WO2016046642A2

WO2016046642A2 - Systems and methods for large-scale nanotemplate and nanowire fabrication

Info

Publication number: WO2016046642A2
Application number: PCT/IB2015/002060
Authority: WO
Inventors: Enrique Vilanova VIDAL; Ahmed ALFADHEL; Iurii Ivanov; Jurgen Kosel
Original assignee: King Abdullah University Of Science And Technology
Priority date: 2014-09-26
Filing date: 2015-09-24
Publication date: 2016-03-31
Also published as: WO2016046642A3

Abstract

Systems and methods for largescale nanotemplate and nanowire fabrication are provided. The system can include a sample holder and one or more chemical containers fluidly connected to the sample holder. The sample holder can be configured to contain a solution and to releasably hold a substrate material within the solution. In other aspects, the system can include a robotic arm including a head configured to releasably hold a substrate material. The methods can include initiating a treatment step by moving a chemical solution from a chemical container to the sample holder to submerge the substrate material for a period of time. The methods can include moving the robotic arm to position the substrate in a chemical container. The treatment steps can be stopped by removing the chemical solution from the sample holder or by moving the robotic arm to remove the substrate from the chemical container. The treatment steps can include degreasing, polishing, rinsing, anodization, and deposition.

Description

SYSTEMS AND METHODS FOR LARGE-SCALE NANOTEMPLATE AND NANOWIRE

FABRICATION CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of and priority to U.S. Provisional Application Serial No. 62/056,1 14, having the title "SYSTEM AND METHOD FOR NANOWIRE

FABRICATION," filed on September 26, 2014, the disclosure of which is incorporated herein in by reference in its entirety.

TECHNICAL FIELD

The present disclosure generally relates to fabrication of nanotemplates and nanowires, in particular systems for large-scale synthesis of nanotemplates and nanowires. BACKGROUND

Nanowires are becoming increasingly attractive for many applications, due to their large surface area to volume ratio, and the many parameters available to tailor their properties in a wide range. For example, there is interest in use of metallic nanowires as nanowire-interconnects, in high-density magnetic recording devices, in high-density nanoelectronic devices such as field-effect transistors (FETs), and in chemical and biological sensors. Nanowires can be fabricated by number of techniques including pulsed laser deposition (PLD), vapor-liquid-solid (VLS) method and chemical vapor deposition (CVD). Template synthesis is one of the more common methods to fabricate nanowires due to its ability to produce highly ordered nanowire arrays cheaply and effectively. It has been found to be a low cost and high yield technique for producing large arrays of nanowires and is useful for producing nanowires from different materials. A number of different structures and materials can be used as the templates or membranes, including polycarbonate membranes, nanochannel array glasses and anodic aluminum oxide (AAO) membranes and films. For purposes of discussion herein we will reference anodic aluminum oxide (AAO) templates or membranes as a non-limiting example, it being understood that other templates or membranes can be used. Template synthesis using AAO templates or membranes typically involves a two-step process. In a first step, the AAO template is prepared from an aluminum material, also referred to herein as a substrate. The aluminum substrate material is cleaned (for example, degreased, electropolished) and anodized in an acidic chemical bath. The aluminum substrate acts as an anode and is placed inside the bath opposite of a cathode (typically made of platinum or titanium). This step is commonly repeated, whereby in- between the aluminum oxide produced during the first time is removed in a chemical solution (e.g. chrome solution), to yield homogenous pores. The final AAO template is then used in template synthesis of nanowires. The AAO template is used as the cathode in an electrodeposition process. The second step, namely electrodeposition, is also carried out in a chemical solution. The chemical solution can be an inorganic or an organic solution. A dimethylsulfoxide (DMSO) solution is commonly used. A chemical bath is formed comprised of the solution and an electrolyte such as a metal chloride. The template used as a cathode is placed in the bath spaced apart from an anode. Electrodeposition of metal ions from the electrolyte onto the template follows typically under AC conditions. The entire process requires different chemical baths, placed in a container, and a tight control over the process parameters (temperature, voltage, etc.).

Currently, fabrication of metallic nanowires by the AAO template process includes several steps that are conducted manually in a fume hood and require close and continuous monitoring for a period of 72-96 hours. This process is time consuming, not user friendly, does not allow mass production, and can result in inconsistent specifications due to lack of experience or mishandling.

Establishing a template synthesis nanowire fabrication process that is reliable requires a specific setup and a lot of experience. Currently, no device or system is available to prepare AAO templates and/or fabricate metallic nanowires by electrodeposition on AAO templates. This is done manually at the different labs where the process is implemented. Especially, the crucial first step of producing AAO templates or membranes requires high control of various process parameters. Such templates or membranes could be purchased, but they are rather expensive, of low quality and render the process inflexible.

The manually implemented processes at various labs, do not allow a cost-efficient fabrication or large-scale production of nanotemplates or nanowires. They cannot satisfy the needs of many emerging markets, which require nanotemplates and nanowires.

SUMMARY

The present disclosure provides fully automated fabrication systems and methods for use in largescale synthesis of nanotemplates and nanowires. In various aspects the system provides automatic production of templates or membranes for use in template synthesis of nanowires onto a template or membrane. In various other aspects the system provides automatic production of nanowires, for example metallic nanowires. In other aspects the system provides automatic production of both templates or membranes for use in template synthesis of nanowires and template synthesis production of nanowires onto the produced templates or membranes. The system provides for production of high quality templates or membranes, nanowires, or both with reproducibility and controlled specifications. In various aspects the system can be operated with a single push of a button without requiring supervision or intermediate processing. The system is compact, user friendly and can be operated outside a fume hood. In various aspects the system can be operated with a single push of a button without requiring supervision or intermediate processing. The system is compact, user friendly and may be operated outside a fume hood. For the purposes herein, we use the terms "template" and "membrane^" interchangeably as having the same meaning. The system saves processing time, initiation cost and production labor for those planning to work with nanowires, including the step of preparing one or more templates for use in nanowire fabrication, the electrodeposition step of fabricating nanowires onto one or more template(s), or both steps. It can save the time required to train users on the conventional nanowires fabrication process. Mass fabrication can be obtained for industrial applications by realizing an advanced version of the present nanowires fabrication system.

