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WO2008143534A1 - Procédé de préparation de capteurs de fluides d'amas d'oxyde métallique en film mince - Google Patents

Procédé de préparation de capteurs de fluides d'amas d'oxyde métallique en film mince Download PDF

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Publication number
WO2008143534A1
WO2008143534A1 PCT/NZ2008/000120 NZ2008000120W WO2008143534A1 WO 2008143534 A1 WO2008143534 A1 WO 2008143534A1 NZ 2008000120 W NZ2008000120 W NZ 2008000120W WO 2008143534 A1 WO2008143534 A1 WO 2008143534A1
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Prior art keywords
clusters
film
cluster
dopant
deposition
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PCT/NZ2008/000120
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English (en)
Inventor
Andreas Lassesson
Joris Van Lith
Simon Anthony Brown
Monica Schulze
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Andreas Lassesson
Joris Van Lith
Simon Anthony Brown
Monica Schulze
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Application filed by Andreas Lassesson, Joris Van Lith, Simon Anthony Brown, Monica Schulze filed Critical Andreas Lassesson
Publication of WO2008143534A1 publication Critical patent/WO2008143534A1/fr

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
    • G01N27/12—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid
    • G01N27/125—Composition of the body, e.g. the composition of its sensitive layer
    • G01N27/127—Composition of the body, e.g. the composition of its sensitive layer comprising nanoparticles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y15/00—Nanotechnology for interacting, sensing or actuating, e.g. quantum dots as markers in protein assays or molecular motors
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • 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
    • C23C14/04—Coating on selected surface areas, e.g. using masks
    • 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
    • C23C14/14—Metallic material, boron or silicon
    • C23C14/18—Metallic material, boron or silicon on other inorganic substrates
    • 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
    • C23C14/5853—Oxidation

Definitions

  • the present invention relates to methods of preparing thin cluster films, which can be applied to the detection of fluids. More particularly but not exclusively the invention relates to a method of making thin films of metal oxide nanoclusters and using such structures for the detection of gases such as hydrogen, ammonia and carbon monoxide.
  • Gas sensors have a wide range of applications in such diverse areas as the automobile industry, process control, environmental monitoring and in-door climate monitoring. There exists however a gap in the performance between the available cheap and compact solid state gas sensors and the expensive and generally bulky spectroscopic instruments with the latter being significantly more sensitive than the former. To fill this gap with cheap and reliable solid state gas sensors it is necessary to develop vacuum compatible methods which allow miniaturized highly sensitive sensor devices to be manufactured.
  • Solid state gas sensors are usually made of materials in which the response to a specific gas occurs due to reactions between the gas and the surface of the material.
  • An example of a commonly used class of such materials is metal oxides, which can be used to detect reducing or oxidizing gases [I].
  • a conventional method for detecting gases is to measure the resistance of a metal oxide in the presence of the gas [I]. If the gas reduces the metal oxide surface, negative charge carriers are released into the bulk of the material. Depending on the type of charge carrier that dominates the conductance of the metal oxide the resistance will either decrease (n-type) or increase (p-type). Oxidising gases typically cause an opposite effect in which negative charge carriers are trapped at the surface [I].
  • a common metal oxide used in gas sensing is n-type SnO 2 , whose conductance increases on exposure to reducing gases, such as hydrogen or ammonia. . ..
  • the active component constitutes a Pd nanocluster film having surface coverage close to the percolation threshold.
  • the resistance of the cluster film is dominated by the tunnelling through tunnelling gaps in the film and expansion of the Pd clusters in the presence of hydrogen leads to partial closing of the gaps.
  • the tunnelling resistance is exponentially dependent on the tunnelling distance, reduction of the tunnelling junctions leads to large changes in the film conductance.
  • the invention described in [9] involves a method whereby a cluster film can be prepared with high control of the coverage below the percolation threshold.
  • the substrate is prepared with a discontinuous film, e.g. metal islands, that has a very low conductance.
  • the discontinuous film can be used to monitor the cluster coverage below the percolation threshold during deposition, illustrated in
  • Figure 1 can be used to achieve measurable currents through cluster films with low coverage.
  • a further invention in [10] describes a method for patterning Si substrates with V- shaped grooves that can be filled with clusters forming nanowires.
  • the deposition of clusters can be carried out such that the clusters hitting the flat surface between the grooves are reflected (bounce) away from the substrate while they slide into the bottom of the trench if hitting the side walls of the groove, see Figure 5.
  • the wires thus formed can be many ⁇ m long while having widths in the tens of nanometres.
  • the present invention is a method for preparing thin films and nanowires of metal oxide clusters for use as gas sensors.
  • the gas sensors are very sensitive to reducing gases such as hydrogen and their properties can be controlled by varying the cluster coverage, the cluster size and the dopant concentration.
  • the method is completely vacuum compatible and is especially suitable for the production of highly sensitive metal oxide nanocluster sensors.
  • the invention provides a method of forming a fluid sensor device comprising or including the steps of: a) providing a substrate; b) forming contacts on the substrate; c) preparing a plurality of metal clusters; d) deposition of a plurality of clusters on the substrate at least in the. region between the contacts, e) oxidising the clusters to achieve a film(s) running substantially between the contacts which is responsive to the presence of a fluid to be detected .
  • the material of the metal clusters can be oxidised. More preferably the material of the metal clusters is one of tin, titanium, tungsten, zinc, molybdenum and indium.
  • the metal oxide material of the film is stoichiometric.
  • the metal oxide material of the film is non-stoichiometric.
  • the clusters are metal clusters and step e) results in the formation of metal oxide clusters.
  • step e) is performed in an oven or furnace or oxygen plasma. More preferably the oxidation is performed in a controlled atmosphere. Preferably the oxidation is performed in air. Preferably the oxidation is performed in oxygen atmosphere or in an atmosphere which is predominantly oxygen.
  • step e) is performed at an elevated temperature.
  • step e) takes place at a temperature in the range 50°C to 450°C. More preferably step e) takes place at a temperature in the range 150°C to 250°C.
  • step e) is performed for a time in the range 10 minutes to 1 day. More preferably step e) is performed for a time in the range 30 minutes to 3 hours.
