Classifications

• • 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
  • G01J5/12—Radiation pyrometry, e.g. infrared or optical thermometry using electric radiation detectors using thermoelectric elements, e.g. thermocouples
  • G01J5/14—Electrical features thereof
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y15/00—Nanotechnology for interacting, sensing or actuating, e.g. quantum dots as markers in protein assays or molecular motors
• • 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
  • G01J5/02—Constructional details
• • 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
  • G01J5/02—Constructional details
  • G01J5/0225—Shape of the cavity itself or of elements contained in or suspended over the cavity
  • G01J5/023—Particular leg structure or construction or shape; 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
  • G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
  • G01J5/02—Constructional details
  • G01J5/08—Optical arrangements
• • 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
  • G01J5/02—Constructional details
  • G01J5/08—Optical arrangements
  • G01J5/0853—Optical arrangements having infrared absorbers other than the usual absorber layers deposited on infrared detectors like bolometers, wherein the heat propagation between the absorber and the detecting element occurs within a solid

Definitions

• This invention relates generally to sensing light energy, and more particularly to using a nanowire to detect photon energy.
• Photons are single light elements, and detection of the energy of single photons can be desirable in several settings.
• Phototubes, photomultipliers, avalanche solid state photodiodes, and HgCdTe detectors are all quantum detectors that can, broadly, be classified as photon-counting and photon-number-resolving detectors.
• Such detectors can in some instances be set-up as heterodyne detectors (which detect interference in laser light moving between a local source and returning laser light). Because the detection in such devices is done through electric charge, without multiplexing, these detectors are color blind.
• a bolometer is another energy detection device. In contrast to the devices described above, in a bolometer, light heats up a tiny piece of material. The bolometer then operates like a calorimeter, measuring power. The temperature change of the bolometer is measured and transformed into an electric signal.
• thermoelectric nanowires described in the following detailed description, particularly when studied in conjunction with the drawings, wherein:
• FIG. 1 comprises a schematic top view of a device as configured in accordance with various embodiments of the invention
• FIG. 2 comprises a perspective view of a portion of a device as configured in accordance with various embodiments of the invention
• FIG. 3 comprises an illustration of a method for preparing nanowires as may be used in various embodiments of the invention as configured in accordance with various embodiments of the invention
• FIG. 4 comprises a flow chart of a method of using a device
• FIG. 5 comprises a perspective view of an array of devices as configured in accordance with various embodiments of the invention.
• a nanothermocouple detector includes a nanowire coupled across two electrodes.
• the two electrodes in turn are electrically connected to an amplifier.
• the two electrodes generally have a separation of about five micrometers to about thirty micrometers across which the nanowire is coupled.
• a focusing element is disposed to admit photons that fall on the focusing element onto the nanowire to heat it.
• a voltage change across the nanowire due to the heating is detected by the amplifier. The voltage change corresponds to the energy absorbed from the light by the nanowire.
• the apparatus includes an amplifier 105 and two electrodes 112 and 114 electrically connected to the amplifier 105.
• the amplifier 105 may be a pre-amp lifter in electrical communication with further circuitry that can amplify and handle signals from the preamplifier relating to the operation of the device, such as to collect and analyze the signals as data.
• the two electrodes 112 and 114 electrically connected to the amplifier 105 have a separation of about five micrometers to about thirty micrometers.
• a nanowire 120 is coupled across the two electrodes 112 and 114.
• the nanowire is bonded to the electrodes 112 and 114 at bonding points 122 and 124, respectively.
• the nanowire comprises a single bismuth tellurium crystal.
• the chemical notation for a typical bismuth (Bi) tellurium (Te) crystal is Bi 2 Te 3 .
• Bi(2)Te(3) has the technical meaning of [Bi(l-x)Sb(x)](2a)[Te(l-y)Se(y)](3b) where x, a, y, and b can assume any value between zero and 1.
• Bi(2)Te(3) designates the family of compounds that are used in thermoelectric energy conversion, and this family is well known to those familiar with the state of the art.
• the focusing element 130 is disposed to admit photons 140 incident on the focusing element 130 onto the nanowire 120 to heat the nanowire 120.
