WO2014146017A1 - Supraconducteurs à base de graphène - Google Patents

Supraconducteurs à base de graphène Download PDF

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Publication number
WO2014146017A1
WO2014146017A1 PCT/US2014/030887 US2014030887W WO2014146017A1 WO 2014146017 A1 WO2014146017 A1 WO 2014146017A1 US 2014030887 W US2014030887 W US 2014030887W WO 2014146017 A1 WO2014146017 A1 WO 2014146017A1
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Prior art keywords
graphene
threshold
stack
level
strain
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PCT/US2014/030887
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English (en)
Inventor
Feng Liu
Zheng Liu
Chen SI
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University of Utah Research Foundation Inc
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University of Utah Research Foundation Inc
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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N60/00—Superconducting devices
    • H10N60/80—Constructional details
    • H10N60/85—Superconducting active materials
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N60/00—Superconducting devices
    • H10N60/01—Manufacture or treatment

Definitions

  • the disclosed implementations relate to superconductors, and in particular, to graphene -based superconductors and methods of producing graphene -based superconductors.
  • intrinsic graphene has a number of distinguishing properties. For example, electrically, intrinsic graphene has the highest carrier mobility of known materials with massless Dirac Fermions. Optically, intrinsic graphene has the largest adsorption per atomic layer in the visible range of known materials. And mechanically, intrinsic graphene is generally considered the strongest two dimensional (2D) material known in nature.
  • 2D two dimensional
  • graphene-based superconductive device includes a stack of charge doped graphene characterized by a doping level within a threshold doping range, a force transference structure that engages respective at least two portions of the stack of charge doped graphene.
  • the force transference structure is provided to transfer a force into the stack of charge doped graphene thereby causing tensile strain in the stack of charge doped graphene.
  • the tensile strain is characterized by a strain level within a threshold strain range. The combination of the doping level and strain level determine the critical temperature of the stack of charge doped graphene.
  • Another aspect of the disclosure is a method of producing a graphene-based superconductive device.
  • the method includes providing a stack of charge doped graphene characterized by a doping level within a threshold doping range, and imparting a force to the stack of charge doped graphene to produce tensile strain in the stack of charge doped graphene.
  • This tensile strain is characterized by a strain level within a threshold strain range. The combination of the doping level and the strain level determine the critical temperature of the stack of charge doped graphene.
  • Figures 1(a) and 1 (b) are graphs showing the density of states and electron- phonon coupling strength.
  • Figure 1(a) the N(0) and ⁇ of p-type graphene under different doping levels is illustrates.
  • V ep versus doping level for unstrained graphene is illustrated.
  • Figure 1(b) V e v under different biaxial strains ( ⁇ ) for 3% p-doped graphene is illustrated.
  • Figures 2(a) and 2(b) are three-dimensional graphs showing the relationship between tensile strain, hole doping and the critical temperature of charge-doped graphene.
  • Figure 2(a) is a three-dimensional plot of ⁇ ( ⁇ , ⁇ )
  • Figure 2(b) is a three-dimensional plot of T c (n,8).
  • Figure 3(a)-3(f) are graphs showing Eliashberg functions for charge-doped graphene.
  • the Eliashberg functions for l%(a), 2%(c) and 3%(e) hole doped graphene under 6% (line 302), 14% (line 304) and 16.5% (line 306), (b), (d) and (f), ( ⁇ 2 ) 1/2 under different tensile strain ( ⁇ ) for 1 %>, 2%> and 3%> hole doped graphene, respectively, with Insets showing ⁇ versus ( ⁇ 2 ) ⁇ 2 .
  • Figure 4 is a graph of logarithmically averaged phonon frequency as a function of tensile strain in charge-doped graphene.
  • FIG. 5 is a perspective view of a graphene-based superconductive device in accordance with some implementations, in which there is a first step in which a charge-doped graphene stack is arranged in between two hollow plates and a second step in which the graphene is stretched using an arcuate member.
  • the disclosed implementations include graphene-based superconductors and methods of producing graphene based superconductors.
  • graphene is converted to a BCS superconductor having a critical temperature substantially above zero Kelvin (K) using a combination of charge doping and tensile strain.
  • K Kelvin
  • a critical temperature T c of 30 K can be achieved by a combination of a doping level of ⁇ 3.5x 10 14 cm - " 2 and a strain level of -16%, which is the highest known critical temperature for a single-element material above the temperature of liquid hydrogen.