  • the clusters prepared in step c) consist of a metal, a doped metal or an alloy of metals that are oxidised after or during deposition on the substrate. Methods of oxidation of the clusters include, but are not limited to exposure to residual oxygen in a vacuum chamber, exposure to ambient air, heating while exposed to oxygen containing atmosphere or exposure to oxygen ion plasma.
  • Methods of preparation of the clusters include, but are not limited to vaporizing a metal precursor in a rare gas atmosphere.
  • the invention provides a method of forming a fluid sensor device comprising or including the steps of: a) providing a substrate; b) forming contacts on the substrate; c) preparing a plurality of metal oxide clusters; d) deposition of a plurality of clusters on the substrate at least in the region between the contacts, to achieve a film(s) responsive to the presence of a fluid to be detected running substantially between the contacts.
  • the material of the metal oxide clusters is one of tin oxide, titanium oxide, tungsten oxide, zinc oxide, molybdenum oxide and indium oxide.
  • the clusters prepared in step c) consist of metal oxide formed during the preparation of the clusters.
  • Methods of preparation of the clusters include, but are not limited to vaporizing a metal oxide precursor in a rare gas atmosphere or vaporizing a metal target in a mixed atmosphere of oxygen and rare gases.
  • Methods of vaporization of the precursor include, but are not limited to DC and AC magnetron sputtering, evaporation from a crucible and laser vaporization.
  • step b) may occur after step d).
  • the metal oxide material of the film is amorphous. More preferably the metal oxide material of the film is crystalline.
  • the thickness of the film is less than lOOnm. More preferably the thickness of the film is less than 20nm. More preferably the thickness of the film is less than 5nm. More preferably the thickness of the film is less than lnm.
  • the metal oxide material of the film is doped by another materal.
  • Suitable doping elements include, but are not limited to, tin, tungsten, molybdenum, zinc, indium, tantalum, copper, gadolinium, palladium, silver, platinum, gold, rhodium, ruthenium, yttrium and/or nickel and their oxides. . ..
  • the doping of the clusters is achieved by doping the precursor material used in the preparation of the clusters.
  • the doping is achieved by depositing the dopant on top of the cluster film.
  • the deposition of the dopant is performed on top of a ⁇ porous cluster film such that it does not create a continuous film.
  • the nominal thickness of the dopant material is less than IOnm. More preferably the nominal thickness of the dopant material is less than 5nm. More preferably the nominal thickness of the dopant material is less than lnm.
  • the deposition of the dopant is performed such that small islands or clusters are formed on or in between the clusters.
  • the doping is by Pd.
  • the doping is by deposition of tin clusters on top of Pd islands or a Pd discontinuous film. More preferably the doping us by e-beam deposition of Pd on the cluster films while still in the vacuum system, or doping of the clusters by letting them pass a vapour of Pd on their way from the source to the target. Even more preferably the doping is by deposition of Pd clusters on top of a pre-existing tin or tin oxide cluster film.
  • the deposition of the dopant is performed such that the dopant atoms are homogeneously distributed in the cluster film.
  • the deposition of the dopant is performed such that the dopant atoms are inhomogeneously distributed in the cluster film.
  • the dopant level is less than 50 atomic percent with respect to the metal oxide material. More preferably the dopant level is less than 10 atomic percent. More preferably the dopant level is less than 1 atomic percent.
  • the response of the f ⁇ lm(s) to the presence of the fluid is a reversible change in electrical resistance, conductance or impedance.
  • the detector will measure the conductance/resistivity of the film(s).
  • the detector will measure the impedance of the films(s).
  • suitable detectors include a galvanometer, an ohmmeter, a potentiostat and a multimeter. Desirably several sensors may be used in a measurement circuit.
  • the film(s) will comprise a network of clusters whose porosity is significantly greater than 0.
  • the film(s) will comprise a network of clusters whose surface coverage is less than 100 monolayers. More preferably the cluster coverage is less than 10 monolayers. More preferably the cluster coverage is in the range 0.5 to 2 monolayers.
  • the detector in communication with the contacts and the f ⁇ lm(s) forms a circuit.
  • the conduction through the film is dominated by surface conduction. More preferably the carrier concentration in the film is altered by reaction of the analyte on the surface of the film.
  • the conductance through the film is dominated by tunnelling.
  • the tunnelling conductance between individual and / or groups of clusters in the film will change, altering the impedance of the circuit.
  • the Surface Acoustic Wave attentuation of the cluster film is monitored.
  • the Surface Acoustic Wave attenuation of the cluster film change.
  • the optical properties of the cluster film are monitored.
  • the optical properties of the cluster film change.
  • the optical properties include one or more of reflectance, absorption, fluorescence or luminescence.
  • the fluid sensor device in the presence of the fluid to be detected, triggers an alarm.
  • the fluid sensor device includes a system control component.
  • the contacts are separated by a distance smaller than 200 microns, more preferably the contacts are separated by a distance less than 1 OOOnm.
  • the substrate is an insulating or semiconductor material, more preferably the substrate is selected from silicon, silicon nitride, silicon oxide, aluminium oxide, germanium, gallium arsenide or any other IH-V semiconductor, quartz, or glass.
  • the film comprises chains of clusters, pathways or nanowires which dominate the conduction through the film.
  • the cluster film is deposited in such a way as to promote the formation of chains of clusters, pathways or nanowires.
  • a template or substrate pattern is used to promote the formation of chains of clusters, pathways or nanowires.
  • the substrate patterning consists of a template which controls or assists assembly of the clusters.
  • the template comprises one or more of naturally occurring substrate features an etched pattern, especially a trench or V-groove a lithographically patterned polymer layer lithographically patterned PMMA, photoresist, SU8 or one of a number of other polymeric resists
  • the nanoclusters may be of uniform or non-uniform size, and the average diameter of the nanoclusters is between 0.5nm and l,000nm.
  • the substrate has been modified by deposition of an intermediate film comprising a discontinuous thin film, metal islands, or semiconductor islands.
  • an intermediate film comprising a discontinuous thin film, metal islands, or semiconductor islands.
  • the material of the intermediate film is Au, Ag, or Pd.
  • the intermediate film can be used to monitor the deposition of the cluster film.
  • the intermediate film comprises a material that improves some aspects of the final sensor. ' . . . .
  • the intermediate film is comprised of a material that lowers the optimum operating temperature and/or improves the sensitivity and/or improves the selectivity and/or lowers the response time of the cluster film to a specific fluid.
