Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
  • C23C14/58—After-treatment
  • C23C14/5846—Reactive treatment
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B32/00—Carbon; Compounds thereof
  • C01B32/90—Carbides
  • C01B32/914—Carbides of single elements
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
  • C23C14/0021—Reactive sputtering or evaporation
  • C23C14/0036—Reactive sputtering
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
  • C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
  • C23C14/08—Oxides
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
  • C23C14/58—After-treatment
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/10—Particle morphology extending in one dimension, e.g. needle-like
  • C01P2004/13—Nanotubes
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/60—Particles characterised by their size
  • C01P2004/64—Nanometer sized, i.e. from 1-100 nanometer
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/80—Particles consisting of a mixture of two or more inorganic phases
  • C01P2004/82—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases

Definitions

• the invention relates to a method for synthesizing nanorods of a metal carbide on a substrate, and more particularly chromium carbide nanorods, as well as to a method for growing such nanorods on a substrate from nanocrystals of this metal.
• the synthesis and growth methods according to the invention lead to the obtaining of nanorods of a metal carbide which, apart from having a rigid and robust structure specific to carbides, are solidly fixed to the substrate on which their synthesis or their growth has been made, perpendicular to the main plane of this substrate, and are physically separated from each other, that is to say without contact with each other.
• nanorods are therefore able to be functionalized by grafting organic, chemical or biological molecules and are therefore of particular interest for the manufacture of microsystems endowed with chemical or biological functionalities, and more particularly useful biosensors, for example, in the fields of medical research and analysis in clinical biology, 1 agrifood, especially for the control of manufacturing processes and the quality of raw materials and finished products, or in the environmental field. They are also capable of serving as field effect spikes for the emission of electrons and thus entering into the constitution of sources emitting electrons, for example for the manufacture of flat screens of televisions or computers, or to be used to modify the optical properties of surfaces such as, for example, luminescence with low wavelength dispersion.
• nanotubes mainly carbon, or nanorods.
• Table I which is located at the end of this description, gives representative examples of these methods, which are essentially of three types.
• Chem., 2000, 10, 2570-2577 discloses a process for the preparation of tungsten disulphide nanotubes, in which a powder composed of nanobaguets or of tungsten oxide nanoc needles is reduced by hydrogen sulfide in an oven heated to 1100 ° C, then the nanotubes thus formed are separated from each other by subjecting the powder to ultrasound in an acetone bath .
• the document [3] (Bo er et al., Appl. Phys. Lett., 2000, 77 (6), 830-832) relates to a process making it possible to obtain a uniform film of carbon nanotubes on a silicon substrate and which implements a chemical vapor deposition assisted by microwave plasma or MPECVD ("Microwave Plasma Enhanced Chemical Vapor Deposi tion") of carbon, by decomposition of acetylene present in a C 2 mixture H 2 / NH 3 .
• the silicon substrate is previously covered with a cobalt layer about 2 nm thick, intended to serve as a catalytic germ for the growth of nanotubes.
• the third type of process brings together those which implement a lithography operation in order to obtain, on a substrate, nano-objects which are both erected vertically and distant from each other.
• the document [5] (Hadobas et al., Nanotechnology, 2000, 11_, 161-164) relates to a process which leads to the production of a grid of silicon nanoplots on a substrate composed of this same material. , which method comprises producing a pattern by optical lithography using an Argon laser, followed by plasma etching with oxygen, then sulfur hexafluoride.
• the nanoplots thus obtained measure from 35 to 190 nm in height depending on the samples and are spaced from each other by 300 nm.
• this method has the advantage of not using lithography, on the other hand it does not make it possible to obtain a regular distribution of the nanotubes and a sufficient spacing between the latter.
• the invention firstly relates to a process for synthesizing nanorods of a carbide of a metal Ml on a substrate, which comprises the following stages: a) the deposition, on this substrate, of a layer formed of nanocrystals of oxide of the metal Ml and of nanocrystals of oxide of at least one metal M2 different from Ml , the metal oxide nanocrystals Ml being dispersed in this layer; b) reduction of the nanocrystals of metal oxides Ml and M2 into nanocrystals of the corresponding metals; and c) the selective growth of the nanocrystals of the metal Ml.
• step a) is preferably carried out by reactive sputtering of a target consisting of the metals Ml and M2 by an oxygen plasma produced by a microwave plasma source with electronic cyclotron resonance (RCE ).