The system can include a sample holder configured to contain a solution and configured to releasably hold a substrate material within the solution when the solution is in the sample holder. The system can include a plurality of chemical containers each fluidly connected to the sample holder. Treatment steps can be initiated by moving a chemical solution from a chemical container to the sample holder to submerge the substrate material for a period of time. Treatment steps can be stopped by removing the chemical solution from the sample holder. Exemplary treatment steps can include degreasing, polishing, rinsing, anodization, and electrodeposition. The movement can be controlled, for instance, by one or more pumps that control the flow of solutions between the sample holder and the chemical containers.

Various sensors can be included to precisely control the treatment steps for reproducibility of the nanotemplate and nanowire fabrication. The system can include a temperature control unit configured to control the temperature of the solution when the solution is in the sample holder. Exemplary temperature control units can include a thermoelectric heating and cooling element and a temperature sensor. The system can include a stirring mechanism configured to agitate the solution when the solution is in the sample holder. The system can include a pH sensor configured to measure the pH of the solution when the solution is in the sample holder.

The system can include a system controller configured to control the treatment steps.

The system controller can be configured to receive temperature data from the temperature control unit and to provide a signal to the temperature control unit to control the temperature of the solution when the solution is in the sample holder. The system controller can be configured to control the flow of solutions between the chemical containers and the sample holder. The system controller can be configured to provide a signal to the stirring mechanism to control the agitation of the solution when the solution is in the sample holder. The system controller can be configured to receive pH data from the pH sensor.

In various aspects, the system can include a controllable robotic arm. The controllable robotic arm can include a head configured to reieasably carry one or more substrates and/or templates. The one or more substrates and/or templates can operate as cathodes in the system. The head can also be configured with a member to hold an anode that can be used in the electrodeposiiion process. The anode and the substrates and/or the cathode tempiate(s) can be held by the head spaced apart from each other. The robotic arm can be configured to controllably lower the head, and thereby insert or immerse the one or more substrates and/or templates into a liquid, solution or chemical bath held by a container and remove the head therefrom. A motor or other means can be provided to rotate the head about a substantially vertical axis, allowing the head to provide a stirring or mixing of the liquid, solution or chemical bath held by the container.

The system can include one or more containers to carry or hold the liquids, solutions and/or a chemical bath to be used in any one or more of the aspects presented herein for the template synthesis of nanowires. The system can further include a stage for holding the one or more containers. Means can be provided to move the robotic arm about the stage allowing the arm to be positioned in relation to multiple containers and to lower and raise the head into and out of a liquid, solution or bath in the containers. In various aspects, a means for moving the robotic arm about the stage can be incorporated with the robotic arm. in various aspects, the stage may be a circular stage and the robotic arm configured for a movement about or around the outside or periphery of the stage. In other aspects, means can be provided for moving the stage, for example rotating the stage, in relation to the robotic arm. Optionally, the system may include a chamber or housing within which the system may be contained to allow control of the atmosphere and/or temperature of the atmosphere for carrying out the e!ectrodeposition process. Controls in the form of program logic and hardware for executing the program logic can be provided for automating use of the system to carry out template synthesis of nanowires.

In an embodiment, a system for largescale nanotemplate and nanowire fabrication is provided. The system can comprise: a sample holder configured to contain a solution and configured to releasably hold a substrate material within the solution when the solution is in the sample holder, a plurality of chemical containers each fluidly connected to the sample holder, a temperature control unit configured to control the temperature of the solution when the solution is in the sample holder, and an electrode configured to contact the solution when the solution is in the sample holder.

In any one or more aspects, the system can include a stirring mechanism configured to agitate the solution when the solution is in the sample holder. The system can include a pH sensor configured to measure the pH of the solution when the solution is in the sample holder. The system can include a plurality of pumps configured to control the flow of solutions between the chemical containers and the sample holder. The sample holder can be configured to hold a substrate material having a surface area up to 2500 cm². The temperature control unit can include a thermoelectric heating and cooling element and a temperature sensor for controlling heating and cooling of the solution.

In any one or more aspects, the system can include a system controller. The system controller can be configured to receive temperature data from the temperature control unit and to provide a signal to the temperature control unit to control the temperature of the solution when the solution is in the sample holder, configured to control the flow of solutions between the chemical containers and the sample holder, configured to provide a signal to the stirring mechanism to control the agitation of the solution when the solution is in the sample holder, or configured to receive pH data from the pH sensor, or any combination thereof. The system can include a display configured to display data from the one or more sensors. The system can include a system housing containing one or more of the components.

In an embodiment a system for largescale nanotemplate and nanowire fabrication is provided, comprising: a robotic arm including a head configured to releasably hold a substrate material, the head having a thermally conductive base configured to hold the substrate material and a chemically resistant coating covering areas of the thermally conductive base not configured to hold the substrate material, the head further comprising a member configured to hold an anode element spaced apart in relation to the substrate material.

In any one or more aspects, the system can include a motor for rotating the head about a substantially vertical axis. The system can include a container and the robotic arm can include a motor configured to controllably raise and lower the head, wherein the motor of the robotic arm is configured to controllably raise and lower the head into and out of the container. The container can include a temperature sensor, or the head can include a temperature sensor, or both, and a heating and/or cooling mechanism to heat and/or cool the container based on a temperature sensed by the temperature sensor of the container or the temperature sensor of the head or both temperature sensors.

In any one or more aspects, the system can include a control system to control the heating and/or cooling of the container in relation to a temperature sensed by the temperature sensor of the head, sensed by the temperature sensor of the container or by both temperature sensors. The system can include a stage on which the container can be placed. The system can include one or more such containers and one or more motors and associated motor controls configured to move the robotic arm about the stage in relation to the position of the one or more containers or to move the stage in relation to the robotic arm to thereby move the one or more containers into position in relation to the robotic arm or both. The system can include programming logic, and hardware for executing the programming logic, for controlling one or more of raising and lowering the head into a container, a temperature of a liquid or solution in the container in relation to a temperature of the head, rotation of the head, or movement of the robotic arm in relation to the one or more containers, or any one or more combinations thereof.

