EP4251569A2 - Synthèse de borophène - Google Patents

Synthèse de borophène

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Publication number
EP4251569A2
EP4251569A2 EP22706539.8A EP22706539A EP4251569A2 EP 4251569 A2 EP4251569 A2 EP 4251569A2 EP 22706539 A EP22706539 A EP 22706539A EP 4251569 A2 EP4251569 A2 EP 4251569A2
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EP
European Patent Office
Prior art keywords
boron
bonds
heteroatom
clusters
multitude
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP22706539.8A
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German (de)
English (en)
Inventor
Georg Duesberg
Wilhelm AUWAERTER
Hermann Sachdev
Marc GONZÁLEZ CUXAT
Knud Johannes SEUFERT
Valeria CHESNYAK
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Technische Universitaet Muenchen
Universitaet der Bundeswehr Muenchen
Original Assignee
Technische Universitaet Muenchen
Universitaet der Bundeswehr Muenchen
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Publication date
Application filed by Technische Universitaet Muenchen, Universitaet der Bundeswehr Muenchen filed Critical Technische Universitaet Muenchen
Publication of EP4251569A2 publication Critical patent/EP4251569A2/fr
Pending legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B35/00—Boron; Compounds thereof
    • C01B35/02—Boron; Borides
    • C01B35/023—Boron
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/20—Particle morphology extending in two dimensions, e.g. plate-like

Definitions

  • the invention relates to a method for the production of a structure containing at least one borophene, and/or at least one boron-heteroatom-domain comprising a 2D boron network, and/or a structure of a 2D-network containing a multitude of boron-containing clusters comprising B-B bonds, wherein at least one of the boron containing clusters comprising B-B bonds may comprise at least one heteroatom, and wherein the multitude of boron- containing clusters comprising B-B bonds are connected by B-B bonds or B-heteroatom bonds, preferably wherein one boron-containing cluster comprises 3 to 20 boron atoms, and/or a structure of a 2D-network containing a multitude of boron-heteroatom clusters having B-heteroatom bonds, wherein the multitude of boron-heteroatom clusters having B- heteroatom bonds are connected by B-B bonds, as well as a product comprising a structure containing at
  • Borophenes which comprise in their definition according to the state of the art usually atomically thin sheets formed by boron, are a prominent member of the family of synthetic 2D materials due to their anisotropic and polymorphic structures and superlative strength and stiffness compared to graphene, as disclosed in Mannix, A. J., Zhang, Z., Guisinger, N. P., Yakobson, B. I., & Hersam, M. C. (2018). Borophene is a prototype for synthetic 2D materials development, as described in Nature Nanotechnology, 13(6), 444 ⁇ 150. https://doi.org/10.1038/s41565-018-0157-4.
  • Borophenes can be considered to be of single atomic thickness, but can also be thought to be extended to structures of 2D aspect ratio due to interconnected cluster subunits, still being different from and not resembling known 3D polymorphs of elemental boron.
  • Chemical vapor deposition (CVD) by using specific precursors has shown to be a flexible and scalable growth method, suitable to produce large single 2D crystals, and nowadays is widely used for the synthesis of numerous 2D materials, as e.g. discussed by Cai, Z., Liu, B., Zou, X., & Cheng, H.-M. (2016). Chemical Vapor Deposition Growth and Applications of Two- Dimensional Materials and Their Heterostructures [Review-article] Chemical Reviews, 118(13), 6091-6133. https://doi.org/10.1021/acs.chemrev.7b00536).
  • boron nanostructures yielded amorphous structures, nanotubes and thick planar structures, as e.g. described by Tian, J., Xu, Z., Shen, C, Liu, F., Xu, N., & Gao, H.-J. (2010).
  • One-dimensional boron nanostructures Prediction, synthesis, characterizations, and applications.
  • Nanoscale 2(8), 1375, https://doi.org/10.1039/c0nr00051e, and Tai, G., Hu, T., Zhou, Y., Wang, X., Kong, J., Zeng, T., ... Wang, Q. (2015). Synthesis of Atomically Thin Boron Films on Copper Foils. Angewandte Chemie International Edition, 54(51), 15473-15477. https://doi.org/10.1002/anie.201509285, but none of them produced single-atom-thick B layers. The main reason that explain the current failure is that adequate precursors are yet to be found, and the lack of well-controlled and clean growth conditions.
  • the present inventors found a reliable and more effective method of producing borophenes, and/or boron-heteroatom-domains comprising 2D boron networks, and/or a structure of a 2D-network containing a multitude of boron-containing clusters comprising B-B bonds, wherein at least one of the boron containing clusters comprising B-B bonds may comprise at least one heteroatom, and wherein the multitude of boron-containing clusters comprising B- B bonds are connected by B-B bonds or B-heteroatom bonds, preferably wherein one boron- containing cluster comprises 3 to 20 boron atoms, and/or a structure of a 2D-network containing a multitude of boron-heteroatom clusters having B-heteroatom bonds, wherein the multitude of boron-heteroatom clusters having B-heteroatom bonds are connected by B- B bonds, which enables production of the structures in increased size and high homogeneity and lower density of defects
  • the structures therein do not resemble known 3D polymorphs of elemental boron, but refer to 2D polymorphs, polymorphs with pronounced 2D aspect ratio and their derivates and products. These borophene based structures do also differ from amorphous boron monolayers which in principle might be feasible by CVD, due to their intrinsic 2D structural ordering.
  • the present invention relates to a method for the production of a structure containing at least one borophene, and/or at least one boron-heteroatom-domain comprising a 2D boron network, and/or a structure of a 2D-network containing a multitude of boron-containing clusters comprising B-B bonds, wherein at least one of the boron containing clusters comprising B-B bonds may comprise at least one heteroatom, and wherein the multitude of boron-containing clusters comprising B-B bonds are connected by B-B bonds or B-heteroatom bonds, preferably wherein one boron-containing cluster comprises 3 to 20 boron atoms, and/or a structure of a 2D-network containing a multitude of boron-heteroatom clusters having B-heteroatom bonds, wherein the multitude of boron- heteroatom clusters having B-heteroatom bonds are connected by B-B bonds, the method comprising: contacting at least one borophene
  • the substrate has a temperature in the range of -196 °C to 3000 °C, and deposition of a structure containing at least one borophene, and/or at least one boron-heteroatom-domain comprising a 2D boron network, and/or a structure of a 2D- network containing a multitude of boron-containing clusters comprising B-B bonds, wherein at least one of the boron containing clusters comprising B-B bonds may comprise at least one heteroatom, and wherein the multitude of boron-containing clusters comprising B-B bonds are connected by B-B bonds or B-heteroatom bonds, preferably wherein one boron- containing cluster comprises 3 to 20 boron atoms, and/or a structure of a 2D-network containing a multitude of boron-heteroatom clusters having B-heteroatom bonds, wherein the multitude of boron-heteroatom clusters having
  • boron-containing precursors can be used to create boron films or boron layers
  • these films or layers created can be amorphous or crystalline and have a 3D connectivity of boron atoms derived from known 3D polytypes of elemental boron.
  • these films or layers do not reveal structures resembling a structure as disclosed herein and obtainable by the present method, resembling pronounced polymorphs with a particular 2D aspect ratio.
  • a product comprising a structure containing at least one borophene, and/or at least one boron-heteroatom-domain comprising a 2D boron network, and/or a structure of a 2D-network containing a multitude of boron-containing clusters comprising B- B bonds, wherein at least one of the boron containing clusters comprising B-B bonds may comprise at least one heteroatom, and wherein the multitude of boron-containing clusters comprising B-B bonds are connected by B-B bonds or B-heteroatom bonds, preferably wherein one boron-containing cluster comprises 3 to 20 boron atoms, and/or a structure of a 2D-network containing a multitude of boron-heteroatom clusters having B-heteroatom bonds, wherein the multitude of boron-heteroatom clusters having B-heteroatom bonds are connected by B-B bonds, particularly produced by the present method, wherein the structure containing at least one borophene
  • Fig. 1 shows schematically growth of a borophene using chemical vapor deposition.
