Materials containing layers of self-organized one-dimensional ZnO crystallites

Abstract

The present invention relates to a multilayer material comprising a solid substrate at least partially covered with a textured α-quartz buffer layer (100), where the crystallographic direction [100] of the α-quartz is parallel to the crystallographic direction [100] of silicon (100); and a layer of one-dimensional epitaxial ZnO crystallites (110) (or epitaxial ZnO microwires) on said α-quartz buffer layer (100), where said crystallites are self-organized. The present invention also relates to a method for producing such a multilayer material and its industrial use in various technical fields.

Description

[Technical field]

[0001] The present invention relates generally to the production of self-assembled one-dimensional microcrystalline layers of (110) ZnO epitaxially grown on solid supports to form materials and various applications of such materials, especially in the fields of catalysis, electronics, and photonics. [Background technology]

[0002] Zinc oxide, with the chemical formula ZnO, is one of the most studied semiconductor materials in the world due to its unique properties and many applications. In bulk, zinc oxide is a transparent material with a refractive index of 2. It is a large-gap n-type semiconductor, and its natural electrical conductivity is due to interstitial zinc atoms and oxygen vacancies. It has a direct wide band gap of 3.37 eV at room temperature. When doped with aluminum or magnesium, zinc oxide has a significant improvement in its electrical conductivity while maintaining its transparency as well as its chemical and thermal stability (Ref. 1). It has therefore been proposed as a suitable material for the fabrication of transparent conductive electrodes in photovoltaics (Ref. 2) and as a natural replacement for indium tin oxide (ITO) in the anodes of liquid crystal displays and organic light-emitting diodes (Ref. 3). Moreover, ZnO has excellent photocatalytic and catalytic activity (Ref. 4), especially in the form of mesocrystals (Refs. 5, 6), and in the form of nanowires has shown high sensitivity for gas detection (Ref. 7).

[0003] Zinc oxide ZnO can crystallize in three main structures: zinc blende, rock salt and wurtzite. The wurtzite structure, which belongs to the hexagonal reticulated crystal system, is the most thermodynamically stable and therefore the most common. In said form, the lattice parameters of ZnO are: a=b=3.25 angstroms; c=5.20 angstroms; α=β=90° and γ=120°.

[0004] Zinc oxide ZnO in the wurtzite form exhibits spontaneous polarization along the hexagonal <0001> direction due to the non-centrosymmetric nature of the zinc and oxygen tetrahedra forming ZnO, which induces remarkable piezoelectric, thermoelectric, optical and catalytic properties. Such polar direction contains the thermodynamically most stable planes, so the preferred orientation of ZnO crystals usually observed in thin films corresponds to the texture (0001). Such preferred orientation along the polar axis and the piezoelectric properties of ZnO make it an ideal material for the manufacture of energy harvesters due to its piezoelectric properties (Ref. 8). There is also strong interest in exposing the ZnO surface associated with its non-polar (or prismatic) facets. In fact, it is possible to improve the catalytic performance of ZnO in synthetic reactions such as the hydrogenation of CO2 to form methanol (Ref. 9) and the photodegradation of pollutants and dyes (Ref. 4). Furthermore, ZnO has other interesting properties, such as its nonlinear optical activity, its luminescence in multiple wavelength regions that depend on the temperature at which the ZnO is annealed (Ref. 10), and in particular its optically stimulated luminescence (OSL) properties (Ref. 11).

[0005] Therefore, there is considerable interest in developing accessible synthetic methods to achieve control of crystal orientation and anisotropy in ZnO thin films, powders, and nanostructures, which are highly useful for a variety of applications.

[0006] Various methods have already been proposed for the preparation of zinc oxide ZnO, such as chemical vapor deposition (CVD) under vacuum using gold as a catalyst (Reference 12). Among these methods, the only conventional method for the preparation of ZnO nanostructures is hydrothermal synthesis (Reference 13), which involves the growth of one-dimensional ZnO nanocrystals on a polycrystalline seed layer, as described in the scientific publication "Effect of ZnO Seed Layer on the growth of ZnO Nanorods on Silicon Substrate" by Toea et al. (Reference 14). This method can only be used for vertical and textured growth of ZnO nanowires and microwires along the polar axis (whose longitudinal axis is outside the plane of the substrate) on different technological substrates, but not for direct heteroepitaxy of different orientations on silicon substrates (References 15, 16).

[0007] The problems outlined above have motivated investigations aimed at the growth of nonpolar planes in ZnO thin films and nanostructures. Research has focused on the use of substrates with different symmetries and the interfacial confinement between the substrate and ZnO (Refs. 17-24).

[0008] However, none of the above mentioned methods can be easily used to achieve self-organization of epitaxially grown planar ZnO one-dimensional crystallites (with their long axes parallel to the plane of the substrate) on silicon with a perfectly controlled single orientation without the use of a catalyst, seed layer or vacuum. Summary of the Invention

[0009] To address the above-mentioned problems, the applicant has developed a multi-layer material comprising: - a solid support at least partially coated with a buffer layer of textured (100) α-quartz, the

[0100] crystallographic direction of the α-quartz being parallel to the

[0100] crystallographic direction of the silicon (100); and - A layer of epitaxially grown (110)ZnO one-dimensional microcrystals (or epitaxially grown ZnO microwires) on the buffer layer of said (100)α-quartz, wherein said microcrystals are self-organized.

[0010] The self-organized microcrystals defined by the present invention refer to microcrystals that are arranged such that their longitudinal axes are located in an average plane parallel to the plane of the quartz buffer layer and are oriented along two mutually perpendicular directions defined by the quartz layer.

[0011] In a specific embodiment of the present invention, the α-quartz buffer layer can include a controlled crystallization in which the growth of ZnO microwires is carried out to control the density and distribution on the silicon substrate.

[0012] Advantageously, the thickness of the epitaxially grown (110)ZnO one-dimensional microcrystals can be from 30 nm to 1.5 μm, and preferably on the order of 750 nm.

[0013] Advantageously, the length of the epitaxially grown (110)ZnO one-dimensional microcrystals can be from 5 nm to 30 μm, and preferably on the order of 11 μm.

[0014] As the solid support, for the materials of the present invention, it is advantageously possible to use a solid support made of a material selected from silicon, solid quartz, mica, corundum, germanium dioxide, magnesium oxide, strontium titanate SrTiO3, LaAlO3, lithium niobate, lithium tantalate, cerium oxide, Ce (1-x) Gd x Gadolinium cerium mixed oxide with O2 where x is 0 < x < 1, lanthanum aluminate, gallium nitride, yttrium-doped zirconium dioxide, and gallium orthophosphate.

[0015] Preferably, a solid support of single-crystalline silicon (100) is used as the solid support.

[0016] Advantageously, the crystallites form a textured microstructure leading to a surface roughness of 50-500 nm.

[0017] Advantageously, the epitaxially grown (110) ZnO one-dimensional crystallites can cover at least 40% of the surface of the (100) α-quartz buffer layer of said solid support, said surface coverage being advantageously greater than 40% of the surface of said buffer layer and can reach up to 90% of said surface.

[0018] Due to the intrinsic piezoelectric, optical, fluorescent and catalytic properties of ZnO, as well as the possibilities offered by the manufacturing method of the invention that serve to synthesize ZnO in the form of planar microwires on a substrate, the multilayer material of the invention can be used in several technical fields of industry.