  • a critical temperature T c of 30 K makes graphene -based superconductors commercially viable for a number of industrial applications.
  • graphite-based structures e.g. graphene quantum dots, graphene nanoribbons (GNRs), graphene nanonetworks, graphene plasmonics and graphene super-lattices
  • GNRs graphene quantum dots
  • graphene nanoribbons GNRs
  • graphene nanonetworks graphene plasmonics
  • graphene super-lattices exhibit many exceptional chemical, mechanical, electronic and optical properties, and are very desirable for use in electronic devices, composite materials, and energy generation and storage.
  • Such graphite-based structures in general comprise a graphene layer, typically nanometers thick and having a characteristic dimension also in the nanometers range.
  • GNRs are required to have a width within a few nanometers due to the inverse relationship between the band gap and the width of the GNRs.
  • various methods are provided for fabricating graphite- based structures while achieving desired size, specified geometries, and characterized electronic properties of the graphite -based structures. These methods include, but are not limited to, (1) the combination of e-beam lithography and oxygen plasma etching; (2) stripping of graphite that is sonochemically processed; and (3) bottom-up chemical synthesis, e.g., by cyclodehydrogenation of l,4-diiodo-2,3,5,6-tetraphenylbenzene6, or 10,10'-dibromo-9,9'-bianthryl, polyanthrylene oligomers self-assembled on Au(l 11), Ag(l 11) or silica substrates, to name a few examples.
  • graphene sheets are stacked, with different pitch and critical dimensions, such that devices have multiple pass functionality.
  • structures comprising multiple levels of graphene layers allow for more versatile and efficient band gap devices.
  • layered materials refer to a material comprising a plurality of sheets, with each sheet having a substantially planar structure.
  • stacks refers to one or more sheets of a material (e.g., one or more layers of graphene).
  • a graphene stack can also refer to one, a few, several, several tens, several hundreds or several thousands sheets of graphene, where each such sheet is a one-atom thick sheet composed of sp -hybridized carbon.
  • graphene structures is used interchangeably with “graphene.”
  • a graphene stack in the plurality of graphene stacks includes one or more sheets of graphene. In some implementations, a graphene stack includes between 1 to 500, 5 to 100, or 10 to 50 graphene sheets.
  • the term “substrate” refers to one layer or multiple layers.
  • a substrate is glass, Si, Si0 2 , SiC, or another material.
  • the term “substrate” is equivalent to and interchangeable with the term “substrate stack.”
  • the term “substrate” hereinafter refers to any combination of layers upon which additional processing operations are performed. For instance, when one or more layers of a respective material (e.g., Si0 2 , S1 3 N 4 ) is grown on a silicon wafer, the term substrate alternatively refers (e.g., depending on context) to the silicon alone or to the silicon wafer inclusive of the one or more layers.
  • foundation material refers to any material that is suitable for growing graphene.
  • foundation materials are catalytic metals, e.g., Pt, Au, Fe, Rh, Ti, Ir, Ru, Ni, or Cu.
  • foundation materials are non-metal materials, such as Si, SiC, non-stoichiometric SiC (e.g., boron doped or otherwise), and other carbon enhanced materials.
  • carbon enhanced refers to any materials into which carbon has been added.
  • a BSC superconductor is triggered by electron-phonon coupling (EPC).
  • EPC electron-phonon coupling
  • the EPC provides an attractive interaction between electrons at the Fermi surface of a material.
  • the critical temperature T c for a material increases when the Fermi surface of a material increases and the EPC of the material increases. Increases in the Fermi surface enable more Cooper pairs to form, and increases in the EPC enable easier Cooper pair formation. Equation (1) provided below provides the general scaling relationship of the critical temperature of a material as a function of the Fermi surface and EPC.
  • the dimensionless parameter ⁇ characterizes the overall EPC strength
  • N(0) is the electron DOS
  • V ep is the unit electron-phonon pairing potential at the Fermi level.
  • the EPC of a material can be classified into three regimes: weak ⁇ « 1, intermediate ⁇ ⁇ ⁇ , and strong ⁇ > 1.
  • a good BCS superconductor requires ⁇ > 1.
  • the EPC of a material plays an important role in determining electron transport properties through electron-phonon scattering as well as giving rise to exotic many-body phenomenon, such as superconductivity.
  • the EPC of intrinsic graphene is very weak because of a diminishing Fermi surface (a point for intrinsic graphene) and a very weak electron- phonon pairing potential (because of the high Fermi temperature of the massless carriers and high energy of the optical phonons).