• the focusing element 130 is disposed to admit photons 140 to be incident onto the nanowire 120 adjacent to a nanowire contact 124 with one of the two electrodes 112 and 114.
• Such an approach can be advantageous because the electromagnetic energy is light and is dispersed in the electromagnetic field over distances of the order of the wavelength of the light.
• the energy of a photon lands instantaneously in a single spot on the nanowire 120 and, in some approaches, on the thermoelectric junction because the thermoelectric junction has the highest resistivity. This absorption process is instantaneous, and after the energy evolves out of the landing spot onto the junction itself, the energy is disposed in a cross-section of the nanowire.
• the time constant for heat diffusion in the junction is approximately d 2 /D.
• the focusing element 130 may comprise any one of a number of different types of known technologies.
• the focusing element includes at least one of a pinhole element or a miniature antenna.
• a miniature antenna may include lenses and/or mirrors that help to direct photons onto a particular portion of the nanowire 120.
• a pinhole element block lights and allows only a certain amount of light through to land on a particular portion of the nanowire 120.
• the amplifier When light impinges upon the nanowire 120, the amplifier is configured to detect a voltage change across the electrodes 112 and 114. A response to photon impingement on the nanowire 120 is the conversion of the photon energy into heat in the nanowire 120. That heating in turn affects the electrical property of the nanowire. In this case, a change in potential or a voltage across the nanowire 120 between the electrodes 112 and 114 is detected.
• the amplifier 105 is configured to detect a voltage change corresponding to energy levels corresponding to single photon energy levels.
• a single photon impinging upon the nanowire 120 can heat the nanowire enough to cause a detectable voltage change across the electrodes 112 and 114, such that the amplifier 105 in combination with supporting circuitry can interpret the voltage change as matching the energy level of the photon impinging upon the nanowire 120.
• the electrodes 112 and 114 and the amplifier 105 are mounted on a substrate 160.
• the nanowire 120 is disposed across the electrodes 112 and 114 without direct contact with the substrate 160.
• the electrodes 212 and 214 are disposed in contact with and are supported by the substrate 260.
• a nanowire 220 is disposed across the two electrodes 212 and 214 with electrical contact at the junctions 222 and 224 with the electrodes 212 and 214, respectively.
• the electrodes are microfabricated with lithographic techniques on a dielectric substrate.
• the fabrication steps have been demonstrated by P. Jones, T.E. Huber, J. Melngailis, J. Barry, M. Ervin, T. S. Zheleva, A. Nikolaeva, L. Konopko, and M.J. Graf, "Electrical contact resistance of individual bismuth telluride nanowires.” Proc. 25 th Int. Conf. Thermoelectrics held 2006 (IEEE, Piscattaway, 2007), pp. 367, which is hereby incorporated by reference as though fully rewritten herein.
• the nanowires 120 are suspended and not in contact with the dielectric substrate 160.
• the nanowires in various approaches are single crystal elements that do not bend easily; thus, because the electrode contacts are raised with respect to the substrate, the nanowire will not contact the substrate.
• the electrodes can be made of materials that have poor thermal contact to the nanowire.
• the nanowire resistance is R and the nanowire-electrode contact resistances is Rc. It is known that R ⁇ 5 K ⁇ and Rc - 100 ⁇ for 200 nm BiTe nanowires.
• the relevant thermal parameter is ⁇ , the heat diffusion time from the nanowire into the electrode.
• ⁇ is found to be 2.5 ⁇ sec independent of wire diameter.
• E(photon) h ⁇ , the reduced Plank constant times the angular frequency of the photon.
• the thermopower of p- n BiTe junctions is about 200 ⁇ V/K, and therefore the voltage generated is 20 ⁇ V.
• the noise of the device has to be considered, and therefore it is advantageous to express the results in terms of noise equivalent power (NEP).
• NEP is the power that, if detected, would give rise to a signal that is barely distinguished from noise.
• Table 1 shows the experimental results for various state-of-the-art bolometric room temperature detectors and the results of models in the case of a 200 nm BiTe nanowire and a 10 nm BiTe nanowire. Table 1 shows that the performance, as gauged by the NEP and speed, where smaller is better for both factors, is in the mid-range for a 200 nm BiTe nanowire and comparatively better for a 10 nm BiTe nanowire. [0023] Table 1. Comparison of bolometric detector performances @ 300 K
• the first factor is the thermal mass that is proportional to the wire cross-section and improvements in fabrication.