  • Fig. 2 shows schematically possible heterolayer and/or multilayer products that can be produced by the present method.
  • FIG. 3 an exemplary experimental, labscale setup used for producing exemplary products in the present Examples is schematically shown.
  • Fig. 4 depicts images of products obtained in the present examples (Fig. 4 a) and of comparative examples produced in the state of the art (Figs. 4b and 4c according to the above Feng et al., 2016, Nature Chemistry, and the above Mannix et al., 2015 Science).
  • Fig. 5 shows STM images of a borophene - h BN lateral heterostructure produced according to the invention.
  • Clusters can formally be considered as molecular building blocks for forming the present structures, but can also be seen as entities being part of the structures, either 2D or 3D.
  • containing can mean that the different atoms, molecules, groups, etc. are formally contained, but are not necessarily to be seen as separate entities as they can be and normally are of the respective network, etc. This particularly applies to clusters within a network, as they are only formally contained but are not isolated and rather form a part of the network.
  • borophene formation are deemed to be valid to any boron isotope ratio, since they can be provided by the precursor, and even isotopically pure domains and heterodomains are feasible.
  • the present structures also may be applicable to applications where specific properties of the different isotopes are required, e.g. for neutron detection, etc.
  • Borophenes are - single or multiple - layers of regular or defective networks of boron atoms which may be corrugated, i.e. slightly shifted in directions out of the 2D plane in each layer. They are based on structural motifs of boron sheets of single atomic thickness, i.e. form a sort of sheet that can be regarded as quasi two-dimensional. Particularly, layers of borophenes do not have to be atomically "flat", i.e. do not only extend in two dimensions, but still may be described as 2D due to their B-B bonds only being within the layer. Borophenes also can be derived from an array of 2 dimensionally interlinked boron clusters (e.g.
  • intrinsically corrugated, symmetry-reduced - with regular defect positions as well as intrinsically buckling patterns - structures may result from a "two dimensional" boron network, which even can be further modulated by the substrate symmetry.
  • planar or partly planar networks are not excluded.
  • borophenes can also form different polymorphs, which are included as well. Borophenes comprise B-B-bonds of variable strength, and may even consist of mainly B-B-bonds of variable strength, and may or may not have additional electronic interactions with a substrate and/or adatoms, dopants, covering layers, etc., which also can be incorporated into a borophene network, e.g.
  • boron-heteroatom-domains comprising a 2D boron network. It is not excluded that borophenes comprise multiple layers that are e.g. arranged on top of each other, similar to graphene heterostructures. Boron-boron bonds do not only comprise classical covalent bonds within the 2D layer structure, but can also comprise different kinds of bonds, e.g. non-classical multi-center bonds and e.g.
  • Boron-heteroatom-domains comprising a 2D boron network are herein defined structures which contain within the 2D boron network one or more species of heteroatoms on substitutional and/or additional sites and/or do contain heteroatoms strongly linked on the surface, and/or also can have heteroatoms like O or N at the rim or incorporated in the 2D lattice.
  • the 2D boron network is sheet-like in a layer but does not have to be flat. It can be a regular or defective network comprising boron atoms with boron boron bonds. It is of single atomic thickness, and may be corrugated, i.e.
  • boron-heteroatom domains comprising a 2D boron network also encompass borophene- based networks with a variable content of heteroatoms like oxygen, nitrogen, carbon and/or hydrogen, stemming e.g. from impurities and/or residues in the production process, as well as borophene-based networks where doping with heteroatoms is intentionally carried out.
  • One heteroatom or multiple heteroatoms can be included which can be the same or different, i.e. the content thereof is variable.
  • Possible heteroatoms include e.g. nitrogen, hydrogen, oxygen, carbon, halogens, metals, etc., and/or mixtures thereof.
  • the boron- heteroatom-domains comprising a 2D boron network thus include borophene-derived layers with variable content of heteroatoms, as well as borophenes doped with heteroatoms, i.e. wherein the heteroatom is purposely introduced. For example, even boron-heteroatom- domains comprising a 2D boron network with large amounts of heteroatoms are included, as long as boron boron bonds are contained, e.g.
  • the boron-heteroatom-domains comprising a 2D boron network can still be rich in boron with respect to the layer stoichiometry, i.e. contain boron with respect to the boron heteroatom domain with 50 at% or more, e.g. more than 50 at%., preferably more than 60 at.%, more preferably more than 70 at%.
  • boron heteroatom domain with 50 at% or more, e.g. more than 50 at%., preferably more than 60 at.%, more preferably more than 70 at%.
  • higher amounts of heteroatoms are not excluded.
  • heteroatoms in boron-heteroatom-domains are not particularly restricted, and in principle any heteroatom of the periodic system of the elements can be incorporated into a boron- heteroatom domain, and also mixtures of heteroatoms.
  • preferred heteroatoms are chosen from the group consisting of H, D, O, N, C, P, S, Se, and/or Te, particularly H, D, O, N, C, P and/or S.
  • further groups and/or heteroatoms may be attached to heteroatoms, e.g. N, C, P, that may have further possible bonding sites, and such heteroatoms and/or groups are not restricted and can e.g. include hydrogen, D, halogens, amines, alcoholates, organyls, aryls, etc.
  • the boron- containing clusters comprising B-B bonds can comprise at least one heteroatom and/or can also comprise no heteroatom, so that structures with only boron-containing clusters comprising B-B bonds with only boron atoms in the clusters are encompassed, structures wherein all boron-containing clusters comprising B-B bonds comprise at least one heteroatom, and structures where at least one or some boron-containing clusters comprising B-B bonds comprise heteroatoms, and at least one or some boron-containing clusters comprising B-B bonds comprise no heteroatoms.
  • structure of a 2D-network with regard to the structure of a 2D-network containing a multitude of boron-containing clusters comprising B-B bonds is therein meant in the sense that the structure forms a layer that extends in two dimensions, e.g. the x and y plane, although also regular or irregular extensions in the further dimension, e.g. the z plane, will occur due to the clusters, but the clusters themselves are again connected within the sheet, thus leading to a 2D network of high aspect ratio.
  • the structure of a 2D- network containing a multitude of boron-containing clusters comprising B-B bonds forms a layer that also covers a surface, but the bonds within the network do not have to be in direct vicinity of the surface, as different boron-containing clusters can be connected next to the surface, or in a different plane above a surface between different boron containing clusters, e.g. through tips of boron-containing icosahedrons, etc.
  • the structure of a 2D-network containing a multitude of boron-containing clusters comprising B-B bonds also forms a network that is sheet-like in a layer, but is not flat due to clusters contained therein.
  • it can be a regular or defective network comprising boron atoms in clusters with boron boron bonds. It is not of single atomic thickness due to the clusters, but at places can have single atomic thickness, e.g. between clusters or at positions where clusters are bonded. It, like the other structures, can even have vacancies if a structural unit is missing, as also described for borophene.
  • the structure of a 2D-network containing a multitude of boron-containing clusters comprising B-B bonds is at least corrugated at clusters, i.e. slightly shifted in directions out of the 2D plane, but can also be corrugated at other places, e.g. between clusters.
  • the structure of a 2D-network containing a multitude of boron-containing clusters comprising B-B bonds can thus also be seen as quasi two-dimensional, with peaks protruding e.g. at positions of clusters.
  • the clusters are not particularly restricted and can be built form at least 3 atoms, e.g. at least 4 atoms, but also more atoms, like 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more.
  • boron clusters of (B2), B3, B4, B5, Bb, Bg, ..., units can be considered to be formally derived from cluster compounds such as (B2H6), B3H7, B4H10, B5H9, ....B10H14, ...
  • cluster compounds such as (B2H6), B3H7, B4H10, B5H9, ....B10H14, ...