[0019] Thereby, when the multilayer material of the invention comprises a solid support of mono-oriented crystalline silicon (100), a subject of the invention is the use of the multilayer material of the invention in an electronic device selected from MEMS, electromechanical materials, piezoelectric components, energy harvesters, photodetectors, mechanical wave specific filter oscillators, mechanical wave to electromagnetic wave converters, acceleration and angular velocity sensors, mass sensors or gas sensors.

[0020] If the solid support multilayer material of the invention is not necessarily mono-oriented crystalline silicon (100), a further subject of the invention is the use of the multilayer material of the invention for: - the production of waveguides in the visible range (thereby taking advantage of the nonlinear optical and fluorescent properties of ZnO), or - the preparation of supported catalysts in the presence or absence of precious metals, or - As an epitaxial template: the crystallinity of ZnO synthesized by the method of the present invention enhances the epitaxial growth of specific crystals while maintaining the same original morphology.

[0021] If the solid support multilayer material of the present invention is not necessarily a single oriented crystalline silicon (100), a further subject of the present invention is the use of the multilayer material of the present invention for the manufacture of transparent conductive electrodes and electronic devices using transparent conductive electrodes. More particularly, such electrodes can be used for the manufacture of various electronic devices in which transparent microelectrodes of controlled size are required, such as photovoltaic cells.

[0022] Nevertheless, for such applications it is preferred that the solid support be made of single oriented crystalline silicon (100).

[0023] A further subject of the invention is a microelectromechanical system in the form of a piezoelectric resonant membrane comprising the multilayer material of the invention.

[0024] Finally, a further subject of the invention is a method for producing a multilayer material according to the invention, comprising the following steps: A) preparing a buffer layer of textured (100) α-quartz at least partially covering a solid support to form a substrate for epitaxial growth of ZnO crystallites (110); B) preparing a first composition comprising a solvent and at least one ZnO precursor; C) preparing a second composition consisting of an aqueous solution of at least one heterocyclic organic compound having a diamond cage structure; D) gradually adding the second composition to the first composition under stirring and then maintaining the mixture under stirring for at least 10 minutes to obtain a reaction mixture; E) preparing the surface of a buffer layer using the second composition prepared during step C) or the reaction mixture prepared during step D) by placing the substrate in a closed hydrothermal reactor at a temperature of at least 60° C. and a pressure of at least 1 bar for at least 15 minutes; F) washing the buffer layer with an acid solution; G) a heat treatment step for epitaxial growth of ZnO crystallites by placing the substrate and the reaction mixture on the substrate in a closed hydrothermal reactor at a temperature of at least 60° C. and a pressure of at least 1 bar for at least 15 minutes; then H) A post-growth washing step with demineralized water and then with ethanol in order to dry the multilayer material thereby obtained.

[0025] Step A) consists in producing a buffer layer of textured (100) α-quartz at least partially covering the solid support to form a substrate intended for the epitaxial growth of (110) ZnO crystallites. Preferentially, such a step can be carried out by a method such as that described by WO 2014 / 016506.

[0026] According to the invention, it is essential that the step of growing ZnO microwires is carried out on a buffer layer in the form of α-quartz. Indeed, the presence of a surface of monocrystalline α-quartz induces the nucleation and growth of one-dimensional crystallites of ZnO along a single crystallographic direction corresponding to the epitaxial relationship. In other words, the quartz layer has the role of a nucleation surface where the growth of ZnO is enhanced along an orientation with similar symmetry and similar distances between the atomic columns. The result is a layer based on one-dimensional crystallites based on a single orientation of ZnO with controllable thickness, length, density and nanostructure.

[0027] During step B of preparing the first composition, as ZnO precursor, it is advantageous to use a zinc salt selected from the nitrates, sulfates, carbonates, hydroxides, chlorides, acetates and oxides. Zinc nitrate is preferentially used, and even better Zn(NO3)2·6H2O, present in said first composition in a proportion of 0.1 M.

[0028] As solvent water, alcohol or water-alcohol mixtures can typically be used.

[0029] During step C of preparing the first composition, hexamethylenetetramine (HMTA) having the formula (CH2)6N4 (preferentially present in a molar concentration of 0.1 M) can be advantageously used as the heterocyclic organic compound comprised in the second composition. Advantageously, one or more additives selected from a pH control agent (for example HCl), a structuring or modifier or a porosity promoter such as a polymer, a quaternary ammonium and urea can be added to the second composition.

[0030] The second composition is then gradually charged into the first composition under stirring (Step D), followed by maintaining the mixture under stirring for at least 10 minutes to obtain a reaction mixture.

[0031] Such step D) is followed by a step E) of preparing the surface of the buffer layer using the second composition prepared during step C) or the reaction mixture prepared during step D) by placing said substrate for at least 15 minutes in a closed hydrothermal reactor at a temperature of at least 60° C. and a pressure of at least 1 bar. The reaction mixture prepared during step D) is preferentially used for such purpose. The heterocyclic organic compound contained in the second composition or reaction mixture (preferentially HMTA) can then be complexed with the strontium used during step A) of preparing the buffer layer (see the teaching of WO 2014 / 016506).

[0032] The surface preparation step E) is followed by a step F) of cleaning the buffer layer with an acid solution in order to remove any surface contamination.

[0033] Step F) can be advantageously carried out using an acid solution to remove Zn residues, preferentially comprising 1 volume of hydrogen peroxide and 4 volumes of sulfuric acid. A hydrochloric acid solution can also be used for such purposes.

[0034] Then, step G) of heat treatment for epitaxial growth of ZnO microcrystals is carried out by placing the substrate (formed during step A) with a solid support covered with a buffer layer of textured (100) α-quartz and the reaction mixture on the substrate obtained during step D) in a closed hydrothermal reactor at a temperature of at least 60° C. (advantageously between 60° C. and 200° C., preferentially 95° C.) and a pressure of at least 1 bar for at least 15 minutes. The holding time of step G) can be chosen depending on the length and width of the epitaxially grown ZnO microwires to be achieved, both of which are more pronounced the longer the holding time of the heat treatment step. Thereby, by way of example, to obtain a length of the order of 11,000 nm and a width of the order of 1,300 nm at 95° C., the holding time of the heat treatment step should be of the order of 125 minutes (as shown in FIG. 3). Furthermore, the density of the ZnO microwires epitaxially grown on the buffer layer of the solid support also depends on the temperature used in the heat treatment step F) (shown in FIG. 4) and on the continuity of the α-quartz buffer layer until the completion of step A).

[0035] In fact, during step G), the substrate is advantageously immersed in the reaction mixture, taking care not to exceed three-quarters of the volume of the reactor. Advantageously, the substrate is placed in the reactor, making sure that a buffer layer is placed at the bottom so that the ZnO precursor powder (coming from the reaction mixture) does not deposit on the surface of the substrate.

[0036] Finally, a heat treatment step G) for the epitaxial growth of ZnO crystallites is followed by a post-growth cleaning step H) in demineralized water and then in ethanol for optimized drying of the sample.

[0037] Steps G) and H) are repeated at least once, preferentially at least twice on the same substrate: for example, a first cycle (comprising steps G) and H)) is used to remove excess catalyst (in particular comprising strontium, as taught by WO 2014 / 016506), followed by an acid attack to thoroughly clean the surface of the layer; then at least a second cycle is carried out for the crystallization and formation of ZnO microwires.

