), including semiconductor SWCNTs (s-SWCNTs) and metal SWCNTs (m-SWCNTs); multi-walled carbon nanotubes (MWCNTs); other types of single-walled and / or multi-walled nanotubes, such as but not limited to boron nitride nanotubes, graphene nanoribbons, cellulose nanofibers (CNFs) and cellulose nanocrystals, metal nanowires (NWs), semiconductor nanowires (such as Si or ZnO nanowires), ceramic nanowires and nanowires made of organic materials.

[0031] A suspension of elongated nanoparticles is formed by dispersing the nanoparticles in a liquid. Whether the liquid forms a suspension will depend on the nanoparticles used, and can be an aqueous medium or an organic medium. A wide variety of liquids and mixtures of organic liquids can be used to form liquid films and suspensions, with the proviso that the liquid used to form the suspension is not miscible with the liquid used to form the liquid film. In some embodiments of the methods, the liquid film is an aqueous medium and the suspension is a non-aqueous organic liquid, or vice versa. Examples of suitable organic liquids include chloroform, toluene, 1,2-dichlorobenzene, carbon tetrachloride, cyclohexane, 1,2-dichloroethane, 1,1,2-trichloroethane, dichloromethane, chlorobenzene, 3-chlorotoluene, o-xylene, m-xylene, p-xylene, and mixtures of two or more thereof.

[0032] If the elongated nanoparticles are not sufficiently dispersed in the selected aqueous medium or non-aqueous organic liquid, the nanoparticles may be surface treated and / or coated with a material that allows the nanoparticles to be sufficiently dispersed. For example, a coating may be used in a pre-sorting step to encapsulate s-SWCNTs therein so as to separate s-SWCNTs from a mixture of s-SWCNTs and m-SWCNTs. These types of coatings are referred to herein as semiconductor selective coatings. A variety of semiconductor selective coatings are known, including semiconductor selective polymer coatings. Descriptions of such polymers may be found, for example, in Nish, A.; Hwang, JY; Doig, J.; Nicholas, RJ Highly selective dispersion of single-walled carbon nanotubes using aromatic polymers. Nat. Nanotechnol. [2007,] 2,640-6. Semiconductor selective polymers are typically organic polymers with a high degree of π conjugation and include polyfluorene derivatives such as poly(9,9-dialkyl-fluorene) derivatives and poly(phenylene vinylene) derivatives. Optionally, the coating can be removed from the elongated nanoparticles after the nanoparticle film is deposited.

[0033] The concentration of the elongated nanoparticles in the suspension will depend on the type of nanoparticles used and the size of the surface area to be covered. In general, at lower nanoparticle concentrations, less substrate surface area will be covered. Substrate surface area coverage increases with increasing nanoparticle concentration in the suspension. At sufficiently high nanoparticle concentrations, the elongated nanoparticles at the liquid / suspension interface can interact and form two-dimensional liquid crystals that float on the liquid surface. These floating liquid crystals can then deposit on the liquid film adsorbed surface area as the liquid film dissipates and the contact line recedes on the substrate. By way of illustration, the elongated nanoparticle concentration (e.g., s-SWCNT concentration) in the suspension can range from 5 μg / mL to 200 μg / ml. However, lower or higher nanoparticle concentrations can be used.

[0034] The substrate on which the elongated nanoparticle film is deposited can be a hydrophilic or hydrophobic substrate. Examples of hydrophilic substrates include silicon and silicon oxides (e.g., SiO2). Other hydrophilic substrate materials that can be used include metal oxides (including but not limited to aluminum oxide, hafnium oxide, and lanthanum oxide), silicon nitride, hydrophilic semiconductor materials (such as germanium), and organic materials (such as hydrophilic polymers or polymers of grafted or crosslinked materials having hydrophilic functional groups (such as poly(ethylene glycol) or zwitterions) on their surfaces). Hydrophobic substrate materials include substrates coated or functionalized with hydrophobic chemical functional groups or coatings (such as HMDS and hydrophobic organic polymers, including those that can be used in flexible electronic applications). Such polymers include but are not limited to polydimethylsiloxane (PDMS), polyethersulfone, poly(ethylene terephthalate), and the like. These materials can constitute the deposition substrate or can be applied as a coating over a bulk substrate base. The liquid film adsorption and / or liquid film repelling regions may be patterned on the substrate surface using known methods, such as surface treatment or patterned coating deposition.

[0035] In embodiments of the method using barriers to define flow channels (e.g., FIG. 2B ), it is desirable (but not necessary) to select the barrier material so that the elongated nanoparticles are less likely to adhere to the surface of the barrier than to the surface of the deposition substrate. It is not necessary to remove the nanoparticles deposited on the barrier. However, if the nanoparticles deposited on the barrier are significant, it may be necessary to periodically replace the barrier or clean the nanoparticles deposited on the barrier.

[0036] The liquid film adsorption surface area can be of various shapes and sizes. Because the elongated nanoparticles are deposited along a contact line having an outline defined by the boundaries of the liquid film adsorption surface area, the deposited elongated nanoparticle film will reflect the shape of the liquid film adsorption area. This enables the deposited elongated nanoparticle film to have complex shapes and different sizes. By way of illustration, the liquid film adsorption surface area and the nanoparticle film deposited thereon can have a square or rectangular shape, can form a straight line, can have curved edges (e.g., circular or oval), or can form a straight line with sharp bends and / or rounded corners.

[0037] The nanoparticle film can be deposited as a highly uniform monolayer film over a large surface area. The area over which the uniform nanoparticle film can be formed is not particularly limited and can be large enough to cover the surface of the entire semiconductor wafer. By way of illustration, the elongated nanoparticle film can be deposited over a surface area of ​​at least 1 mm2, at least 10 mm2, at least 100 mm2, or at least 1 m2.