In an embodiment, a method of largescale nanowire fabrication using any one or more of the aforementioned systems in any one or more of their aspects of any one or more of its embodiments is provided. The method can comprise: initiating a treatment step by moving a chemical solution from a chemical container to the sample holder or container to submerge the substrate material for a period of time, stopping the treatment step by removing the chemical solution from the sample holder or container, and repeating the treatment step to produce the nanowires, wherein each treatment step is selected from the group consisting of degreasing, polishing, rinsing, anodization, electrodeposition, and electroless deposition.

In any one or more aspects, the treatment step can include a degreasing step, wherein the degreasing step is initiated by moving a degreaser solution from a chemical container to the sample holder or container to submerge the substrate material for a period of time; and wherein the degreasing step is stopped by removing the degreaser solution from the sample holder or container back to the chemical container. The treatment step can include a polishing step, wherein the polishing step is initiated by moving a polishing solution from a chemical container to the sample holder or container to submerge the substrate material for a period of time; and wherein the polishing step is stopped by removing the polishing solution from the sample holder or container back to the chemical container. The treatment step can include an anodization step, wherein the anodization step is initiated by moving a anodization solution from a chemical container to the sample holder or container to submerge the substrate material for a period of time; and wherein the anodization step is stopped by removing the anodization solution from the sample holder or container back to the chemical container. The treatment step can include an electrodeposition or electroless step to produce the nanowires, wherein the treatment step is initiated by moving a deposition solution from a chemical container to the sample holder or container to submerge the substrate material for a period of time; and wherein the treatment step is stopped by removing the deposition solution from the sample holder or container back to the chemical container.

Other systems, methods, features, and advantages of the present disclosure of a fabrication system for nanowire template synthesis, will be or become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description, be within the scope of the present disclosure, and be protected by the accompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings like reference numerals designate corresponding parts throughout the several views.

FIG. 1 depicts an exemplary container design for use in the present fabrication system for nanowire template synthesis.

FIG. 2A depicts a design of an exemplary robotic arm, while FIGS. 2B and 2C depict a front view and a side view, respectively, of an exemplary substrate or template holder for use with the robotic arm for use with a container such as that of Fig. 1 .

FIG. 3 depicts an exemplary stage design of the present system.

FIG. 4 depicts an exemplary system for the largescale fabrication of nanotemplates and nanowires. DETAILED DESCRIPTION

Described below are various embodiments of the present systems and methods for nanotemplate and nanowire template synthesis. Although particular embodiments are described, those embodiments are mere exemplary implementations of the system and method. One skilled in the art will recognize other embodiments are possible. All such embodiments are intended to fall within the scope of this disclosure. Moreover, all references cited herein are intended to be and are hereby incorporated by reference into this disclosure as if fully set forth herein. While the disclosure will now be described in reference to the above drawings, there is no intent to limit it to the embodiment or embodiments disclosed herein. On the contrary, the intent is to cover all alternatives, modifications and equivalents included within the spirit and scope of the disclosure.

The present disclosure provides a system and method for largescale fabrication of nanotemplates and nanowires. In particular, it provides a system for largescale production or preparation of nanotemplates and nanowires from suitable metal substrate materials. The system can be used for the production of a template from a suitable metal substrate material followed by deposition of the nanowires onto the template.

The present system can be configured to automate the largescale preparation and/or production of the nanowires from a suitable metal substrate material, such as an anodic aluminum oxide (AAO) substrate. The present system can be configured to automate the preparation of a template, such as an AAO, from a suitable metal substrate material. The present system can also be configured to automate by template synthesis nanowire fabrication onto the template.

1. Systems Having a Robotic Arm

In any one or more aspects, the system can include a robotic arm including a head configured to releasably hold a substrate material, the head having a thermally conductive base configured to hold the substrate material and a chemically resistant coating covering areas of the thermally conductive base not configured to hold the substrate material, the head further comprising a member configured to hold an anode element spaced apart in relation to the substrate material. The robotic arm can include a motor configured to controllabiy raise and lower the head. The system can further include a container and the motor of the robotic arm can be configured to controllabiy raise and lower the head into and out of the container. The system can include a stage on which the container can be placed. In various aspects the system can include one or more containers and one or more motors and associated motor controls configured to move the robotic arm about the stage in relation to the position of the one or more containers or to move the stage in relation to the robotic arm to thereby move the one or more containers into position in relation to the robotic arm or both. The system can also include programming logic, and hardware for executing the programming logic, for controlling one or more of raising and lowering the head of the robotic arm into a container, a temperature of a liquid or solution in the container in relation to a temperature of the head, rotation of the head, or movement of the robotic arm in relation to the one or more containers, or any one or more combinations thereof. These and other aspects of the system are discussed in more detail below.

1.1. Chemical resistant and thermally conductive containers

The system includes one or more containers 10 (Fig. 1 ) to carry the liquids, solutions and/or chemical baths to be used in the nanowire fabrication process, including both the template preparation and electrodeposition stages of template synthesis. In various aspects the system can include five containers, though one skilled in the art will recognize that more than five or less than five containers can be included. Preferably, the liquids, solutions and/or chemical baths should have not only a controlled environment, but also a stable temperature to achieve a stable, homogenous and repeatable fabrication process. One or more temperature sensors 14 can be provided. In various aspects the one or more temperature sensors 14 can be mounted inside the container(s) 10 and connected to a system programmed to monitor the temperature throughout the entire process.