  • Suitable materials include palladium, platinum, gold or combinations and alloys thereof.
  • the film(s) is/are coated with a protective layer permeable to the fluid to be detected but substantially impermeable to species which may contaminate the film.
  • a protective layer permeable to the fluid to be detected but substantially impermeable to species which may contaminate the film.
  • an activated carbon barrier is provided to prevent species contaminating the film while allowing the passage of the fluid to be detected.
  • the film(s) comprises a plurality of films, said plurality of films arranged in a Wheatstone Bridge configuration.
  • the senor is contained in a package with, or measured in conjunction with, other gas sensors for the purposes of detection of contaminating species.
  • a resist or other organic compound or an oxide or other insulating layer is applied to the substrate and then processed using lithography to define a region or regions where the clusters may form a continuous or discontinuous web between the contacts and another region where the clusters will be insulated from the conducting network.
  • one or more of the devices described above is connected to a circuit comprising a power source and a method of monitoring the current flowing through the circuit.
  • a method of assessing the fluid content in an environment including contacting the device of as above and/or apparatus as above with the environment and reading or otherwise assessing the output of the detector.
  • fluid sensing apparatus substantially as herein described with reference to one or more of the Figures and/or Examples.
  • a method of assessing the ammonia gas content in an environment including contacting the device of as above and/or apparatus as above with the environment and reading or otherwise assessing the output of the detector.
  • ammonia sensor device substantially as herein described with reference to one or more of the Figures and/or Examples.
  • Ammonia sensing apparatus substantially as herein described with reference to one or more of the Figures and/or Examples.
  • a method of assessing the hydrogen gas content in an environment including contacting the device of as above and/or apparatus as above with the environment and reading or otherwise assessing the output of the detector.
  • a hydrogen sensor device substantially as herein described with reference to one or more of the Figures and/or Examples.
  • Nanoscale as used herein has the following meaning - having one or more dimensions in the range 0.5 to 1000 nanometres.
  • Fluid as used herein has the following meaning - a liquid or a gas or a mixture of liquids or gases.
  • Particle as used herein has the following meaning - an aggregate of atoms or molecules with dimensions in the range 0.5 nanometres to 1000 micrometres. Examples include atomic clusters.
  • Nanowire as used herein has the following meaning - a pathway formed by the assembly nanoparticles which is electrically conducting (via ohmic conduction or tunnelling conduction, for example). It is not restricted to a single linear form but may be direct, or indirect. It may also have side branches or other structures associated with it.
  • the nanoclusters may or may not be partially or fully coalesced, so long as they are able to conduct.
  • the definition of nanowire may even include a film of clusters which is homogeneous in parts but which has a limited number of critical pathways; it does not include homogeneous films of nanoclusters or homogeneous films resulting from the deposition of nanoclusters.
  • Contact as used herein has the following meaning - an area on a substrate, usually but not exclusively comprising an evaporated metal layer, whose purpose is to provide an electrical connection between the islands, the thin film or discontinuous thin film and an external circuit or any other electronic device.
  • a single contact has a width, w; in respect of two contacts they are separated by a separation L.
  • Atomic Cluster or “Cluster” or “Nanocluster” as used herein has the following meaning - a nanoscale aggregate of atoms formed by any gas aggregation, or one of a number of other techniques, with diameter in the range 0.5nm to lOOOnm, and typically comprising between 2 and 10 9 atoms.
  • Substrate as used herein has the following meaning - an insulating or semiconducting material comprising one or more layers which is used as the structural foundation for the fabrication of the device.
  • the substrate may be modified by the deposition of electrical contacts, by doping or by lithographic processes intended to cause the formation of surface texturing.
  • Island as used herein has the following meaning - a nanoscale or microscale aggregate of atoms situated on a substrate.
  • the island may be hemispherical, oblate, cylindrical or of irregular shape.
  • the shape of the island may be as deposited (e.g. defined by the interaction ("wetting") between the island atoms and the underlying substrate atoms) or it may be defined by external means (e.g. lithographical processing techniques such as photolithography or e- beam lithography).
  • Conduction as used herein has the following meaning - electrical conduction which includes ohmic conduction and tunnelling conduction.
  • the conduction may be highly temperature dependent as might be expected for tunnelling devices or a semiconducting nanowire as well as only moderately temperature dependent as might be expected for metallic conduction.
  • Tunneling conduction is conduction by quantum mechanical transport of electrons through a classically insulating barrier between two classically conducting materials or particles.
  • Ohmic conduction as used herein describes all other forms of conduction, excluding tunnelling conduction.
  • “Film” as used herein has the following meaning - a layer of atoms with homogenous or inhomogeneous cross-section tcovering a substrate. Typically the film has a thickness from a few to many million atomic monolayers (0.1 nm to lOO ⁇ m).
  • “Chain” as used herein has the following meaning - a pathway or other structure made up of individual units which may be part of a connected network. Like a nanowire it is not restricted to a single linear form but may be direct, or indirect. It may also have side branches or other structures associated with it. The nanoclusters may or may not be partially or fully coalesced, so long as they are able to conduct.
  • chain may even include a film of clusters which is homogeneous in parts but which has a limited number of critical pathways; it does not include homogeneous films of nanoclusters or homogeneous films resulting from the deposition of nanoclusters.
  • Interdigitated Contacts as used herein has the following definition - a pair of contacts arranged so that one or more digits from each contact are interleaved among digits from the other.
  • Discontinuous film means a film made up of individual units or islands, which may or may not be part of a connected network. It is not restricted to a single linear form but may include direct or indirect conducting pathways between contacts. It may also have side branches or other structures associated with it. It may include regular or irregular arrays of isolated islands, expecially nanoscale islands. It does not include a film having a homogeneous cross- section throughout and includes at least some discontinuities. Conduction may be entirely or partially by tunnelling.
  • Percolation Theory as used herein has the following definition- An understanding of the formation of connected structures of randomly occupied sites, where there is a regular lattice of sites (site percolation) or not (continuum percolation). It includes all variations on this theory which allow calculations of important parameters such as the conductivity of a network of sites, probability of percolation and correlation length. It also includes variations on this theory which focus on bonds connecting the site (bond percolation).
  • Percolation Threshold as used herein has the following definition- The least occupancy of the available sites in Percolation Theory at which a connected structure of sites exist which spans one of the dimensions of the system and / or allows electrical conduction across the system.
