WO2008054871A2 - Nanométrologie, purification et séparation de nanotubes de carbone - Google Patents

Nanométrologie, purification et séparation de nanotubes de carbone Download PDF

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Publication number
WO2008054871A2
WO2008054871A2 PCT/US2007/068547 US2007068547W WO2008054871A2 WO 2008054871 A2 WO2008054871 A2 WO 2008054871A2 US 2007068547 W US2007068547 W US 2007068547W WO 2008054871 A2 WO2008054871 A2 WO 2008054871A2
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Prior art keywords
sample
fullerenes
electromagnetic radiation
energy beam
laser
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PCT/US2007/068547
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English (en)
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WO2008054871A3 (fr
Inventor
Thomas A. Campbell
Kent D. Henry
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Ada Technologies, Inc.
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Priority claimed from US11/745,808 external-priority patent/US20080069758A1/en
Priority claimed from US11/745,779 external-priority patent/US7564549B2/en
Application filed by Ada Technologies, Inc. filed Critical Ada Technologies, Inc.
Publication of WO2008054871A2 publication Critical patent/WO2008054871A2/fr
Publication of WO2008054871A3 publication Critical patent/WO2008054871A3/fr

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/15—Nano-sized carbon materials
    • C01B32/158—Carbon nanotubes
    • C01B32/168—After-treatment
    • C01B32/17—Purification
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/15—Nano-sized carbon materials
    • C01B32/158—Carbon nanotubes
    • C01B32/168—After-treatment
    • C01B32/172—Sorting
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/02—Details
    • G01J3/10—Arrangements of light sources specially adapted for spectrometry or colorimetry
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/12—Generating the spectrum; Monochromators
    • G01J3/18—Generating the spectrum; Monochromators using diffraction elements, e.g. grating
    • G01J3/1804—Plane gratings
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/28—Investigating the spectrum
    • G01J3/44—Raman spectrometry; Scattering spectrometry ; Fluorescence spectrometry
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
    • G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
    • G01N21/65—Raman scattering
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2202/00—Structure or properties of carbon nanotubes
    • C01B2202/02—Single-walled nanotubes
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J1/00—Photometry, e.g. photographic exposure meter
    • G01J1/42—Photometry, e.g. photographic exposure meter using electric radiation detectors
    • G01J1/4257—Photometry, e.g. photographic exposure meter using electric radiation detectors applied to monitoring the characteristics of a beam, e.g. laser beam, headlamp beam
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/28—Investigating the spectrum
    • G01J2003/2866—Markers; Calibrating of scan
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
    • G01J5/10—Radiation pyrometry, e.g. infrared or optical thermometry using electric radiation detectors
    • G01J5/34—Radiation pyrometry, e.g. infrared or optical thermometry using electric radiation detectors using capacitors, e.g. pyroelectric capacitors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J9/00—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength
    • G01J9/02—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength by interferometric methods
    • G01J9/0246—Measuring optical wavelength

Definitions

  • Carbon nanotubes are revolutionary materials having valuable electrical, optical, mechanical, and thermal characteristics due to their unique quasi-one-dimensional electron confinement.
  • CNTs Carbon nanotubes
  • the nanomanufacturing environment for CNTs is still in an inchoate situation.
  • Industrial companies claim they are expanding and refining their processes, yet if one purchases CNTs on the open market, more often than not one obtains a vial of unlabeled, uncharacterized material. Accordingly, current manufacturing processes do not simply produce a single type of CNT. Instead, yields are a mixture of species, along with unwanted chemical impurities (3-50%).
  • SWNTs single walled nanotubes
  • CNTs continue to have a significant allure for materials scientists. Their fundamental properties have been advocated to be applicable in a wide range of industries, including chemical, aerospace, automotive, electronics, etc. SWNTs are of special interest to these communities for their prospective properties tunability. The challenge before the industry is to overcome the quality control issue now present at both the raw material supplier and OEM levels. Additionally, there is a challenge of doing this economically and efficiently if commercial manufacturing is to be achieved.
  • Embodiments of the present invention provide systems and methods for quantifying, purifying and separating fullerenes, such as single wall carbon nanotubes (SWNTs).
  • the purification methods offer the ability to obtain nearly 100% carbonaceous impurity-free SWNT content from a given impure, as-prepared SWNT bundle without any destruction, defect creation or functionalization of the SWNTs.
  • the separation methods offer the ability to obtain the desired range of chirality and diameter from a given non-separated, as-produced SWNT bundle.
  • Nanometrological validation of the success of purification and separation uses a pyroelectric detector and Raman spectroscopy in a single system, thus providing a critical aspect for the nanomanufacturing environment.
  • the present invention offers the ability to avoid 'wet' chemistry, as some embodiments process dry SWNTs (i.e. the SWNTs are not in solution).
  • the SWNTs will thus be available as-is for a variety of applications without any further chemistry processing.
  • a system for performing metrology of a sample of fullerenes.
  • a first energy beam is sent from an illumination source to a monochromator, which selects a band of wavelengths to transmit to the sample.
  • the sample is attached to a pyroelectric detector, which produces a first output signal in response to the first energy beam.
  • a laser is arranged to provide a second energy beam to the sample, which emits a third energy beam to the monochromator in response to the second energy beam.
  • the monochromator selects a band of wavelengths of the third energy beam to send to a Raman detector, which produces a second output signal in response to the third energy beam.
  • the fullerenes are carbon nanotubes. Additionally, the system is able take measurements when the sample is dry. In another embodiment, the illumination source is a 3400K tungsten lamp. In yet another embodiment, a data acquisition system receives the first and second output signals. In one aspect, the data acquisition system includes a computer system containing instructions for applying an effective medium approximation (EMA) to calculate a volume fraction of metallic and semiconducting fullerenes.
  • EMA effective medium approximation
  • the first beam enters the monochomator through a first input aperture and leaves the monochomator at a first output aperture.
  • the third beam enters the monochomator through a second input aperture and leaves the monochomator at a second output aperture.
  • a light-tight enclosure encloses the illumination source, monochromator, and laser.
  • the light-tight enclosure has a slit for transmitting an energy beam to the sample.
  • a light-tight barrier separates the enclosure into at least two portions, and the illumination source and the slit are in different portions of the light-tight enclosure.
  • the light-tight enclosure also encloses the Raman detector, and the laser and the Raman detector are in different portions of the light-tight enclosure.
  • a reference detector may receives a portion of the first energy beam, and the reference detector is in the same portion of the light-tight enclosure as the slit of the light tight enclosure.
  • a system for performing metrology of a sample of fullerenes.