[0038] Conventional methods of patterning substrate surfaces, such as lithography, can be used to provide the substrate with liquid film adsorption and liquid film repulsion surface regions. A novel method of forming a deposition substrate 302 with liquid film adsorption and liquid film repulsion surface regions starting with a silicon oxide (SiO 2) substrate 302 is schematically depicted in FIG3 . In the specific example of the method shown in FIG3 , the SiO 2 surface is disposed on an underlying silicon substrate 303. The method begins by depositing a layer of positive resist 330 (such as an electron beam or photoresist) on the SiO 2 substrate 302, and developing and lithographically patterning the resist to expose one or more regions of the underlying SiO 2 substrate surface (inset (a) of FIG3 ). PMMA is used as the resist 330 in the method shown in FIG3 , but other resist materials may be used. The resist layer 330 is then cleaned using an ultraviolet (UV) / ozone exposer as needed (inset (b) of FIG3 ). A thin layer of yttrium or scandium metal 333 is then deposited over the patterned resist layer 330 and the exposed surface areas of the SiO2 substrate 302 (inset (c) of FIG. 3). Next, the resist layer 330 is removed using a resist lift off, leaving the yttrium or scandium metal 333 on the SiO2 substrate 302 in the areas that have been exposed through the patterned resist layer 330 (inset (d) of FIG. 3). The sample is then exposed to an oxygen-containing atmosphere at a sufficient temperature and for a sufficient time to oxidize the yttrium or scandium metal 333 and increase the degree of oxidation of the SiO2 surface (inset (e) of FIG. 3). By way of illustration only, the sample may be exposed to ozone and ultraviolet light at a temperature of at least 60°C (e.g., 60°C to 100°C) for a period of at least 5 minutes (e.g., 5 to 20 minutes). A coating 335 based on a hydrophobic polymer or molecule, such as a HMDS coating, is then deposited on the exposed surface area of ​​the SiO2 substrate 302 and the yttrium oxide or scandium oxide 337 (Fig. 3, inset (f)). The yttrium oxide or scandium oxide 337 is then selectively etched to form a deposition surface comprising one or more hydrophilic SiO2 surface regions 304 and one or more hydrophobic regions 306. Example

[0039] Example 1: Surface water-assisted TaFISA.

[0040] This example demonstrates a method for using a thin film of water to guide s-SWCNTs to form a high-density film on a chemically patterned surface, where the s-SWCNTs are arranged along the solvent-water-substrate or air-water-substrate contact line. To demonstrate this process, narrow hydrophilic strips were used on a Si / SiO2 wafer as water film adsorption areas, and narrow films of s-SWCNTs were deposited near the edges of the patterned hydrophilic strips (panels (a) to (d) of Figure 4). The proposed film formation mechanism is confirmed by the following evidences in this example: first, during deposition, the substrate selectively retains surface water on the hydrophilic surface area; second, s-SWCNTs can be fixed in place at the contact line on the substrate; third, s-SWCNTs are not deposited on the interior of the hydrophilic surface containing water; and fourth, the presence of water allows s-SWCNTs to automatically arrange themselves according to the previously deposited s-SWCNTs in a monolayer and form a very densely packed and uniformly arranged film with an s-SWCNT packing density of up to 250 μm-1. Field effect transistors using these films as semiconductor channel materials are fabricated to exhibit high current density and transconductance achieved by such densely packed films.

[0041] Films formed with low s-SWCNT concentration:

[0042] The samples in panels (a) to (d) of FIG. 4 were patterned to have a broad hydrophilic strip with a 50 μm water contact angle (WCA) <10° surrounded by a less hydrophilic surface with a WCA of 40°. This surface chemical pattern was formed by lithographically depositing yttrium metal in the desired hydrophilic areas, using UV / ozone treatment to clean and hydroxylate the entire substrate and also oxidize the yttrium metal, functionalizing the surface with HMDS to create a less hydrophilic surface, and then etching the yttrium oxide by exposure to dilute aqueous hydrochloric acid for 5 seconds to reveal the hydrophilic surface where the yttrium oxide was located, while preserving the HMDS functionalized surface in all other areas (panels (a) to (g) of FIG. 3). The s-SWCNT films were deposited using a variation of the TaFISA procedure, which is described in detail elsewhere. (KR Jinkins, Aligned 2D carbon nanotube liquid crystals for wafer-scale electronics, Science Advances, 2021, Vol. 7, No. 37). Briefly, as shown in FIG2A , a patterned substrate and a barrier are held parallel to each other to form a narrow flow channel therebetween, and they are immersed in a deionized (DI) water bath. A suspension of polymer-surrounded semiconductor s-SWCNTs in chloroform (an s-SWCNT ink) is injected into the channel between the substrates and the suspension flows along the water surface while lifting the substrate across the ink-water interface. As the substrate crosses the interface, s-SWCNT deposition occurs. In the liquid film-repelling HMDS surface regions, s-SWCNTs are deposited as a uniform film aligned in the direction of the ink-water-substrate contact line. Because the s-SWCNT ink concentration is low (approximately 5 μg mL -1), the film in these regions is relatively thin, with only 10-30 μm -1 s-SWCNTs. The morphology of s-SWCNTs on the hydrophilic strips is very different. These regions were imaged using AFM, as it produces an image of the surface topography of the s-SWCNTs and can also indicate different surface chemistries, and show the boundaries between the hydrophilic and relatively hydrophobic (HMDS) regions (white dashed lines in panels (b) to (c) of FIG. 4 ). The center of the hydrophilic surface region is bare and has no s-SWCNTs. Within and near the boundaries of the hydrophilic regions, a very uniform s-SWCNT film is formed and a high packing density film is formed near the edge of the hydrophilic strip. Between the surface chemical boundary and the high packing density film are regions with one or more gaps in the film. Topographic imaging by AFM indicates that all s-SWCNTs in both the high packing density film and the less densely packed film are at the same height from the substrate and are a single layer, with occasional stray s-SWCNTs appearing in the second layer.The s-SWCNTs in the high packing density film are not resolvable by a typical AFM probe (2 to 10 nm tip radius), but are resolvable by a sharper specialized probe (tip radius of about 1 nm), as shown in inset (d) of Figure 4. The high packing density film has an s-SWCNT packing density of about 250 μm -1.

[0043] Proposed mechanism of surface water-assisted film deposition:

[0044] The proposed mechanism for forming these s-SWCNT films is described above and schematically shown in FIGS. 2A-2H . The images in FIGS. 2B-2H show how this mechanism operates during a TaFISA-type deposition process and how retained surface water remains on the substrate as it passes through the ink-water interface, then the ink-air interface, and eventually evaporates, leaving a surface-dry film. The black dots in FIG. 2B represent s-SWCNTs aligned parallel to the direction of ink flow and perpendicular to the substrate surface; black lines indicate s-SWCNTs with other orientations. For simplicity, all s-SWCNTs on the interface are represented by aligned dots, but mobile s-SWCNTs on the water surface may have other orientations. Individual s-SWCNTs floating on the retained surface water migrate to the ink-retained water film-substrate contact line and deposit at the contact line, while s-SWCNTs deposited on the HMDS surface area do not move after deposition. The plausibility of the mechanism can be confirmed by observing specific parts of the deposition process, analyzing the s-SWCNT film morphology, and independent control experiments. This is done by breaking the mechanism down into smaller parts that are easier to evaluate: maintaining surface water as a film on the hydrophilic surface area, depositing s-SWCNTs at the suspension-water-substrate contact line, allowing s-SWCNTs to migrate to the water surface, and self-alignment and dense packing of s-SWCNTs in the presence of surface water.