  • clusters like (boron or boron-containing) icosahedral structures like e.g .alpha rhombohedral boron in the 3D case can be considered, in the real formation of the structure of a 2D-network containing a multitude of boron-containing clusters comprising B- B bonds from cluster compounds having e.g.
  • the structure of a 2D-network containing a multitude of boron-containing clusters comprising B-B bonds can also be considered to be derived from a multitude of boron- containing clusters that are connected. While it is not excluded that the structure of a 2D- network containing a multitude of boron-containing clusters comprising B-B bonds comprises only boron atoms, it is also not excluded that one heteroatom or more heteroatoms is contained, that are not restricted and can be the same as in the boron- heteroatom-domain comprising a 2D-network.
  • the cluster In the structure of a 2D-network containing a multitude of boron-containing clusters comprising B-B bonds the cluster cannot be isolated, as they are connected, but they are present in a step before formation of the layer.
  • the bonds between clusters are not particularly restricted and can be connected by B-B bonds or B-heteroatom bonds, depending on the location where clusters are bonded, and B-heteroatom bonds between clusters can e.g. be formed if at least one cluster contains at least one heteroatom.
  • the structure of a 2D-network containing a multitude of boron-heteroatom clusters having B-heteroatom bonds, wherein the multitude of boron-heteroatom clusters having B- heteroatom bonds are connected by B-B bonds is not restricted.
  • structure of a 2D-network containing a multitude of boron-containing clusters comprising B- B bonds defined above
  • structure of a 2D-network containing a multitude of boron-heteroatom clusters having B-heteroatom bonds
  • structure of a 2D-network is therein meant in the sense that the structure forms a layer that extends in two dimensions, e.g.
  • the clusters being bonded to such a network with B-B bonds at least somewhere, preferably in direct vicinity to the cluster.
  • the same considerations apply to the clusters and the heteroatoms in the structure of a 2D-network containing a multitude of boron-heteroatom clusters having B-heteroatom bonds as apply to the structure of a 2D-network containing a multitude of boron-containing clusters comprising B-B bonds, i.e. will also particularly have a defined 2D aspect ratio, as defined above for other structures.
  • the present method as well as in the present product it is not excluded that, apart from the at least one borophene, and/or at least one boron-heteroatom-domain comprising a 2D boron network, and/or a structure of a 2D-network containing a multitude of boron- containing clusters comprising B-B bonds, wherein at least one of the boron containing clusters comprising B-B bonds may comprise at least one heteroatom, and wherein the multitude of boron-containing clusters comprising B-B bonds are connected by B-B bonds or B-heteroatom bonds, preferably wherein one boron-containing cluster comprises 3 to 20 boron atoms, and/or a structure of a 2D-network containing a multitude of boron- heteroatom clusters having B-heteroatom bonds, wherein the multitude of boron- heteroatom clusters having B-heteroatom bonds are connected by B-B bonds, further heterostructures that do or do not contain boron,
  • the present invention relates to a method for the production of a structure containing at least one borophene, and/or at least one boron-heteroatom-domain comprising a 2D boron network, and/or a structure of a 2D-network containing a multitude of boron-containing clusters comprising B-B bonds, wherein at least one of the boron containing clusters comprising B-B bonds may comprise at least one heteroatom, and wherein the multitude of boron-containing clusters comprising B-B bonds are connected by B-B bonds or B-heteroatom bonds, preferably wherein one boron-containing cluster comprises 3 to 20, e.g.
  • boron atoms and/or a structure of a 2D- network containing a multitude of boron-heteroatom clusters having B-heteroatom bonds, wherein the multitude of boron-heteroatom clusters having B-heteroatom bonds are connected by B-B bonds, on the at least one surface of the substrate, wherein a pressure of the at least one precursor in the gaseous or otherwise atomic- molecular excited state is in the range of 10 10 mbar to 10 bar, and wherein the at least one precursor in the gaseous or otherwise atomic-molecular excited state comprises at least one precursor, chosen from the group of substituted and unsubstituted boranes - including substituted and unsubstituted aminoboranes and substituted and unsubstituted iminoboranes, substituted and unsubstituted heteroboranes, substituted and unsubstituted polyboranes, substituted and unsubstituted poly-boron
  • substituted poly-boron compounds e.g. polyboron halides
  • substituted and unsubstituted organoboron compounds e.g. boron aryls
  • substituted and unsubstituted organopolyboron compounds e.g.
  • polyboron aryls substituted and unsubstituted borazines, substituted and unsubstituted boroxines, and boron halides, as well as adducts of substituted and unsubstituted boranes - including substituted and unsubstituted aminoboranes and substituted and unsubstituted iminoboranes, substituted and unsubstituted heteroboranes, substituted and unsubstituted polyboranes, substituted and unsubstituted poly-boron-heteroatom compounds, substituted and unsubstituted poly-boron compounds, substituted and unsubstituted organoboron compounds, substituted and unsubstituted organopolyboron compounds, substituted and unsubstituted borazines, substituted and unsubstituted boroxines, and boron halides.
  • the at least one borophene is not particularly restricted.
  • the at least one boron-heteroatom-domain comprising a 2D boron network is not particularly restricted.
  • it can be a 2D network mainly formed by individually interlinked boron atoms that contains heteroatoms interspersed, alone or in clusters, and the heteroatoms are not particularly restricted.
  • more than one boron-heteroatom-domain can be included, e.g. with different heteroatom concentration and/or different heteroatoms.
  • the boron-heteroatom-domain comprising a 2D boron network can still comprise defects.
  • the bonding between any of the atoms in the layer can be classical single or multiple 2 electron 2 center bonds; nonclassical electron deficient bonds, nonclassical electron deficient multi center bonds, interacting by either donating electron density to the substrate and/or
  • the boron-containing clusters comprising B-B bonds may also comprise boron-heteroatom and/or even heteroatom-heteroatom bonds if heteroatoms are contained, and the heteroatoms are not particularly restricted and can be e.g. H, halogen, O, S, P, N, C, metals, etc. Also, the boron-containing clusters comprising B-B bonds do not necessarily have to have a regular structure like a tetrahedron, octahedron, icosahedron, but can also have irregular forms, e.g. be skewed, with or without heteroatoms.
  • the clusters for example, boron-containing tetrahedrons, octahedrons, and/or icosahedrons can be interconnected by boron-boron bonds or boron- heteroatoms with each other and thus form a 2D-network.
  • the structure of a 2D-network containing a multitude of boron-heteroatom clusters having B-heteroatom bonds, wherein the multitude of boron-heteroatom clusters having B- heteroatom bonds are connected by B-B bonds is not particularly restricted, as long as the boron heteroatom clusters only have B-heteroatom bonds and the individual clusters are connected by B-B bonds.
  • the borophene and/or boron-heteroatom-domain comprising a 2D boron network may also contain therein different structures comprising boron, e.g. boron-containing clusters comprising B-B bonds and/or boron-containing clusters having B-heteroatom bonds, e.g. regular stoichiometric 2D networks like B2O3 or hexagonal boron nitride (h BN). Also, e.g. heteroatoms may be bonded at fringes of the borophene, etc.
  • borophene one or more boron-heteroatom-domains, a structure of a 2D-network containing a multitude of boron- containing clusters comprising B-B bonds, wherein at least one of the boron containing clusters comprising B-B bonds may comprise at least one heteroatom, and wherein the multitude of boron-containing clusters comprising B-B bonds are connected by B-B bonds or B-heteroatom bonds, and/or a structure of a 2D-network containing a multitude of boron- heteroatom clusters having B-heteroatom bonds, wherein the multitude of boron- heteroatom clusters having B-heteroatom bonds are connected by B-B bonds, are produced together, e.g. boron icosahedrons within a borophene layer, boron-heteroatom-domains within borophene, etc.
  • the at least one precursor is diluted in a further gas or gas mixtures that can be reactive and/or inert gases and which are not particularly restricted.
  • a further gas or gas mixtures that can be reactive and/or inert gases and which are not particularly restricted.