  • a first energy beam is sent from an illumination source to the sample that is attached to a pyroelectric detector, which produces a first output signal in response to the first energy beam.
  • a laser is arranged to provide a second energy beam to the sample, which emits a third energy beam to a Raman detector in response to the second energy beam.
  • the Raman detector produces a second output signal in response to the third energy beam.
  • a light-tight enclosure encloses the illumination source and laser and has a slit for transmitting an energy beam to the sample.
  • a light-tight barrier separates the enclosure into at least two portions, where the illumination source and the slit are in different portions of the light-tight enclosure.
  • the light-tight enclosure also encloses the Raman detector, and the laser and the Raman detector are in different portions of the light-tight enclosure.
  • a reference detector receives a portion of the first energy beam, and the reference detector is in the same portion of the light-tight enclosure as the slit of the light tight enclosure.
  • a first monochromator receives the first energy beam and selects a band of wavelengths of the first energy beam to transmit to the sample.
  • a second monochromator may receive the third energy beam and select a band of wavelengths of the third energy beam to transmit to the Raman detector.
  • a system for obtaining a satisfactory sample of fullerenes.
  • a metrology system provides data associated with particular properties of the fullerenes.
  • the metrology system includes a pyroelectric detector for determining a semiconductormetallic ratio of different types of fullerenes in the sample.
  • a separation system separates different types of the fullerenes by transmitting electromagnetic radiation at a first predetermined energy.
  • a mobility apparatus moves the sample between the metrology system and the separation system.
  • a control system receives data from the metrology system and analyzes the data to produce data results. The data results are compared to determine if the sample satisfies certain predetermined requirements; and based on the comparison, the control system controls the mobility apparatus to move the sample.
  • the metrology system further includes a Raman spectroscope, and the separation system also purifies the sample by using electromagnetic radiation at a second predetermined energy such that impurities are oxidized from the sample.
  • the separation system includes a separation subsystem for separating different types of fullerenes and a purification subsystem for purifying the sample of impurities. The mobility apparatus then can move the sample between the separation subsystem and the purification subsystem.
  • a method for obtaining a refined sample of fullerenes.
  • a sample including impurities and multiple types of fullerenes is received.
  • the sample is purified by transmitting, to the sample, a first dosage of electromagnetic radiation at a first predetermined energy such that a significant amount of the impurities are removed from the sample, thereby disentangling the fullerenes.
  • the first predetermined energy excites a plasmon resonance in the fullerenes.
  • a significant portion of one or more types of fullerenes is removed from the sample by transmitting a second dosage of electromagnetic radiation at respective predetermined energies for each type of fullerene removed.
  • Each of respective predetermined energies matches a respective absorption energy level of at least one type of the fullerenes.
  • the sample comprises carbon nanotubes.
  • purifying removes a significant portion of carbonaceous impurities via oxidation.
  • removing one or more types of fullerenes includes oxidizing carbon nanotubes of a particular chirality or diameter that correspond to a respective predetermined energy.
  • the first dosage of electromagnetic radiation excites a ⁇ -plasmon resonance around 248nm (5eV) in the fullerenes.
  • the first dosage of electromagnetic radiation has a pulse width of approximately 20 ns and a pulse repetition frequency of 10 Hz.
  • the first dosage of electromagnetic radiation is transmitted to the sample through multiple exposures that are each of set period. The exposures may be controlled by a shutter.
  • the second dosage of electromagnetic radiation utilizes a frequency comb to obtain at least two of the respective predetermined energies.
  • second dosage of electromagnetic radiation utilizes a frequency comb to verify that the predetermined energies are reached.
  • the sample is dry.
  • properties of the refined sample are measured. Based on the measured properties, a setting for the purifying or separating is altered for purifying or separating of additional samples.
  • purifying the sample is controlled such that an amount of impurities removed is optimized so as to provide a maximal range of efficiency in removing a significant portion of the one or more types of fullerenes.
  • a system for obtaining a refined sample of fullerenes.
  • a laser module includes a purifying laser and one or more separating lasers.
  • the purifying laser is operable to transmit, to a sample, a first dosage of electromagnetic radiation at a first predetermined energy such that a significant amount of the impurities are removed from the sample, thereby disentangling the fullerenes.
  • the first predetermined energy is used to excite a plasmon resonance in the fullerenes.
  • the purifying laser operates at a frequency of 248nm.
  • the separating lasers are each operable to transmit an additional dosage of electromagnetic radiation at a respective set of energies such that a significant portion of a respective group of fullerenes are removed from the sample.
  • the energies in each set match a respective absorption energy level of at least one type of a respective group of fullerenes.
  • a mechanism for aligning each of the lasers with the sample such that a selected laser is in an operating position to use an optical component for focusing electromagnetic radiation to the sample.
  • the mechanism rotates each laser into the operating position.
  • a frequency comb that disperses a range of energies of a dosage of electromagnetic radiation.
  • a shutter is activated to be used when the purifying laser is moved into the operating position.
  • the optical component functions as a lenselet array for spatially homogenizing the first dosage of electromagnetic radiation and functions as a focusing optic for expanding laser light for the additional dosages of electromagnetic radiation to a larger spot size.
  • an optics module provides additional focusing of the additional dosages of electromagnetic radiation.
  • the optical component is an optics module for focusing of the additional dosages of electromagnetic radiation on the sample and functions as a lenselet array for spatially homogenizing the first dosage of electromagnetic radiation.
  • a method for obtaining a satisfactory sample of fullerenes.
  • a sample including multiple types of fullerenes is received.
  • a significant portion of one or more types of fullerenes is removed from the sample by transmitting a first dosage of electromagnetic radiation at a first set of respective predetermined energies.
  • Removing is performed with a separation system.
  • the sample is transferring by a mobility apparatus from the separation system to a metrology system. The transferring is controlled by a control system.
  • the metrology system measures a spectral response of a pyroelectric detector, on which the sample resides, to a second dosage of electromagnetic radiation absorbed by the sample.
  • Data of the spectral response is received at the control system.
  • The is analyzed data to determine one or more properties of the sample; the properties include a semiconducto ⁇ metallic ratio. It is determined whether the properties of the sample satisfy one or more predetermined requirements. When the requirements are not satisfied, the sample is transferred back to the separation system, and removing one or more types of fullerenes with additional dosages of electromagnetic radiation is repeated.
  • the properties include a diameter distribution of the sample.
  • the sample is purified by transmitting, to the sample, a third dosage of electromagnetic radiation at a second predetermined energy such that a significant amount of impurities in the sample are removed from the sample, thereby disentangling the fullerenes.
  • the purifying is performed with a purification system.