[0045] The first part of the study confirmed that water was retained on the hydrophilic surface regions of the substrate. During the preparation of the substrate, surface water in the hydrophilic surface regions could be observed by eye after etching with dilute aqueous HCl and rinsing with deionized water. To confirm that surface water was retained even during deposition conditions where the chloroform-based s-SWCNT ink flowed across the substrate surface, surface videos were collected through a transparent quartz substrate and the retention of water was clearly visible. In the videos, some chloroform solvent also appeared on the substrate, although it evaporated quickly within 1-2 seconds, while the water remained longer, up to 3-4 seconds.

[0046] The second part of this study confirmed that s-SWCNTs were deposited at the liquid-liquid-solid contact line formed by a water film retained on the surface surrounded by the chloroform ink.

[0047] The third part of this study confirmed that s-SWCNTs deposited on the retained surface water film are mobile and do not pass through the surface water film to deposit on the interior of the hydrophilic region in the presence of water. This was inferred to be the case by observing the solubility of s-SWCNTs, the properties of the hydrophilic surface region in the presence of water, and the morphology of the deposited film. Initially, the polymer-surrounded s-SWCNTs used were insoluble in water, so when they diffused from the chloroform ink to the chloroform-bulk water interface, they remained at the interface. The retained surface water film on the substrate can be thin enough to behave differently from the bulk water. To examine this, surfaces with water-adsorbing and water-repelling surface regions were prepared, sparse s-SWCNTs were deposited directly from chloroform via spin coating without the use of water, and the samples were then immersed in water. Prior to water exposure, the s-SWCNTs were randomly distributed throughout the surface on both the hydrophilic water-adsorbing regions and the less hydrophilic (relatively hydrophobic) water-repelling regions. After water exposure, all s-SWCNTs on the hydrophilic water-adsorbed surface area left, and all s-SWCNTs on the relatively hydrophobic surface remained in place. The ability to remove s-SWCNTs by a simple water rinse suggests that any s-SWCNTs that attempt to penetrate the retained water film will not adhere to the hydrophilic surface and will diffuse back to the ink-water film interface or the ink-water film-substrate contact line. When the experiment was repeated with high packing density, randomly oriented s-SWCNTs that formed an interconnected network, most of the s-SWCNTs on the hydrophilic surface area could not be removed by a simple water rinse, suggesting that adhesion forces between neighboring s-SWCNTs stabilize the position of the deposited s-SWCNTs.

[0048] Next, the morphology of the films deposited on the water-repelling and water-adsorbing regions was investigated (panels (a) to (d) of Figure 4). The images are from two regions on the same substrate from a single deposition process. The relatively hydrophobic, water-repelling surface region has relatively uniform s-SWCNT deposition in the film (approximately 20 μm -1 s-SWCNT), while the hydrophilic, stripe-like surface region has s-SWCNT only at the edges of the stripe, with bare regions in the interior of the stripe. Based on the uniform s-SWCNT density in the relatively hydrophobic region, it is inferred that the solvent-water interface of the retained surface water begins to uniformly distribute s-SWCNTs. If the s-SWCNTs remain in place when the water evaporates, they will transfer to the substrate in a similarly uniform distribution, but all deposited s-SWCNTs are seen near the edges of the stripe. Based on this, it can be inferred that the s-SWCNTs that are initially uniformly distributed on the surface of the retained water film are able to migrate to the edge of the water stripe before the water evaporates.

[0049] The final part of this study confirmed that s-SWCNTs in hydrophilic surface regions self-align to form more densely packed s-SWCNT films compared to less densely packed s-SWCNT films deposited onto relatively hydrophobic surface regions. In this example, the s-SWCNT films were examined using high-resolution AFM imaging with an extremely sharp probe with a tip radius approaching 1 nm. With the high-resolution probe and under very careful imaging conditions, individual s-SWCNTs with a spacing of 3.5 to 4 nm could be resolved. The high-packing density film near the boundary of the hydrophilic surface region (Figure 5A and corresponding histogram in Figure 5C) was observed to have an s-SWCNT packing density of about 250 μm-1 and a relatively uniform height of about 3 nm from the substrate. In the films formed in the uniform relatively hydrophobic surface region (FIG. 5B and the corresponding histogram in FIG. 5D), the s-SWCNTs are arranged in an interconnected film via a Y-branching pattern, arranged in strands of about 1 to 10 s-SWCNTs, where, for example, a strand of 5 s-SWCNTs will have two s-SWCNTs separated from the original strand and fused to the adjacent strand. Within each strand, the s-SWCNTs are also densely packed with about 250 μm-1 s-SWCNTs. Both types of films were also imaged with cross-sectional transmission electron microscopy (TEM), which confirmed that high-resolution AFM images showed an average spacing of 3.5 and 3.4 nm for the monolayers of the film on both the hydrophilic and relatively hydrophobic regions (insets in FIG. 5A and 5B). Similar to the high packing density films, almost all strands are 3 nm in height, but some clearly have multiple layers of s-SWCNTs that are collinear with lower layers, thereby forming bundles as described in previous work (SM Foradori, KR Jinkins, MS Arnold, Journal of Applied Physics 128(23), 234301(2020)],[SM Foradori, JH Dwyer, A. Suresh, P. Gopalan, MS Arnold, Applied Physics Letters 121(7), 073504(2022)).

[0050] The more complete packing morphology on the hydrophilic surface region can be explained as follows. Because the hydrophilic surface region retains a water film, the contact line on the surface close to the boundary of the hydrophilic and relatively hydrophobic regions is relatively stable compared to the moving contact line on the uniform relatively hydrophobic region, and the interaction time between the s-SWCNT and the substrate is longer than on the relatively hydrophobic surface region. The extra interaction time obtained by the relatively stable contact line can explain the extremely dense packing of the film. This extra time will allow the s-SWCNT to migrate right to the previously deposited s-SWCNT, follow their auto-arrangement, and form a densely packed film with very few gaps.