[0038] Such a method has the advantage of mild sol-gel chemistry. More specifically, the method is easy, cheap and short to perform. The method can be used to obtain epitaxially grown (110) ZnO self-organized one-dimensional crystallites (or epitaxially grown ZnO microwires) with high yield and with full control of the orientation, self-organization, length, width, density and nanostructure (presence of homogeneous porosity that is controllable) of the epitaxially grown ZnO microwires. The method of the present invention is also very flexible from a chemical point of view in that the mosaicity of the α-quartz buffer layer can be modified to some extent to control the degree of orientation of the resulting material (as shown in Figures 1 and 2, which represent the control of the orientation of ZnO by controlling the mosaicity of the α-quartz buffer layer). Finally, an additional advantage of the method of the present invention is the use of wet process deposition, which makes the method compatible with micro- and nano-fabrication techniques such as nanoimprint lithography.

[0039] A further subject of the invention is a method for nanostructuring the multilayer material of the invention by controlled chemical etching using an acid solution.

[0040] Other advantages and characteristics of the invention arise in connection with the following description, the accompanying figures and examples, given by way of example and without limitation. [Brief description of the drawings]

[0041] The following examples illustrate the invention with reference to the figures discussed herein, but are not intended to limit the scope of the figures. [Figure 1] Figure 1 shows the angle of misorientation of the material resulting from the mosaicity of the α-quartz buffer layer (curve a) and the change in the mosaic structure and crystal quality of the quartz (100) layer and the ZnO (110) microwires (curve b). [Diagram 2] Figure 2 shows the correlation between the mosaic structure and crystal quality of the quartz layer (100) and the ZnO microwires (110) from X-ray diffraction data. [Diagram 3] FIG. 3 includes two empirical curves that represent the change in length (left curve) and width (right curve) as a function of time of epitaxially grown ZnO microwires synthesized on an α-quartz buffer layer according to the method of the present invention. [Figure 4] FIG. 4 includes an empirical curve showing the variation in density as a function of temperature for epitaxial ZnO microwires synthesized on an α-quartz buffer layer according to the method of the present invention, as well as five SEM images of the epitaxial ZnO microwires used to plot the curve. [Diagram 5] Figure 5 shows two XRD diffractograms (b) (intensity in arbitrary units as a function of the angle 2θ in degrees) related to the structural study of the quartz layer, 2D and 1D. The additional figure inserted in part b) shows the analysis of the mosaicity of a ZnO microwire layer with a mosaicity of 1.3°. Figure 5c shows a pole figure: quartz (100) 2θ = 20.8° and a 3D representation of the orientation and relationship of two crystallographic domains of an epitaxial quartz layer on silicon. [Figure 6] FIG. 6 relates to the study of the microstructure of the quartz layer by optical microscopy (a), SEM (b and d) and AFM (c). [Figure 7]Figure 7 relates to the structural study of the ZnO microwire layer: a) two-dimensional XRD diffractogram (intensity in arbitrary units as a function of the angle 2θ in degrees); b) analysis of the mosaicity of the ZnO microwire layer showing a mosaicity of 2.5°; c) SEM image showing the microstructure of the ZnO microwire and the two crystallographic domains; d) Pole figure: ZnO(110)2θ=56.7° and 3D representation of the orientation and relationship of the two crystallographic domains of the ZnO microwire layer on an α-quartz layer epitaxially grown on silicon; e) MET image of two ZnO microwires (crystallographic domains 1 and 2) on a quartz layer on a silicon substrate; f) High resolution MET image of the cross section of a ZnO microwire on a quartz layer on a silicon substrate oriented along the crystallographic direction [1-10]; f) Crystallographic model representing the HRTEM image with the

[0110] ZnO(110) / /

[0100] *α-quartz(100) epitaxy relationship between the ZnO microwire and the α-quartz layer. [Figure 8] FIG. 8 relates to the microstructural study of the ZnO microwire layers, including analysis of the crystallite size characterized by using optical images (a), SEM (b and c) and AFM (d and e). [Figure 9] Figure 9a shows chemical analysis by EDS highlighting the zinc and oxygen elemental composition of the ZnO microwires, Figure 9b shows the light-guiding ability of the ZnO crystallites using optical microscopy, and Figure 9c shows the fluorescent activity of the ZnO microwires. [Figure 10] FIG. 10 is an illustration known to those skilled in the art showing a cycle for catalytic conversion of CO2 to methanol when hydrogen is obtained from a source that does not contain CO2. [Figure 11] FIG. 11 is a calibration curve of CO during catalytic conversion of CO to methanol (Example 2). [Figure 12] FIG. 12 is a calibration curve of CO2 during catalytic conversion of CO2 to methanol (Example 2). [Figure 13] FIG. 13 is a curve of methanol during catalytic conversion of CO2 to methanol (Example 2). [Figure 14]FIG. 14 shows the change in STY of the material of Example 1 used as a catalyst during the catalytic conversion of CO2 to methanol, and a comparison of the change in STY of a commercial catalyst (CatCom) under different conditions (Example 2). [Figure 15] FIG. 15 shows the correlation between methanol conversion and selectivity (Example 2). [Figure 16] FIG. 16 relates to the structural study of the ZnO microwire layers (a and b), including respectively the 2D and 1D XRD diffractograms (intensity in arbitrary units as a function of the angle 2θ in degrees) (inset image) and the analysis of the mosaicity along the crystallographic direction

[0110] of the obtained ZnO microwire layers. [Figure 17] FIG. 17 relates to the microstructural study of the ZnO microwire layers, where the crystallite size analysis is characterized by optical images (a), SEM (b and c) and AFM (d and e). [Figure 18] FIG. 18 (corresponding to Example 4) shows the use of the catalyst obtained in Example 4 as a low-frequency energy harvester (61 Hz). [Figure 19] FIG. 19 (corresponding to example 5) shows a microelectromechanical system (MEMS) based on epitaxially grown ZnO microcrystals in the form of a piezoelectric resonator film with a surface area of ​​1 mm2, 4 mm2, 9 mm2 and 16 mm2, which, after etching, makes it possible to obtain a film with a thickness of 1 μm capable of diffusing light (red squares 10a and 10b), and also shows the vibration spectrum of a (MEMS) comprising epitaxially grown ZnO microcrystals as a piezoelectric resonator film with a surface area of ​​9 mm2 (10c). [Figure 20]Figure 20 includes a graph showing the increase in STY value with the degree of chemical attack and low magnification SEM images (20a) and MET images (20b) of ZnO-on-quartz samples subjected to different degrees of attack with HCl concentrations: 0.37, 0.75, 1.48 and 2.94, as well as a high magnification SEM image (20c) of the cross section of a ZnO microwire along the crystallographic direction (001) after etching with dilute 2.94 mM aqueous HCl for 5 minutes under ultrasound. Figures 1-4 are described in the preceding description section, while Figures 5-20 are described in more detail along with the following examples to illustrate the invention without limiting its scope. EXAMPLES

[0042] The following details the nature of the products, the reactor and method used to prepare the ZnO crystallites, and the characterization methods.