  • the mobility apparatus transfers the sample from the purification system to the metrology system.
  • Impurity data is measuring with the metrology system and then received at the control system.
  • the impurity data is analyzed to determine one or more impurity levels, and the requirements involve an impurity level of the sample.
  • the purification system and the separation system are operated with the sample in a same location.
  • an amount of types of fullerenes is measured in the sample prior to removing a significant portion of one or more types of fullerenes by transmitting a first dosage of electromagnetic radiation, an amount of types of fullerenes is measured in the sample.
  • FIG. 1 is a flowchart illustrating a method for providing a satisfactory sample of fullerenes according to an embodiment of the present invention.
  • FIG. 2 is a flowchart of a method illustrating steps for achieving high-quality CNTs according to an embodiment of the present invention.
  • FIG. 3 illustrates a purification system according to an embodiment of the present invention.
  • FIG. 4A-4C show a schematic illustration of a laser resonance selection method and system according to an embodiment of the present invention.
  • FIG. 5 illustrates a system for purification/separation of a sample of fullerenes according to an embodiment of the present invention.
  • FIG. 6 shows a system for measuring pyroelectric spectral responsivity according to an embodiment of the present invention.
  • FIG. 7 illustrates a plot showing a relative response of a SWNT-coated pyroelectric detector compared with predicted responses for films made exclusively of either semiconductor SWNTs or metallic SWNTs.
  • FIG. 8 shows a plot of example calculations for volume fractions other than what were measured.
  • FIG. 9A illustrates a system usable in detecting broadband thermal properties of pyroelectric crystals to analyze carbon nanotube (CNT) according to an embodiment of the present invention.
  • FIG. 9B illustrates the same system as usable in performing Raman spectroscopy according to an embodiment of the present invention.
  • FIG. 10 is a flowchart illustrating a method of performing purification and/or separation in a feedback loop with metrology techniques according to an embodiment of the present invention.
  • FIG. 11 illustrates a system for obtaining a satisfactory sample of fullerenes from a given sample including fullerenes and impurities according to an embodiment of the present invention.
  • Embodiments of the present invention provide systems and methods for quantifying, purifying and separating fullerenes, such as carbon nanotubes (CNTs).
  • the purification methods offer the ability to obtain nearly 100% impurity- free single walled nanotubes
  • SWNT content from a given impure, as-produced SWNT bundle without any destruction, defect creation or functionalization of the SWNTs.
  • the separation methods offer the ability to obtain the desired range of chirality and diameter from a given non-separated, as-produced SWNT bundle.
  • Nanometrological validation of the success of purification and separation uses a pyroelectric detector and Raman spectroscopy in a single system, thus providing a critical aspect for the nanomanufacturing environment.
  • the present invention offers the ability to avoid 'wet' chemistry, as some embodiments process dry SWNTs (i.e. the SWNTs arenot in solution). The SWNTs will thus be available as-is for a variety of applications without any further chemistry processing.
  • FIG. 1 is a flowchart illustrating a method 100 for providing a satisfactory sample of fullerenes according to an embodiment of the present invention.
  • the sample is deemed satisfactory by measuring one or more properties and comparing them to predetermined requirements.
  • the sample may be a single batch of fullerenes or multiple batches.
  • a sample of fullerenes is received.
  • the fullerenes are nanotubes, e.g., made of carbon (CNTs), boron nitride, silicon, etc.
  • the fullerenes are spherical such as C 60 .
  • carbon fullerenes are predominantly made of carbon, but may have a few impurities.
  • the sample is dry in that the fullerenes are not in a solution.
  • step 1 characteristics of one or more batches of the sample are measured. For example, nanometrology equipment will quantify the as-prepared original quality of the carbon nanotubes prior to purification and separation steps 120 and/or 130. If the characteristics are satisfactory based on the measurements, then the method stops at step 115. If the characteristics are not satisfactory based on the measurements, then the method proceeds to steps 120 and/or 130 for purification and separation. In one aspect, specific settings of the purification and/or separation may be derived from the measurements.
  • the sample is purified of certain impurities.
  • the impurities may include carbonaceous impurities (such as amorphous carbon), metallic impurities, catalysts, and other nanoparticles.
  • certain types of fullerenes are separated or removed from the sample.
  • the separation may simply be separating by allotrope.
  • the separation is by characteristics within an allotrope, such as nanotubes. Examples of the characteristics (properties) are chirality, electronic structure, and diameter.
  • the separation results in the removal of certain types from a batch.
  • the separation results in the removal of one or more batches from a sample.
  • step 140 characteristics of one or more batches of the sample are measured. For example, nanometrology equipment will quantify the success of the purification/separation efforts using novel techniques which exceed the capabilities of current nanotools on the market for their reproducibility, quantification capability, relatively lower instrumentation cost, and rapidity of measurement. If the characteristics are satisfactory based on the measurements, then the method stops at step 150. If the characteristics are not satisfactory based on the measurements, then the method returns to steps 120 and/or 130 for further purification and separation. In one embodiment, only purification needs to be repeated and thus after the repeated purification control passes directly to the measurement in step 140. In another embodiment, only separation needs to be repeated and thus control passes from the measurement in step 150 to the separation in step 140, and then passes directly back to the measurement in step 150.
  • the feedback data obtained from the measurements in step 140 is not used to further purification/separation of that same sample of fullerenes. Instead, the feedback data may be used to alter one or more settings for the purification and/or separation for other samples of fullerenes that have not undergone purification and/or separation yet.
  • Original, as-prepared SWNT material is oftentimes rife with impurities (carbonaceous, metallic, and general nanoparticles), of a wide range of chiralities, and of a diversity of supramolecular structures (diameters and lengths).
  • impurities carbonaceous, metallic, and general nanoparticles
  • as-prepared fullerenes, such as SWNTs by purification and separation is desirable.
  • FIG. 2 is a flowchart of a method 200 illustrating steps for achieving high-quality CNTs according to an embodiment of the present invention.
  • the right hand side shows the three main steps: preparation, purification, and separation.
  • the left hand side shows a state of the CNTs during each step.
  • the center of the flowchart shows exemplary processes involved in each step.
  • step 210 single walled nanotubes (SWNT) are prepared.
  • multi-walled nanotubes are prepared and subsequently purified and separated..
  • SWNT single walled nanotubes
  • the carbon nanotubes are purified.
  • Such purification can include removing catalysts, amorphous carbon (or other carbonaceous impurities), and other nanoparticles.
  • Embodiments of the present invention are particularly aimed at removing amorphous carbon via electromagnetic (EM) radiation.