[0051] High resolution imaging allows the degree of alignment as well as packing density to be measured. Each s-SWCNT in a 325 nm square section of the film was manually scribed to determine the length and angle of each visible s-SWCNT segment. Histograms were then prepared and using a Gaussian fit and standard deviation for high packing density films on the hydrophilic region, these lengths and angles were approximately 3.5°. The packing density results are summarized in Table 1.

[0052] FIG6A to FIG6C show high-resolution AFM height images of s-SWCNT films (panel (a)), manual scribing of visible s-SWCNT segments (panel (b)), and histograms of the angular distribution of visible s-SWCNT segments for three s-SWCNT films deposited using surface water-assisted TaFISA (panel (c)). The histograms are all centered at zero degrees to compensate for the sample's misalignment with respect to the AFM probe scan direction and any phase shift that would occur with long scans (each high-resolution image scan was approximately 77 minutes). The curves in the histograms are Gaussian functions fitted to the grouped histogram data using Origin and the standard deviations and R2 values ​​listed in Table 1 below.

[0053] Table 1. Gaussian curve fitting of s-SWCNT film arrangement histogram [Histogram] [Figure Number] [s-SWCNT] [Ink density] [(] [μ] [g mL , -1 , ] [)] [Standard Deviation] [(angle)] [R , 2 , ] Fig. 6A 5 3.64 ±0.05 0.9980 Figure 6B 5 3.50 ±0.04 0.9987 Figure 6C 100 4.74 ± 0.13 0.9868

[0054] More concentrated inks (>20 μg mL -1) can deposit more s-SWCNTs at the ink-water interface, where the s-SWCNTs can interact and form two-dimensional liquid crystals. These interfacial liquid crystals can also be aligned by the shear force of the flowing ink. When this interfacial liquid crystal is deposited on a hydrophilic surface region, it transfers the retained water film to the surface rather than depositing directly on the substrate surface. When the hydrophilic surface region is patterned into strips oriented in the liquid crystal alignment direction, the retained water film-substrate contact lines define the liquid crystals and preserve the overall alignment of the s-SWCNT film. The self-alignment process aggregates the defined liquid crystals into a high packing density film. In narrow hydrophilic strips (<= about 100 μm), the aggregated s-SWCNT film is typically deposited near the first edge of the hydrophilic surface region, across the ink-water interface, and leaves a gap on the bottom edge of the strip where the retained surface water may prevent the deposition of other s-SWCNTs. In wider strips (200 μm and 300 μm), the s-SWCNT film was held in the center of the strip by connection to the film anchored in place on relatively hydrophobic surface areas on either end of the strip.

[0055] Many applications require large area deposition, so the films were deposited on samples with a set of 100 μm × 2 mm stripes spanning a 25 × 25 mm area with densely packed, well-aligned films deposited in nearly every hydrophilic stripe.

[0056] To determine how the improved alignment and increased packing density of the s-SWCNT films affect their electronic performance, top-gated FETs were fabricated using 5 nm HfO2 atomic layer deposition insulator. Films were made from high packing density films on 100 μm hydrophilic strips (Figure 7) using 100 μg mL-1 s-SWCNT ink. Exemplary transfer curves for these devices and plots of current density and transconductance are shown in Figures 8A to 8D.

[0057] Methods and Materials:

[0058] [Hydrophilic pattern production] [:]Hydrophilic patterns were made on thermal oxide coated Si wafers using lithography methods. The desired hydrophilic patterns were formed using an electron beam lithography system with polymethyl methacrylate (PMMA) resist. Very large areas were patterned using a foil shadow mask and UV / ozone chamber dry etching of the resist. After development, the patterned wafers were cleaned in a UV / ozone chamber and then 2 or 3 nm of yttrium metal was deposited in a thermal evaporator built in a nitrogen glove box. After removal from the glove box and completion of a standard stripping process using hot acetone, the substrates were placed again in a UV / ozone chamber at 90°C for 8 minutes to clean and oxidize all surfaces, as well as to oxidize the deposited yttrium metal. The samples were then treated with HMDS using either a vapor phase or liquid method. The exposure time and concentration were calibrated to partially functionalize the non-patterned areas to a water contact angle of 35-45 degrees. Alternatively, samples were prepared by overexposure to HMDS to produce WCA values ​​greater than 45 degrees, followed by a short exposure in a UV / ozone chamber to reduce the WCA to a target of 35-45 degrees. Prior to the s-SWCNT deposition process, the yttrium oxide film (now about 3-5 nm thick due to oxidation) was removed using a 5 second dip in dilute aqueous hydrochloric acid (1:25 v / v, about 0.1 molar concentration), followed by a quick dip / rinse in clean deionized water, followed by drying with compressed nitrogen. At this point, the prepared samples had a 35-45° WCA in the unpatterned areas and a very hydrophilic surface (<10° WCA) in the areas that previously had the yttrium oxide film.

[0059] [s-SWCNT] [Deposition procedure] [:] s-SWCNT inks were made from s-SWCNTs dispersed in chloroform surrounded by poly[(9,9-dioctylfluorenyl-2,7-diyl)-alternative-(6,6'-[2,2'-bipyridine])](PFO-BPy) and sorted arc-discharged (GJ Brady, AJ Way, NS Safron, HT Evensen, P. Gopalan, MS Arnold, Science Advances, 2(9)(2016)). s-SWCNT films were prepared using two deposition procedures. Films made using the TaFISA method were made using a previously published method. (KR Jinkins, Aligned 2D carbon nanotube liquid crystals for wafer-scale electronics, Science Advances, 2021, Vol. 7, No. 37). The two substrates were inserted into a water bath at 45° with their surfaces facing each other to make a 3 mm wide channel. Chloroform-based s-SWCNT ink (4 mL min-1) was injected with a needle across the top of the water surface in the channel between the two substrates while the substrate was lifted through the ink-water interface at 40 mm min-1. In this example, one of the substrates had a hydrophilic chemical pattern and the other sacrificial substrate was treated with HMDS to have a WCA of about 40°. Films for calibrating Raman-based packing density measurements were made using a shear alignment technique using previously published methods. (Jinkins, Katherine R. et al. "Substrate-Wide Confined Shear Alignment of Carbon Nanotubes for Thin Film Transistors". Advanced Electronic Materials 5.2(2019): 1800593). Chloroform-based s-SWCNT ink was injected at a high volume flow rate into a sub-millimeter height and approximately 1 cm wide and 2.5 cm long channel formed between the substrate and a highly polished metal surface. The high flow rate and defined channel dimensions generate substantial shear forces that align the s-SWCNTs along the direction of ink flow as they are deposited on the substrate.