[0043] Products and raw materials: - 98% Tetraethoxyorthosilane (TEOS), sold by Sigma-Aldrich; - Ethanol (EtOH), - Ultra pure water. - Hydrochloric acid (HCl), sold by Sigma-Aldrich; - Strontium chloride (SrCl2·6H2O), sold by Sigma-Aldrich; - Zinc nitrate (Zn(NO3)2·6H2O), sold by Sigma-Aldrich; - Hexamethylenetetramine (HMTA)(CH2)6N4, sold by Sigma-Aldrich; - polyethylene glycol hexadecyl ether sold under the name Brij-58® by Sigma-Aldrich; - Sulfuric acid (H2SO4), sold by Sigma-Aldrich; - Hydrogen peroxide (H2O2), sold by Sigma-Aldrich.

[0044] Equipment and tests for structural and microstructural characterization

[0045] To evaluate the formed fluoride layers, a complete physical and chemical characterization was carried out using complementary techniques at different scales, using: - A digital optical microscope sold by KEYENCE under the trade name VHX7000; - a field emission scanning electron microscope (SEM-FEG) sold by Hitachi under the name SU6600; - Atomic Force Microscope (AFM) sold by Veeco under the name MULTIMODE; - A copper 1.54056 angstrom diffractometer sold under the name GADDS D8 by Bruker assembly; - a high-resolution transmission electron microscope sold by FEI under the trade name TITAN (hereinafter referred to as METHR); - Chemical analysis by EDS (Energy Dispersive X-ray Spectroscopy); - Zeiss LSM880 confocal microscope with 63X / 1.4 lens - 405nm Diode Laser - Airyscan detector (GaAsP 32 channel photomultiplier array detector (PMT)); - ImageJ software. - 3 / 4D image analysis software sold under the name Imaris by Oxford Instruments; - Gas chromatograph Agilent 7890B equipped with a 25-meter CarboPlot P7 column and a TDC detector; - Gas chromatograph with flame ionization detector (GC-FID);

[0046] Example 1: Preparation of a first example of a multi-layer material according to the invention.

[0047] Preparation and characterization of α-quartz buffer layer (Step A)

[0048] The preparation is carried out based on the teachings of WO 2014 / 016506 as shown below.

[0049] Prepare a precursor solution with the following initial composition (in moles): 1 TEOS, 0.3 Brij-58, 25 EtOH, 0.7 HCl, 0.05 SrCl 6H O.

[0050] The precursor solution of the buffer layer 21 was deposited on a silicon Si(100) substrate 2 with a thickness of 100 μm and a surface area of ​​2 cm×6 cm. The silicon substrate 2 used contained a native SiO2 layer with a thickness of 2.2 nm. The precursor solution was deposited on the substrate by centrifugal coating at a speed of 1500 rpm for 30 seconds at room temperature.

[0051] After deposition of the precursor solution, the silicon substrate 2 was subjected to a heat treatment in a tube furnace under air and atmospheric pressure to strengthen the silica layer: a direct soak at 450° C., followed by a 5 min hold at 450° C. At the end of the treatment, a silicon support (100) was obtained, coated with an amorphous silica precursor layer of α-quartz.

[0052] The silicon substrate thereby obtained was then subjected to a second heat treatment in a tube furnace under air at 12 L / min: a direct 980° C. soak followed by a 980° C. hold for 5 min.

[0053] The furnace was then switched off and the substrate was cooled to 25° C. at a rate of 3° C. / min.

[0054] At the end of cooling, a silicon substrate (100) coated with an α-quartz layer 21 was obtained and then characterized. The results of the structural and microstructural study of the obtained α-quartz layer are shown in Figures 5 and 6, respectively.

[0055] Figures 5a and 5b show the XRD diffractograms (intensity in arbitrary units as a function of the angle 2θ in degrees) and the mosaicity of the resulting quartz layer. The XRD analysis shows that the quartz is textured (100) with the crystallographic direction of α-quartz

[0100] parallel to the crystallographic direction of silicon (100)

[0100] . Figure 5c shows the pole figure of α-quartz (100) 2θ = 20.9° associated with the reflection of the α-quartz face (100), confirming that the latter is indeed epitaxially grown and showing the presence of two quartz domains oriented at 90° to each other. The bottom figure of Figure 5c shows a model of a three-dimensional representation of the orientation and relationship of the two crystalline domains of a dense layer of α-quartz epitaxially grown on silicon.

[0056] The optical images in Figure 6 show the continuity of the α-quartz layer 21 (Figure 6 a, b and c) obtained with a roughness (RMS = 30 nm) determined using an atomic force microscope (usually known by the acronym AFM) sold by Veeco. The thickness of the layer is characterized by a field emission scanning electron microscope (SEM-FEG) image using a Hitachi SU6600 SEB, showing a thickness of 180 nm (Figure 6 d).

[0057] Preparation and characterization of ZnO microwires (steps B) to F)

[0058] The growth of ZnO microwires 3 on an α-quartz buffer layer 21 was carried out by hydrothermal synthesis at low temperature and pressure. Such conditions allow the use of different types of glass (Pyrex) or Teflon reactors, making the invention affordable, cheap and feasible for large-scale implementation.

[0059] First, the molar concentration C Zn = A 0.1 M aqueous solution of zinc nitrate hexahydrate, Zn(NO3)2·6H2O (Step B), was prepared.

[0060] In parallel, molar concentration C HMTA = A 0.1 M solution of hexamethylenetetramine (HMTA) ((CH2)6N4) in water (Step C) was prepared.

[0061] The HMTA solution was then rotated at 450 rpm -1 The zinc nitrate solution was added dropwise with a pipette while stirring at RT. The mixture was then stirred for 10 min (Step D). The buffer layer was then washed (Step E).

[0062] Epitaxial growth of ZnO microwires 3 was carried out on the surface of a quartz epitaxy layer (100) on a silicon substrate (Si(100) (dimensions: thickness 100 μm and surface area 2 cm × 6 cm) by hydrothermal synthesis at 95 °C and a pressure of about 210 kPa (2.1 bar) for 300 min (step F). This step was performed at least twice. - The first cycle was carried out to remove the excess Sr catalyst on the surface, which was used during the crystallization of the α-quartz buffer layer. - The samples were washed with a mixture of sulfuric acid and hydrogen peroxide in a ratio of 4:1 to remove any ZnO residues resulting from the first cycle. - A second cycle was necessary for the actual crystallization and formation of the ZnO microwires.

[0063] The new epitaxy between the ZnO and the α-quartz buffer layer 21 was determined by X-ray diffraction using a diffractometer.

[0064] Figures 7a and 7b show the XRD diffractograms (intensity in arbitrary units as a function of the angle 2θ in degrees) of the obtained layer 3 containing ZnO microwires and the mosaicity mentioned above. The XRD analysis shows that the ZnO is textured (110) with the crystallographic direction of α-quartz

[0110] parallel to the crystallographic direction

[0100] of the quartz (100) and the silicon substrate (100). Figure 7b shows a mosaicity of 2.5°. The SEM image in Figure 7c shows the microstructure of the ZnO microwires 3 and the two possible crystallographic regions. Figure 7d shows the pole figure with ZnO (110) 2θ = 56.7°. The pole figure with 2θ = 56.7° associated with the reflection of the (110) plane of ZnO confirms that the ZnO is indeed epitaxially grown and further shows the presence of two ZnO regions oriented at 90° to each other, similar to the quartz regions. The bottom part of Fig. 7d shows a model representing two crystallographic domains in three dimensions, together with the orientation and epitaxial relationship between the layer 3 of ZnO microwires and the dense layer 21 of α-quartz. The ZnO microwires grow according to the relationship 0110 ZnO(110) / / 0100 * α-quartz(100) / / 0100 * Si(100) and are located on two domains of quartz. Such results show for the first time the heteroepitaxy of ZnO(110) microwires on silicon 2 at temperatures below 100 °C by using an inexpensive chemical solution deposition method that can be carried out on a large scale. Fig. 7e shows a low-magnification MET image in bright field mode of a cross section of two ZnO microwires (crystallographic domains 1 and 2) in a quartz layer on a silicon substrate oriented along the crystallographic direction (100). Figure 7f shows a high-resolution image in bright-field mode of the cross section of ZnO microwires in a quartz layer on a silicon substrate oriented along the crystallographic direction [1-10] (refs. 1-10). The METHR analysis confirms the results obtained by XRD, in particular the epitaxial relationship of

[0110] ZnO(110) / /

[0100] *α-quartz(100) between the ZnO microwires and the α-quartz layer, as well as the texture of the ZnO(110) microwires 3 (see the crystallographic model shown in Figure 7g).