  • Dopant as used herein has the following meaning - an element or combination of elements that can be added to the film so as to improve the properties of the film.
  • Surface coverage is the fraction of a surface covered by a number of deposited clusters or other metal islands. For thick depostions surface coverages may be greater than 1 , indicating for example that there is more than one layer of clusters.
  • Figure 1 Schematic side view depicting the preparation of a SiN substrate with contacts and a discontinuous film of metal islands on the substrate and the use of the islands to monitor the deposition of clusters between the contacts.
  • Figure 2 Schematic side view depicting the preparation of a SiN substrate with contacts, deposition of clusters between the contacts and the use of the cluster film as a fluid sensor device.
  • Figure 3 Schematic side view depicting the deposition of clusters between contacts, doping of the cluster film by surface doping, and the use of the doped cluster film as a fluid sensor device.
  • Figure 4 Schematic side view depicting the preparation of a SiN substrate with a discontinuous film of islands of a dopant material, deposition of clusters on the metal islands and the use of the device as a fluid sensor.
  • Figure 5 Schematic side view depicting the preparation of a Si substrate with V-grooves and the deposition of clusters on the sample.
  • Figure 6 Top view of a typical sensor device layout with interdigitated fingers and three individual sensors.
  • the dark spot in the centre of the device is a thin layer of SnO2 clusters doped by deposition of lnm of Pd on top of the cluster film.
  • Figure 8 TEM image taken on a grid deposited with neutral Sn clusters.
  • Figure 10 Ion intensity versus velocity for 6nm Sn clusters.
  • the velocity of the experimental data was calculated from the voltages in Figure 9 and fitted with the reciprocal integral (full line) of a Lorentzian centred at 185m/s (dashed line).
  • Figure 1 Velocity versus diameter for Sn clusters accelerated by supersonic expansion of gas from the magnetron sputtering source.
  • Figure 12 Current versus time for the deposition of tin clusters between two contacts separated by lO ⁇ m. The deposition was turned on after 50 seconds and turned off after 830 seconds.
  • Figure 13 Current versus coverage for the deposition of tin clusters. The coverage was calculated from the deposition rate measured on a thickness rate monitor prior to deposition.
  • Figure 14 SEM image of a tin cluster film (baked at 19O 0 C for 18 hours) showing high porosity and clusters with diameters around 8-12nm.
  • Figure 15 SEM image of an unbaked tin cluster film showing clusters that has been melted by the SEM electron beam.
  • the initial cluster size was similar to the cluster size in Figure 14.
  • Figure 16 Resistance versus time for a film of tin clusters before and during air exposure. The air is introduced after 100 seconds.
  • Figure 17 Resistance in ambient conditions versus film thickness for films with 6.5nm clusters at different stages of the tin oxide cluster sensor production. In vacuum after deposition (circles), after air exposure (diamonds), after baking at 19O 0 C for 18 hours (triangles) and after top doping with lnm Pd (boxes).
  • Figure 18 SEM image of a thin layer of clusters deposited on top of a discontinuous film of Pd with a nominal thickness of 0.4nm.
  • Figure 19 Current versus time for the deposition of a film of tin clusters on 0.4nm Pd (between 50 and 450 seconds), stabilisation (between 450 and 1000 seconds) and exposure to air (from 1000 seconds).
  • Figure 20 TEM electron diffraction image taken on a grid deposited with neutral Sn clusters (see Figure 8). The clusters are most probably amorphous since no diffraction rings are visible.
  • Figure 21 Resistance versus time for a film of tin oxide clusters exposed to varying concentrations of hydrogen in dry air at 8O 0 C.
  • Figure 22 Resistance versus time for a film of tin oxide clusters doped with 1 nm Pd exposed to varying concentrations of hydrogen in dry air at 8O 0 C.
  • Figure 23 Resistance versus hydrogen concentration for a film of tin oxide clusters doped with lnm Pd at 80°C.
  • Figure 24 Resistance versus time for a film of tin oxide clusters, deposited on a 0.4nm thick discontinuous film of Pd, exposed to varying concentrations of hydrogen in dry air at 8O 0 C.
  • Figure 25 Response at 8O 0 C expressed as the ratio between the resistance in hydrogen and the resistance in dry air, versus cluster coverage for tin oxide cluster sensors doped with lnm Pd.
  • Figure 26 Response at 8O 0 C expressed as the ratio between the resistance in hydrogen and the resistance in dry air, versus Pd thickness for tin oxide cluster sensors of varying coverage.
  • Figure 27 The response time at 8O 0 C versus Pd thickness for tin oxide cluster sensors with varying cluster coverage.
  • Figure 28 The response time at 8O 0 C versus hydrogen concentration for tin oxide cluster sensors with varying cluster coverage and 0.8nm Pd.
  • Figure 29 The response times at 3O 0 C and 8O 0 C versus hydrogen concentration for the same tin oxide cluster sensor as in Figure 22.
  • Figure 30 Resistance versus time for a film of tin oxide clusters, doped with lnm Pd and exposed to varying concentrations of ammonia in dry air at 12O 0 C.
  • Figure 31 Resistance versus time for a film of tin oxide clusters, doped with lnm Pd and exposed to varying concentrations of ammonia in dry air at 16O 0 C.
  • Figure 32 The response versus ammonia concentration for a tin oxide cluster sensors with lnm Pd at 16O 0 C.
  • Figure 33 The response times versus ammonia concentration for a tin oxide cluster sensors with lnm Pd at 16O 0 C.
  • Figure 34 SEM image of a 7 ⁇ m wide V-groove deposited with 15nm Sn clusters.
  • Figure 35 SEM image showing part of a V-groove (top) and flat surface (bottom) deposited with 15nm Sn clusters.
  • Figure 36 SEM image of a 3 ⁇ m wide V-groove deposited with 15nm Sn clusters.
  • the present invention relates to a method of fabrication thin films of clusters that can be used as fluid sensors.
  • the invention relates to a method for preparing thin films of metal oxide nanoclusters for use as detectors of reducing and oxidising gases.
  • the clusters are formed by inert gas aggregation of metal or metal oxide vapour created by magnetron sputtering or thermal evaporation. Cluster formation and deposition is carried out under high vacuum conditions to reduce impurities in the resulting cluster film. In the case of metal cluster deposition, the cluster film is then oxidised by exposure to ambient air, pure oxygen or oxygen plasma.