  • EM electromagnetic
  • the carbon nanotubes undergo separation, where certain types of nanotubes are separated into different batches or certain types are removed from a batch, e.g. by destroying them.
  • Exemplary separation characteristics are length of the nanotubes, the diameter of the nanotubes, and a chirality of the nanotubes.
  • the separation involves a measurement of such characteristics and the removal of a batch not having the proper characteristics. For example, a measurement of a percentage of metallic or semiconductor nanotubes, which relates to chirality, may be measured.
  • certain nanotubes are actively removed from a batch, e.g. by destroying nanotubes of a certain chirality, thus isolating, or "separating," the desired species of nanotubes.
  • Embodiments of the present invention overcome barriers of current methods with a series of purification and separation techniques using photonic processing.
  • the proposed purification and separation techniques leverage the fundamental properties of carbon nanotubes (specifically, SWNTs) to remove carbonaceous impurities and separate the SWNTs for diameter and chirality without inducing new defects in the SWNTs of interest.
  • embodiments for purification/separation are compatible with metrological considerations to quantif ⁇ ably validate the success of purification/separation and compatible with a desired form of the end product, e.g., being in a dry and undamaged state.
  • CNTs carbon nanotubes
  • Current CNT synthesis techniques produce only limited yield of significant purity CNTs (i.e., »95% CNT content).
  • CNT synthesis techniques produce only limited yield of significant purity CNTs (i.e., »95% CNT content).
  • purification methods often destroy the majority of the originally produced nanotubes (up to 99% in bulk samples) and/or damage or functionalize the nanotube surfaces, thereby altering fundamental CNT properties [I]. This situation severely limits implementation of CNTs into a variety of applications.
  • embodiments of the present invention utilize electromagnetic radiation to remove impurities.
  • the electromagnetic radiation is transmitted at a resonance frequency of the nanotubes.
  • a SWNT exhibits a ⁇ -plasmon frequency around 248nm (5eV), although other plasmon resonances and resonant frequencies may be used.
  • BN nanotubes, buckyballs, or other fullerenes will exhibit a different resonant frequency.
  • the electrons in the fullerenes resonate when the resonant frequency equals the frequency of some outside force, e.g., the electromagnetic radiation, and momentum from the photons may be imparted to the impurities, which readily react with oxygen or ozone in the surrounding air and become oxidized.
  • EM radiation at a plasmon resonance may be used to remove carbonaceous impurities from as-produced SWNTs using laser ablation, as described in [2], which is herein incorporated by reference.
  • Embodiments of the present invention utilize this technique.
  • FIG. 3 illustrates a purification system 300 according to an embodiment of the present invention.
  • a 248 nm laser 310 operating with a pulse width of approximately 20 ns and a pulse repetition frequency of 10 Hz is used.
  • Other embodiments may use other laser wavelengths, pulse widths and/or repetition frequencies.
  • the beam exiting the laser may be spatially homogenized by means of two lenses 320.
  • each lens consisted of an array of cylindrical lenselets with the cylindrical axis of the first lens perpendicular to the second.
  • the beam size is about 1 cm 2 .
  • Each laser exposure may be defined by opening a manual shutter 330 for a set period of time, such as 30 s.
  • the purification can remove sufficient impurities such that a subsequent separation process is improved. For example, with less graphitic material
  • an increased porosity results.
  • the increased porosity causes the nanotubes to be less connected or entangled, which can have benefits during separation.
  • one minute of irradiation at 755 mW/cm 3 is used.
  • the amount of impurities removed is optimized so as to provide a maximal range of improvement in the separation.
  • such laser ablation purification can also have important implications in removal of metallic catalysts from as-produced SWNTs.
  • the laser treatment does not appear to remove metals, the laser purification might be useful for removing the carbon impurities that encapsulate the metals. The exposed metals may then be removed. Thus, removal of carbonaceous impurities may also aid later removal of metallic catalysts. These metallic catalysts and impurities may also be removed by the electromagnetic radiation directly.
  • Embodiments utilizing this purification technique do not: (1) destroy CNTs during the purification process, (2) create defects in the CNTs, or (3) functionalize with other atoms/molecules the CNTs. Moreover, a significant portion (greater than 90%) of the carbonaceous impurities are removed. In some embodiments, 100% or nearly 100% (e.g. >98%) of the carbonaceous impurities are removed. Additionally, embodiments of the present invention offer the ability to avoid 'wet' chemistry. The SWNTs will thus be available as-is for a variety of applications without any further chemical processing
  • the chirality and diameter are controlled through the application of laser resonant frequencies to match a resonant frequency, e.g., when an incident photon matches the energy of the allowed electronic transitions of the fullerene.
  • Individual SWNTs of different chirality and diameters will have different allowed electronic transitions as evidenced in their density of states (DOS). It is proposed to take advantage of this SWNT phenomenon by replacing the outside macro-forces in the Tacoma Narrows Bridge example with photons from specific frequency lasers impinging upon the SWNT C-C bonds. This resonance is a function not only of the C-C bonding, but also of the chirality (the
  • FIG. 4 shows a schematic illustration of a laser resonance selection method according to an embodiment of the present invention.
  • SWNTs are one-dimensional materials, the SWNT DOS is characterized by multiple van Hove singularities, which have sharp peaks.
  • the DOS of SWNTs is strongly dependent on their chirality.
  • absorption of the exciting beam can be strongly enhanced for the SWNTs with specific chirality, whose energies of the allowed electronic transitions match the energy (hvi) of the incident photon from laser 410.
  • each one of the laser beams of a different energy may be from a different laser apparatus.
  • tuning features allow for different laser beams of different energies to be achieved from a single apparatus, and allow for multiple simultaneous energies to be applied.
  • This method allows the selection of SWNTs with specific chirality.
  • the irradiation at the resonance frequency may reduce some of the nanotubes with desired characteristics. In part, this may be due to bonding or other physical connections between the different nanotubes. These connections may arise from impurities linking the different types of nanotubes together. If the purification described above is done first, the connections can be decreased. Thus, once impurities are removed and porosity is increased, separation of the nanotubes may be enhanced and higher yields may be produced.
  • Embodiments also take this technique significantly further, namely not only to select for chirality, but also for diameter, thereby providing a true separation technology in an integrated system designed for the nanomanufacturing environment.
  • Fig. 4C shows a separation system according to an embodiment of the present invention.
  • a laser 430 provides a laser beam at energy (hv 3 ).
  • a focusing optic 440 may be used to expand the laser light to a larger spot size than the original laser.
  • a frequency comb 450 is used to measure the energy beam of laser 430, and thus calibrate the laser 430 so that it produces the desired laser wavelength from a range of wavelengths that the laser is capable of producing.