For example the container 10 can have a cooling system and/or a heating system 12 to maintain the temperature of the container stable and thereby the liquid, solution and/or chemical bath contained therein. In various aspects the heating/cooling system 12 can limit temperature variation of the liquid, solution and/or chemical bath to less than ± 0.5°C of the desired temperature. The cooling system can use a chiller to provide the cooling. A resistive heater can be provided for heating. One skilled in the art will recognize, however, that other modes of heating and cooling can be provided. For example a feedback loop can be employed between the one or more temperature sensors 14 and the heating/cooling system 12 to monitor and control the temperature of the liquid, solution and/or chemical bath in the container(s) 10.

The container(s) 10 can be chemically resistant and configured to have good thermal conductivity to heat/cool the chemicals. The container(s) 10 can have a core made of a thermally conductive material 16 coated with a chemically resistant material 18. A good compromise between chemical resistance and thermal conductivity can be obtained with a metal core coated with a chemically resistant material. Suitable materials for the thermally conductive core 16 include metals, such as copper, gold, titanium or any non-magnetic conductive material. The chemically resistant coating can be any coating resistant to the liquid, solution or chemical bath held within the container. Suitable materials for the chemically resistant coating include Teflon®, Viton®, chemical resistant PVC or any chemical resistant plastic.

The container(s) 10 can be of any shape that will hold the liquids, solutions, or chemical baths needed for the process(es). In one or more aspects the container(s) can be square or circularly shaped. In one or more aspects the container(s) can be rectangularly shaped, having a length that exceeds their width. In one or more aspects the dimensions of each container can be 10 cm long, 7 cm wide and 10 cm deep (Fig. 1 ), though other dimensions are possible.

1 .2. Controllable robotic arm

The system can include a controllable robotic arm 20 (Figs. 2A-2C). The arm 20 can be used that to hold one or more substrates, also referred to as sample(s), and/or templates 22 and perform the template preparation and nanowire fabrication stages of nanowire template synthesis including the transition between the one or more containers 10. The arm can include one or more sensors (not shown) for collecting information of the system conditions before starting the process. The arm 20 can include a head 30 for releasably holding the sample(s) 22, for example substrate material from which templates can be prepared, and also templates on which nanowires can be fabricated. The head 30 can have a base 32 configured to easily allow mounting and dismounting of the sample(s)/template(s) 22 onto the base 32. The base 32 can be made of a conductive material to provide an electrical connection to the sample(s)/ template(s) 22. Suitable electrically conductive materials include conductive metals, such as copper, gold, titanium or any non-magnetic conductive material. The arm 20 and/or the head 30 can be protected by a coating 34, for example a chemically resistant coating. The chemically resistant material can cover areas of the thermally conductive base 32 that are not configured to hold the sample(s)/templates(s). Suitable protective coatings include Teflon®, Viton®, chemical resistant PVC or any chemical resistant plastic.

The arm 20 can include a motor (not shown) and/or other means to controllably lower the head 30 into a container 10 and a liquid, solution or chemical bath in the container and raise the head 30 out of the container and its liquid, solution or chemical bath. The arm can also include a motor and/or other means to move the arm about a stage, described below, to move the arm 20 and the head 30 from one container into position with respect to another container. The arm 20 and/or the head 30 can also include one or more sensors 36. The sensor(s) 36 can be one or more temperature sensors or one or more pH sensors, of both types of sensors can be included. The one or more temperature sensors can measure the temperature of the sample(s) / template(s) 22 and match the temperature of the sample(s) / template(s) 22 with the temperature of the liquid, solution or chemical bath in a container 10 measured by the container temperature sensor 14. The fabrication process can be triggered once the temperatures of the sample(s)/template(s) and the liquid, solution or chemical bath are matched to prevent thermal fluctuation.

Maintaining a stable pH for the chemicals can be desirable to have a consistent and homogeneous fabrication process. One or more pH sensors can be utilized and connected to the system program to monitor pH level and warn the user via a user interface if the pH level is changing.

An anode 38 for the process can be connected to or held by the head 30 by a member or arm 37. The anode can be positioned on the head 30 at a fixed distance from the sample(s)/ template(s) 22. The anode electrode can consist of a metal, such as platinum or palladium. The anode 38 can be configured as a mesh or as a solid substrate. A motor 39 can be used to provide mixing of the solution or chemical bath in the container(s) 10 during the fabrication process. The motor 39 can be designed to rotate the head 30 when it is submersed in a liquid, solution or chemical bath in a container 10. The head 30 can be coupled to the robotic arm 20 by a shaft or arm 31. The shaft or arm 31 can be substantially vertically suspended from an end of the robotic arm 20, thereby providing a substantially vertical axis about which the head 30 can be rotated. Controls can be provided to start and stop the motor 39 and the rotation of the head 30.

1.3. Motorized and precisely controlled stage

The system can include a stage 40 for holding the one or more containers 10 or on which the one or more containers 10 can be mounted. The stage 40 can include a plate 40 on top of which the container(s) 10 can be placed or mounted. The plate 42 can be a circular plate and can have, for example a radius smaller than 30 cm, though it can have a larger or smaller radius. The plate 42 need not be circular in its horizontal dimension depicted in Fig. 3. It can have other configurations. The stage 40 can include heating / cooling elements 46. Various electronics and power sources 48 can be provided, for example stored underneath stage 42.

A rotating ring 44 can be provided about the periphery of the plate 42. The rotating ring 44 can be configured to hold the robotic arm 20. The rotating ring 44 can include a motor and associated hardware and motor controls (not shown) to rotate the robotic arm about the stage 40 to move one or more sample(s) or template(s) 22 held by the robotic arm 20 from one container to another container about the stage 40 (Fig. 3). For example positioning sensors and/or one or more magnetic locking mechanisms (not shown) can be used to control movement of the arm 20 and the head 30 of the arm 20 to specific container location(s) with high precision. Alternatively the stage 40 can include a motor and associated hardware and motor controls to rotate the stage 44 with respect to the robotic arm 20 thereby causing the container(s) 10 placed or mounted on the stage 40 to be moved into and out of position with respect to the robotic arm 20.