  • the weak EPC is responsible for some of the many distinguishing properties graphene has, such as extremely high electrical and thermal conductivity.
  • the weak EPC prevents graphene from being a superconductor.
  • the EPC of graphene ( ⁇ ) can be increased by increasing at least one of the electron DOS [N(0)] and the electron-phonon pairing potential (V ep ) at the Fermi level.
  • N(0) can be increased by doping of either electrons and holes.
  • Figure la shows calculated results of N(0) and ⁇ as a function of hole concentration for p-type graphene (e.g., graphene doped with a material providing holes).
  • graphene is adapted to increase the electron-phonon pairing potential V ep in addition to and/or as an alternative to charge doping.
  • applying tensile strain to graphene is used to weaken carbon-carbon (C- C) bonds and hence lower the optical phonon energy.
  • C- C carbon-carbon
  • first- principles calculations show uniform phonon mode softening under tensile strain.
  • tensile strain tends to enhance the Kohn anomaly in graphene, which in turn produces increases in EPC strength.
  • V ep was determined for a range of strain values.
  • Fig. lb illustrates the results of calculations for the V ep of graphene as a function of biaxial tensile strain for a hole-
  • V ep increases substantially with the increasing strain. In particular, at the 16.5% of strain, V ep reaches as high as 3.3 eV, which is even larger than that in the B-doped diamond.
  • Fig. 2(a) illustrates values for ⁇ calculated as a function of hole doping and tensile strain. At threshold high doping levels and strains, ⁇ becomes larger than 1.0, indicating that the EPC of graphene is in the strong coupling regime, which will trigger superconductivity at a critical temperature T c substantially above zero Kelvin.
  • T c is obtained using the McMillan- Allen-Dynes formula, provided as equation (2) as follows: fa log -1.04(1+ ⁇ )
  • ⁇ * is the screened electron Coulomb pseudo-potential, which is known to be in the order of 0.1 in most sp-electron metals.
  • Fig. 2(b) shows T c as a function of hole doping and tensile strain.
  • the critical temperature T c increases monotonically with both the increasing doping level at the given strain level and the increasing strain level at the given doping level. At the 16.5% strain, T c can reach as high as 18.6 K, 23.0 K and 30.2 K for the doping level of 1.52x l0 14 , 4.58xl0 14 and 7.63xl0 14 cm "2 , respectively.
  • Figs. 3(a), (c) and (e) show the Eliashberg function of equation (3): ⁇ 2 ⁇ E F ) (3)
  • Fig. 4 shows co og as a function of ⁇ . It is seen that co og decreases as ⁇ increase, which is related to the decrease of the characteristic phonon energy ⁇ 0 . The opposite variation of ⁇ versus co 0 g under strain indicates that T c would reach a maximum value at a certain strain. This is seen in Fig.
  • T c increases continuously from 0.3 K to 30.2 K when ⁇ increases from 10% to 16.5%, but decreases slightly from 30.2 K to 29.2 K when ⁇ further increases from 16.5% to 17%, even though ⁇ increases continuously in all range of strains. It indicates that first the increase of ⁇ dominates the increase of T c , and then the decrease of co og hinders the further increase of T c .
  • doping levels above 10 cm " in graphene can be achieved by either chemical doping or electrical doping. Additionally and/or alternatively, in some implementations, graphene is able to sustain up to 20% tensile strain without breaking. Additionally and/or alternatively, in some implementations, doping is used to further strengthen graphene so that the doped graphene able to sustain levels of strain greater than 20%.
  • the superconductivity transition of doped graphene is triggered at least by enhancing EPC using a force to create tensile strain, which is different from the transition observed in metal-decorated graphene.
  • the enhancement of EPC ⁇ in metal- decorated graphene arises from additional metal-related electronic states around the Fermi level, which will couple strongly with low-frequency out-of-plan modes of graphene and the phonon modes of adsorbed metal. From this perspective, metal-decorated graphene is similar to intercalated graphite and to MgB 2 .
  • first could be termed a second contact
  • a second contact could be termed a first contact, which changing the meaning of the description, so long as all occurrences of the "first contact” are renamed consistently and all occurrences of the second contact are renamed consistently.
  • the first contact and the second contact are both contacts, but they are not the same contact.
  • the phrase “if it is determined [that a stated condition precedent is true]” or “if [a stated condition precedent is true]” or “when [a stated condition precedent is true]” may be construed to mean “upon determining” or “in response to determining” or “in accordance with a determination” or “upon detecting” or “in response to detecting” that the stated condition precedent is true, depending on the context.