  • our procedure can be used to prepare films of nanoclusters with high control of both cluster size and surface coverage.
  • Resultant cluster sizes are typically in the range 1-1 Onm and the mean thickness of deposited material may also be in the range 1-1 Onm (corresponding surface coverages may be less than 1 monolayer of clusters).
  • our method can be employed to create highly sensitive fluid sensors.
  • An additional advantage of our method is that it creates very porous cluster films which can easily be modified by doping with catalytic metals such as palladium.
  • the porosity is also advantageous in that fluids can easily reach all parts of the film.
  • the response and response time is hence expected to be higher for sensors made using our method than those made using conventional methods.
  • the substrates are formed using only simple and straightforward techniques i.e. vapour deposition and relatively low resolution lithography.
  • the preparation of the cluster film and the subsequent treatment, such as doping and oxidation, is entirely vacuum compatible.
  • the clusters can be prepared with good size control.
  • the cluster films can be prepared with good coverage control.
  • the cluster films can be prepared with high porosity.
  • In-situ monitoring of the film conductance during deposition of the clusters allows a high degree of control of the coverage and the conducting / sensing properties.
  • the cluster film preparation can be applied to many different sensor materials. No manipulation of the clusters is required to form the sensor. Fabrication of microscale or nanoscale devices using the method of the invention may be relatively straightforward.
  • This method described herein can be used to create thin films of nanoclusters with high control of cluster size, coverage, purity and porosity. These parameters are all expected to be important for the production of sensitive, selective, fast and reliable fluid sensors. This is especially the case for the most common class of materials, metal oxides, that is in use in solid state sensors.
  • the ⁇ processes that occurs in metal oxides when exposed to reducing or oxidising gases are surface reactions, which, through adsorption and desorption of gas species, change the carrier density and hence the conductance of the metal oxides.
  • the change in conductance is typically very strongly dependent on the increase/decrease of the charge carrier density, which in turn is dependent on the surface to volume ratio of the metal oxide. This means that the response, response times and other properties of metal oxide sensors are highly dependent on the grain or particle size; see e.g. [4, 5, 6, 7].
  • the particles e.g. metal oxide clusters
  • an inert gas condensation cluster source such as a magnetron sputtering cluster source.
  • the clusters may consist of either pure metal (which, in a preferred embodiment, are subsequently oxidised) or metal oxide, with or without doping and the cluster size can be narrowly controlled within a wide size range.
  • the clusters are typically deposited between two or several lithographically defined contacts thus creating a conducting film that constitutes the sensor element, see
  • the cluster coverage can be minutely controlled by monitoring the film conductance.
  • the film properties can be tuned such that several different sensing processes contribute to the response of the sensor.
  • the tunnelling junctions may occur as gaps between clusters or groups of clusters as in [9], as cluster - cluster neck tunnelling junctions or cluster - electrode tunnelling junctions. Changing the properties of these junctions, by e.g. surface adsorption of fluids on the clusters, changes the overall conductance of the device. Changes in tunnelling junctions are however only one of many possible processes than can occur in films prepared by the method described herein.
  • the clusters can either be doped when they are produced by using a doped precursor or they can be doped by depositing the dopant on top of the cluster film, see Figure 3.
  • the small cluster size, low cluster film thickness and high film porosity that can be achieved with our method allows for a high doping efficiency when dopant deposition is applied.
  • Additional doping methods that can be incorporated into our method include; letting the clusters pass a vapour of dopants on their flight to the substrate, depositing them on a discontinuous film of dopant material, as in [9] ( Figure 4), or using electrodes made of a dopant material.
  • the method disclosed herein combines bottom-up approaches to the creation of nanostructures with conventional top-down methods such as e-beam or photo-lithographic definition of microscale structures. Applied to the creation of nanocluster sensors it provides minute control of such parameters as cluster size, cluster film thickness and doping levels.
  • One of the main advantages of the method is that the creation of the sensing layer and the doping and treatment thereof can be carried out in its entirety in a vacuum environment. This provide for well controlled impurity levels and means that the sensor production is fully compatible with tools and processes in use by the microelectronics industry. It can thus be easily modified for mass production.
  • the cluster film connects immediately to the contacts upon -cluster deposition one can apply the sensing layer in-situ to various forms of integrated circuit or printed circuit boards. It can also be envisioned that the sensor production system is equipped with a multitude of cluster and doping sources to provide a wide range of sensing materials with varying selectivities and sensitivities that can be applied to individual sensors on the same circuit board.
  • Table 1 summarizes a few of the cluster material which can be produced using our method, the gases that can be detected with the sensors and in which application they can be used.
  • the table is intended to be illustrative, and is by no means exclusive. Further metallic oxide materials and the gases that they are sensitive to are described in the literature (see e.g. [H]).
  • Nitrogen oxide nitrogen Automobile industry, Environmental WO, dioxide monitoring
  • Contact pads are formed on a SiN substrate by thermal evaporation of 5 nm NiCr (80% Ni and 20% Cr) followed by 50 nm of Au through a shadow mask which defines four contacts.
  • the contacts are arranged in an interdigitated finger structure such that three individual sensors are created, see Figure 6.
  • the spacing between the fingers of the substrate shown in Figure 6 is lOO ⁇ m, but for some of the results presented below, samples with lO ⁇ m finger spacing have been used.
  • Au is chosen as it is inert and readily available and NiCr is necessary to improve the adhesion to the SiN, but we note that other elements can be used, e.g. Pd (see below).
  • This simple contact geometry and fabrication procedure is adequate for the testing of the principle and simpler applications, but we note that many more sophisticated lithographic procedures can be used to produce contacts of smaller dimensions, or of other geometries. Many examples have been described in our previous work [8].
  • a thin PMMA polymer layer is spun on top. This layer is removed after the dicing using a standard cleaning procedure.
  • the empty SiN surface between the contacts can, optionally, be modified by depositing a thin layer of Au, Pd or other metal (thickness typically 0.1-lnm) in order to create metal islands between the contacts.
  • the metal islands can be applied in order to control the deposition of clusters at low coverage [9], see
  • Pd is known to act as a catalyst and increases the sensitivity of metal oxide sensors towards gases such as CO and H 2 [6] and islands of Pd may hence be used to improve the sensitivity of the cluster films, see Figure 4.