  • heteroatoms may be added by e.g. co-dosing of other gases.
  • the contacting of at least one surface of a substrate with at least one precursor in the gaseous or otherwise atomic-molecular excited state is not particularly restricted, and the at least one precursor in the gaseous or otherwise atomic-molecular excited state can e.g. be in a gaseous state, a plasma phase, or other state where atoms and/or molecules are present separately, i.e. without intermolecular interaction.
  • the at least one precursor is in a gaseous state, i.e. a precursor gas, as this is easier to obtain from a suitable source, e.g. a source comprising borazine and/or diborane.
  • the precursor in a gaseous or otherwise atomic-molecular excited state is diluted with other compounds in a gaseous or otherwise excited state, e.g. with gases, e.g. inert gases like hydrogen, nitrogen, etc.
  • gases e.g. inert gases like hydrogen, nitrogen, etc.
  • the at least one precursor in the gaseous or otherwise atomic-molecular excited state comprises at least one precursor, chosen from the group of substituted and unsubstituted boranes - including substituted and unsubstituted aminoboranes and substituted and unsubstituted iminoboranes, substituted and unsubstituted heteroboranes, substituted and unsubstituted polyboranes, substituted and unsubstituted poly-boron-heteroatom compounds - e.g. with a boron number of 2 or more, e.g. 2 - 20, substituted poly-boron compounds - e.g. with a boron number of 2 or more, e.g. 2-20, e.g.
  • polyboron halides substituted and unsubstituted organoboron compounds, e.g. boron aryls, substituted and unsubstituted organopolyboron compounds, e.g. polyboron aryls, substituted and unsubstituted borazines, substituted and unsubstituted boroxines, and boron halides, particularly fluorides, chlorides, bromides and/or iodides, as well as adducts of substituted and unsubstituted boranes - including substituted and unsubstituted aminoboranes and substituted and unsubstituted iminoboranes, substituted and unsubstituted heteroboranes, substituted and unsubstituted polyboranes, substituted and unsubstituted poly-boron- heteroatom compounds, substituted and unsubstituted poly-boron compounds, substituted and unsubstituted organoboron compounds, substituted and un
  • mixtures of these compounds can be comprised in the at least one precursor in the gaseous or otherwise atomic-molecular excited state.
  • the compounds are readily available commercially or as by-products in technically produced compounds, e.g. borazine, where usually e.g. boranes are present as side products, e.g. during synthesis, and/or decomposition products. From such commercially available sources like technical borazine the at least one precursor then can be suitably isolated, e.g. by separation in a cooling trap, e.g. in a vacuum, evaporation, etc., or separately added, etc.
  • Suitable substituents include e.g. azido, amino, nitro, halogen (particularly F, Cl, Br, I), and/or hydroxy groups, particularly amino groups, e.g.
  • aminodiborane like in aminodiborane (B2H7N).
  • aminodiborane m-aminodiborane, B2H5NH2
  • polymer aminoboranes ((NH2BH2) n )
  • borane adducts of polymer aminoboranes e.g. NBB-(NH2-BH2)2-N H2) also borane (BH3) and/or diborane (B2H6) can be liberated.
  • the substituted and unsubstituted organoboron compounds are not particularly restricted and can comprise 1 or more boron atoms and one or more organic residues, like e.g. RBH2, R2B, R3B, etc.
  • Suitable organoboron compound include e.g. BCI3, B2CI4, B4CI4.
  • Suitable borane adducts include e.g. BH3-XTHF, adducts of BCI3, B2CI4, B4CI4, B5H9, B10H14, etc., B2H7N-THF adduct etc.
  • Especially suitable precursors are diborane, which can be e.g.
  • evaporation of BbO, B13N2 can lead to borophene, and substituted borophenes.
  • the at least one precursor is chosen from the group of substituted and unsubstituted boranes, particularly boranes and substituted boranes from which boranes can be easily liberated, like aminodiborane, preferably boranes with 1 to 20 boron atoms, more preferably boranes with 2 to 10 boron atoms, e.g. diborane (B2H6), tetraborane (B4H10), pentaborane (B5H9), decaborane (B10H14), and particularly preferably diborane.
  • the at least one precursor in the gaseous or otherwise atomic-molecular excited state comprises diborane.
  • diborane Particularly with diborane a good and strong film can be easily produced on the at least one surface of the substrate.
  • a suitable precursor is diborane, which is not particularly restricted.
  • diborane is a far better controllable, defined and easily adjustable boron source compared to the evaporation of elemental boron, where elemental boron leads to a manifold of uncontrollable clusters in the gas phase.
  • one or more further gases is present, e.g. an inert and/or otherwise reactive gas, like nitrogen, a noble gas like neon, argon, etc., hydrogen, etc., and/or mixtures thereof, e.g. with an amount of 0 to 99.999999999 Vol.%, e.g. 0 to 99.99999999 Vol.%, e.g. 0 to 99.9999999 Vol.%, e.g. 0 to 99.999999 Vol.%, e.g.
  • the at least one precursor in a gaseous or otherwise atomic-molecular excited state comprises diborane in a range of from 0.000000001 to 100 Vol.%, e.g. 0.00000001 to 100 Vol.%, e.g.
  • 0.0000001 to 100 Vol.% e.g. 0.000001 to 100 Vol.%, e.g. 0.00001 to 100 Vol.%, e.g. 0.0001 to 100 Vol.%, e.g. 0.001 to 100 Vol.%, e.g. 0.01 to 100 vol.%, preferably from 0.1 to 30 vol.%, e.g. in mixtures with other gases.
  • the structure can also be generated on or in other substrates, etc. or on or in mixed substrates.
  • Other phases besides the above structures can be in general of any material, either already present, co-deposited, and/or deposited thereafter.
  • the other substrates and mixed substrates are not particularly restricted and can e.g. encompass metals, alloys, insulators, semiconductors, oxides, nitrides, phosphides, selenides, tellurides, all of them being either single crystalline, multicrystalline, having individual facets or not, having 2D or 3D structures, being of any type of 2D material, or being a combination thereof.
  • the present method it is sufficient to contact only one surface of a substrate, but it is not excluded that more than one surface, e.g. the upper and side surfaces, of the substrates are being contacted, or any three-dimensional structure. It is also included that only distinct crystallographic facets are contacted as one surface, or that these are contacted together with other surface areas. According to certain embodiments distinct crystallographic facets are at least contacted.
  • the substrate is not particularly restricted. It can be a bulk substrate or a layered substrate, etc., and any substrate, e.g. a solid or a molten substrate or a substrate with a molten surface, can be used onto which the at least one precursor can be deposited.
  • the substrate is chosen from a metal substrate - including alloys, a semiconductor substrate, or an insulator, which are not particularly restricted, including non-metallic substrates like graphene, carbides, nitrides like boron nitride, silicon nitride, and/or gallium nitride, phosphides, oxide compounds which are not particularly restricted, or mixtures thereof.
  • Substrates can also be processed semiconductors.
  • Suitable substrates are commercially available, e.g. as wafers.
  • a preferable substrate is a metal substrate, and any metal can be used as the substrate, e.g. late transition metals like Cu, Ag, Au, Pt, Ir, etc., as well as a silicon-based mutlilayer substrates.
  • the at least one surface of the substrate has essentially a homogeneous crystal structure.
  • the at least one surface of the substrate can have a specific surface termination, like 111 faceted, or otherwise faceted, or can be reconstructed or unreconstructed.
  • Suitable substrates include e.g.
  • the at least one surface comprises or is a (111) surface, like I r( 111 ) and/or Cu(111).
  • rotational domains with preferential orientation e.g. dictated by the substrate symmetry, can be formed, but they can also be randomly oriented.
  • the structures can have an epitaxial relation to the substrate, and/or they can be superstructured. Structures, e.g. layers, formed by the deposition can be supported by metals, semiconductors and/or insulators, e.g.