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Abstract

Les modes de réalisation de l'invention concernent les supraconducteurs à base de graphène et des procédés de production de supraconducteurs à base de graphène. Plus particulièrement, en dépit des caractéristiques électriques inhérentes du graphène, les modes de réalisation de l'invention impliquent la conversion du graphène en un supraconducteur BCS présentant un température critique sensiblement supérieure à zéro Kelvin (K), au moyen d'une combinaison de dopage par transfert de charge et de déformation de traction. Le dopage par transfert de charge permet d'agrandir la surface de Fermi du graphène et la déformation de traction permet d'accroître le couplage électrons/photons. Par exemple, une température critique Tc de 30 K peut être atteinte par une combinaison d'un niveau de dopage de ~3,5x1014 cm-2 et un niveau de traction de ~16%. Selon certains modes de réalisation, une température critique Tc de 30 K assure la viabilité commerciale des supraconducteurs à base de graphène pour un grand nombre d'applications industrielles.
PCT/US2014/030887 2013-03-15 2014-03-17 Supraconducteurs à base de graphène Ceased WO2014146017A1 (fr)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110429174A (zh) * 2019-08-14 2019-11-08 孙旭阳 石墨烯/掺杂二维层状材料范德瓦尔斯异质结超导复合结构、超导器件及其制备方法

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US20110269629A1 (en) * 2010-03-18 2011-11-03 Isis Innovation Limited Superconducting materials
WO2011139236A1 (fr) * 2010-05-05 2011-11-10 National University Of Singapore Dopage de graphène par trous
US20120003438A1 (en) * 2009-02-20 2012-01-05 University Of Florida Research Foundation, Inc. Graphene processing for device and sensor applications
US20120156424A1 (en) * 2010-12-15 2012-06-21 Academia Sinica Graphene-silicon carbide-graphene nanosheets
US20120288433A1 (en) * 2011-05-11 2012-11-15 Brookhaven Science Associates, Llc Processing of Monolayer Materials Via Interfacial Reactions

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20120003438A1 (en) * 2009-02-20 2012-01-05 University Of Florida Research Foundation, Inc. Graphene processing for device and sensor applications
US20110269629A1 (en) * 2010-03-18 2011-11-03 Isis Innovation Limited Superconducting materials
WO2011139236A1 (fr) * 2010-05-05 2011-11-10 National University Of Singapore Dopage de graphène par trous
US20120156424A1 (en) * 2010-12-15 2012-06-21 Academia Sinica Graphene-silicon carbide-graphene nanosheets
US20120288433A1 (en) * 2011-05-11 2012-11-15 Brookhaven Science Associates, Llc Processing of Monolayer Materials Via Interfacial Reactions

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110429174A (zh) * 2019-08-14 2019-11-08 孙旭阳 石墨烯/掺杂二维层状材料范德瓦尔斯异质结超导复合结构、超导器件及其制备方法
WO2021027816A1 (fr) * 2019-08-14 2021-02-18 孙旭阳 Structure composite supraconductrice à hétérojonction de van der waals en matériau stratifié 2d de graphène/dopé, dispositif supraconducteur et son procédé de fabrication
US11737378B2 (en) 2019-08-14 2023-08-22 Xuyang SUN Graphene/doped 2D layered material van der Waals heterojunction superconducting composite structure, superconducting device, and manufacturing method therefor

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