• RCE electronic cyclotron resonance
• Reactive sputtering of a metal target with a plasma of a gas produced by a microwave plasma source at the RCE as a technique of depositing a metal or a metal oxide on a substrate, is well known to date.
• the principle of this technique as well as a device with strong magnetic confinement allowing to implement it on large substrates have been described by Delaunay and Touchais in Kev. Sci. Instrum. , 1998, 69 (6), 2320-2324 [11].
• microwave power for example, of frequency equal to 2.45 GHz
• a plasma chamber consisting of one or more guides wave and including an electronic cyclotron resonance zone (for example, 875 Gauss when the frequency of the microwave power is 2.45 GHz), which produces a dissociation of the gas which is introduced into the plasma chamber and which is under low pressure, generally less than 10 "3 mbar.
• the ions and electrons thus created diffuse along the magnetic field lines and will bombard a negatively polarized metal target.
• the sputtering of this target in turn generates metallic atoms which will deposit on the substrate located opposite the target, thus forming a metallic or metallic oxide layer on this substrate.
• the sputtering of the metal target must lead to the deposition, on the substrate, of a layer formed of nanocrystals of at least two different metal oxides.
• This layer must, in fact, comprise, on the one hand, nanocrystals of metal oxide Ml, that is to say metal intended to enter into the constitution of nanorods of metallic carbide which it is desired to synthesize, and oxide nanocrystals of one or more M2 metals different from Ml, whose role is to ensure a dispersion of the oxide nanocrystals of metal Ml within this layer, so that the latter are physically separated one another.
• Ml nanocrystals of metal oxide Ml
• M2 metals oxide nanocrystals of one or more M2 metals different from Ml
• the invention it is possible to adjust the fluxes of atoms of the metals Ml and M2 produced by the metal target during its sputtering, and thus to adjust the density of the oxide nanocrystals of the metal Ml present in the layer of nanocrystals covering the substrate at the end of step a), by varying the composition of this target and / or its polarization.
• the metallic target can be made up of a mixture of metals Ml and M2, in which case it is subjected to a single negative bias voltage over its entire surface.
• the metals Ml and M2 are then present in this mixture in atomic proportions (that is to say expressed in number of atoms) which:
• step a either corresponds to those in which it is desired to find them in the layer of nanocrystals covering the substrate at the end of step a), if it turns out that the sputtering rates of said metals Ml and M2 are substantially identical under the conditions chosen operating procedures,
• the metal target may comprise several zones, adjacent to each other or distant from each other, at least one of these zones then being made of the metal Ml, while that the other or the others of these zones consist of the metal (s) M2.
• the reduction of the nanocrystals of metal oxides Ml and M2 deposited on the substrate during step a) into nanocrystals of the corresponding metals - or step b) of the synthesis process according to the invention - is preferably carried out by a hydrogen plasma produced by a microwave plasma source at the RCE, the substrate then being heated.
• the selective growth of the nanocrystals of the metal Ml - or step c) of the synthesis process according to the invention - is preferably carried out by a plasma of at least one hydrocarbon produced by a microwave plasma source at the RCE, the substrate also being heated.
• This RCE microwave plasma source is preferably a source with high magnetic confinement of the type described in document [11], making it possible to generate plasmas under low pressure with very energetic electrons and, therefore, to ensure a very thorough dissociation of the gases in the plasma chamber.
• the metal M1 is preferably chosen from the metals capable of reacting, in step c), with organic molecules or radicals being in gaseous form to form with them a metal carbide and thus lead to the growth of nanorods made of this carbide from the nanocrystals of this metal Ml.
• Metals of this type are, in particular, chromium and molybdenum, chromium being preferred in the context of the invention.
• the metal or metals M2 are, for their part, chosen from metals having an affinity with respect to molecules or carbon radicals being in gaseous form, which allows them, in step c), to fix these molecules and radicals through metal-carbon bonds and induce the formation of a layer protective graphite blocking any growth from nanocrystals of this or these M2 metals.
• Such metals are those known as catalysts for organic chemistry. These are, in particular, iron, nickel and cobalt, iron and nickel being preferred in the context of the invention.
• step a) is preferably carried out by reactive sputtering of a target made of a stainless steel composed of iron and chromium, or iron, chromium and nickel, such as for example an austenitic stainless steel composed of 68% iron, 18% chromium and 14% nickel.