1 .4. Chamber or Housing

The present system can be placed within a chamber or housing to control the environment within which the system is operated. The atmosphere and/or the temperature within the chamber can be controlled. For example the system can be kept or maintained in an inert gas environment. Suitable inert gases include Nitrogen and Argon. The system can include equipment, such as one or more conduits, pumps and gas tanks or reservoirs to evacuate the chamber and to fill the chamber with the inert gas during operation of the system for nanowire fabrication. Cooling and/or heating systems can be included to cool or heat the inert gas for temperature control within the chamber. 1 .5. Controlling program

The system can further include program logic and hardware for executing the program logic. For example, a LabVIEW program can be provided to provide a control for the fabrication process with detailed process monitoring over time. The program logic can control fabrication parameters, such as duration, type of process, degree of precision, temperatures, positioning of the robotic arm 20 with respect to one or more container(s) 10, raising and lowering of the head 30 of the robotic arm for submersion into a solution or chemical bath in a container, duration of submersion and many other parameters. The fabrication parameters can be controlled easily using the developed program logic. For example, the program logic can maintain one or more of constant temperature or constant pH through feedback loops with the power supplies and sensor(s) to provide high accuracy.

We now describe the operation of the present system in one exemplary mode of operation, among many different modes of operation. In various aspects the system may be used for both a first and a second stage of nanowire template synthesis, namely the first stage of template preparation and the second stage of nanowire fabrication using one or more prepared templates. One skilled in the art, however, would recognize that the system may be used to prepare templates or membranes for nanowire preparation for others. Similarly, pre-prepared templates or membranes prepared by another may be used in the system for nanowire fabrication.

One or more templates or membranes may be prepared by first obtaining a metal or metal oxide film or foil, also referred to herein as a substrate. The one or more substrates 22 can be placed or mounted in the head 30 attached to a controllable robotic arm 20. The substrate may then be subjected to a number of treatment steps to prepare the one or more substrates to be used as a template(s) in the fabrication of nanowires. In an aspect, the one or more substrates may first be degreased, for example by submersing the head 30 including one or more substrates 22 in ethanol or other grease solvent. The grease solvent can be held in a first container 10 on a stage 40. The robotic arm 20 can be used or programmed to immerse the head 30 including the one or more substrates 22 into the solvent for a period of time and then withdraw the substrate(s) 22 from the solvent held in the first container.

The one or more substrates 22 may then be polished to remove any native oxide layer on the substrate(s). Polishing may be achieved by soft chemical polishing such as immersing the substrate(s) in a solution such as an acetone solution. The acetone solution bath may be an ultrasonic bath to assist in the polishing. The acetone bath solution may be held in a second container 10 on stage 40. The robotic arm 20 can be programmed to move head 30 from the first container into position over the second container including the polishing solution and further to immerse the head 30 into the polishing solution for a period of time and then remove the head 30 including the one or more substrates 22 from the polishing solution.

After polishing the one or more substrates 22 may then be rinsed to remove residual polishing solution on the substrate(s) and head 30. The rinsing may be accomplished in a third container holding a rinsing liquid or solution, for example deionized water. The robotic arm 20 can be programmed after completing the polishing step to move the head 30 including the one or more substrates 22 into position over the third container, to then immerse the head and substrate(s) into the rinsing solution for a period of time and then upon completion of the rinsing withdraw the head from the rinsing solution in the third container.

In various aspects an anodization procedure can then be applied to the substrate(s) 22 in order to achieve desired organization and structure of the surface of the substrate(s). The anodization procedure can take place in one or more steps. An exemplary anodization procedure may involve two steps. A first anodization step can involve applying a given voltage such as a 40V for a given period of time such as 30 minutes more or less while the substrate(s) 22 are immersed in an acid solution such as an oxalic acid solution. The acid solution can be held in at a fourth container positioned on stage 40. The robotic arm 20 can be programmed to move the head 30 including substrate(s) 22 into position over the fourth container and immerse the head including the substrate(s) into the acid solution in the fourth container for anodization. The substrate(s) 22 may be rinsed by programming the robotic arm to return the head including the substrate(s) back to the third container containing a rinsing liquid or solution, or to another container containing a rinsing liquid or solution. The substrate(s) 22 may then be further anodized, if desired, in a second anodization step under different conditions for example under different voltages or for a different time period of immersion and/or at a different temperature in an acid solution such as the oxalic acid solution. One or more templates have now been prepared than can be used in an electrodeposition stage for nanowire fabrication.

Electrodeposition of nanowires onto one or more templates 22 can be carried out in a chemical bath. The chemical bath can be an organic or an inorganic chemical bath and can include an electrolyte such as a desired metal halide. An exemplary chemical bath may be a dimethylsulfoxide (DMSO) solution including a metal chloride. One skilled in the art will recognize that the solution and the electrolyte selected for the electrodeposition chemical bath can be selected depending upon the type of nanowires to be produced. For example, in another aspect, the organic may bath contain an acid solution of CuS0₄, 5H₂0 as an electrolyte. The chemical bath can be held in a fifth container. The robotic arm can be used or programmed to move the head 30 into position over the fifth container and immerse the head 30 including the template(s) 22 into the bath for a period of time after which the head 30 can be removed from the bath. The head 30 can include an anode 38, and the template(s) 22 held by the head 30 can serve as the cathode(s) for the electrodeposition process. By employing one or more temperature sensors 14 in the fifth container for sensing the temperature of the chemical bath and one or more temperature sensors for sensing the temperature of the template(s) 22 held by the head 30 heating and/or cooling devices can be programmed to maintain the template(s) 22 and the chemical bath at the same temperature or within a narrow variation of a desired temperature for example ±0.5°C. Nanowires can thereby be fabricated onto the one or more templates.

After the desired amount of electrodeposition has been achieved, the template(s) 22 may be immersed in an acid solution to dissolve the template(s) thereby liberating the nanowires from the host template(s). The nanowires can then be washed or rinsed in a solution, such as in distilled water and then dried for example in an oven at an elevated temperature to achieve the final desired nanowires.