  • frequency comb 450 receives light from a laser, such as 430, and provides one or more output energy beams at defined energies.
  • the energy of the output laser beam matches an absorption level of the fullerenes, such as an electronic transition.
  • the energy of the received energy beam may thus match the electronic level as well since the output energy beam is derived from the received energy beam.
  • Frequency combs are described in [12] and [13], which are herein incorporated by reference.
  • An optics module 460 is used to focus the photons previously measured and/or calibrated for the desired range of wavelengths through the frequency comb to the carbon nanotubes 470 on a substrate 480.
  • the sample resides within an environment containing oxygen.
  • the exposure time of the sample to the electromagnetic radiation, and the electromagnetic radiation intensity is strictly controlled, e.g., so as not to damage the desired type of nanotube.
  • the intensity of the electromagnetic radiation in the separation is higher than for the purification.
  • FIG. 5 illustrates a system 500 for purification/separation of a sample of fullerenes according to an embodiment of the present invention.
  • Laser module 505 provides multiple wavelengths for purifying and separating the fullerenes.
  • multiple lasers are used to both purify and separate the SWNTs.
  • a first laser such as purifying laser 510
  • Additional lasers such as a first separating laser 520 and a second separating laser 530, can then remove different types of fullerenes based on chirality and/or diameter.
  • Various and any number of different laser frequencies could be applied with possible comparable effects in purification and separation technologies.
  • Each laser is operable to transmit electromagnetic radiation to a sample 580 when a laser is moved into a position to transmit energy beam 535.
  • the lasers can be moved into position by a rotation mechanism with each laser occupying a slot of the mechanism.
  • a rotation mechanism with each laser occupying a slot of the mechanism.
  • One skilled in the art will appreciate the many embodiments for providing such a mechanism.
  • a broad wavelength or multi-wavelength laser could be used.
  • a focusing optic 540 may be used to expand the laser light to a larger spot size than the original laser.
  • focusing optic 540 can act as the lenselet arrays 320 when performing purification.
  • the frequency comb 550 can measure the wavelength of the laser light so that the currently operating laser could be calibrated to produce the desired wavelength (energy), thus keeping costs down by reducing the number of lasers that are needed.
  • Optics module 570 provides the ability to expand and/or focus the laser beam 535 on the sample 580.
  • the homogenizer lenselet array 320 for the purification system 300 is used as the optics module 570.
  • frequency comb 550 may be moved out of the laser beam 535 when the purifying step is done and/or the frequency comb 550 is or is not needed in the separation steps. This action is shown by the dashed box frequency comb 550 to the right of laser beam 535. In one embodiment, motion of frequency comb 550 could occur via a standard x-y translation stage, with accommodations for the frequency comb 550 optics to avoid their damage. Similarly, the shutter 560 may be removed during the separating step. In one embodiment, the sample 580 is moved and the lasers are stationary.
  • frequency comb 550 maybe used to provide a first set of one or more beams at different energies from a single laser. Note that by different energies, a particular energy may correspond to a range of energies centered around a particular energy of interest.
  • the first set of energy beams may be transmitted simultaneous (e.g., during overlapping time periods) or at different discrete times. Additional sets of energy beams may be provided from additional lasers. Each of the energies of a set would then correspond to a absorption level of a type of fullerenes.
  • alternative means could be used to induce the resonance of the SWNTs, for example, acoustics. Also, if a bundle of SWNTs is not of the proper topology or has not been produced by the appropriate technique for which the matrix of purification and separation parameters has been constructed and calibrated, it is possible that the resonant frequencies may not be achieved.
  • Embodiments of the present invention purifies the SWNTs of carbonaceous impurities (e.g., such that there are 0% carbonaceous impurities) and separates the SWNTs into narrow-band chirality and diameter ranges. However, it goes further by doing so in a 'dry' chemistry environment, purifying them to a hyper-pure condition (0% carbonaceous impurities), separating them also into diameter ranges, and validating the success of these procedures with nanometrology systems built into the system.
  • carbonaceous impurities e.g., such that there are 0% carbonaceous impurities
  • Metrology techniques provide such quantification. Such techniques include transmission electron microscopy (TEM), scanning electron microscopy (SEM), x-ray diffraction (XRD), Raman spectroscopy, fluorescence spectroscopy, near-infrared spectroscopy, nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR), temperature programmed desorption (TPD), thermogravimetric analysis (TGA), neutron scattering, scanning tunneling microscopy (STM), and atomic force microscopy (AFM).
  • TEM transmission electron microscopy
  • SEM scanning electron microscopy
  • XRD x-ray diffraction
  • Raman spectroscopy Raman spectroscopy
  • fluorescence spectroscopy fluorescence spectroscopy
  • near-infrared spectroscopy nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR), temperature programmed desorption (TPD), thermogravimetric analysis (TGA), neutron scattering, scanning tunneling microscopy (STM), and atomic force
  • embodiments of the present invention offer new functionality over existing systems.
  • nanometrology techniques there does not exist a system that provides species ratio (metallic:semiconductor SWNTs), impurity content, and diameter distribution. Knowledge of these properties will be helpful in process improvement in SWNT production and routine quality validation in SWNT research.
  • Embodiments of the present invention extend the prior art by its implementation into other existing metrology techniques to meet these critical metrology criteria, including a low cost instrument that all carbon nanotube producers and end users presently need.
  • Embodiments of the present invention couple a pyroelectric detector with Raman spectroscopy for its impurity metrology.
  • a pyroelectric detector with Raman and AFM embodiments of the present invention provide the ability to measure species ratio (metallic:semiconductor SWNTs), impurity content, and diameter distribution.
  • species ratio metallic:semiconductor SWNTs
  • impurity content and diameter distribution.
  • Embodiments may also measure supramolecular structure (e.g., atomic spacing, diameter distribution, crystallography, etc.), for example, with an AFM.
  • the sample contains not much more than carbonaceous impurities (i.e., the sample possesses low metallic impurity content).
  • Embodiments of the present invention may ultimately measure: (1) volume fraction of semiconductor to metallic carbon nanotube types; (2) purity (through integral area under the spectra curves); (3) signature of specific CNT fabrication techniques (tubes from different processes appear to demonstrate different spectra); (4) multi-walled carbon nanotubes (MWNTs) - identification of MWNTs vs. SWNTs; (5) functionalization - the attachment of other molecular groups to a carbon nanotube's interior and/or exterior to ameliorate the CNT' s acceptance into another matrix material, such as a nanocomposite; and (5) supramolecular structure, i.e., atomic spacing, diameter and length distributions, and chirality.