• This target is advantageously polarized at a voltage less than or equal to -200 V and, preferably, from -400 to -200 V, while the oxygen plasma is maintained at a pressure generally less than or equal to 10 ⁇ 3 mbar, and preferably from 10 "4 to 10 -3 mbar, so as to optimize the energy of the electrons produced by the plasma.
• the hydrogen plasma is maintained at a pressure less than or equal to 10 ⁇ 2 mbar, and advantageously from 10 -3 to 10 "2 mbar, while the substrate is heated to a temperature ranging from 300 to 600 ° C. depending on the speed at which it is desired to reduce the metal oxide nanocrystals.
• the nanocrystals of chromium oxide, of iron oxide, and optionally of nickel oxide are reduced to nanocrystals of chromium, of iron, and if necessary of nickel, which typically measure of the order from 5 to 100 nm in diameter, within 5 to 20 minutes.
• step c) it is preferred that the hydrocarbon plasma (s) is maintained at a pressure less than or equal to 10 ⁇ 2 mbar, and preferably from 10 ⁇ 3 to 10 "2 mbar, and that the substrate is heated to a temperature greater than or equal to 600 ° C, and preferably between 600 and 800 ° C, to provide the activation energy necessary for the growth of carbide nanorods.
• the hydrocarbon or hydrocarbons used in step c) are chosen from alkanes, alkenes and alkynes such as, for example, methane, ethane, propane, ethylene, acetylene and their mixtures.
• Ethylene is preferably used.
• a structure of the nail board type is thus obtained, formed of a substrate and of chromium carbide rods of nanometric diameter, that is to say typically of the order of 5 to 100 nm, which are firmly fixed on the surface of this substrate and perpendicular to the main plane of the latter and which are, moreover, physically separated from each other.
• the length of these nanorods depends on the duration of step c).
• the substrate can be chosen from a wide variety of materials whose deformation temperature is higher than the temperature to which this substrate must be heated during step c), such as, for example, silicon, certain glasses such as borosilicates, quartz or a metal or a metal alloy such as stainless steel. he may, moreover, be solid or perforated, that is to say it may be, for example, in the form of a mesh.
• the heating of this substrate can be carried out inter alia by means of a substrate holder provided with heating means such as, for example, an electrical resistance.
• the invention also relates to a process for growing nanorods of a carbide of a metal Ml on a substrate, which consists in subjecting nanocrystals of the metal Ml dispersed in a layer of nanocrystals of at least one metal M2 different from Ml previously deposited on the substrate, to the action of a plasma of at least one hydrocarbon produced by a 'plasma plasma source at the RCE.
• this growth method is preferably implemented using the same metals Ml and M2 as those previously mentioned, a microwave plasma source with RCE with high magnetic confinement of the type of that described in document [11] and operating conditions similar to those used during step c) of the synthesis process described above.
• the microwave plasma source at the RCE can comprise a magnetic structure made up either of coils (solenoids) as in document [11], or of permanent magnets as described in FR-A-98 00777 [12].
• the invention also relates to a substrate which comprises nanorods of a metal carbide fixed on its surface, perpendicular to the main plane of this substrate, and physically separated from each other.
• these metal carbide nanorods measure from 5 to 100 nm in diameter and from 100 nm to 1 ⁇ m in length.
• these metallic carbide nanorods are chromium carbide nanorods.
• the substrates which are provided with them are likely to find very numerous applications.
• they are able to enter into the constitution of microsystems endowed with chemical or biological functionalities, and more particularly biosensors, after functionalization of said nanorods by grafting of organic molecules such as, for example, proteins such as antibodies, antigens or enzymes, or nucleotide fragments (DNA or RNA).
• organic molecules such as, for example, proteins such as antibodies, antigens or enzymes, or nucleotide fragments (DNA or RNA).
• the substrates according to the invention are also capable of entering into the constitution of electron emitting sources, for example for the manufacture of flat screens of televisions or computers, or of being used to modify the optical properties of surfaces such as, for example, luminescence with low wavelength dispersion.
• the invention also comprises other arrangements which will emerge from the additional description which follows, which refers to examples of implementation of the synthesis process according to the invention and of metal carbide nanorods obtained by this process.
• FIGS. 1, 2 and 3 are diagrams illustrating three exemplary embodiments of a metal target capable of being used in step a) of the synthesis method according to the invention for depositing, on a substrate, a layer comprising 90 % of iron oxide nanocrystals and 10% of nanocrystals chromium oxide, when this step a) is carried out by reactive sputtering of such a target with an oxygen plasma produced by a microwave plasma source at the RCE.