2. Systems Having Chemical Containers Fluidly Connected to a Sample Holder In any one or more aspects, the system can include chemical containers fluidly connected to a sample holder. The sample holder can be configured to receive a solution from a chemical container and configured to releasably hold a substrate material within the solution when the solution is in the sample holder. The system can include a temperature control unit configured to control the temperature of the solution when the solution is in the sample holder. The system can also include an electrode configured to contact the solution when the solution is in the sample holder. These and other aspects of the system are discussed in more detail below.

2.1. Sample Holder

The system 100 (see FIG. 4) can include a sample holder configured to releasably hold a substrate material or to releasably hold a template. The sample holder is configured to hold a solution and to hold the substrate material within the solution when the solution is in the sample holder. The sample holder can be configured to hold any suitably sized substrate material to produce the desired amount of nanowires. In some embodiments the sample holder is configured to hold a metal foil substrate having a surface area of about 50 cm², 100 cm², 150 cm², 180 cm², 200 cm², 250 cm² or more. The sample holder can be configured to hold a substrate material having a largest dimension of about 10-100 cm, 20-100 cm, 20-80 cm, 30-80cm, 30-60 cm, 50-60 cm, or about 50 cm. The sample holder can be made of a chemically resistant material or can be coated with a chemically resistant material. The chemically resistant coating can be any coating resistant to the liquid, solution or chemicals being passed into the sample holder. Suitable materials for the chemically resistant material include Teflon®, Viton®, chemical resistant PVC or any chemical resistant plastic.

The sample holder can be made from a thermally conductive material. In some embodiments the sample holder is made from a thermally conductive material that is coated with a chemically resistant material. For example, the thermally conductive material can be a metal such as copper, gold, titanium or can be any non-magnetic conductive material.

The sample holder can include mounting points for easily mounting and dismounting the substrate material or template in the sample holder such that the substrate material or template will contact a solution when the solution is in the sample holder. The mounting points can be made from or include an electrically conductive material to provide electrical contact to the substrate material or template, e.g. for applying a voltage in the

electrodepostion steps.

2.2. Electrodes

The system can include an electrode configured to contact the solution when the solution is in the sample holder. The electrode can include a metal, such as platinum or palladium and any conductive metal coated with the materials cited before. The electrode can be configured as a mesh or as a solid substrate. The electrode is separated from the substrate or template with a distance of between 1 mm and 10 cm.

2.3. Chemical containers

The system can include one or more chemical containers 120 fluidly connected to the sample holder 110. Each chemical container 120 can be fluidly connected to the sample holder 110 via a hose 130. The system can include 3, 4, 5, or more chemical containers. Each of the containers 120 can be the same or can be configured specifically to contain a different solution. The properties of each of the containers 120 can be designed to accommodate the various chemical solutions needed for the manufacture of the nanowires.

The chemical solutions can include one or more of water, an electro-polishing solution, an acid solution, a chrome solution, and an electrodeposition solution.

The chemical containers can be chemically resistant and configured to have good thermal conductivity to heat/cool the chemical solutions. The chemical containers can have a core made of a thermally conductive material coated with a chemically resistant material.

The chemical containers can have a metal core coated with a chemically resistant material.

Suitable materials for the thermally conductive core can include metals, such as copper, gold, titanium or any non-magnetic conductive material or non-magnetic alloy. The chemically resistant coating can be any coating resistant to the chemical solution held within the container. Suitable materials for the chemically resistant coating include Teflon®,

Viton®, chemical resistant PVC or any chemical resistant plastic.

The chemical containers can be of any shape that will hold the chemical solutions for producing the nanotemplates or nanowires. In one or more aspects the chemical containers can be square or circularly shaped. In one or more aspects the chemical containers can be rectangularly shaped, having a length that exceeds their width.

Each chemical container 120 can be fluidly connected to the sample holder 110 via a hose 130. The movement of chemical solutions between a chemical container 120 and the sample holder 110 can be controlled by a pump. The system can include a plurality of pumps to control the movement of solutions between the sample holder 110 and the chemical containers 120.

2.4. Temperature Control Units

The system can include one or more temperature control units. One or more temperature control units can be mounted inside the sample holder. Additionally, temperature control units can be mounted inside one or more of the chemical containers.

The temperature control unit(s) can provide a stable temperature to achieve a stable, homogenous and repeatable fabrication process. In various aspects the temperature control unit(s) can limit temperature variation of the chemical solution in the chemical containers and/or in the sample holder to less than ± 0.5°C of the desired temperature. The

temperature control unit(s) will adapt the temperature without causing and to avoid pronounced temperature oscillations. Typical temperature ranges are between -10°C and +50°C.

The temperature control unit can include a cooling system and/or a heating system to maintain the temperature. The temperature control unit can include a thermoelectric heating and cooling element (also referred to as a thermoelectric heat pump, Peltier cooler, or Peltier heater). The thermoelectric heating and cooling element is a solid-state active heat pump that transfers heat from one side of a device to the opposing side. The direction of heat transfer can be controlled by the direction of the current applied to the thermoelectric. A variety of chillers and resistive heaters can be used in the temperature control unit. One skilled in the art will recognize many alternative heating and cooling elements that can be provided.

The temperature control unit can include a temperature sensor such as a digital thermometer that can be configured to contact a solution when the solution is in the sample holder or can be configured to contact a solution in one of the chemical containers. Many suitable temperature sensors are known in the art. The temperature sensor can display or otherwise communicate a signal indicating the temperature to a system controller configured to control the temperature.

2.5. Stirring mechanism

The system can include one or more stirring mechanisms. The stirring mechanisms can be mounted in the sample holder, mounted in one or more chemical containers, or can be mounted both in the sample holder and one or more chemical containers. The stirring mechanism can be mounted in the sample holder to provide mixing of the solution when in the sample holder, e.g. during the chemical polishing or electro-deposition. The system can include a stirring mechanism mounted within one or more of the chemical containers to ensure mixing of the chemical solutions prior to flowing into the sample holder, e.g. prior to being pumped into the sample holder.