  • MWNTs multi-walled carbon nanotubes
  • Embodiments of the present invention use the broadband thermal properties of pyroelectric crystals could be used to analyze carbon nanotube (CNT) quality by interrogating coated crystals with a spectral responsivity measurement system, described in [4], which is herein incorporated by reference.
  • This pyroelectric metrology technique provides a rapid, low cost means to measure the volume fraction of metallic and semiconducting single-wall carbon nanotubes (SWNTs) in bulk samples.
  • a surface of a LiTaO 3 pyroelectric detector is used as a platform for the sample of fullerenes. Optical, acoustic, and thermal probes are focused upon the surface and elicit a response on the pyroelectric platform.
  • FIG. 6 shows a system 600 for measuring a pyroelectric spectral responsivity according to an embodiment of the present invention.
  • System 600 includes a lamp source 610, a grating monochromator 620, and a detector 640.
  • the method of direct substitution provides absolute spectral responsivity relative to a NIST standard at 10 nm wavelength increments from 600-2000 nm with a relative expanded uncertainty of 1.24 %.
  • the pyroelectric detector 640 to which the SWNTs 630 are applied is prepared from a z-cut LiTaO 3 plate 12 mm in diameter and 60 ⁇ m thick.
  • the electrodes centered on the back side of the LiTaO 3 plate are 10 mm in diameter and consist of 50 nm of gold on top of 25 nm of chromium.
  • the front electrode, to which the SWNTs are applied is 25 nm of chromium.
  • the back electrode is connected to the signal input of a current amplifier with, e.g., a 10 "10 A/V gain, and the front electrode is connected to ground.
  • the optical input to the detector may be modulated at, e.g., 15 Hz and measured with a lock-in detection scheme, as described in [5], which is herein incorporated by reference.
  • a sample of fullerenes on bucky paper is placed on the front with a drop of chloroform to facilitate adhesion.
  • the sample then remains attached to the detector after the chloroform has evaporated.
  • the beam exiting the monochromator 620 was focused on the sample to a beam size of approximately 2 mm x 2 mm, normal to the plane of the detector surface, with a bandwidth of 6 nm.
  • the current generated by a pyroelectric detector is proportional to the volume average of the change in temperature as a function of time. Its spectral responsivity depends only on conversion of optical energy to thermal energy by the coating. Thus, the spectral responsivity of a pyroelectric detector coated with purified nanotubes can reveal optical properties of the coating from the ultraviolet to far into the infrared spectrum.
  • ⁇ ⁇ is the electronic core contribution
  • ⁇ p is the plasma frequency of charge carriers
  • ⁇ 0 is the center frequency
  • ⁇ is the photon frequency
  • ⁇ and T are the relative relaxation rates of the charge carriers of the metal and semiconductor systems. Representative values from [6] for these parameters are shown in Table 1.
  • FIG. 7 illustrates a plot 700 showing a relative response of a SWNT-coated pyroelectric detector compared with predicted responses for films made exclusively of either semiconductor SWNTs or metallic SWNTs.
  • Plot 700 thus provides the extreme metallic and semiconducting cases of/ A typical measurement of a bundle of SWNTs on the pyroelectric detector shows a curve in-between these extrema. This would seem to indicate that there is a mix of both metallic and semiconducting tubes within the same batch of SWNTs.
  • FIG. 8 shows a plot 800 of example calculations for volume fractions other than what were measured.
  • the measurements of purified SWNTs produced by laser vaporization and applied to a pyroelectric detector have sufficient length and lack of defects to exhibit a spectral character in the wavelength range 600-2000nm to reveal interband transitions that are characteristic of either metallic or semiconducting SWNTs.
  • the sample shown in plot 800 as evaluated by means of spectral responsivity and EMA indicates that such SWNTs produced by laser (755nm) vaporization at 55W/cm 2 have a proportion of SWNT material content that is 20% metallic and 80% semiconducting.
  • a model may thus be derived to estimate the relative concentration of metallic to semiconducting SWNTs applicable for highly pure samples.
  • the nanometrology tool will not work with un-pure carbon nanotubes. Purity levels of >97% are currently used as standard in the test samples. Without purity levels close to this, spectral noise will result in loss of measurement resolution, and the EMA estimation of the CNT species proportions will be difficult, if not impossible. Measurement results can also vary depending on the roughness, texture, and thickness of the layer of CNTs being assessed.
  • Raman is an inexpensive technique to provide nanometrology of carbon nanotubes.
  • Raman spectroscopy may be employed to analyze the FWHM of the D-band for the purified sample and determine if it is consistent with material that is virtually free of non- nanotube carbon impurities. General defect values may also be measured.
  • the frequencies of the radial breathing modes (RBMs) may also indicate the resonant diameter distribution. The number or variation of chirality of a sample may also be measured by Raman.
  • Raman spectroscopy a powerful tool for the determination of the diameter distribution within a bulk CNT sample, involves the probing by laser light of the intramolecular vibrational and electronic states of the material. Incident monochromatic radiation promotes a bound electron into a 'virtual' excited state. Because this virtual state does not exist in the energy dispersion, it immediately decays into an available real state within the same electronic sub-band, resulting in the emission of a photon. Sometimes this event is inelastic, such that the emitted (scattered) photon has more or less energy than the incident photon. This energy difference is due to a concomitant vibrational transition during the electronic excitation-decay process and is called the Raman shift...
  • the RBM [radial breathing mode] of a SWNT is Raman active because of its symmetry. Therefore, the Raman spectrum (i.e., intensity versus Raman shift) of a sample of nanotubes is a direct probe of the allowed RBMs and therefore of the diameter distribution.
  • the D-mode In addition to the RBMs, there is another characteristic disorder band called the D-mode, whose intensity relates to the fraction of disordered carbons in a SWNT sample; the D-mode is expected to be observed in multi- walled carbon nanotubes (MWNTs). The D-mode has been sometimes used as a qualitative metric for sample purity. Lastly, there is a characteristic spectral mode for carbon nanotubes called the G-mode, whose intensity relates to the stretching mode of the C-C bond in the graphite plane.
  • Embodiments of the present invention extend the pyroelectric technology into the complementary metrology technique of Raman spectroscopy.
  • the proposed metrology system provides an inexpensive, rapid means to characterize SWNTs for the parameters critical to the carbon nanotube industry while staying non-destructive.
  • FIG. 9A illustrates a system 900 usable in detecting broadband thermal properties of pyroelectric crystals to analyze carbon nanotube (CNT) according to an embodiment of the present invention.