  • An alternative method for preparing the substrates with a catalytic dopant before cluster deposition is to use Pd or other catalysts for the preparation of the contacts.
  • the cluster production and deposition is carried out in a vacuum system that has previously been described in detail [12]. It consists of a nanocluster source, a mass selection stage and a deposition stage.
  • Sn clusters are created by DC magnetron sputtering of a 99.99% tin target in an atmosphere of argon and helium (pressures from 0.1-1 Torr) [13].
  • the magnetron sputtering cluster source is capable of creating an intense, continuous beam of clusters containing an approximately equal number of neutral and singly charged (both positive and negative) clusters.
  • the cluster size can be controlled in the range 1-20 nm by changing the Ar/He mixture and source inlet gas flow rates (in the range 1-lOOOsccm), adjusting the sputter power, changing the cluster growth distance between the target and the source nozzle and changing the operating temperature of the source.
  • the source walls was cooled to liquid nitrogen temperatures while the source was kept at room temperature for the V-groove experiments, see below.
  • the magnetron sputtering source can be replaced by an inert gas aggregation cluster source in which the metal vapour is created by thermal evaporation from a crucible [12].
  • This source is suitable for materials with low melting points, but we note that the magnetron sputtering cluster source is especially flexible in that a wide variety of materials can be used for cluster production, such as titanium, indium, zinc and other metals whose oxides are commonly used in metal oxide sensors.
  • the target material can in addition be of significantly higher purity than that used in this example and it can also be doped with appropriate elements if need be.
  • the source can easily be modified for AC magnetron sputtering of metal oxide targets.
  • Metal oxide clusters can also be produced by introducing oxygen into the source cavity.
  • the cluster beam and the inert gas mixture exits the source through a nozzle and is supersonically expanded into a series of differentially pumped vacuum stages where the gas is separated from the clusters.
  • the source inlet gas flow rates and the gas temperature control the velocity of the clusters via the velocity of the gas exiting the source chamber [12].
  • the cluster beam passes a mass filter [14, 15] that, in combination with a Faraday cup, can be used to investigate the size of the charged clusters.
  • Figure 7 shows a size distribution of negative tin clusters, measured using the mass filter, compared to the sizes of neutral clusters deposited on a TEM grid, see Figure 8. There is an excellent agreement in size between the ions and the neutral clusters deposited on the TEM grid.
  • the mass filter is hence a reliable tool for monitoring the size of the neutral clusters deposited on the samples.
  • the kinetic energy of the clusters can be estimated by setting the mass filter to a fixed ion mass and measuring the ion current for different retarding voltages on the Faraday cup.
  • the result for tin clusters with a diameter of 6nm is shown in Figure 9.
  • the velocity can be calculated from the kinetic energy using the known ion mass (selected by the mass filter).
  • Figure 10 shows that the 6nm diameter clusters have a velocity of around 185m/s.
  • the ion intensity has been fitted using the integral of a Lorentzian velocity distribution in order to estimate the mean velocity accurately.
  • the Lorentzian which describes the velocity distribution, is shown as a dashed line in Figure 10.
  • the final part of the vacuum system is a separate deposition chamber that can be isolated from the source and mass filter stages by a computer controlled solenoid valve, which is also used to turn the cluster beam on and off during deposition runs.
  • the deposition stage is pumped with a turbopump to around 10 "3 Torr during deposition of the clusters and below 10 ⁇ 6 Torr when the solenoid valve is closed prior to deposition.
  • the deposition chamber contains a quartz crystal thickness rate monitor mounted in the path of the cluster beam at the end of the apparatus and a cryogenic sample mount that can be inserted into the beam for deposition of the samples.
  • the clusters are deposited while simultaneously measuring the conductance of the samples.
  • the conductance of the 3 individual sensors on the samples (shown in Figure 6) is measured by applying a voltage, usually 1.25V to the common electrode (bottom electrode in Figure 1) while measuring the current on the other three electrodes with electrometers.
  • Figure 12 shows the current versus time during deposition of 6.5nm clusters between two contacts separated by lO ⁇ m.
  • the deposition was started after 50 seconds by opening the solenoid valve.
  • the start of cluster deposition is marked by a sudden increase of current that can not be due to connections between the contacts since the cluster coverage is much too low. It is probably due to ejection of electrons caused by the impact of the clusters on the electrodes. This phenomenon has previously been observed in cluster deposition experiments [17].
  • the cluster coverage is calculated from the deposition rate measured with the thickness rate monitor prior to the deposition, assuming that the clusters are arranged in neat hexagonal patterns with maximum packing. This is clearly unrealistic for thicker films with coverage near and above a monolayer since the cluster film is expected to be very porous i.e. it is expected that the actual thickness of a film is greater than that estimated from the deposition rate monitor. This is confirmed in SEM images of the cluster films, e.g. Figure 14, which shows a very porous structure.
  • the cluster deposition for the sample shown in Figure 13 was turned off as the coverage reached approximately 3.8 monolayers.
  • the conductance through the sample changes slightly after deposition, presumably due to restructuring, oxidation and other processes occurring in the cluster film. These changes are however negligible in comparison to the changes that occur when the chamber is vented and the samples exposed to ambient air, see Figure 16.
  • the resistance of the film increases many orders of magnitude upon contact with air due to fast oxidation of the clusters. The fluctuations at higher resistances are most likely due to noise in the measurement as the current becomes close to the leakage current in our measurement rig.
  • the resistance of cluster films before and after air exposure is shown in Figure 17 for varying cluster thicknesses. As expected the resistance is higher for lower coverage. The resistance increases by approximately one to two orders of magnitude when the films are exposed to air indicating rapid oxidation of the clusters.
  • Figure 18 shows an SEM image taken on a thin layer of tin clusters deposited on a discontinuous film of Pd.
  • the Pd was deposited to a nominal thickness of 0.4nm and formed islands of slightly smaller diameter than the clusters.
  • the Sn clusters are distinguished as brighter spots against the background of darker Pd islands.
  • the deposition of tin clusters on the discontinuous Pd film can be controlled to a high degree by monitoring the current through the film.
  • the current changes nearly exponentially with time and coverage and can be monitored from the very onset of deposition (at 50 seconds in Figure 19) until a thickness corresponding to approximately one monolayer of clusters has been achieved (at 450 seconds).