[0065] Microstructural analysis and dimensional measurements of the microwires were performed by optical microscopy and field emission scanning electron microscopy. The microstructural analysis shows that the multilayer material of the invention obtained at the end of the two cycles comprises a support composed of a layer of quartz (100) on silicon (100) coated with a layer containing ZnO microwires (110), as shown in FIG.

[0066] Figure 8 shows the results of a topographical and microstructural study of the ZnO microwire layer 3 obtained by using optical microscopy (Figure 8a) and SEM (Figures 8b and 8c). The crystal size and layer continuity are characterized by SEB and AFM images (Figure 8d). The obtained layer is 70% covered with ZnO crystals with a length of 11,000 nm, a width of 1,400 nm and a height of 750 nm. The distribution of the microwires is completely uniform over the entire sample surface.

[0067] The detailed characterization of the ZnO microwires is explained in more detail in Figure 9 . - Figure 9a shows the EDS chemical analysis revealing the zinc and oxygen elemental composition of the ZnO microwires. - Figure 9b shows the light guiding ability of ZnO crystallites using optical microscopy. - Figure 9c shows the extraordinary fluorescent activity of ZnO microwires.

[0068] The images in Figure 9 were acquired on a Zeiss LSM880 confocal microscope with a 63X / 1.4 lens. The excitation light source used was a 405 nm diode laser, with wavelength emission tuned to 552 nm providing maximum photon collection with a 495-550 nm bandpass filter. Multidimensional scans were acquired via an Airyscan detector (GaAsP 32 channel tube array detector (PMT) photomultiplier tube). 3D images were acquired by taking z-images every 0.18 μm. 2D images were produced by taking z-projections of the z-stacks with ImageJ software. 3D renderings of the z-stacks were produced with the image analysis software 3 / 4D Imaris (Oxford Instruments).

[0069] Example 2: A first example of application of the multilayer material 1 of the present invention obtained in Example 1 to a catalytic reaction.

[0070] Methanol is a potential liquid energy or hydrogen carrier and is also an important feedstock for producing basic chemicals and key chemical intermediates. The catalytic conversion of CO2 to methanol has been considered a highly desirable method in a sustainable methanol-based economy, as it is also an important approach for greenhouse gas mitigation when hydrogen is obtained from CO2-free sources (see Figure 10).

[0071] Supported copper materials (e.g., Cu-ZnO, Cu-ZrO2, and Cu-ZnO-ZrO2) have proven to be promising catalysts for such transformations due to their high performance (Ref. 25).

[0072] This example aims to demonstrate the catalytic properties of a layer 3 comprising (110) ZnO nanowires epitaxially grown on a buffer layer 21 comprising (100) quartz on a substrate 2 of (100) silicon, such as the layer obtained in example 1, during the CO2 to methanol conversion process.

[0073] It is shown below that the yield of the new catalyst 1 for the conversion of CO2 to methanol is 30 to 50 times higher than the best commercial catalyst available to date, with 100% selectivity.

[0074] A catalyst of the invention based on (110)ZnO / (100)quartz / (100)Si (multilayer material obtained in example 1) was tested using 107 μg of ZnO in a quartz layer on a silicon substrate.

[0075] methodology

[0076] The catalyst of the invention (multilayer material 1 obtained in Example 1) was placed in a fixed bed reactor or a plug flow reactor. H2 and CO2 were sent to the reactor. The catalytic reaction produced methanol and sometimes carbon monoxide CO (depending on the selectivity of the catalyst). Gas analysis was carried out at the outlet, which was entrained by a flow of N2.

[0077] First, the temperature was increased to 160°C at a rate of 5°C / min, and simultaneously, a mixture of CO2 and H2 was fed into the reactor at a rate of 10 ml / min at a pressure of 5 bar with a theoretical ratio of 1:3. Once the desired conditions were reached, the system was allowed to stabilize for 30 minutes. Then, a sample was taken using a sampling bag to reduce the pressure of the gas after the reaction. The catalytic properties of the sample (110)ZnO / (100)Quartz / (100)Si were then compared with a high-performance commercial catalyst with the following composition: 10.1%Al2O3, 63.5%CuO, 24.7%ZnO and 1.3%MgO (by ALPHA AESAR).

[0078] The same procedure was carried out with the commercial catalyst, where 0.025 mg of catalyst was deposited in the reactor in powder form.

[0079] Table 1 below shows the catalytic conditions tested: [Table 1]

[0080] After each change in the system conditions, the reaction was allowed to stabilize for 20 min. An Agilent 7890B series gas chromatograph equipped with a 25 m CarboPlot P7 column and a TDC detector was used to analyze the CO2 and CO contents after the reaction.

[0081] Calibration of CO (see FIG. 11) was performed using pure CO for concentrations above 1% by volume and a mixture of 1% CO in N2 for concentrations below 1% by volume, giving a detection limit of 0.1% by volume.

[0082] The methanol concentration of the gas leaving the reactor was also analyzed using FID chromatography to calculate the methanol concentration in the resulting gas. Such results are then used to calculate the space-time yield (STY), which gives the amount of methanol obtained per gram of catalyst used in the catalytic test. The methanol calibration (see Figure 13) was performed using a technique called the "Marriott bottle". Methanol was placed in a flask and various amounts of the bottle heads, containing evaporated methanol, were analyzed using FID gas chromatography.

[0083] The conversion and selectivity of the tested catalysts were calculated using the following equations:

[0084]

number

[0085]

number

[0086]

number

[0087] X CO20 is the initial CO2 concentration (without catalytic reaction), X COi is the CO concentration under each set of conditions, and X MeOHi represents the methanol concentration under each set of conditions.

[0088] The space-time yield, STY, was calculated using the following formula:

[0089]

number

[0090] M MeOH is the molecular weight of methanol (32.04 g / mol), T is the temperature, Pa is the atmospheric pressure, and GHSV is L / (g cath) is the hourly space velocity.

[0091] result

[0092] The catalyst comparison results after preparation of the quartz buffer layer 21 and preparation of the ZnO microwires 3 are shown in FIG.

[0093] Figure 14 shows that the ZnO nanowire catalyst has a significantly higher STY than the commercial catalyst. As expected, the STY of the commercial catalyst increases from 160 to 240 °C, but decreases after the latter value. Moreover, increasing the pressure increases the amount of methanol produced at low temperatures.