• FIG. 4 is a diagram illustrating the reactions occurring during step a) of the synthesis method according to the invention, when this step is carried out by reactive sputtering of a target made of an austenitic stainless steel by a plasma of oxygen produced by a microwave plasma source at the RCE.
• FIG. 5 is a diagram illustrating the reactions occurring during step c) of the synthesis method according to the invention, when this step is carried out with an ethylene plasma produced by a microwave plasma source at the NCE.
• FIG. 6 represents the mass spectrum of the dissociation of ethylene by electronic impacts as obtained during step c) of the synthesis process according to the invention, when this step is carried out with an ethylene plasma produced by a microwave plasma source at the RCE.
• FIG. 7 is an image taken with a scanning electron microscope, at a magnification of 30,000, showing the start of the growth of chromium carbide nanorods on a silicon wafer as observed during the implementation of the synthesis according to the invention.
• FIG. 8 is an image taken with a scanning electron microscope, at a magnification of 80,000, of chromium carbide nanorods synthesized on a silicon wafer by the synthesis method according to the invention.
• FIG. 9 is an image taken with a scanning electron microscope, at a magnification of 200,000, of a chromium carbide nanorod synthesized on a silicon wafer by the synthesis method according to the invention.
• FIG. 10 is an image taken with an electron microscope in transmission, at a magnification of 300,000, of chromium carbide nanorods synthesized on a stainless steel mesh by the synthesis method according to the invention.
• FIG. 11 shows the spectra obtained by spectrometry in loss of energy (spectra Si, S2, S3 and S4) as well as the images obtained with the transmission electron microscope (images II, 12, 13 and 14) for the iron atoms, of carbon, chromium and oxygen present in chromium carbide nanorods synthesized by the synthesis process according to the invention, the spectrum Si and image II corresponding to iron, the spectrum S2 and image 12 corresponding to carbon, the spectrum S3 and image 13 corresponding to chromium and the spectrum S4 and image 14 corresponding to oxygen.
• the same references serve to designate the same elements.
• FIGS. 1, 2 and 3 schematically represent three exemplary embodiments of a metal target capable of being used in step a) of the synthesis method according to the invention for depositing, on a substrate 11, a layer comprising approximately 90% of iron oxide nanocrystals and approximately 10% of chromium oxide nanocrystals, when this step a) is carried out by reactive sputtering of a metal target with an oxygen plasma produced by a microwave plasma source at the RCE.
• the metal target shown in Figure 1 is in the form of a plate 10, which is arranged opposite the substrate 11, substantially parallel to the latter. This plate is connected to a voltage generator 12 allowing it to apply a single negative bias voltage over its entire surface, for example of -400 V.
• target 10 is made up of a mixture of iron and chromium, for example stainless steel, in atomic proportions of 90% and 10%.
• the metal target shown in FIG. 2 is in the form of 3 plates, respectively 10a, 10b, and 10c, which are located in the same plane opposite the substrate 11, but being slightly spaced from each other. These plates are connected to a voltage generator 12 making it possible to apply to them the same negative bias voltage, for example of -400 V.
• the plates 10a and 10c are made of iron, while the plate 10b is made of chromium. So that their spraying leads to the deposition, on the substrate, of a layer comprising approximately
• the metal target shown in FIG. 3 is also in the form of 3 plates, respectively 10a, 10b and 10c, located in the same plane opposite the substrate 11, and slightly spaced from each other.
• the plates 10a and 10c are made of iron, while the plate 10b is made of chromium.
• this metallic target differs from that illustrated in FIG. 2, by the fact that, on the one hand, the sum of the areas of the plates 10a and 10c is equal to the area of the plate 10b, and, on the other apart, the plates 10a and 10c and the plate 10b are connected to two different voltage generators, respectively 13 and 14.
• the adjustment of the fluxes of iron and chromium atoms produced by the target is carried out by applying a bias voltage negative at plates 10a and 10c higher than that applied to plate 10b, for example -1000 V versus -100 V.
• FIG. 4 schematically illustrates the reactions occurring during step a) of the synthesis method according to the invention, when this step is carried out by reactive sputtering of a target 10 consisting of a austenitic stainless steel, for example 68% iron, 18% chromium and 14% nickel, by an oxygen plasma produced by a microwave plasma source at the RCE, with strong magnetic confinement of the type from that described in document [11].