  • domains and layers of borophene and lateral and vertical structures based on building blocks of borophene and heteroatom-substituted borophene are produced by the present method as well. For example, it is also not excluded to produce lateral interfaces of at least one borophene with h BN, e.g. using borazine as a source and activating/deactivating a cold trap for trapping borazine or not.
  • superstructures can be produced that may vary due to the substrate and preparation conditions, as well as the crystallographic orientation of the substrate, e.g. distorted epitaxial growth, etc., but also multiple superstructures might occur within one sample.
  • the purity of the substrate as well as the substrate surface termination are not particularly restricted.
  • the deposition of a structure containing at least one borophene, and/or at least one boron-heteroatom-domain comprising a 2D boron network, and/or a structure of a 2D- network containing a multitude of boron-containing clusters comprising B-B bonds, wherein at least one of the boron containing clusters comprising B-B bonds may comprise at least one heteroatom, and wherein the multitude of boron-containing clusters comprising B-B bonds are connected by B-B bonds or B-heteroatom bonds, preferably wherein one boron- containing cluster comprises 3 to 20 boron atoms, and/or a structure of a 2D-network containing a multitude of boron-heteroatom clusters having B-heteroatom bonds, wherein the multitude of boron-heteroatom clusters having B-heteroatom bonds are connected by B- B bonds, on the at least one surface of the substrate is not particularly restricted.
  • the at least one precursor can be guided to at least one surface of the substrate, e.g. using a nozzle.
  • a nozzle e.g., a nozzle
  • other methods for depositing are not excluded.
  • the deposition can be carried out using a precursor that is already present on the surface that is then "activated" and thus the final structure is generated.
  • the deposition can be directed in a way that the at least one substrate can be fully covered. However, it is not excluded that an uncomplete or co-doped, e.g. by ubiquitous impurities, boron lattice is formed.
  • the 2D-network can also be formed, e.g. by suitable contacting with a dopant gas, so that it is regularly or irregularly doped with heteroelements, and/or to produce heterostructures, e.g. lateral heterostructures.
  • the dopant gas is not particularly restricted and can e.g. comprise further boron-containing compounds like borazine, organometallic compounds, metal halides, silanes, phosphorus-containing compounds, transition metal compounds, hydrocarbons, etc.
  • lateral and/or vertical heterostructures can be formed, e.g. with other heterostructures that can comprise boron, e.g. with boron nitride, e.g. h BN, and/or with heterostructures that do not comprise boron, like phosphorene, silicene, graphene, 2D transition metal dichalcogenides (TMDs), etc., wherein the further heterostructures are not restricted and can comprise structures in layers, i.e. with a 2D structure, and/or with 3D structure.
  • TMDs transition metal dichalcogenides
  • the shape of the deposited material is not particularly restricted, and can be any shape, e.g. in the form of stripes, dots, circles, squares, etc.
  • other domains can be formed next and/or on top to the deposited at least one borophene, and/or the at least one boron-heteroatom-domain comprising a 2D boron network, and/or the structure of a 2D- network containing a multitude of boron-containing clusters comprising B-B bonds, wherein at least one of the boron containing clusters comprising B-B bonds may comprise at least one heteroatom, and wherein the multitude of boron-containing clusters comprising B-B bonds are connected by B-B bonds or B-heteroatom bonds, preferably wherein one boron- containing cluster comprises 3 to 20 boron atoms, and/or the structure of a 2D-network containing a multitude of boron-heteroatom clusters having B-heteroatom bonds, wherein the multitude
  • the structure comprising at least one borophene and/or at least one boron-heteroatom-domain comprising a 2D boron network, and/or a structure of a 2D- network containing a multitude of boron-containing clusters comprising B-B bonds, wherein at least one of the boron containing clusters comprising B-B bonds may comprise at least one heteroatom, and wherein the multitude of boron-containing clusters comprising B-B bonds are connected by B-B bonds or B-heteroatom bonds, preferably wherein one boron- containing cluster comprises 3 to 20 boron atoms, and/or a structure of a 2D-network containing a multitude of boron-heteroatom clusters having B-heteroatom bonds, wherein the multitude of boron-heteroatom clusters having B-heteroatom bonds are connected by B- B bonds, or even the at least one borophene and/or at least one boron-heteroatom
  • the alignment can be induced in preferential orientation depending e.g. on the substrate's electronic and geometric structure, which can lead to a pre-alignment of nuclei on specific crystallographic substrate patterns/surfaces/epitaxial relations, by preferential bonding of nuclei, e.g. boron, to specific substrate atoms, and/or by the growth mode of the structure itself, e.g. due to its intrinsic symmetry, as is e.g. the case of borophene.
  • This will allow a tuning of the domains, orientations etc., as well as the growth of an oriented, confined pattern, e.g. stripes of varying width in atomic scale, islands of specific shape, etc., of a secondary phase, which makes the method particularly adaptable for nanoscale device development.
  • the substrate has a temperature in the range of -196 °C to 3000 °C.
  • the temperature of the substrate is in the range of 0 °C to 1600 °C, e.g. 22 °C to 1500°C, particularly in the range of 500 °C to 1000 °C.
  • the substrate is pre-heated or activated by other means of energy input, allowing a relatively homogeneous formation of a film thereon. It is also not excluded that a chamber, a reactor, etc., in which the production is carried out is pre-heated, e.g. to the same temperature.
  • a heating device used for heating, etc. is therein not particularly restricted.
  • the pressure of the at least one precursor in the gaseous or otherwise atomic-molecular excited state is in the range of 10 10 mbar to 10 bar.
  • it can be in a range from 10 4 to 10 9 mbar, or in a range from 10 4 mbar to 10 bar.
  • the pressure of the at least one precursor in the gaseous or otherwise atomic- molecular excited state is in the range of 10 9 mbar to 10 4 mbar, optionally in the range of 10 8 mbar to 10 7 mbar.
  • a higher vacuum a more homogeneous film can be produced with lower density of defects.
  • Particularly lower pressures are preferable, but also at high pressure and /or in diluted atmosphere a 2D formation may occur.
  • the at least one precursor in the gaseous or otherwise atomic-molecular excited state is dosed onto the at least one surface of the substrate. Dosing enables a good control of crystal growth. The dosing is not particularly restricted and can be carried out using suitable dosing methods.
  • the at least one precursor in the gaseous or otherwise atomic-molecular excited state further comprises a dopant and/or a further boron containing compound like molecular compounds containing B-H, B-O, B-N, B-C, B-Hal (halogen), B-P, and/or B-S bonds, etc., or mixtures thereof, for example borazine, wherein heterostructures of boron and at least one further atom can be formed, e.g. in addition to the structure containing at least one borophene. These can be formed in lateral and/or vertical arrangement.
  • the dopant is not particularly restricted, and dopant elements can be any elements, e.g. N, O, or mixtures thereof, also with other elements.
  • transition metal atoms can be used to increase the storage capacity of some molecules, like h , and/or can be also applied for magnetic functionalization.
  • Chalcogenide atoms may be used to suitably set band gaps so that the structure containing at least one borophene, and/or at least one boron- heteroatom-domain comprising a 2D boron network, and/or a structure of a 2D-network containing a multitude of boron-containing clusters comprising B-B bonds, wherein at least one of the boron containing clusters comprising B-B bonds may comprise at least one heteroatom, and wherein the multitude of boron-containing clusters comprising B-B bonds are connected by B-B bonds or B-heteroatom bonds, preferably wherein one boron- containing cluster comprises 3 to 20 boron atoms, and/or a structure of a 2D-network containing a multitude of boron-heteroatom
  • Alkali atoms may be added also e.g. for electrical application, e.g. for use of the present structure as electrode material, e.g. anode material, for ion-based batteries.
  • electrode material e.g. anode material
  • organic materials e.g. small organic molecules, like porphyrines or phthalocyanines, is possible for sensing applications.