[0094] For layer 3 of epitaxially grown nanowires of ZnO (catalyst designated ZnO-1), the STY is observed to increase exponentially from 220° C. At low temperatures, pressure does not seem to be a significant factor, since at 10 and 15 bar the STY values ​​are almost the same. At temperatures above 200° C., the pressure becomes higher.

[0095] In comparison, samples of epitaxially grown ZnO nanowires on quartz produce about 30 to 50 times more methanol per gram of catalyst than commercial catalysts (which use noble metals), depending on the conditions used.

[0096] By applying a heat treatment at 900°C for 5 hours to the catalyst of the present invention, it is possible to improve its catalytic properties in the catalytic conversion process of CO2 to methanol.

[0097] Selectivity

[0098] By increasing the temperature, the conversion increases, but it was observed that the STY decreases when the commercial catalyst is used at temperatures above 260 °C. Such a phenomenon can be explained by the selectivity. As observed in Figure 15, when the conversion increases, the selectivity of the reaction to methanol decreases significantly.

[0099] For the so-called ZnO-1 catalyst based on ZnO crystallites, no CO signal is observed at temperatures below 240° C. At 10 bar, no CO signal is observed either at 240° C. At 15 bar, a small amount of CO is observed and the methanol selectivity drops to about 52% at 240° C. and 48% at 260° C. However, this is the first noble metal-free catalyst with 100% selectivity and 50 times the methanol productivity of any other catalyst.

[0100] Example 3: Production of a second embodiment of the multi-layer material 1 of the invention.

[0101] This example shows the preparation of a layer 3 containing ZnO microwires with sufficient length and density to completely infiltrate. The planar geometry of the ZnO microwires can then be used to fabricate a prototype of a low-frequency energy harvester using a vibration system and interdigitated electrodes. The ultrathin silicon substrate 2 is completely flexible, allowing the device to function properly. Such a device operates similarly to an axial photodetector.

[0102] Preparation and characterization of a-quartz buffer layer 21 (Step A)

[0103] A precursor solution was prepared with the following initial composition (in moles): 1 TEOS, 0.3 Brij-58, 25 EtOH, 0.7 HCl, and 0.05 SrCl2·6H2O.

[0104] The precursor solution of the buffer layer was deposited on a silicon substrate (Si(100)) (dimensions: 100 μm thick, surface area 2 cm × 6 cm) containing a 2.2 nm thick native SiO2 layer using spin coating at room temperature at a speed of 1,500 rpm for 30 s.

[0105] After deposition of the precursor solution, the silicon substrate was subjected to a heat treatment in a tube furnace under air and atmospheric pressure to strengthen the subsequent silica layer: direct soaking at a temperature of 450° C. followed by a hold at 450° C. for 5 min.

[0106] After the consolidation of the amorphous silica layer precursor of α-quartz, the silicon substrate was subjected to a post-heat treatment in a tube furnace under air at a rate of 12 l / min: direct soaking at a temperature of 980°C followed by a hold time of 980°C for 5 h.

[0107] The furnace was then switched off and the substrate was cooled to 25° C. at a rate of 3° C. / min.

[0108] At the end of cooling, a silicon substrate (100) covered with an α-quartz layer was obtained, which was then characterized (FIGS. 5 and 6).

[0109] Preparation and characterization of ZnO microwire layers (steps B) to F)

[0110] The growth of ZnO microwires on an α-quartz buffer layer was carried out by hydrothermal synthesis at low temperature and pressure. These conditions allow the use of various types of reactors based on glass (Pyrex) or Teflon, making the invention affordable and inexpensive for large-scale implementation.

[0111] First, the molar concentration C Zn An aqueous solution of zinc nitrate hexahydrate, Zn(NO3)2·6H2O, containing 0.1 M was prepared (Step B).

[0112] Separately, molar concentration C HMTA An aqueous solution of hexamethylenetetramine ((HMTA)(CH2)6N4) containing 0.1 M was prepared (Step C).

[0113] The HMTA solution was then added dropwise with a pipette to the zinc nitrate solution under stirring at 450 rpm. The mixture was then stirred for 10 minutes (Step D). The buffer layer was then washed (Step E).

[0114] The epitaxial growth of ZnO microwires (step F) was carried out by hydrothermal synthesis at a temperature of 110 °C and a pressure of about 210 kPa (2.1 bar) for 300 minutes on the surface of an epitaxy layer of quartz (100) on a silicon substrate (Si (100)) (dimensions: thickness 100 μm, surface area 2 cm × 6 cm). This step is advantageously carried out at least twice. The first cycle is carried out to remove the excess SR catalyst on the surface, used during the crystallization of the buffer layer 21 of α-quartz. The sample is then washed with a mixture of sulfuric acid and hydrogen peroxide in a ratio of 4:1 to clean the ZnO residues resulting from the first cycle. Finally, a second cycle is necessary for the crystallization and formation of the ZnO microwires.

[0115] Measurements of the microwire dimensions were performed by optical microscopy and field emission scanning electron microscopy.

[0116] A substrate consisting of a layer of quartz (100) on silicon (100) coated with a layer (3) containing ZnO (110) microwires was obtained and then characterized.

[0117] The new epitaxy between the ZnO and α-quartz buffer layer 21 was determined by X-ray diffraction through a diffractometer sold under the trade name GADDS D8 by Bruker assembly, 1.54056 Angstrom copper radiation.

[0118] The resulting ZnO microwires have a density of 85% of the surface area, a thickness of 750 nm, a length of 12,000 nm and a width of 1,400 nm. The infiltration of the microwires is complete over the entire surface of the sample.

[0119] 16a and 16b show the XRD diffractograms (intensity in arbitrary units as a function of the angle 2θ in degrees) and the mosaicity of the obtained ZnO microwire layer 3, the XRD analysis shows that the ZnO is textured (110) with the crystallographic direction of α-quartz

[0110] parallel to the crystallographic direction

[0100] of the quartz (100) and silicon substrate (100). The ZnO microwires are grown as in the previous case according to the relationship

[0110] ZnO (110) / /

[0100] * α-quartz (100) / /

[0100] * Si (100) and are located on two areas of quartz.

[0120] Figure 17 gives the results of a topographical and microstructural study of the ZnO microlayer layer 3 obtained by SEM in a vertical cross section of the layer. The continuity of the layer and the size of the crystallites were characterized by SEB and AFM images. The obtained layer was formed of percolated uniform ZnO crystallites with a length of 12,000 nm, a width of 1,400 nm and a height of 750 nm. The continuity and the size of the crystallites of layer 3 were characterized by MEB and AFM images. The obtained layer was formed of percolated uniform ZnO crystallites with a length of 12,000 nm, a width of 1,400 nm and a height of 750 nm.

[0121] Example 4: Use of the multilayer material 1 according to the invention obtained in example 3 in a second embodiment for energy recovery applications.

[0122] Figure 18 shows the use of the multilayer material of the invention obtained in Example 3 in a low frequency (61 Hz) energy harvesting device. Such a device can also harvest energy and / or detect light by the photoelectric effect due to the axial pn coupling between the ZnO crystals and the gold electrodes.

[0123] Example 5: Precise control of resonant frequency by controlling the size and thickness of α-quartz piezoelectric film

[0124] The resonant frequency and displacement of an α-quartz piezoelectric film depend on its surface area and thickness. By controlling these two morphological parameters, the resonant frequency can be precisely controlled and the film morphology can be tailored to the frequency range of the intended application.