  • the tin cluster deposition can hence be controlled minutely even at low thicknesses.
  • the Sn cluster / Pd island device reacts similarly as the pure Sn cluster film upon initial air exposure (at 1000 seconds in Figure 19), but with a smaller total change of the resistance and a slight decrease after the initial rapid increase.
  • the Pd islands may enhance the performance of the metal oxide sensors formed.
  • the performance of these sensors is discussed below (in relation to Figure 24).
  • the resistance of the cluster films decreases more than four orders of magnitude when they are baked. Note the difference between diamonds and triangles in Figure 17. This is somewhat counter intuitive since one would expect that the resistance of many oxides, which are insulators, would increase with further oxidation. In the present case the decrease in resistance is likely to be due to formation of a semiconducting oxide material but may also be due to differences in the electrical properties of SnO and SnO 2 or due ⁇ to ripening of amorphous oxides into more crystalline structures.
  • the oxidation can be performed in-situ in the vacuum system, it can be performed at higher temperatures and in pure oxygen and other oxidation processes can be applied such as exposing the cluster films to oxygen plasma.
  • Tin dioxide is one of the most commonly used materials in metal oxide sensors and can be used to detect a wide range of fluids [I].
  • hydrogen is a strong reducing agent for tin dioxide and is readily available. It reacts with surface oxygen on the tin oxide cluster surface forming hydroxyl groups and water. In this process electrons will be released into the conduction band of the tin oxide material decreasing the overall resistance of the cluster film.
  • Pd doped SnO 2 has for example been shown to be very sensitive to carbon monoxide in particular and show similar properties in the presence of this gas as when exposed to hydrogen [22].
  • a flow chamber specially designed for this purpose. It is equipped with pins for measuring the conductivity of the individual sensors on each chip and an inlet and an outlet for gas mixtures.
  • the flow chamber is placed on top of a hot plate capable of reaching 10O 0 C.
  • Two flow controllers are used to mix dry air with the analyte gas.
  • the controllers operate at 90-lOOsccm and 0-lOsccm respectively.
  • the flow chamber has a volume such that the system response time is ⁇ 7-8s for these typical flow rates and so this is the minimum response time that can be measured.
  • FIG. 21 shows the response of a film comprising 4 monolayers of 6.5nm tin oxide clusters to varying hydrogen concentrations in dry air at 8O 0 C.
  • the response is not especially fast or large, which might be expected for undoped SnO 2 sensors, which usually must be operated at higher temperatures (300-400 0 C) in order to show large and fast responses [I].
  • Pd can act as a catalyst to improve the response, the response time and selectivity of metal oxides, see e.g. [6, 22] and references therein.
  • a layer of Pd on top of the cluster film (see Figure 3) after it has been exposed to air and baked for 18 hours at 19O 0 C.
  • the resistance after deposition of lnm Pd (boxes in Figure 17) is higher than the resistance prior to Pd (triangles in Figure 17) for most sensors with more than 2 monolayers of clusters.
  • the increase of resistance indicates that the Pd does not form a continuous layer on the cluster film as this would result in a reduction of the resistance, but is distributed somewhat homogeneously in the very porous cluster film.
  • Figure 22 shows the response of a 4ML thick tin oxide cluster film, modified with lnm Pd, to varying concentrations of hydrogen in dry air at 8O 0 C.
  • the response ' time is greatly reduced and the response has improved dramatically compared with Figure 19.
  • the resistance of the Pd doped film decreases 4 orders of magnitude within 10 seconds when exposed to 5000ppm of hydrogen.
  • the response of the sensor in Figure 22 shows a power-law behaviour (Figure 23) with respect to the hydrogen concentration.
  • Pd doping can be used in combination with our method, e.g. the method described above in which tin clusters were deposited on top of Pd islands (see Figure 4), in-situ or co-deposition by e-beam deposition of Pd on the cluster films while it is still kept in the vacuum system, or doping of the clusters by letting them pass a vapour of Pd on their way from the source to the target.
  • An additional method for providing Pd doping to the cluster film is to use Pd instead of Au in the contacts.
  • Figure 25 shows the ratio of resistances with and without hydrogen as a function of cluster coverage for three different concentrations of hydrogen.
  • the sensors have all been baked at 19O 0 C and covered with lnm Pd. The response of the sensors is clearly dependent on the cluster coverage with the thicker cluster layers responding less than the thinner layers to hydrogen.
  • The. optimum atomic ratio was calculated from the cluster coverage and the optimum Pd thickness to be around 25%. This result indicates that the Pd is relatively homogeneously distributed in the cluster film such that most clusters have similar amount of dopants. Pd that is deposited onto SnO 2 particles is thought to form small clusters, see e.g. [22], and we expect that something similar happens in our films.
  • the Pd thickness should be limited in order to not form metallic current paths through the device.
  • Nanowires have particularly high surface - volume ratios and may provide particularly sensitive sensors. It is a specific embodiment of the invention that templating or other assembly methods are used to promote formation of nanowires. One such method is described further in a subsequent section. Sensor response time versus tin cluster coverage & Pd thickness
  • Figure 27 shows the response time for three cluster films to 5000ppm hydrogen as a function of the amount of Pd that has been added in the stepwise manner described in the previous section.
  • Figure 28 shows the response times of three sensors with a fixed Pd doping level (i.e. 0.8nm), and with different cluster coverages, as a function of hydrogen pressure. The thinnest cluster film is clearly faster than the films with higher cluster coverage.
  • the thinner layer of tin oxide means that any surface effects are felt more strongly, and more quickly, in the interior of the film.
  • Figure 30 shows the resistance of a 4ML tin oxide cluster sensor at 12O 0 C.
  • the sensor has been doped with lnm Pd and is clearly responding to ammonia concentrations as low as 400ppb although the response time is slower than for hydrogen at 8O 0 C.
  • Performing the same experiment at 16O 0 C shows much improved response time and slightly better response (Figure 31 ).
  • the sensor responds to ammonia down to concentrations of lOOppb with nearly 99% change in resistance for 50ppm (Figure 32).
  • nanowires suitable for use as gas sensors, can be created by depositing clusters on patterned substrates.
  • the method for creating the nanowires has already been described in detail in earlier publications [10, 23] and will only be explained briefly here.