  • Exemplary suitable methods for implementing the present method include chemical vapor deposition (CVD), including techniques like plasma enhanced CVD and MOCVD (metal organic CVD) as well as similar techniques like atomic layer deposition (ALD), spincoating of the at least one precursor or another method of depositing the precursor, all of them not being particularly restricted, and then producing the structure by bringing it into a gaseous and/or otherwise atomic-molecular excited state, even on the substrate, for contacting in this state, etc.
  • Spincoating and other deposition methods of solid and/or liquid precursors can be carried out using suitable precursors, e.g. also in solution, in a step of contacting according the present method.
  • Solid and/or liquid precursors are preferably leading to a monolayer, and further excess material can e.g. be suitably evaporated, etc.
  • solid precursors also a sublimation is possible.
  • decaborane (B- IO H M ) heteroclosoboranes like SeBnHn and/or carboranes, but also compounds like phenyl dichloroborane, can be dissolved in an organic solute and be spincoated, followed by heating and evaporation, thus being an alternative to contacting e.g. triphenyl borane from the gas or otherwise molecularly excited state, e.g. in a plasma.
  • the structure then can be generated e.g. by thermal annealing upon spincoating.
  • CVD chemical vapor deposition
  • Chemical vapor deposition is a deposition method in controlled atmosphere, and according to certain embodiments also under vacuum, wherein at least one surface of a substrate or the whole substrate is exposed to one or more precursors in the gas phase, particularly one or more volatile precursors.
  • the at least one or more precursors then can react and/or decompose on the at least one substrate surface to produce a desired deposit.
  • volatile by-products are also produced, which can be suitably removed, e.g. by a gas flow through a reaction chamber.
  • the present method it is not excluded to remove the structure containing at least one borophene, and/or at least one boron-heteroatom-domain comprising a 2D boron network, and/or the structure of a 2D-network containing a multitude of boron-containing clusters comprising B-B bonds, wherein at least one of the boron containing clusters comprising B-B bonds may comprise at least one heteroatom, and wherein the multitude of boron- containing clusters comprising B-B bonds are connected by B-B bonds or B-heteroatom bonds, preferably wherein one boron-containing cluster comprises 3 to 20 boron atoms, and/or the structure of a 2D-network containing a multitude of boron-heteroatom clusters having B-heteroatom bonds, wherein the multitude of boron-heteroatom clusters having B- heteroatom bonds are connected by B-B bonds, from the substrate by a suitable method, and a step of removing the structure containing
  • a layer will remain on the substrate and be used in connection with the substrate.
  • the structure is produced substrate stabilized, and there can be considerable electronic and/or electronic interaction between the substrate, e.g. a metal, and the structure, e.g. a borophene layer, which in itself would then show valuable properties.
  • the substrate e.g. a metal
  • the structure e.g. a borophene layer
  • the structure containing at least one borophene and/or at least one boron- heteroatom-domain comprising a 2D boron network and/or the structure of a 2D-network containing a multitude of boron-containing clusters comprising B-B bonds, wherein at least one of the boron containing clusters comprising B-B bonds may comprise at least one heteroatom, and wherein the multitude of boron-containing clusters comprising B-B bonds are connected by B-B bonds or B-heteroatom bonds, preferably wherein one boron- containing cluster comprises 3 to 20 boron atoms, and/or the structure of a 2D-network containing a multitude of boron-heteroatom clusters having B-heteroatom bonds, wherein the multitude of boron-heteroatom clusters having B-heteroatom bonds are connected by B- B bonds, can be combined with suitable other structures which are not restricted, like boron- heteroatom layers with only boron-heter
  • h BN other structures like graphene, perylene 3,4,9, 10-tetracarboxylic dianhydride (PTCDA), transition metal dichalcogenides (TMDs), e.g. TMD monolayers, like M0S2, WS2, MoSe2, WSe2, MoTe2, etc., thus opening up further applications, e.g. in the area of nanoscale devices.
  • PTCDA 10-tetracarboxylic dianhydride
  • TMDs transition metal dichalcogenides
  • TMD monolayers like M0S2, WS2, MoSe2, WSe2, MoTe2, etc.
  • Figure 1 shows a schematic of a borophene single-structure grown by CVD on a substrate, here a metallic support. According to certain embodiments also further layers are produced below and/or on the structure containing at least one borophene, and/or at least one boron-heteroatom-domain comprising a 2D boron network, and/or a structure of a 2D-network containing a multitude of boron-containing clusters comprising B-B bonds, wherein at least one of the boron containing clusters comprising B-B bonds may comprise at least one heteroatom, and wherein the multitude of boron-containing clusters comprising B-B bonds are connected by B-B bonds or B-heteroatom bonds, preferably wherein one boron-containing cluster comprises 3 to 20 boron atoms, and/or a structure of a 2D-network containing a multitude of boron-heteroatom clusters having B-heteroatom bonds, wherein the multitude of boron- heteroatom
  • borazine, a metal, etc., before and/or after contacting it with the at least one precursor in the gaseous or otherwise atomic-molecular excited state comprising at least one precursor, chosen from the group of substituted and unsubstituted boranes, substituted and unsubstituted heteroboranes - including substituted and unsubstituted aminoboranes and substituted and unsubstituted iminoboranes, substituted and unsubstituted polyboranes, substituted and unsubstituted poly-boron-heteroatom compounds, substituted poly-boron compounds, substituted and unsubstituted organoboron compounds, substituted and unsubstituted organopolyboron compounds, substituted and unsubstituted borazines, substituted and unsubstituted boroxines, and boron halides, as well as adducts of substituted and unsubstituted boranes - including substituted and unsubstitute
  • heterostructures with e.g. multiple layers can be formed on the substrate.
  • a monolayer of a hexagonal boron nitride which is grown on top of any borophene layer or borophene submonolayer structure as described previously, produced from e.g. borazine, a structure of sub monolayer domains of borophenes, lateral heterostructures of borophenes and other 2 D materials like h BN, graphene, etc., e.g. lateral heterostructures of borophenes and h BN, or overgrown heterostructures, e.g. of borophenes and h BN, can be formed, where the domain size can correspond to a sub monolayer coverage or a full monolayer coverage.
  • Fig. 2 This is shown schematically in Fig. 2, wherein left top to bottom lateral heterostructures are shown, and right top to bottom vertical heterostructures are shown, e.g. here of borophene type domains or layers (black) and h BN domains or layers (white).
  • a product comprising a structure containing at least one borophene, and/or at least one boron-heteroatom-domain comprising a 2D boron network, and/or a structure of a 2D-network containing a multitude of boron-containing clusters comprising B- B bonds, wherein at least one of the boron containing clusters comprising B-B bonds may comprise at least one heteroatom, and wherein the multitude of boron-containing clusters comprising B-B bonds are connected by B-B bonds or B-heteroatom bonds, preferably wherein one boron-containing cluster comprises 3 to 20, e.g.
  • certain aspects thereof will be applicable based on the description of the present method, so that these aspects also apply to the present product.
  • the product can also be coupled to a substrate, as mentioned above.