  • Basic components include an illumination source 905 and a single-grating monochromator 920 (e.g. in a Czerny-Turner configuration) with order sorting colored-glass filters.
  • Monochromator 920 transmits a selectable narrow band of wavelengths of light or other radiation chosen from a wider range of wavelengths produced by the illumination source 905.
  • monochromator 920 is advantageously used for both a pyroelectric detector and Raman spectroscopy.
  • illumination source 905 is a broad-spectrum light source composed of a tungsten-filament, quartz-envelope light bulb.
  • the bulb has a rated filament temperature of 3400 K, at 6.25 A and 24 V as described in [1 1], which is incorporated herein by reference.
  • a translation stage 913 on the input side of the monochromator 920 allows a chopper 915 to be moved in and out of the beam path 907, to accommodate a reference detector 940. Additionally, a focusing optic 917 may be used to prevent the light beam 907 from spreading out too much.
  • a band pass filter 919 e.g. colored glass filters, are used to reduce transmission of the unwanted orders and to reject stray light.
  • the filters are chosen to maximize throughput and also to minimize the magnitude of overlapping orders over the useful wavelength range.
  • four filters are used.
  • the filters are mounted on a motorized disk that rotates each filter into the path of the input light, for each wavelength range.
  • the monochromator grating 924 is mounted in a Czerny-Turner configuration. In one aspect, one grating is used. In another aspect, two or more gratings are available, depending on the wavelength range of the desired calibration. For example, one grating is blazed at one amount (e.g. 500 nm) and the other grating is blazed at a larger amount (e.g. 1000 nm). The useful range of the monochromator using both gratings is 400 nm tol 800 nm.
  • a mechanical device moves a specific one of the different gratings into place.
  • a specific grating may be moved using a stepper motor coupled to an absolute encoder.
  • the stepper motor is coupled to a lead screw that drives a sine-bar mechanism.
  • the grating position algorithm can be calibrated using a single offset value.
  • different offsets may be used, e.g., when different line densities exist.
  • the precision may be controlled by the resolution of the encoder by the number of steps per revolution it resolves, e.g., 16384 steps per revolution.
  • the mechanical relationship of the grating placement and the wavelength selection provides for a certain number of nm (e.g. 10 nm) per revolution. Therefore, the mechanism would be capable of 1638.4 steps per nm, which would provide a positioning resolution of 0.0006 nm.
  • the grating resolution is the practical limit. Realistically, the measurement resolution is decreased by the need for increased throughput. To increase the throughput, the monochromator input and output aperture slits may be widened.
  • the light path 907 is extended using mirrors 922 on both the input and output of the monochromator 920, to accommodate a variety of shapes and sizes of meters.
  • a beam splitter 930 splits the light beam 907 to send the light to a reference detector 940, which calculates a baseline or background response, and to the sample 950, which lies on top of a pyroelectric detector 955, via beam splitter 945.
  • the output from pyroelectric detector 955 is from current generation from the sample, such as carbon nanotubes.
  • the focusing optic 935 provides focused light to the reference detector 940.
  • reference detector 940 A pyroelectric detector is used as reference detector 940.
  • Reference detector 940 is actively thermally stabilized and is electrically connected to dedicated current amplifier, lock- in amplifier, and optical chopper, which may be included within data acquisition system 960.
  • reference detector 955 is a pyroelectric trap.
  • the trap design is based on a lithium tantalate (LiTaO 3 ), pyroelectric disc coated with gold black, positioned opposite a gold mirror in a wedge configuration. The low-reflectance gold black coating, along with the wedge-trap structure, ensures that the pyroelectric disc absorbs 99% of the light entering the aperture.
  • a light-tight enclosure 990 encloses lamp 905 and the optic instrumentation, including the monochromator 920, monochromator mirrors 922, bandpass filters 919, test and reference detector 940, and output optics and fixtures of the monochromator.
  • Light-tight enclosure 990 has a slit for transmitting a portion of light beam 907 to the sample 950.
  • a light-tight barrier 925 separates light-tight enclosure 990 into two portions, thus separating the pyroelectric detection light source's stray light from the sample 950. This effectively restricts the only normally detectable light (more than a picowatt) transmitted to the test and reference detector 940 to be from the monochromator 920.
  • the sample 950, data acquisition system, pyroelectric detector 955, and data acquisition system 960 are not enclosed within the light-tight enclosure 990.
  • the entire measurement system rests on a commercial, vibration- damping tabletop.
  • pyroelectric detector 955 is also connected to computer acquisition system 960 for current amplification and/or measurement.
  • computer acquisition system 960 includes a computer for applying an effective medium approximation (EMA) to convert the collected data into a volume fraction of metallic and semiconducting carbon single-wall nanotubes.
  • EMA effective medium approximation
  • the computer may be any type of suitable processor, such as a typical desktop PC containing a general purpose processor, or may be a chip such as an ASIC or FPGA built to perform the desired calculations.
  • Software running on the data acquisition system 960 is written to control the electronic instrumentation and collect data over an interface, such as the General Purpose Interface Bus (GPIB).
  • the software interface may resemble a virtual instrument with push buttons, slider keys, and numerical and graphical displays.
  • By use of the software one can set the positioning stage locations, adjust the lamp current and voltage, control the detector electronics, and set up data collection parameters.
  • the wavelength scan range, time delays, file destinations, and number of data points to average can be input into the program.
  • FIG. 9B illustrates the same system 900 as usable in performing Raman spectroscopy according to an embodiment of the present invention.
  • the Raman spectroscope offers diametrical distribution quantification and knowledge of impurity content. This knowledge base is augmented with the pyroelectric detector. Both Raman spectroscopy and the pyroelectric detection satisfy all qualitative metrology characteristics of being nondestructive and repeatable, possessing low complexity, having integration potential with other techniques, and capable of ⁇ 1 day's measurement time.
  • a laser 965 pulses its photonic source to the beamsplitter 945.
  • this beamsplitter contains a 10:90 reflective:transmittive capability, so 10% of the light goes to sample 950.
  • the fullerenes are then stimulated and emit their energy, depicted as rays 968 directed upward to monochromator 920.
  • These emissions return through the beamsplitter 945, into the monochromator 920, bounce off mirrors, the diffraction grating 972, more mirrors, and then are detected by the Raman charge-coupled device (CCD) 970, or other suitable detector.
  • Diffraction grating 972 may be the same or different than the diffraction grating 924 used for the pyro electric detector.