[0060] [Water contact angle measurement] [:]Static water contact angle measurements were performed using a Dataphysics OCA 15 optical contact angle system. Depending on the surface conditions, a 2 to 5 pL drop of deionized water was dispensed and the contact angle was measured immediately.

[0061] [Atomic force microscopy] [:]AFM images were collected on a Bruker Icon instrument using TESPA and / or ScanAsist-Air probes for low-resolution imaging and SAA- HPI-SS probes for high-resolution imaging. High-resolution images were collected with a square pixel size of approximately 0.3 nm.

[0062] [Transmission Electron Microscopy] [:] s-SWCNT films on Si / SiO2 substrates were sent to Eurofins EAG Laboratories (Santa Clara, CA, USA) for sample preparation and TEM imaging. Samples were prepared on a FEI Dual Beam FIB / SEM using ex situ focused ion beam (FIB) extraction and capped with carbon-based epoxy / IC before grinding. TEM imaging was performed on a FEI Tecnai Osiri FEG / TEM operated at 200 kV in bright field TEM mode and high resolution TEM mode.

[0063] [FET] [Device Manufacturing] [:]The device was lithographically patterned using a multi-step approach using a 100 kV electron beam system (Elionix G-100). After deposition of alignment marks and s-SWCNT film, unwanted s-SWCNTs were removed using radio frequency (RF) oxygen plasma etching. Electrodes were deposited in two steps: first for high-precision channel formation, and second for large contact pads. A conformal 5 nm HfO2 insulator for the top gate was deposited by atomic layer deposition (Veeco Fiji G2 PE-ALD). The top gate metal was deposited on top of the insulating layer.

[0064] s-SWCNT sorting and ink preparation: Single-walled arc-discharge carbon nanotubes (Aldrich, 698695) were purchased and sorted by sonication with a toluene solution with PFO-BPy (ADS dye, ADS153UV, poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(6,6'-{2,2'-bipyridine})], MW N = about 40 to 100 kDa) to isolate semiconducting s-SWCNTs. A mixture of 120 mg of raw s-SWCNT powder and 60 mL of toluene containing 2 mg mL-1 PFO-BPy was sonicated for 30 min at 40% power using a Fisher sonic dismembrator model 500 (400 W) in a 150 mL beaker surrounded by a static water bath for cooling. The solution was then divided into six tubes and centrifuged at 41.000 rpm (300.000 g, max) for 10 minutes using a swinging bucket rotor (Sorval WX, TH-641, Thermo Scientific) to remove soot and undispersed s-SWCNTs. The top 90% of the suspension was collected, and this process was repeated for a total of six batches. The combined suspension from all six batches was concentrated to approximately 50 mL using a rotary evaporator and then centrifuged again (same rotor and speed) for 1 hour to precipitate any poorly dispersed s-SWCNTs. The top suspension was collected, diluted to 60 mL with toluene, and centrifuged again (F65L-6x13 rotor, 24 hours at 25.500 rpm; in a 10 Ml PTFE tube with ETFE cap, part 3114-0010, Thermo Scientific Nalgene) to form an agglomerate of all suspended semiconductor s-SWCNTs. The pellets were separated from the PFO-BPy-rich supernatant and the supernatant was discarded. The semiconducting s-SWCNT pellets were redispersed in fresh toluene with stirring on a hot plate set at 80°C, and the pelletization process was repeated two or three more times to reduce the mass ratio of PFO-BPy:s-SWCNT to about 0.5:1 (measured by UV / Vis / NIR absorption spectroscopy). The s-SWCNT ink was prepared by dispersing the final pellets in chloroform (Fisher Scientific, C606-4) and diluting to a s-SWCNT concentration of 100 μg mL-1.

[0065] Raman spectroscopy measurement results of s-SWCNT film filling density:

[0066] Raman spectroscopy was also used to characterize the packing density and alignment of the s-SWCNT films, and the results confirmed high packing density and excellent alignment results. When using Raman spectroscopy to measure the packing density of s-SWCNTs in a film, a calibration curve is necessary. The intensity of the s-SWCNT peaks in the Raman spectrum depends on many spectrometer and sample prep factors, so care must be taken to ensure that calibration and unknown samples are measured under the same conditions. Two sets of calibration samples were made using the shear force alignment method (ShASAM) described elsewhere (Jinkins, Katherine R. et al. "Substrate-Wide Confined Shear Alignment of Carbon Nanotubes for Thin Film Transistors". Advanced Electronic Materials 5.2 (2019): 1800593). AFM was used to measure the s-SWCNT packing density at the marked locations because this imaging technique does not contaminate the sample surface. This deposition technique was used because it is expected to deposit individual s-SWCNTs in relatively well-aligned films. The deposition of individualized s-SWCNTs is important because calibration relies on manually counting s-SWCNTs in specific locations to determine density. If s-SWCNT bundles are deposited, the number of s-SWCNTs present in any location will not be counted because a feature that looks like a single s-SWCNT may be two or more s-SWCNTs that are not resolved. Raman spectra were collected at these same locations, and the packing density and spectral information were used to generate the calibration curve shown in Figure 9. Since all samples were prepared on Si / SiO2 wafers, the intensity of the Si peak at 520 cm-1 was used as a type of internal standard, and the ratio of the s-SWCNT G peak height to the Si peak height at about 1580 cm-1 was used as the measurement signal. The calibration curve spans s-SWCNT packing densities from about 3 to about 30 μm-1 and G / Si ratios from about 0.1 to 2.3 (Figure 9). Calibration curves were measured for HMDS-treated SiO 2 and s-SWCNT arrays on hydrophilic SiO 2 fabricated using the same yttrium-based method used to prepare the patterned areas, and the calibration curves on the two surfaces were found to be equivalent.

[0067] The spectrum of the high packing density of the film was collected using the same conditions and was found to have a maximum G / Si ratio of about 17, corresponding to an s-SWCNT packing density of about 210 μm-1. This indicates a very high packing density beyond the range of the calibration curve. This calibration curve, extrapolated beyond the measurement range, provides a rough estimate of the s-SWCNT packing density of greater than 200 μm-1 s-SWCNTs.