  • the product can comprise multiple layers, of which at least one is a layer comprising a structure containing at least one borophene, and/or at least one boron-heteroatom-domain comprising a 2D boron network, and/or a structure of a 2D-network containing a multitude of boron-containing clusters comprising B-B bonds, wherein at least one of the boron containing clusters comprising B-B bonds may comprise at least one heteroatom, and wherein the multitude of boron-containing clusters comprising B-B bonds are connected by B-B bonds or B- heteroatom bonds, preferably wherein one boron-containing cluster comprises 3 to 20 boron atoms, and/or a structure of a 2D-network containing a multitude of boron-heteroatom clusters having B-heteroatom bonds, wherein the multitude of boron-heteroatom clusters having B-
  • the further layer or layers are not restricted and can be below and/or above the structure containing at least one borophene, and/or at least one boron-heteroatom-domain comprising a 2D boron network, and/or a structure of a 2D-network containing a multitude of boron-containing clusters comprising B- B bonds, wherein at least one of the boron containing clusters comprising B-B bonds may comprise at least one heteroatom, and wherein the multitude of boron-containing clusters comprising B-B bonds are connected by B-B bonds or B-heteroatom bonds, preferably wherein one boron-containing cluster comprises 3 to 20 boron atoms, and/or a structure of a 2D-network containing a multitude of boron-heteroatom clusters having B-heteroatom bonds, wherein the multitude of boron-heteroatom clusters having B-heteroatom bonds are connected by B-B bonds. Also different domains and/or structures can be
  • At least one layer is contained below and/or on the structure containing at least one borophene, and/or at least one boron-heteroatom-domain comprising a 2D boron network, and/or a structure of a 2D-network containing a multitude of boron-containing clusters comprising B-B bonds, wherein at least one of the boron containing clusters comprising B-B bonds may comprise at least one heteroatom, and wherein the multitude of boron-containing clusters comprising B-B bonds are connected by B-B bonds or B-heteroatom bonds, preferably wherein one boron-containing cluster comprises 3 to 20 boron atoms, and/or a structure of a 2D-network containing a multitude of boron-heteroatom clusters having B-heteroatom bonds, wherein the multitude of boron- heteroatom clusters having B-heteroatom bonds are connected by B-B bonds, which can be the same or different, also as discussed above,
  • a monolayer of a hexagonal boron nitride which is grown on top of any borophene layer or a borophene submonolayer structure as described previously.
  • lateral heterostructures with other 2D materials like h BN, graphene, etc. e.g. lateral heterostructures of borophenes and h BN, or overgrown heterostructures, e.g. of borophenes and h BN.
  • further layers e.g. 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more, can be included in the product, which are not particularly restricted, like boron- heteroatom layers with only boron-heteroatom bonds, e.g.
  • BN e.g. h BN, other structures like graphene, perylene 3,4,9, 10-tetracarboxylic dianhydride (PTCDA), transition metal dichalcogenides (TMDs), e.g. TMD monolayers, like M0S2, WS2, MoSe2, WSe2, MoTe2, etc.
  • PTCDA 10-tetracarboxylic dianhydride
  • TMDs transition metal dichalcogenides
  • TMD monolayers like M0S2, WS2, MoSe2, WSe2, MoTe2, etc.
  • At least one borophene and/or at least one boron- heteroatom-domain comprising a 2D boron network is present as a monoatomic layer on the surface of the substrate.
  • STM/STS data were acquired by a CreaTec STM operating at 6K under ultra-high vacuum conditions (P ⁇ 2 c 10 10 mbar). STM images were taken at constant current mode and treated using the WSxM software.
  • borazine B 3 H 6 N 3 available from a commercial supplier (Katchem) and borazine prepared according to literature methods, it was observed that both materials do contain considerable amounts of additional volatile boron species. These originate from the decompositon of amine-borane H3N-BH3, and m-aminodiborane B2H5NH2, which are both intermediates occurring during the borazine synthesis and are in itself sources of borane BH 3 , and diborane B 2 H 6 , also leading to higher and thermally instable aminoboranes (Nh Bhy n , and borane adducts of polymer amineboranes HsB-(NH2-BH2) n - NH 2 , and from the borane and diborane formation, side reactions to higher boranes may occur.
  • Diborane can lead in separate side reactions to the formation of higher boranes, such as e.g. pentaborane B 5 H 9 , which is stable enough and not too volatile to be released fully into the gas phase, so it also could be detected as an intermediate in the NMR spectra. Also hydrolysis and oxidation due to mandatory technological processing, solvent purities, refilling, handling, etc., volatile hydrido-oxo-mino compounds of variable stoichiometry may occur leading to the formation of non-volatile polymer boron compounds and borane/diborane in the borazine.
  • boranes such as e.g. pentaborane B 5 H 9 , which is stable enough and not too volatile to be released fully into the gas phase, so it also could be detected as an intermediate in the NMR spectra.
  • hydrolysis and oxidation due to mandatory technological processing, solvent purities, refilling, handling, etc. volatile hydrido-oxo-mino compounds of variable
  • Borazine handling and preparation was made by Schlenk-techniques under Argon; ⁇ B-NMR measurements were made with a Bruker ACP 200 spectrometer in molten NMR tubes with separately sealed lock capillaries (CeDe) inside.
  • a borophene film has been grown on atomically pure lr(111) and Cu(111) substrates using the setup shown in Figure 3.
  • the lr(111) single crystal was prepared by repeated cycles of sputtering (Ar+ ions at an energy of 1 keV) and annealing (resistive heating at 1000°C).
  • the Cu(111) single crystal was prepared by repeated cycles of sputtering (Ar+ ions at an energy of 1 keV) and annealing (resistive heating at 760°C for Cu(111)).
  • a precursor gas container 1 technical borazine comprising additives leading to diborane was provided, which was then led through a cold trap 2 to separate the diborane from other volatile species, which was then led as precursor gas 3 onto the respective substrate 6 in the growth chamber 4 under controlled pressure and temperature, a pumping system 5 providing for a suitable pressure.
  • Diborane gas (B2H6) was therein confirmed as a compound occurring in commercially available borazine (B3H6N3), being e.g.
  • Fig. 4 therein shows a comparison between borophene grown by the exemplary CVD method applied with those by the current PVD (physical vapor deposition)
  • Inset High-resolution STM image showing the borophene appearance identified previously in literature (Vinogradov, N. A., Lyalin, A., Taketsugu, T., Vinogradov, A. S., & Preobrajenski, A. (2019).
  • White protrusions observed on top of the borophene layer in the STM spectra correspond to physisorbed 3D clusters, as indicated by the ease of displacing them with the STM tip and the lack of additional boron bonds observed in the XPS B 1s. They could be originated by trace contaminants present in the UHV chamber, such as N 3 ⁇ 4 O2 or H2O.
  • Complementary XPS chemical characterization of the polymorph grown by CVD confirmed the absence of nitrogen and presence of boron in the 2D sheet.
  • the B 1s core-level signal consists of a symmetric peak that can be well-reproduced by a Voigt-like function centered at 188.7 ⁇ 0.1 eV binding energy, thus being shifted by 1 - 1.6 eV with respect to other borophenes on Ag(111) and Cu(111) in the state of the art.
  • the shift is consistent with the reduction of adsorption distance on I r( 111 ) (2.1 A) compared to Ag (111) (2.4 A) and Cu(111) (2.3 A), and points towards a stronger borophene-substrate interaction for lr(111), reminiscent of the trend observed for other 2D materials.
  • the full width at half maximum of 1.3 eV (larger than the energy resolution of the apparatus ⁇ 1 eV) of the B 1s peak suggests a multiple-peak sub-structure. This could be explained by the large variations of charge density within this borophene sheet on lr(111) and/or the presence of diverse B bonding schemes with heteroatoms residually present, e.g. from the precursor or the synthesis chamber.
  • CVD-grown borophene on Cu(111) exhibits domains with a periodic structure defined by a rhomboidal unit cell.
  • the evaluation of the fast Fourier transforms (FFT) calculated for independent borophene domains reveals that these prefer to grow forming two mirror- symmetric structures, each one rotated by 5.0 ⁇ 1.5°.
  • these mirror-symmetric domains can also grow along three different orientations rotated by 120°, thus forming a 3- fold alignment of pairs of mirror-symmetric domains with the (111) surface. This result corroborates the (V73xV39)R ⁇ 5.8° on Cu(111) superstructure reported before, hence endorsing the identification of our borophene polymorph as c3— like polymorph.
  • boron clusters e.g. derived from tetrahedrons, octahedrons and/or icosahedrons, either isolated or connected, also could be observed, which is also to be expected from the extremely variable bonding chemistry of boron.
  • heteroatoms could be included in such clusters. Such clusters might account to a broadening in the lower binding region in XPS spectra observed.