The stirring mechanism can be coated with a chemically resistant coating. The chemically resistant coating can be any coating resistant to the chemical solution held within the container. Suitable materials for the chemically resistant coating include Teflon®,

Viton®, chemical resistant PVC or any chemical resistant plastic. The stirring speed can be adjusted depending on the performed process and the nanowire materials.

2.6. pH sensor

The system can include one or more pH sensors. A pH sensor can be in the sample holder and configured to contact a solution when the solution is in the sample holder. A pH sensor can be in a chemical container and configured to contact the chemical solution when the chemical solution is in the chemical container. The pH sensor can display or otherwise communicate a signal indicating the pH to a system controller configured to control or monitor the pH. The pH sensor will enable a process interruption under certain conditions either in the nanotemplate fabrication or the nanowire fabrication.

2.7. System Controller

The system can further include a system controller to monitor and/or control various aspects of the process of producing the nanowires. The system controller can be configured to receive temperature data from the temperature control unit and to provide a signal to the temperature control unit to control the temperature of a solution when the solution is in the sample holder. The system controller can be configured to control the flow of solutions between the chemical containers and the sample holder. The system controller can be configured to provide a signal to the stirring mechanism to control the agitation of the solution when the solution is in the sample holder. The system controller can be configured to receive pH data from the pH sensor.

The system controller can include program logic and hardware for executing the program logic. For example, a LabVIEW program can be provided to provide a control for the fabrication process with detailed process monitoring over time. The program logic can control fabrication parameters, such as duration, type of process, degree of precision, temperatures, and many other parameters. The fabrication parameters can be controlled easily using the developed program logic. For example, the program logic can maintain one or more of constant temperature or constant pH through feedback loops with the power supplies and sensor(s) to provide high accuracy.

2.8. Display

The system can include a display configured to display data from the one or more sensors. The display can receive data from a temperature sensor and display the temperature of a solution in the sample holder, in a chemical container, or both. The display can receive data from a pH sensor and display the pH of a solution in the sample holder, in a chemical container, or both. The display can include a time display such as to display the timing of a process.

2.9. System Housing

The present system can be placed within a system housing 170 to hold the one or more components of the system. The system housing can include equipment, such as one or more conduits, pumps gas tanks, drains, or reservoirs. The system housing can be made of a durable, chemically resistant material. The housing can also provide moisture control, gas pressure control and humidity control.

2.10. Methods of nanowire fabrication

We now describe various methods for the largescale fabrication of nanotemplates and nanowires. We describe the operation of the present system in one exemplary mode of operation, among many different modes of operation. In various aspects the system can be used for both a first and a second stage of nanowire synthesis, namely a first stage of template preparation and a second stage of nanowire fabrication using one or more prepared templates. One skilled in the art, however, would recognize that the system may be used to prepare templates or membranes for nanowire preparation for others. Similarly, pre-prepared templates or membranes prepared by another may be used in the system for nanowire fabrication.

A template can be prepared by first obtaining a substrate material such as a metal foil. The substrate material can be placed or mounted in the sample holder. The substrate material can then be subjected to a number of treatment steps to prepare the substrate material to be used as a template in the fabrication of nanowires. The treatment steps can be initiated and stopped by the movement of chemical solutions between the chemical container(s) and the sample holder.

In an aspect, the substrate material may first be degreased. In some aspects a chemical degreaser solution may be moved from a chemical container into the sample holder to contact the substrate material. The sample holder can be filed with the degreaser solution to submerge the substrate material for a period of time. The degreaser solution can then be moved from the sample holder back into the chemical container or into a different chemical container.

The substrate material can be polished using an electro-polishing solution. The substrate material can be polished to remove oxide layer from the substrate. The electro- polishing solution can be a soft chemical polishing solution such as acetone. The electro- polishing solution can include an acid solution such as a sulfuric acid, phosphoric acid or perchloric acid. The sample holder can filled with the electro-polishing solution to submerge the substrate material for a period of time. The electro-polishing solution can then be moved from the sample holder back into the chemical container or into a different chemical container. The electro polishing process takes typically place at temperatures about 10C and its specifics parameter change according to the polishing area.

The substrate material can be rinsed to remove residual polishing solution from the substrate material and the sample holder. The rinse solution can be water, particularly deionized (Dl) water, or another aqueous rinse solution. The sample holder can be filled with the rinse solution to submerge the substrate material for a period of time. The rinse solution can then be moved from the sample holder back into the chemical container or into a drain for draining the rinse solution.

An anodization procedure can be applied to the substrate material. The anodization procedure can take place in one or more steps. In some embodiments the anodization includes a step of moving an anodization solution into the sample holder to submerge the substrate material. The anodization solution can include, for example, oxalic acid or other suitable acid solution. The anodization can include applying a given voltage for a given period of time while the substrate material is immersed in an acidic solution such as an oxalic acid solution, phosphoric solution or sulfuric solution. The given voltage varies according to the acid and the final membrane desired. For the particular case of oxalic acid and following a soft anodization the most common parameters can be about 30 V-50 V, 35 V to 45 V, or about 40 V. The period of time can be about 12 hours to 24 hours. After each anodization step the substrate material can be rinsed again as described above and/or can be subjected to a second anodization step. The second anodization step can include moving an anodization solution into the sample holder to submerge the substrate material. The anodization solution can be a different anodization solution or the same anodization solution used in the first anodization step. The one or more anodization step steps can be used to create a template from the substrate material.

A deposition step, e.g. an electrodeposition or electroless deposition step, can be applied to the template, either to a template prepared separately and mounted in the sample holder or a template prepared from a substrate material using methods described above. The sample holder can be filled with an electrodeposition solution to submerge the template. The electrodeposition solution can be an organic or an inorganic chemical bath and can include an electrolyte such as a desired metal halide. An exemplary chemical bath may be a dimethylsulfoxide (DMSO) solution including a metal chloride. One skilled in the art will recognize that the solution and the electrolyte selected for the electrodeposition chemical bath can be selected depending upon the type of nanowires to be produced. For example, in another aspect, the organic may bath contain an acid solution with CuS0₄ 5H₂0 as an electrolyte. The electrodeposition can be performed for a period of time at a specific temperature, voltage or current. According to the specific material and crystal structure required, one can apply different procedures: DC, AC, pulsed deposition or a combination between AC and DC or pulsed deposition and DC.