[0068] Polarized Raman spectroscopy can be used to determine the degree of alignment of s-SWCNT films due to the one-dimensional nature of s-SWCNTs combined with the Raman signal enhancement due to electronic transitions of s-SWCNTs near the Raman laser energy. The intensity of the Raman signal is highly enhanced if the excitation laser energy is near an optically active electronic transition. In s-SWCNTs arranged on a surface, the absorption cross section of photons approaching perpendicular to the surface is proportional to the square of the cosine of the angle α between the photon polarization and the direction of the s-SWCNT long axis. When a polarizing filter is used before the detector, the Raman signal of the s-SWCNT is also proportional to the square of the cosine of the angle between the polarizer and the long axis of the s-SWCNT. When combining a light source and a polarized scattered photon at the same angle, the Raman signal intensity of the s-SWCNT oriented at an angle α to the polarizers is proportional to cos 4(α). By knowing the orientation of the polarizer, the Raman signal can be used to determine the orientation of the s-SWCNTs by holding the polarizer in a fixed position and rotating the s-SWCNTs using a rotating stage (β). If a film of s-SWCNTs is measured instead of a single s-SWCNT, each s-SWCNT in the film will contribute to the signal intensity based on its angle relative to the angle of the polarizer. If the film is perfectly aligned, the Raman signal will be proportional to cos 4(β) when the sample is rotated.

[0069] Practical considerations of the spectroscopy equipment must be taken into account to ensure accurate measurements. The polarizers must be arranged at the same angle and that angle must be aligned with the beam splitter. If the polarizer is misaligned, the signal will be artificially attenuated. If the laser polarization is not aligned with the beam splitter, the light striking the beam splitter will be elliptically polarized rather than linearly polarized. The equipment used in this measurement uses a half-wave plate to adjust the polarization angle of the laser and an adjustable polarizer in the beam path just before the detector mirror, grating, and detector. These optical components are all mounted in a holder with a stepper motor and are only mounted in the spectrometer when needed. Matching the laser and detector polarization angles and matching that angle with the beam splitter requires careful measurements. This data was collected on a confocal Raman microscope using a 50x long working distance objective and a spot size of approximately 1-3 μm, depending on how tightly the beam is focused. This small spot size means that the rotating sample stage must be very accurately centered (and flat), otherwise different parts of the film are measured while the sample is rotated.

[0070] After aligning the polarizer, a high packing density and highly aligned film was mounted on a rotating stage and measured at various angles. The intensity of the G peak versus sample rotation is plotted in Figures 10A and 10B. Low power and long exposure were used to avoid damaging the s-SWCNTs due to exposure to highly focused lasers. Also plotted in these figures are simulated curves for a perfectly aligned film and curves for an alignment modeled using a surrounding normal distribution with increased offset. Comparison of the measured data with the simulated curves shows that the film alignment matches the modeled film with σ between 5 and 15 degrees in the 15-75 degree stage rotation position. When plotted on a logarithmic scale, the data closely matches the σ=10 degree simulated film. The intensity of the 521 cm-1Si peak measured under these polarization conditions and the Si <100> The expected intensity for an oriented sample. A close match of the Si measured intensity to the expected value indicates that the polarization optics are properly aligned for this measurement, and the minimum peak height also provides an indication of the quality of the polarization optics and stage alignment. This represents a combination of the absorptivity of the polarizer, the relative polarization of the laser to the detector polarizer, the alignment of the laser polarization to the beam splitter, the flatness of the stage, the polarization ratio of the Raman laser, and the alignment of the rest of the optical elements in the optical path, so it combines many experimental factors.

[0071] The intensity ratio of the s-SWCNT Raman spectra parallel to and perpendicular to the film matching the laser and detector polarizer alignment has been used to determine the degree of alignment of the s-SWCNT film. For the measured data, the ratio is (8465 / 18) = 470, and this corresponds to a surrounding normal distribution with a standard deviation of approximately 9.4°. When comparing the measured ratio of 470 to the expected polarization ratio of the Raman laser (nominal 1000:1) and including all potential sources of error described above, it becomes apparent that this measurement may be close to the performance limit of this equipment. In order to see how this measurement limit relates to the expected results for densely packed films, the film alignment measurements provided by the AFM images were used to calculate the expected parallel and perpendicular ratios (Table 2).

[0072] Table 2: Predicted polarized Raman measurements [Histogram] [describe] [Prediction Parallel] [ / ] [Vertical peak height ratio] 6A The first low concentration 3253 6B The second lowest concentration 2133 6C Center of dense filling film 5301 *This table refers to the same images listed in Table 1 and the images are listed in the same order for ease of comparison.

[0073] FET Manufacturing:

[0074] Highly p-doped silicon wafers with about 15 nm dry thermal oxide are cut into desired sizes.

[0075] Alignment marks (global and local) were fabricated using electron beam lithography and 0.7 / 50 nm Cr / Au using approximately 290 nm thick PMMA resist (475 PMMA A6, 4000 rpm, 60 sec, soft bake at 185°C for 90 sec; develop in an ice bath at 0°C for 40 sec using 2:1 (v / v) isopropyl alcohol / methyl isobutyl ketone; strip using hot acetone. These soft bake, develop, and strip procedures were identical for all subsequent process steps.).

[0076] Yttrium metal strips (3 nm thick) were fabricated using electron beam lithography and approximately 55 nm thick PMMA resist (950 PMMA C1, 2000 rpm, 60 seconds). UV / ozone cleaning was performed at 90°C for 8 minutes (and 3 minutes air rinse, also at 90°C). In areas without yttrium oxide, a water contact angle of approximately 40° was obtained using HMDS surface treatment (vapor or liquid). Yttrium oxide was etched using a 5 second immersion in dilute aqueous hydrochloric acid (1:25 v / v, approximately 0.1 molar HCl concentration), followed by a immersion rinse in deionized water and blow dried with nitrogen. Deposition of s-SWCNT films using the TaFISA method was as described above.