  • Example 2 Production of lateral interfaces of a borophene with hexagonal boron nitride A film was produced as in Example 1, except that at certain points in time the cold trap 2 was deactivated, resulting in lateral interfaces of borophene with hexagonal boron nitride (h BN). Again, large borophene domains on fully covered lr(111) exceeding lateral sizes reported previously by more than one order of magnitude were obtained, with atomically precise lateral interfaces to h BN.
  • the precursors for borophene and h BN were selectively dosed by activating and deactivating the cold trap, as they coexist in the same precursor gas.
  • 0.03 L of borazine were dosed onto lr(111) kept at 1233 K in a first step, followed by 2.7 L of diborane in a second step.
  • the dose of borazine corresponds to that of sub-monolayer growth of h BN, therefore allowing enough free catalytic surface for the following borophene synthesis.
  • the resulting 2D layer reveals coexisting domains of borophene and h BN that fully cover the lr(111) surface, hence forming lateral heterostructures.
  • FIG. 5 An exemplary lateral heterostructure of the produced borophene and h BN with a sharp interface is shown in Fig. 5, a structure that is not feasible to obtain by other methods.
  • the STM image in Fig. 5(a) therein shows a higher magnification than the one in Fig. 5(b), clearly showing the sharp border between the two structures.
  • Borophene domains feature the three orientations and the stripy appearance with zigzag motifs discussed above, while h BN domains also preserve the characteristic appearance reported for pristine /iBN/lr(111).
  • the latter represents a single 12-on-11 moire superstructure with a periodicity of 2.89 nm, consequence of the small lattice mismatch and locked orientation along the high symmetry directions of the surface h BN zigzag edges (and the corresponding h BN symmetry axis) are oriented in parallel to the borophene stripes, which both are aligned to one of the three high-symmetry axis of lr(111).
  • borophene edges parallel to the stripes are energetically preferred, as indicated by their prevalence in borophene islands and edges to h BN. This promotes the formation of straight heterojunctions oriented in three equivalent directions with fixed lateral stacking.
  • the borophene-related density of states extends to the very interface with h BN.
  • the spectroscopical features are better visualized in the single dl/dV spectrum, where a minimum of intensity is observed around 0.7 V. While the line-shape compares reasonably well with those measured for borophenes c3 and b12 on Ag(111) and c6 on Cu(111), as produced above, the position of the minima is shifted considerably towards higher voltage. This observation is consistent with the depopulation of states near EF as compared to the cases of borophene on Ag and Cu, consistent to the charge transfer from such substrates occurring in the opposite direction (0.08e to lr(111), in contrast to 0.03 and 0.23e from Ag(111) and Cu(111) respectively).
  • h BN presents an electronic structure with lower density of states at EF, that it is spatially modulated along the moire pattern as a consequence of the registry-dependent hybridization of N with Ir atoms (36).
  • Fig. 2C the crossing between dl/dV spectra corresponding to h BN "pore" and “wire” regions is consistent with the STM contrast inversion observed at different bias voltages, likewise the crossing between h BN and borophene dl/dV curves at ⁇ 1.5 V accounts for the contrast inversion between both 2D layers.
  • Borophene-ZiBN lateral heterostructures grown on lr(111) by CVD were further characterized using extended STM and STS (scanning tunneling spectroscopy) characterization.
  • Large-area STM images evidence that borophene domains preserve the three orientations reflecting the symmetry of the underlying (111) surface upon formation of lateral heterostructures with h BN.
  • h BN domains appear oriented in three possible degenerated orientations, in which its moire superstructure is aligned along the three possible alignments of the c6 borophene stripes (i.e. along the high symmetry axis of lr(111 )).
  • Borophene domains presented elongated shapes in the direction of its zigzag ("wavy") stripes, thus indicating that the borophene facets parallel to the stripes are energetically preferred upon lateral bonding with h BN, and that borophene crystallizes at higher temperatures than h BN during the cooling process h BN domains appear mostly truncated along the high-symmetry axis of its moire superstructure, which indicates that they preferably bond with borophene via zigzag- terminated edges. This is observed in atomically-resolved STM images. A series of dl/dV spectra around the Fermi level taken across the borophene-ZiBN interface show that the electronic transition takes place without apparent formation of interfacial states. The anisotropic growth morphology of borophene domains furthermore enabled atomically precise alignment and contacting of other subsequently grown phases like it is shown for hm. Relevance of the invention
  • this system allows to easily grow large scale borophenes, it particularly shows the typical advantages of a process from the gaseous or otherwise atomic-molecular excited phase, particularly in a CVD process over other growth processes.
  • a particularly important advantage is to be seen in the use of diborane gas, particularly high purity diborane gas.
  • the present findings open new perspectives for the synthesis of borophene-type compounds, with direct impact in semiconductors, flexible/stretchable electronics, wear resistant/tribology, hard materials/interfaces, magnetic applications, biomedical applications, etc. e.g. with metal, semimetal or nonmetal interfaces, involving e.g.
  • nanotribology electronic, photonic and/or spintronic aspects of quantum confinement and/or further atomic-level properties, e.g. tribology, in particular for nano- and micromechanical devices, particularly in the fabrication of (semi-)conducting films for e.g. nanoscale electronic devices and applications, e.g. for energy conversion and storage systems, as e.g. disclosed in "Disclosing boron's thinnest side” (Sachdev, H. (2015). Disclosing boron's thinnest side. Science, 350(6267), 1468-1469.
  • particularly tough films comprising borophenes, and/or at least one boron-heteroatom-domain comprising a 2D boron network, and/or a structure of a 2D- network containing a multitude of boron-containing clusters comprising B-B bonds, wherein at least one of the boron containing clusters comprising B-B bonds may comprise at least one heteroatom, and wherein the multitude of boron-containing clusters comprising B-B bonds are connected by B-B bonds or B-heteroatom bonds, preferably wherein one boron- containing cluster comprises 3 to 20 boron atoms, and/or a structure of a 2D-network containing a multitude of boron-heteroatom clusters having B-heteroatom bonds, wherein the multitude of boron-heteroatom clusters having B-heteroatom bonds are connected by B- B bonds, can be produced on a larger scale.

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Abstract

L'invention concerne un procédé pour la production d'une structure contenant au moins un borophène, et/ou au moins un domaine bore-hétéroatome comprenant un réseau de bore 2D, et/ou une structure d'un réseau 2D contenant une multitude d'agrégats contenant du bore comprenant des liaisons B-B. Au moins l'un des agrégats contenant du bore comprenant des liaisons B-B peut comprendre au moins un hétéroatome, et la multitude d'agrégats contenant du bore comprenant des liaisons B-B sont reliés au moyen de liaisons B-B ou de liaisons B-hétéroatome, un agrégat contenant du bore comprenant de préférence de 3 à 20 atomes de bore, et/ou une structure d'un réseau 2D contenant une multitude d'agrégats bore-hétéroatome comprenant des liaisons B-hétéroatome, la multitude d'agrégats bore-hétéroatome comprenant des liaisons B-hétéroatome étant reliés par des liaisons B-B. L'invention concerne également un produit comprenant une structure contenant au moins un borophène, et/ou au moins un domaine bore-hétéroatome comprenant un réseau de bore 2D, et/ou une structure d'un réseau 2D contenant une multitude d'agrégats contenant du bore comprenant des liaisons B-B. Au moins l'un des agrégats contenant du bore comprenant des liaisons B-B peut comprendre au moins un hétéroatome, et la multitude d'agrégats contenant du bore comprenant des liaisons B-B sont reliés au moyen de liaisons B-B ou de liaisons B-hétéroatome, un agrégat contenant du bore comprenant de préférence de 3 à 20 atomes de bore, et/ou une structure d'un réseau 2D contenant une multitude d'agrégats bore-hétéroatome comprenant des liaisons B-hétéroatome, la multitude d'agrégats bore-hétéroatome comprenant des liaisons B-hétéroatome étant reliés par des liaisons B-B.
EP22706539.8A 2021-02-09 2022-02-03 Synthèse de borophène Pending EP4251569A2 (fr)

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