• a target 10 consisting of a austenitic stainless steel, for example 68% iron, 18% chromium and 14% nickel
• the oxygen present in this chamber and which is under low pressure, for example of some 10 ⁇ 4 mbar dissociates by generating electrons (e " ) and ions (0 2 + , 0 + ) which pulverize target 10.
• This spraying in turn generates fluxes of iron, chromium and nickel atoms which are deposited on the substrate 11, together with oxygen atoms (0), giving rise to the formation of a layer 21 formed of nanocrystals of iron oxide (Fe 2 0 3 ), nickel oxide (NiO) and chromium oxide (Cr 2 0 3 ) and in which the chromium oxide nanocrystals (symbolized by black circles in FIG. 4) are dispersed.
• Figure 5 is a schematic representation similar to that of Figure 4, but which shows the reactions occurring during step c) of the synthesis process according to the invention, when this step is carried out with an ethylene plasma produced by a microwave plasma source at the RCE, with strong magnetic confinement.
• the layer 21 of nanocrystals covering the substrate 11 is formed of nanocrystals of iron, chromium and nickel and results from the reduction of a layer of nanocrystals of oxides of iron, chromium and of nickel obtained as illustrated in FIG. 4.
• the latter react with the chromium present in the chromium nanocrystals present on the surface of the substrate 11 to form with it chromium carbide and thus lead to the growth, from these nanocrystals, of nanorods of chromium carbide (symbolized by black rectangles in FIG. 5), and, on the other hand, are fixed by the nanocrystals of iron and nickel, which induces the formation of a protective graphitic layer preventing any growth from iron and nickel nanocrystals.
• Chromium carbide nanorods were synthesized on silicon substrates using for the three stages a), b) and c) an RCE microwave plasma source with high magnetic confinement similar to that described in the document [ 11].
• microwave power 50-150 watts for a frequency of 2.45 GHz
• ethylene pressure 10 "3 -3.10 " 3 mbar
• FIG. 6 represents the mass spectrum of the dissociation of ethylene C 2 H 4 by electronic impacts as obtained under these operating conditions. This spectrum shows that ethylene is strongly dissociated into atoms and ions H + , H 2 + , C + , C 2+ , CH + , CH 2 + , ...., fragments of this dissociation.
• FIGS. 7 to 9 are images taken with a scanning electron microscope, respectively at magnifications of 30,000, 80,000 and 200,000, which show for the first time the start of the growth of carbide nanorods. chromium on the substrate and, for the other two, chromium carbide nanorods as obtained at the end of step c).
• these nanowires (0 ⁇ 37 nm, L ⁇ 190 nm for the nanowires shown in Figure 8; 0 ⁇ 50 nm, L ⁇ 250 nm for the nanowire shown in Figure 9) are fixed on the substrate perpendicular to its main plane, are rectilinear and are, moreover, physically separated from each other, in this case by a distance of about 800 nm ( Figure 8).
• Example 2 Synthesis of chromium carbide nanorods on a stainless steel mesh
• Chromium carbide nanorods were synthesized on a substrate consisting of a stainless steel mesh using also, for the three stages a), b) and c), a microwave plasma source with RCE with high analog magnetic confinement. to that described in document [11].
• microwave power 50 watts for a frequency of 2.45 GHz
• the chromium carbide nanorods visible in FIG. 10 were thus obtained, which corresponds to an image taken with an transmission electron microscope, at a magnification of 300,000.
• these nanorods which measure approximately 10 nm in diameter and a little more than a hundred nm in length, are fixed to the substrate perpendicular to its main plane, are rectilinear and are, moreover, physically separated from each other. others, in this case by a distance slightly greater than 100 nm.
• FIG. 11 shows the spectra obtained by spectrometry in loss of energy (spectra SI, S2, S3 and S4) as well as the images obtained with the transmission electron microscope (images II, 12, 13 and 14) for the iron atoms, of carbon, chromium and oxygen present in these nanorods, the spectrum SI and image II corresponding to iron, the spectrum S2 and image 12 corresponding to carbon, the spectrum S3 and image 13 corresponding to chromium and the spectrum S4 and image 14 corresponding to oxygen.
• nanorods synthesized in accordance with the invention do indeed consist mainly of chromium carbide, iron and oxygen being present only in the residual state.

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