After the desired amount of electrodeposition has been achieved, the

electrodeposition solution may be moved from the sample holder back into the chemical container. The sample holder may be removed to facilitate removal of the nanowires or additional rinse steps may be performed. The nanowires can be washed with an acidic solution to remove them from the template and/or can be rinsed with a rinse solution.

Additional processing such as additional rinses or oven drying can be performed on the as- produced nanowires after removal from the sample holder.

It should be emphasized that the above-described embodiments are merely examples of possible implementations. Many variations and modifications may be made to the above-described embodiments without departing from the principles of the present disclosure. One skilled in the art will understand that many different materials can be used in the nanowire fabrication process. One skilled in the art will also understand that many different modes of operation of the system are possible. For example, the number of containers, the liquids held in the one or more containers, the order of operation of the robotic arm in relation to the one or more containers can all be varied. All such modifications and variations are intended to be included herein within the scope of this disclosure and protected by the following claims.

Claims

We claim:

1. A system for largescale nanotemplate and nanowire fabrication, the system comprising:

a sample holder configured to contain a solution and configured to releasably hold a substrate material within the solution when the solution is in the sample holder,

a plurality of chemical containers each fluidly connected to the sample holder, a temperature control unit configured to control the temperature of the solution when the solution is in the sample holder, and

an electrode configured to contact the solution when the solution is in the sample holder.

2. The system of claim 1 , further comprising a stirring mechanism configured to agitate the solution when the solution is in the sample holder.

3. The system of claim 1 or claim 2, further comprising a pH sensor configured to measure the pH of the solution when the solution is in the sample holder.

4. The system of any one of claims 1-3, further comprising a plurality of pumps configured to control the flow of solutions between the chemical containers and the sample holder.

5. The system of any one of claims 1-4, wherein the sample holder is configured to hold a substrate material having a surface area up to 2500 cm².

6. The system of any one of claims 1-5, wherein the temperature control unit includes a thermoelectric heating and cooling element and a temperature sensor.

7. The system of any one of claims 1-6, further comprising a system controller, wherein the system controller is configured to receive temperature data from the temperature control unit and to provide a signal to the temperature control unit to control the temperature of the solution when the solution is in the sample holder, configured to control the flow of solutions between the chemical containers and the sample holder, configured to provide a signal to the stirring mechanism to control the agitation of the solution when the solution is in the sample holder, or configured to receive pH data from the pH sensor, or any combination thereof.

8. A method of largescale nanowire fabrication using the system of any one of claims 1- 7, the method comprising:

initiating a treatment step by moving a chemical solution from a chemical container to the sample holder to submerge the substrate material for a period of time,

stopping the treatment step by removing the chemical solution from the sample holder, and

repeating the treatment step to produce the nanowires,

wherein each treatment step is selected from the group consisting of degreasing, polishing, rinsing, anodization, electrodeposition, and electroless deposition.

9. The method of claim 8, wherein the treatment step includes a degreasing step, wherein the degreasing step is initiated by moving a degreaser solution from a chemical container to the sample holder to submerge the substrate material for a period of time; and

wherein the degreasing step is stopped by removing the degreaser solution from the sample holder back to the chemical container.

10. The method of claim 8, wherein the treatment step includes a polishing step, wherein the polishing step is initiated by moving a polishing solution from a chemical container to the sample holder to submerge the substrate material for a period of time; and wherein the polishing step is stopped by removing the polishing solution from the sample holder back to the chemical container.

1 1. The method of claim 8, wherein the treatment step includes an anodization step, wherein the anodization step is initiated by moving a anodization solution from a chemical container to the sample holder to submerge the substrate material for a period of time; and

wherein the anodization step is stopped by removing the anodization solution from the sample holder back to the chemical container.

12. The method of claim 8, wherein the treatment step includes an electrodeposition or electroless step to produce the nanowires,

wherein the treatment step is initiated by moving a deposition solution from a chemical container to the sample holder to submerge the substrate material for a period of time; and

wherein the treatment step is stopped by removing the deposition solution from the sample holder back to the chemical container.

13. A system for largescale nanotemplate and nanowire fabrication, comprising:

a robotic arm including a head configured to releasably hold a substrate material, the head having a thermally conductive base configured to hold the substrate material and a chemically resistant coating covering areas of the thermally conductive base not configured to hold the substrate material, the head further comprising a member configured to hold an anode element spaced apart in relation to the substrate material.

14. The system of claim 13, further including a motor for rotating the head about a substantially vertical axis.

15. The system of claim 13 or 14, including a container and the robotic arm includes a motor configured to controllably raise and lower the head, wherein the motor of the robotic arm is configured to controllably raise and lower the head into and out of the container.

16. The system of any of claims 13-15, wherein the container includes a temperature sensor, or the head includes a temperature sensor, or both and a heating and/or cooling mechanism to heat and/or cool the container based on a temperature sensed by the temperature sensor of the container or the temperature sensor of the head, or both temperature sensors.

17. The system of claim 16, further including a control system to control the heating and/or cooling of the container in relation to a temperature sensed by the temperature sensor of the head, sensed by the temperature sensor of the container or by both temperature sensors.

18. The system of any of claims 13-17, including a stage on which the container can be placed.

19. The system of claim 18, including one or more containers and one or more motors and associated motor controls configured to move the robotic arm about the stage in relation to the position of the one or more containers or to move the stage in relation to the robotic arm to thereby move the one or more containers into position in relation to the robotic arm or both.

20. The system of claim 19, including programming logic, and hardware for executing the programming logic, for controlling one or more of raising and lowering the head into a container, a temperature of a liquid or solution in the container in relation to a temperature of the head, rotation of the head, or movement of the robotic arm in relation to the one or more containers, or any one or more combinations thereof.