[0125] A number of quartz-based piezoelectric films with different dimensions were fabricated according to Example 2. The films were square with sides of 2 mm, 2.5 mm, 3 mm, 3.5 mm, and 4 mm. Each film was fabricated in two series, a 2 μm thick series and a 13 μm thick series.

[0126] This study demonstrated the control of the membrane size and thickness. It highlights the effect of these parameters on the resonant frequency and maximum amplitude of the device. As the surface area of ​​the membrane increases, the value of the resonant frequency decreases, but its maximum displacement increases. For a thickness of 2 μm, the maximum displacement of 4 mm 2 The membrane resonates at a frequency of 10.66 kHz at a displacement of 1.5 nm, and 2 The membrane resonates at 3.35 kHz at a displacement of 36.35 nm.

[0127] 4mm 2 , 6.25mm 2 , 9mm 2 , 12.25mm 2 , 16mm 2 The resonant frequency f of each film with a surface area of ​​2 μm and a thickness of 13 μm is r The experimental data results, including the maximum deflection and the deflection, are summarized in Table 1 below. Figure 19 also shows that the thin membrane resonates at a lower frequency than the thick membrane. 2 The 2 μm thick membrane has a displacement D of 16.58 nm. max In f r = 8.16 kHz, and the 13 μm thick membrane has a displacement D of 6.6 nm. max In f r = 26.55 kHz. Moreover, the 13 μm thick membrane sweeps a wider frequency range than the 2 μm thick membrane. [Table 2]

[0128] Example 6: Preparation of ZnO nanostructured microwire-based layers heteroepitaxially grown on silicon substrates from an α-quartz buffer layer according to the method of the present invention for catalytic applications

[0129] In this example, it is shown that chemical etching of ZnO microwires with a dilute hydrochloric acid (HCl) solution allows nanostructuring by generating textures on the surface of epitaxially grown ZnO microwires. Indeed, after hydrothermal growth of the ZnO microwires, chemically attacking the surface of the microwires with an HCl solution is used to control the ZnO surface (forming nanotextures). The planar structure of the microwires and the method of nanostructuring by subsequent chemical attack of the ZnO microwires increase the specific surface area of ​​the material and therefore the catalytic activity. As an example, the yield of a catalyst for hydrogenating CO2 to produce methanol after attacking the ZnO microwires to different degrees is shown.

[0130] For this purpose, a first example of a multilayer material according to the invention obtained in Example 1 is used.

[0131] A chemical attack was then performed by placing the multilayer material samples in HCl solutions with concentrations ranging from 0.30 to 12 mM for 5 min under ultrasonic agitation. The following HCl concentrations were used: 0.37 mM, 0.75 mM, 1.48 mM, and 2.94 mM.

[0132] Figure 20 shows low magnification SEM images (20a) and higher magnification MET (20b) and SEB (20c) images of a ZnO on quartz sample at different degrees of attack, of the cross section of the microwire along the crystallographic direction (001), after etching with a 2.94 mM dilute hydrochloric acid solution for 5 min under ultrasound. In the figure, the anisotropy of the attack in the crystallographic plane (001) can be seen. The resulting ZnO microwires have a density of 85% of the surface area, a thickness of 500 nm, a length of 12,000 nm and a width of 1000 nm. The graph in Figure 20a shows that the STY increases significantly with the degree of chemical attack.

[0133] Prior art documents References 1. Byeong-Yun Oh, Min-Chang Jeong, Tae-Hyoung Moon, Woong Lee, Jae-minutes Myoung, Jeoung-Yeon Hwang, and Dae-Shik Seo. Transparent conductive Al-doped zno films for liquid crystal displays. Journal of applied Physics, 99(12):124505, 2006. Reference 2. Albert Polman, Mark Knight, Erik C. Garnett, Bruno Ehrler, and Wim C. Sinke. Photovoltaic materials: Present efficiencies and future challenges. Science, 352(6283), 2016. Reference 3. H. Kim, CMGilmore, JS Horwitz, A. Pique, H. Murata, GP Kushto, R. Schlaf, ZHKafafi, and DB Chrisey. Transparent conducting aluminum-doped zinc oxide thin films for organic light-emitting devices. Applied Physics Letters, 76(3):259-261, 2000. Reference 4. Chin Boon, Law Yong, and Abdul Wahab. A review of ZnO nanoparticles as solar photocatalysts: Synthesis, mechanisms and applications. Renewable and Sustainable Energy Reviews, 81:536 - 551, 2018. Reference 5. Shuhua Liang, Xufeng Gou, Jie Cui, Yongguang Luo, Hongtao Qu, TE Zhang, Zhimao Yang, Qing Yang, and Shaodong Sun. Novel cone - like zno mesocrystals with co - exposed (10 - 11) and (000 - 1) facets and enhanced photocatalytic activity. Inorg.Chem.Forehead., 5:2257 - 2267, 2018. Reference 6. Shaodong Sun, Xiaojing Yu, Qing Yang, Zhimao Yang, and Shuhua Liang. Mesocrystals for photocatalysis: A comprehensive review on synthesis engineering and functional modifications. Nanoscale Adv.1:34 - 63, 2019. Reference 7. Martin Drobek, Jae - Hun Kim, Mikhael Bechelany, Cyril Vallicari, Anne Julbe, and sang Sub Kim. MOF - based membrane encapsulated zno nanowires for enhanced gas sensor selectivity. ACS applied Materials & Interfaces, 8(13):8323 - 8328, 2016. Reference 8. Wang, ZL; Song, JH. Piezoelectric nanogenerators based on zinc oxide nanowire arrays DOI: 10.1126 / SCIENCE.1124005. Reference 9. R. Raji and K.G. Gopchandran. ZnO nanostructures with tunable visible luminescence: Effects of kinetics of chemical reduction and annealing. Journal of Science: Advanced Materials and devices, 2: 51 - 58, 2017. Reference 10. Daniel Laudenschleger, Holger Ruland & Martin Muhler. Identifying the nature of the active sites in methanol synthesis over Cu / ZnO / Al2O3 catalysts. Nature Communications volume11, Article number: 3898 (2020). Reference 11. A.F. Soares, S.H. Tatumi, T.M. Mazzo, R.R. Rocca, and L.C. Courrol. Study of morphological and luminescent properties (TL and OSL) of ZnO nanocrystals synthetized by coprecipitation method. Journal of luminescence, 186: 135 - 143, 2017. Reference 12. Jianhua Hu and Roy G. Gordon. Textured aluminum - doped zinc oxide thin films from atmospheric pressure chemical vapor deposition. Journal of applied Physics, 71(2): 880 - 890, 1992. Reference 13. Alessandro Fraleoni - morgera, Ilaria Cesini, and Pramod Kumar. Hydrogrown ZnO nanorods as promising materials for low cost electronic skin. ChemNanoMat, 9: 1 - 18, 2019. Reference 14. M. Z. Toea N. A. H. N. Jusoha S. Y. Punga K. A. Yaacoba A. Matsudab W. K. Tanb S. S. Hanc. Effect of ZnO Seed Layer on the growth of ZnO Nanorods on Silicon Substrate. Materials today: Proceedings, Volume17, Part3, 2019, pages 553 - 559. Reference 15. Yuhai Sun, Liminutes Chen, Yunfeng Bao, Yujun Zhang, Jing Wang, Mingli Fu, Junliang Wu, and Daiqi Ye. The Applications of morphology controlled ZnO in catalysis. Catalysts, 6(188), 2016. Reference 16. Tong Zhou, minutes Hu, Jia he, Ruicong Xie, Cuihua an, Chao Li, and Jun Luo. Enhanced catalytic performance of zinc oxide nanorods with crystal plane control. CrystEngComm, 21: 5526 - 5532, 2019. Reference 17. G. Sun, K. Zhao, Y. Wu, Y. Wang, N. Liu, L. Zhang, J. Phys. Condens. Matter 2012, 24, 295801. Reference 18. X. H. WEI, Y. R. Li, J. Zhu, W. Huang, Y. Zhang, W. B. Luo, H. Ji, Appl. Phys. Lett., 2007, 90, 151918. Reference 19. Wang et al., Chem6, 419 - 430. https: / / doi.org / 10.1016 / j.chempr.2019.10.023. Reference 20. J. Koike and H. Ieki, “Zinc oxide piezoelectric crystal film,” U.S. Patent 5 432 397, 1995 - 07 - 11. Reference 21. T. Yamaguchi, N. Fujimura, S. Goto, and T. Ito, “formation of (11 - 20) ZnO Films by controlling the Selftexture and the relaxation of Film stress,” Mrs Proceedings, Vol. 263, pp. 297 - 302, 1992. Reference 22. N. Emanetoglu, S. Liang, C. Gorla, Y. LU, S. Jen, and R. Subramanian, “epitaxial growth and characterization of high quality ZnO films for surface acoustic wave applications,” in IEEE Ultrasonics Symposium Proceedings. An International Symposium, Vol. 1, pp. 195 - 200, 1997. Reference 23. J.-T. Luo, A.-J. Quan, Z.-H. Zheng, G.-X. Liang, F. Li, A.-h. Zhong, H.-L. MA, X.-H.. Zhang, and P. Fan, “Study on the growth of Al-doped ZnO thin films with(11 - 20)and(0002)Preferential orientations and their thermoelectric characteristics,” RSC advances, Vol. 8, no. 11, pp. 6063 - 6068, 2018. Reference 24. Y.. Xiao, Y. Tian, S. Sun, C. Chen, and B. Wang, “Growth modulation of simultaneous epitaxy of ZnO obliquely aligned nanowire arrays and film on r-plane sapphire substrate,” Nano Research, Vol. 11, no. 7, pp. 3864 - 3876, 2018. Reference 25. Y.-T. Ho, W.-L. Wang, C.-Y. Peng, M.-H. Liang, J.-S. Tian, C.-W. LIN, and L. Chang, “Growth of nonpolar (11 - 20)(001) ZnO Films on LaAlO3() substrates,” Applied Physics Letters, Vol. 93, no. 12, p. 121911, 2008.