  • a Si wafer is KOH etched such that V-shaped grooves running across the substrate are formed, see Figure 5.
  • the V-grooves can be formed such that their length across the substrate is several hundreds of micrometers. Contacts can be formed at the end of the V- grooves, but in this example we will only consider noncontacted V-grooves to show the principle of wire formation.
  • Nanowire formation occurs as the clusters are reflected from the planar surfaces while being collected in the V-grooves.
  • the clusters need to be faster and/or larger than in the experiments described above.
  • the clusters are prepared very similarly with the only difference being that the source is not cooled by liquid nitrogen, but instead kept at room temperature. This has the effect that the clusters grow slightly larger (approximately twice the diameter) in the source and are accelerated to higher velocities by the gas expansion in the source nozzle [12].
  • the grooves can be designed in any way that provides a slanting surface for the clusters to bounce on.
  • the width of the V-groove will lower the uptake area of each groove, but increase the possible groove density on the substrate.
  • the SEM image in Figure 36 shows a tin cluster wire was formed in a 3 ⁇ m wide V-groove by deposition of 15nm clusters. The higher cluster coverage on the flat plateaus indicates that the sample had to be deposited with a larger number of clusters than that in Figure 34 for a wire to form.
  • Sn cluster wires may be baked and doped as the films described above and hence made into very responsive tin oxide sensors.
  • the material usage can be reduced, the response time is expected to be lower due to less reduction of the local pressure during reactive gas loading, the resistance of the device may be increased (thereby reducing power consumption) and / or the surface to volume ratio for the metal oxide material may be increased.

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Abstract

L'invention concerne un procédé de formation d'un dispositif de capteur de fluides comprenant la formation de contacts sur un substrat ; la préparation d'une pluralité d'amas métalliques ; le dépôt des amas sur le substrat entre les contacts ; et l'oxydation des amas pour obtenir un film entre les contacts qui répond à la présence d'un fluide à détecter.
PCT/NZ2008/000120 2007-05-22 2008-05-22 Procédé de préparation de capteurs de fluides d'amas d'oxyde métallique en film mince WO2008143534A1 (fr)

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102009000315A1 (de) * 2009-01-20 2010-08-19 Robert Bosch Gmbh Flüssigkeitssensor
RU2417155C2 (ru) * 2009-01-22 2011-04-27 Закрытое акционерное общество "Объединенная компания высокорискового инновационного финансирования ОК ВИНФИН" Способ получения наноразмерных частиц, наноструктуирования, упрочнения поверхности и устройство для его реализации
CN102602882A (zh) * 2011-01-21 2012-07-25 曾亚东 高速离心式纳米粒子制备法
WO2017117342A1 (fr) * 2015-12-31 2017-07-06 Saint-Gobain Performance Plastics Corporation Substrat fonctionnalisé
CN119000803A (zh) * 2024-10-24 2024-11-22 中国石油大学(华东) 一种养鸡场环境监测系统

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US5989990A (en) * 1995-08-04 1999-11-23 Korea Gas Corporation Tinoxide thin film, preparation thereof, and gas detecting sensor using thereof
JP2002328109A (ja) * 2001-05-02 2002-11-15 Ngk Spark Plug Co Ltd 水素ガス検出素子及びその製造方法
JP2003306319A (ja) * 2002-04-10 2003-10-28 Japan Atom Energy Res Inst 金属酸化物ナノ微粒子の製造方法
DE10260857A1 (de) * 2002-12-23 2004-07-08 Robert Bosch Gmbh Verfahren und Vorrichtung zur Detektion mehrerer Gasbestandteile eines Gasgemisches
JP2005331364A (ja) * 2004-05-20 2005-12-02 Matsushita Electric Ind Co Ltd 水素ガス検知膜及び水素ガスセンサ
WO2006007802A1 (fr) * 2004-07-20 2006-01-26 T.E.M.. Technologische Entwicklungen Und Management Gmbh Detecteur pour detecter des gaz ou des vapeurs present(e)s dans l'air, comprenant une couche active d'oxyde metallique, sensible aux gaz
WO2006121349A1 (fr) * 2005-05-09 2006-11-16 Nano Cluster Devices Limited Capteurs d'hydrogene et leurs methodes de fabrication

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US5989990A (en) * 1995-08-04 1999-11-23 Korea Gas Corporation Tinoxide thin film, preparation thereof, and gas detecting sensor using thereof
JP2002328109A (ja) * 2001-05-02 2002-11-15 Ngk Spark Plug Co Ltd 水素ガス検出素子及びその製造方法
JP2003306319A (ja) * 2002-04-10 2003-10-28 Japan Atom Energy Res Inst 金属酸化物ナノ微粒子の製造方法
DE10260857A1 (de) * 2002-12-23 2004-07-08 Robert Bosch Gmbh Verfahren und Vorrichtung zur Detektion mehrerer Gasbestandteile eines Gasgemisches
JP2005331364A (ja) * 2004-05-20 2005-12-02 Matsushita Electric Ind Co Ltd 水素ガス検知膜及び水素ガスセンサ
WO2006007802A1 (fr) * 2004-07-20 2006-01-26 T.E.M.. Technologische Entwicklungen Und Management Gmbh Detecteur pour detecter des gaz ou des vapeurs present(e)s dans l'air, comprenant une couche active d'oxyde metallique, sensible aux gaz
WO2006121349A1 (fr) * 2005-05-09 2006-11-16 Nano Cluster Devices Limited Capteurs d'hydrogene et leurs methodes de fabrication

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102009000315A1 (de) * 2009-01-20 2010-08-19 Robert Bosch Gmbh Flüssigkeitssensor
RU2417155C2 (ru) * 2009-01-22 2011-04-27 Закрытое акционерное общество "Объединенная компания высокорискового инновационного финансирования ОК ВИНФИН" Способ получения наноразмерных частиц, наноструктуирования, упрочнения поверхности и устройство для его реализации
CN102602882A (zh) * 2011-01-21 2012-07-25 曾亚东 高速离心式纳米粒子制备法
WO2017117342A1 (fr) * 2015-12-31 2017-07-06 Saint-Gobain Performance Plastics Corporation Substrat fonctionnalisé
CN119000803A (zh) * 2024-10-24 2024-11-22 中国石油大学(华东) 一种养鸡场环境监测系统

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