• the estimate of NEP is changed to 0.04 relative to the 200 nm model, a small noise level for operating at about room temperature.
• the second factor is phonon size effects. It has been shown using individual Si nanowires that the phonon thermal conductivity in nanowires is decreased drastically, by about two orders of magnitude because the phonons are effectively stopped by the boundaries of the nanowires. In other words, the boundaries are rough to phonons. This effect is expected theoretically and has been observed in other nanowires such as bismuth. The entry for ⁇ in Table 1 reflects the uncertainty regarding this parameter.
• a nanothermocouple detector including a nanowire that is between about 5 micrometers to about 30 micrometers in length can be configured to have energy sensitivity high enough to sense the color of individual photons impinging upon the nanowire.
• a porous alumina template 310 includes pores 320 disposed throughout the template 310.
• the template 310 comprises porous anodic alumninium oxide (PAAO) and is approximately 50 to 100 micrometers deep with the individual pores in the template being between 7 and 200 nanometers wide.
• PAAO porous anodic alumninium oxide
• the template 310 is designed to achieve crystalline orientation with the Bi trigonal axis (a high-symmetry direction) along the wire length, a high-density Bi phase (no empty channels in the template), and low contact resistance of the Bi nanowire array, generally less than 10 "7 ⁇ .cm 2 .
• a bismuth tellurium melt 330 is injected into the porous alumina template 310 at high pressures, such as, for example, approximately one kBar. When cooled, the combined bismuth tellurium melt and porous alumina template create a bismuth tellurium wire array 340. The alumina is dissolved away resulting in free standing bismuth tellurium nanowires 350 floating in the dissolving solution 360. Individual of these nanowires can then be incorporated into a nanothermocouple detector as described above.
• an example of such an apparatus includes a detecting array 410 wherein individual detecting elements 415 of the detecting array 410 comprise nanothermocouple detectors such as those described above.
• Optics 420 include a focal plane wherein the detecting array 410 is disposed in the focal plane of the optics 420.
• the optics 420 include individual optic elements 425 configured such that photons 440 collected by the optics 420 are directed to impinge upon the detecting array 410 for admittance by focusing elements of the individual detecting elements 415 that correspond to the individual optic elements 425.
• the optics 420 may comprises any number of devices including, for example, lenses, optic arrays, fiber optic elements, or the like disposed to collect and direct light toward the detecting array 410.
• a computing device 430 is configured to be in communication with the detecting elements 415 of the detector array 410.
• a computing device 430 can comprise a fixed-purpose hard- wired platform or can comprise a partially or wholly programmable platform. All of these architectural options are well known and understood in the art and require no further description here.
• the computing device 430 is configured to collect signals from the detector array 410 to create an image relating the radiation incident on the optics 420.
• the computing device 430 can collect signals from individual amplifiers 105 from individual detecting elements 415 of the detector array 410.
• the individual signals correspond to individual voltage variations experienced by nanowires in the detecting elements 415. These voltage variations can then be correlated to the light energy impinging upon the optics at the particular focal point of the optics 420.
• Such a detecting array having color-level sensitivity can therefore provide an image showing minute energy changes across an area on which light is impinging.
• a method of using a nanothermocouple detector will be described with reference to FIG. 5.
• the method includes receiving 510 light through a focusing element on a nanowire coupled across two electrodes.
• the method also includes sensing 520 a voltage change in response to receiving the light through the focusing element on the nanowire with an amplifier electrically coupled to the two electrodes.
• the two electrodes may have a separation of between about 5 micrometers to about 30 micrometers across which a nanowire is disposed.
• light is focused 530 through optics onto a detector array disposed in a focal plane of the optics such that photons collected by the optics impinge upon the detecting array.
• computing device collects signals 540 from the detector array to create an image relating to the radiation energy incident upon the optics.
• computing device collects signals 540 from the detector array to create an image relating to the radiation energy incident upon the optics.

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