Claims

1. a solid support (2) at least partially covered with a buffer layer (21) of textured α-quartz (100), the [100] crystallographic direction of the α-quartz being parallel to the [100] crystallographic direction of the silicon (100); and a layer (3) of epitaxially grown one-dimensional crystallites of (110) ZnO on said buffer layer (21) of (100) α-quartz, said crystallites being self-organized; A multilayer material (1) comprising:

2. 2. A multilayer material (1) according to claim 1, wherein the thickness of the epitaxially grown (110) ZnO one-dimensional crystallites is between 30 nm and 1.5 μm, preferentially of the order of 750 nm.

3. 2. A multilayer material (1) according to claim 1, wherein the length of the epitaxially grown (110) ZnO one-dimensional crystallites is between 5 nm and 30 μm, preferentially of the order of 11 μm.

4. The solid support (2) is preferably made of silicon, solid quartz, mica, corundum, germanium dioxide, magnesium oxide, strontium titanate SrTiO ３ , LaAlO ３ , lithium niobate, lithium tantalate, cerium oxide, Ce （１－ｘ） G.D. ｘ O ２ 2. The multilayer material (1) according to claim 1, characterized in that the material is selected from the group consisting of gadolinium cerium mixed oxides, lanthanum aluminate, gallium nitride, yttrium doped zirconium dioxide and gallium orthophosphate, with x being 0<x<1.

5. The multilayer material (1) according to claim 4, wherein the solid support (2) is made of mono-oriented crystalline silicon (100).

6. 2. The multilayer material (1) of claim 1, wherein the epitaxially grown (110) ZnO one-dimensional crystallites cover at least 40% of the surface area of ​​the (100) α-quartz buffer layer of the solid support (2).

7. 6. Use of the multilayer material (1) according to claim 5 in an electronic device selected from MEMS, electromechanical materials, piezoelectric components, energy harvesters, photodetectors, mechanical wave specific filter oscillators, mechanical wave to electromagnetic wave converters, acceleration and angular velocity sensors, mass sensors or gas sensors.

8. Use of the multilayer material (1) according to any one of claims 1 to 5 for the production of waveguides in the visible light range, for the production of supported catalysts in the presence or absence of noble metals or as epitaxy template.

9. Use of the multilayer material (1) according to any one of claims 1 to 5 for the manufacture of a transparent conductive electrode and for the manufacture of an electronic device using said transparent conductive electrode.

10. A method for producing a multilayer material (1) according to any one of claims 1 to 5, comprising the steps of: A) preparing a buffer layer (21) of textured (100) α-quartz at least partially covering a solid support (2) to form a substrate for the epitaxial growth of (100) ZnO crystallites; B) preparing a first composition comprising a solvent and at least one ZnO precursor; - C) preparing a second composition consisting of an aqueous solution of at least one heterocyclic organic compound having a diamond cage structure; - D) gradually adding said second composition to said first composition under stirring and maintaining stirring for at least 10 minutes to obtain a reaction mixture; - E) preparing the surface of said buffer layer (21) using said second composition prepared during step C) or said reaction mixture prepared during step D) by placing said substrate in a closed hydrothermal reactor at a temperature of at least 60°C and a pressure of at least 1 bar for at least 15 minutes; - F) washing said buffer layer (21) with an acid solution; then G) heat treating the epitaxial growth of ZnO crystallites by placing the substrate and the reaction mixture on the substrate in a closed hydrothermal reactor at a temperature of at least 60° C. and a pressure of at least 1 bar for at least 15 minutes; and H) washing after growth successively with demineralized water and then with ethanol in order to dry the multilayer material obtained; A method comprising:

11. During step B), zinc nitrate, preferentially Zn(NO), present in said first composition in a proportion of 0.1M ３ ) ２ ・6H ２ The method of claim 10, wherein O is used as a ZnO precursor.

12. The heterocyclic organic compound contained in the second composition is represented by the formula (CH ２ ) ６ N ４ 11. The method according to claim 10, wherein hexamethylenetetramine (HTMA) is used during step C).

13. 11. The method of claim 10, wherein during step C) one or more additives selected from among pH control agents, pH control agents (e.g. HCl), structuring or modifying agents, or porosity promoters such as polymers, quaternary ammonium and urea are added to the second composition.

14. The method of claim 10 , wherein steps G) and H) are repeated one or more times on the same substrate.

15. A microelectromechanical system in the form of a piezoelectric resonant membrane comprising a multilayer material (1) according to any one of the preceding claims.

16. A method for nanostructuring a multilayer material (1) according to any one of claims 1 to 6 by controlled chemical etching using an acid solution.

Images