  • the CCD camera 970 sends the resulting output signals to data acquisition system 960 that runs software to ultimately show the Raman spectra. From this spectra, the data acquisition system 960 can determine the Radial Breathing Modes (RBMs), which can be used to calculate an average diameter for the sample, D-modes that are indicative of defects in the nanotubes, and G-modes that are indicative of excitations of the nanotubes. All this information may be assembled and displayed in an easy-to-understand fashion for the user. In one embodiment, the data processing models may evolve to produce more information from fewer discrete techniques and to involve complementary data from more than one technique simultaneously.
  • RBMs Radial Breathing Modes
  • the light-tight barrier 925 that separate the lamp 905 stray light from the sample also separates lamp 905 stray light from the Raman system. Additionally, light-tight barrier 925 can separate stray energy of the Raman laser and stray energy emitted from the sample 950 from the CCD 970.
  • a translation table is provided to extend the range of the bulk characterization.
  • the samples may be mounted on a piezoelectric translation table or some other means of mechanical/electric motion (automated or manual).
  • a translation table will serve to move the mounted pyroelectric detector in the XY directions. This action will facilitate mapping of the bulk carbon nanotube sample for measurement parameters such as species, impurities, surface texture, atomic spacing and diameter distribution. Moreover, by this motion, the whole bulk sample may be purified beyond its original state.
  • the translation table a means to translate the detection system while holding the specimen stationary, provides specimen mapping.
  • the translation table can be manual, automated, mechanical and/or electrically activated.
  • the specimen may remain stationary or the instrument may remain stationary. Sample size of the CNTs is presently on the order of a few millimeters in area.
  • the addition of an XY translation stage will overcome this limitation.
  • FIG. 10 is a flowchart 1000 illustrating a method of performing purification and/or separation in a feedback loop with metrology techniques according to an embodiment of the present invention.
  • the sample may be purified by any methods as described above.
  • the energy (such as electromagnetic energy) used in this first purification step is termed a first dosage. Future repeated steps of purification or of other steps involving energy would be other dosages.
  • Each dosage may include particles (e.g. photons) at many different energies during a single round of the purification step, or may include photons with an energy distribution centered around a specific energy, but with multiple rounds that each have a different energy distribution.
  • step 1020 system 900 may be used to perform Raman spectroscopy to measure the impurity levels of the sample. If the impurity levels are not satisfactory, then the method reverts back to step 1010 to perform additional purification. If the impurity levels are satisfactory, the method may proceed separation in step 1030, which may be performed by any methods described herein.
  • the determination of whether or a not a sample is satisfactory can be determined from the spectral data of the measurements.
  • a variety of different settings and requirements may be used in the determination. For example, certain threshold levels for the ratio of semiconductormetallic may be set. The diameter distribution may be required to have a center within a predetermined amount of a desired value and the mean, variance, or other statistical value of the distribution may be required. Also, threshold levels may be set on the purity value of the sample, as well as the separation discreteness desired - within a predetermined amount of the respective desired values and the means, variances, or other statistical values of the distribution.
  • the pyroelectric detector may be used to measure chirality and semiconducto ⁇ metallic ratio and/or Raman spectroscopy may be used to measure the diameter distribution. If the separation measurements are not satisfactory, then the method reverts back to step 1030 to perform additional separation. If the separation measurements are satisfactory, the method may terminate at 1050. Note that alternate embodiments may have measurements performed before any purification/separation to test which purification/separation techniques or settings are to be used. [0119] FIG. 1 1 illustrates a system 1100 for obtaining a satisfactory sample of fullerenes from a given sample including fullerenes and impurities according to an embodiment of the present invention.
  • a metrology system 1 110 measures properties of the sample.
  • One or more outputs of metrology system 1110 provide data associated with particular properties measured.
  • a purification/separation system 1 120 uses electromagnetic radiation at a predetermined energy window such that the impurities are oxidized from the sample and separates different types of the fullerenes by transmitting electromagnetic radiation at a predetermined energy.
  • purification/separation system 1100 is system 500.
  • a mobility apparatus 1 130 moves the sample among the metrology system 1110 and the purification/separation system 1 120. In one embodiment, mobility apparatus 1 130 also moves the sample between the purification part and the separation part of system 1 120.
  • a control system 1 140 receives data from the metrology system, the purification system, and the separation system; analyzes the data to produce data results; and compares the data results to determine if the sample satisfies certain predetermined requirements. Based on the comparison, control system 1 140 controls the mobility apparatus 1 130 for alternating the sample.
  • One skilled in the art will appreciate the many methods for implementing such a mobility apparatus.
  • an AFM may be used for mapping of the supramolecular structure, which also may provide feedback measurements for the purification and/or separation stages.
  • Such supramolecular structure includes determination of surface texture, atomic spacing and diameter distribution along the full width and depth of the carbon nanotube sample.
  • Any of the software components or functions described in this application may be implemented as software code to be executed by a processor using any suitable computer language such as, for example, Java, C++ or Perl using, for example, conventional or object- oriented techniques.
  • the software code may be stored as a series of instructions, or commands on a computer readable medium, such as a random access memory (RAM), a read only memory (ROM), a magnetic medium such as a hard-drive or a floppy disk, or an optical medium such as a CD-ROM.
  • RAM random access memory
  • ROM read only memory
  • magnetic medium such as a hard-drive or a floppy disk
  • an optical medium such as a CD-ROM.
  • Any such computer readable medium may reside on or within a single computational apparatus, along with a processor which can execute instructions on the computer readable medium, and may be present on or within different computational apparatuses within a system or network.

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Abstract

La présente invention concerne des systèmes et des procédés destinés à quantifier, purifier et séparer des fullerènes, tels que des nanotubes de carbone à une paroi (SWNT). La combinaison purification/séparation permet d'obtenir des SWNT exempts à presque 100 % d'impuretés carbonées à partir d'un échantillon impur donné et permet d'obtenir la chiralité voulue et le diamètre voulu à partir d'un échantillon non séparé donné. La validation nanométrologique de la réussite de la purification et de la séparation utilise un détecteur pyroélectrique et la spectroscopie Raman dans un système unique, constituant ainsi un aspect crucial de l'environnement de nanofabrication. Les validations de purification/séparation et nanométrologiques peuvent être réalisées avec une boucle de retour d'informations de manière à obtenir un échantillon raffiné de manière satisfaisante et des paramètres de purification/séparation optimisés.
PCT/US2007/068547 2006-05-09 2007-05-09 Nanométrologie, purification et séparation de nanotubes de carbone WO2008054871A2 (fr)

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US11/745,808 US20080069758A1 (en) 2006-05-09 2007-05-08 Carbon Nanotube Purification and Separation System
US11/745,779 US7564549B2 (en) 2006-05-09 2007-05-08 Carbon nanotube nanometrology system
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