[0077] RF oxygen plasma etching was used to define the FET channel. The desired s-SWCNTs were protected with an electron beam patterned PMMA mask (~100 nm, 950 PMMA C2, 4000 rpm, 60 seconds). Electrodes defining the FET channel were precisely written using electron beam lithography and thermal evaporation of ~100 nm thick PMMA resist (950 PMMA C2, 4000 rpm, 60 seconds) and 10 / 10 nm Pd / Au. Thick contact pads were deposited on the channel electrodes to ensure low device electrode resistance and were fabricated using electron beam lithography and ~290 nm thick PMMA resist (475 PMMA A6, 4000 rpm, 60 seconds) and 10 / 80 nm Pd / Au.

[0078] Atomic layer deposition (Veeco Fiji G2 PE-ALD) was used to deposit 5 nm of HfO2 on all surfaces (150°C, 41 cycles of alternating Hf-TDMAH [tetrakis(dimethylamido)hafnium(IV)] and water pulses).

[0079] The top gate metal was deposited using electron beam lithography and thermal evaporation of approximately 100 nm thick PMMA resist (950 PMMA C2, 4000 rpm, 60 seconds) and 0.7 / 20 nm of Cr / Au.

[0080] Contact to the source and drain electrode pads was made using gold coated tungsten needles in a custom probe station. The 10 / 80 nm Pd / Au on the SiO2 electrode pads had moderate adhesion strength, and moderate pressure applied with the probe needle caused the metal to scratch / delamate and penetrate the thin 5 nm HfO2 insulating layer.

[0081] Some devices were fabricated with an intentional short across the channel to measure electrode impedance, which was 20-40 ohms.

[0082] Table 3: FET device dimensions and parameters: [parameter] [value] Channel length 60, 80 or 130 nm Channel width 1.08 μm Channel electrode composition 10 nm Pd / 10 nm Au Probe contact electrode composition 10 nm Pd / ~80 nm Au Gate Metal Composition 0.7 nm Cr / 30 nm Au Substrate insulator composition About 15 nm dry thermal oxide Top gate insulator composition 5 nm ALD HfO2 (deposited at 150°C) Short circuit material composition (only used to measure electrode resistance) 10 nm Pd / ~80 nm Au (fabricated using the same steps as the probe contact electrode) Electrode resistance 20 to 40 ohms

[0083] Example 2: Surface water-assisted ShASAM.

[0084] This example demonstrates an elongated nanoparticle film deposition process that delivers water and s-SWCNT-containing ink (i.e., s-SWCNT suspension) to a substrate different from that described in Example 1. For this example, the principles of the film deposition mechanism are the same as described in Example 1, and thus demonstrate that the methods are not limited to any particular method for delivering the liquid or s-SWCNT ink to the substrate.

[0085] The s-SWCNT films were deposited using a variation of the ShASAM method, which is described in detail elsewhere (Jinkins, Katherine R. et al. "Substrate-Wide Confined Shear Alignment of Carbon Nanotubes for Thin Film Transistors". Advanced Electronic Materials 5.2 (2019): 1800593). The flow channel device used in this example is shown in Figure 1 of Jinkins et al. (2019). The substrate was placed between two metal plates with the target surface facing the smooth polished side of one plate wall, with a gasket and a stainless steel foil spacer in between. The foil spacer is slightly thinner than the gasket, so when the screws holding the metal plates together are tightened, the gasket is compressed to the thickness of the foil spacer. This forms an open flow channel between the substrate surface and the polished metal surface with a liquid-tight seal and a gap equal to the thickness of the foil spacer. The polished metal plate has a liquid inlet at one end of the substrate and the gasket is open at the other end so that the liquid injected into the channel flows in one direction across the substrate from the inlet to the gasket opening. First, water was injected into the channel and allowed to drain. Next, a set of three liquids was layered in the inlet line; the first layer was 0.5 mL of chloroform saturated with water, followed by 0.25 mL of chloroform containing 125 μm / mL s-SWCNTs, and finally 3.25 mL of anhydrous chloroform. This set of liquids was injected into the channel inlet at a volume flow rate of 100 mL / min, and then about 10 mL of 2-propanol was manually injected. High-speed injection of s-SWCNT ink into narrow channels produces high shear rates of up to 10,000 s-1. On the patterned hydrophilic areas of this sample that retain surface water, s-SWCNTs deposit on the chloroform-water interface and migrate to the chloroform-water-substrate contact line, where they are deposited aligned with the direction of the contact line (which may or may not be aligned with the direction of liquid flow). On substrates without patterning and without retained surface water, as s-SWCNTs were deposited directly from chloroform ink on the substrate, the high shear liquid flow aligned them with the direction of the ink flow.

[0086] Figures 11A and 11B show cross-polarized optical images of s-SWCNT films deposited as described above, including rectangular regions retaining surface water. The contrast of carbon nanotube arrays imaged by cross-polarized light depends on their arrangement direction and packing density. (Deng, Shibin et al., "High-Throughput Determination of Statistical Structure Information for Horizontal Carbon Nanotube Arrays by Optical Imaging" Advanced Materials, 2016, Vol. 28, No. 10, pp. 2018-2023). If the polarization directions of the linear polarizing filters on the light source and detector are set to about 80° to 89° relative to each other, and the carbon nanotube array is configured at 45° to one of the polarizing filters, the contrast of the carbon nanotube array depends on the direction and packing density of the array. An array in one direction will appear bright relative to a neutral background, and an array in a perpendicular direction will appear dark relative to a neutral background. The degree of contrast varies with the packing density of the array and the uniformity of the orientation of the nanotubes within the array, as well as the relative angle between the two linear polarizing filters. In FIGS. 11A and 11B , the polarizers are set to show the horizontally aligned array as bright and the vertically aligned array as dark. FIG. 11B is a replica of FIG. 11A , showing the region of retained water as a white dashed rectangle with rounded corners. The s-SWCNT array (i.e., the deposited film) within the region of retained surface water is bright along the horizontal sides of the rectangle and in most of the interior region, indicating that the s-SWCNTs in the deposited film are horizontally aligned by the guidance of the horizontal chloroform-water-substrate contact lines. However, on the left and right sides, the film image is dark, indicating that the s-SWCNTs in the film are vertically aligned by the guidance of the vertical chloroform-substrate-water level lines on the sides of the region of retained surface water. The region surrounding the region of retained water also has s-SWCNTs deposited, but its packing density and degree of alignment are lower relative to the region with retained surface water, so it has very little contrast in these imaging conditions. The images in Figures 12A and 12B are AFM height images showing representative s-SWCNT films from an unpatterned sample with no retained surface water (Figure 12A) and a patterned sample with retained surface water in the regions (Figure 12B) fabricated as described above, fabricated under similar ink concentration, volume, and flow rate conditions and without filling the channels with water prior to deposition. These images show the increase in packing density and improvement in alignment direction uniformity obtained by using the present invention.

[0087] Cross-polarized optical microscopy: Optical images were collected on a Nikon Optiphot-2 microscope with a fixed-direction linear polarizing filter in the camera light path and a rotatable linear polarizing filter in the light source path.

[0088] The foregoing description of illustrative embodiments of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the exact form disclosed, and modifications and variations are possible in light of the above teachings or may be obtained from the practice of the invention. The embodiments are selected and described in order to explain the principles of the invention and as a practical application of the invention to enable one of ordinary skill in the art to utilize the invention in various embodiments and various modifications as are suitable for the particular use covered. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.

[0089] 102:Substrate 104: Surface area 106: Liquid film exclusion area 108: Liquid film 109: Suspension 111: Elongated Nanoparticles 112: Film of aligned nanoparticles 202:Substrate 204: Liquid film adsorption surface area 205:Liquid 206: Liquid film repellent surface area 207: Interface 208: Liquid Film 209: Suspension 211:Slim Nanoparticles 212: Slender Nanoparticle Film 213: wall 226: Water-immiscible solvent 302: Deposition substrate 303: bottom substrate 304: Hydrophilic surface area 306: Hydrophobic surface area 330: Anti-corrosion agent 333: Yttrium or scandium metal 335: Hydrophobic polymer or polymer based on molecule 337: Yttrium oxide or scandium oxide

Claims

1. A method for forming a film of arranged elongated nanoparticles on a substrate, the method comprising: providing a substrate having at least one liquid film adsorption surface region defined by at least one liquid film repulsion surface region; forming a liquid film on the at least one liquid film adsorption surface region, wherein the liquid film is defined by the at least one liquid film repulsion surface region; contacting a suspension containing dispersed elongated nanoparticles with the at least one liquid film, wherein the suspension and the at least one liquid film are immiscible, such that the at least one liquid film and the suspension form an interface and the elongated nanoparticles transfer from the suspension to the surface of the at least one liquid film at the interface; and dissipating the at least one liquid film, whereby, as the liquid film dissipates, the elongated nanoparticles are deposited along a contact line defined by: the liquid film; the substrate; and the suspension or air.

2. The method of claim 1, wherein the hydrophilicity of the at least one liquid film adsorption surface region is greater than that of the at least one liquid film repulsion surface region.

3. The method of claim 2, wherein the at least one liquid film is an aqueous liquid film.

4. The method of claim 1, wherein the hydrophilicity of the at least one liquid film adsorption surface region is less than that of the at least one liquid film repulsion surface region.

5. The method of claim 1, wherein forming the liquid film on the at least one liquid film adsorption surface region comprises flowing a liquid over the at least one liquid film adsorption surface region to wet the at least one liquid film adsorption surface region, whereby the liquid is retained on the at least one liquid film adsorption surface region and not retained on the at least one liquid film repulsion surface region.

6. The method of claim 1, wherein contacting the suspension with the at least one liquid film comprises causing the suspension to flow 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 adsorption surface region comprises immersing the at least one liquid film adsorption surface region in a liquid and withdrawing the at least one liquid film adsorption surface region from the liquid, wherein the liquid film remains on the at least one liquid film adsorption surface region after the at least one liquid film adsorption surface region has been withdrawn from the liquid.

8. The method of claim 1, wherein the steps of forming the liquid film on the at least one liquid film adsorption surface region and contacting the at least one liquid film with the suspension containing dispersed elongated nanoparticles are performed by: forming a layer of the suspension on the liquid, immersing the at least one liquid film adsorption surface region in the liquid, and extracting the at least one liquid film adsorption surface region from the liquid and through the layer of the suspension.

9. The method of claim 8, wherein the suspension layer continuously flows above the liquid as the at least one liquid film adsorption surface region is extracted from the liquid and passes through the suspension layer.

10. The method of claim 1, wherein the elongated nanoparticles are carbon nanotubes.

11. The method of claim 10, wherein the elongated nanoparticles are semiconductor single-walled carbon nanotubes.

12. The method of claim 11, wherein the semiconductor single-walled carbon nanotubes form a liquid crystal on the surface of the liquid film.

13. The method of claim 11, wherein the semiconductor single-walled carbon nanotubes in the film of arranged semiconductor single-walled carbon nanotubes have a linear packing density of at least 200 μm-1.

14. The method of claim 1, wherein the film of arranged elongated nanoparticles has an area of ​​at least 50 cm².

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 film adsorption surface region comprises silicon dioxide.

17. The method of claim 16, wherein the at least one liquid film repulsive surface region comprises an organic polymer or an organic functional group.

18. A method for patterning a silicon dioxide surface of a substrate, the silicon dioxide surface having one or more hydrophilic surface regions defined by one or more less hydrophilic surface regions, the method comprising: forming a resist layer on the silicon dioxide surface; patterning the resist layer to expose one or more regions of the silicon dioxide surface through the resist layer; depositing a yttrium metal layer or a scandium metal layer over the resist layer and the one or more exposed regions of the silicon dioxide surface to form yttrium metal-coated or scandium-coated surface regions on the silicon dioxide surface; removing the patterned resist layer from the silicon dioxide surface; and oxidizing the yttrium metal or the scandium metal on the silicon dioxide surface. A layer of material with a lower hydrophilicity than silicon dioxide is formed on the surface of silicon dioxide and above yttrium oxide or scandium oxide; and the yttrium oxide or scandium oxide is removed from the surface of silicon dioxide to form one or more hydrophilic silicon dioxide surface regions defined by the material with a lower hydrophilicity than silicon dioxide.

19. A field-effect transistor comprising: a source electrode; a drain electrode; a gate electrode; and a conductive channel electrically contacting the source electrode and the drain electrode, the conductive channel comprising a film containing an array of single-walled carbon nanotubes, the field-effect transistor having a current density of at least 1.8 mA μm⁻¹ and a transconductance of at least 1.14 mS μm⁻¹ as measured at a drain voltage of 0.6 V.

20. The field-effect transistor of claim 19, having a current density in the range of 1.8 mA μm⁻¹ to 2.2 mA μm⁻¹ and a transconductance in the range of 1.14 mS μm⁻¹ to 1.4 mS μm⁻¹ as measured at a 0.6 V bleed voltage.

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