TARGET FOR OBTAINING COLOURED GLAZING

Abstract

A cathode sputtering target is formed, on the one hand, from an oxide of at least one element chosen from the group of titanium, silicon and zirconium and, on the other hand, of particles of a metal included in the group formed by silver, gold, platinum, copper and nickel or particles of an alloy formed from at least two of these metals, the atomic ratio M/Me in the target being less than 1.5, M representing all of the atoms of the elements of the group of titanium, silicon and zirconium present in the layer and Me representing all of the atoms of the metals of the group formed by silver, gold, platinum, copper and nickel present in the layer.

Claims

1. A cathode sputtering target formed from an oxide of at least one element chosen from a group of titanium, silicon and zirconium and of particles of a metal included in a group formed by silver, gold, platinum, copper and nickel or particles of an alloy formed from at least two of the metals, the M/Me atomic ratio in said target being less than 1.5, M representing all of the atoms of the elements of the group of titanium, silicon and zirconium and Me representing all of the atoms of the metals of the group formed by silver, gold, platinum, copper and nickel.

2. The target as claimed in claim 1, in which the M/Me atomic ratio is less than 1.2.

3. The target as claimed in claim 1, in which the M/Me atomic ratio is less than 1.0.

4. The target as claimed in claim 1, in which the M/Me atomic ratio is less than 0.8.

5. The target as claimed in claim 1, in which M represents a single element.

6. The target as claimed in claim 1, in which said oxide is a titanium oxide of formula TiO.sub.x with x2.

7. The target as claimed in claim 6, in which said oxide is a titanium oxide of formula TiO.sub.x with x<2.

8. The target as claimed in claim 1, in which the metal is silver, gold, platinum, copper or nickel.

9. The target as claimed in claim 1, in which the metal is silver, gold or platinum.

10. The target as claimed in claim 1, in which the metal is silver.

11. The target as claimed in claim 1, wherein the target is made from a mixture of titanium oxide and of silver particles, the Ti/Ag atomic ratio in said target being less than 1.5.

12. The target as claimed in claim 1, in which the electrical resistivity, as measured according to standard ASTM F76), is less than 5 .Math.cm.

13. The target as claimed in claim 1, in which the porosity is less than 10%.

14. The target as claimed in claim 1, in which the distribution of Me relative to M is such that the difference D between the maximum content of Me phase measured in said target and the minimum content of Me phase measured in said target, on a plurality of analysis zones of the same area 7070 m.sup.2, is less than 50% of the mean content of Me phase measured on said target.

15. The target as claimed in claim 1, in which the overall standard deviation calculated on the total number of measurements is less than 25% of the mean content of Me phase measured on said target.

16. A process for manufacturing a target as claimed in claim 1, comprising: thermal sputtering onto a support a mixture of the oxide of at least one element chosen from the group of titanium, silicon and zirconium and of particles of a metal included in the group formed by silver, gold, platinum, copper and nickel or particles of an alloy formed from at least two of these metals.

17. A process for manufacturing a target as claimed in claim 1, comprising: mixing the oxide of at least one element chosen from the group of titanium, silicon and zirconium in a molten bath of the metal included in the group formed by silver, gold, platinum, copper and nickel or an alloy formed from at least two of these metals; and forming said target.

18. The process for manufacturing a target as claimed in the claim 17, in which the mixing step comprises sputtering or gravity deposition of the particles of the oxide of at least one element chosen from the group of titanium, silicon and zirconium in the bath of molten metal.

19. The target as claimed in claim 7, in which said oxide is a titanium oxide of formula TiO.sub.x in which 1.70<x<2.0.

20. The target as claimed in claim 11, wherein the Ti/Ag atomic ratio in said target being less than 0.6.

Description

[0117] More precisely:

[0118] FIG. 2 corresponds to a bright-field TEM image of sample A (violet shade) obtained without inclining.

[0119] FIG. 3 corresponds to a bright-field TEM image of sample A obtained by inclining the observation axis by 15 relative to the plane of the glass surface.

[0120] FIG. 4 corresponds to a bright-field TEM image of sample D (blue shade) obtained without inclining.

[0121] FIG. 5 corresponds to a bright-field TEM image of sample D by inclining the observation axis by 15 relative to the plane of the glass surface.

[0122] FIG. 6 reports the results of the energy-dispersive x-ray (X-EDS) analysis of the sample according to Example A.

[0123] FIGS. 7 and 8 are images, respectively, of a flat target and of a tubular target according to the invention from which the glazing may be obtained.

[0124] It is observed that silver nanoparticles of substantially globular form are concentrated in the layer (of the matrix). The dimensions of said nanoparticles can be measured, as indicated in FIGS. 2 and 3. These nanoparticles have, along their longest dimension and on average, a size from about 3 to 12 nm, depending on the sample.

Table 4 below indicates the main characteristics of the silver nanoparticles included in the TiOx layer, measured for samples A to D according to the TEM technique.

TABLE-US-00004 TABLE 4 Layer A B C D Particle size distribution* 2 to 10 3 to 5 5 to 12 3 to 6 (nm) Mean particle size* (nm) 5 5 8 5 Particle morphology round round ovoid round *length along their longest dimension

[0125] In order more precisely to characterize the distribution of the nanoparticles in the colored layer according to the invention, an energy-dispersive x-ray (X-EDS) analysis of the sample according to Example A (violet shade) is also performed. The distribution of the elements, as reported in the attached FIG. 6, shows in the TiOx/Ag colored layer a greater concentration of the silver nanoparticles at the center of said layer. This same characteristic distribution was observed on all the layers A to D obtained according via process according to the invention.

[0126] In a second series of examples, it is sought to deposit, according to the first process according to the invention described previously, a colored layer formed from an oxide matrix of the element Ti in which are dispersed silver metal particles on a colorless glass substrate. The clear glass used is marketed under the reference Planiclear by the Applicant Company.

[0127] The colored layers according to the invention are deposited on a glass substrate in a magnetron-type cathode sputtering housing delimiting a chamber in which a secondary vacuum may be applied. In this housing (constituting the anode), the targets (constituting the cathodes) are installed in the chamber so that, during the deposition, an RF or DC power source makes it possible to ignite a plasma of a plasma-generating gas, usually essentially argon, krypton or helium, in front of said targets, the substrate passing parallel to this target. It is possible according to this installation to choose the speed of passage of the substrate and thus the deposition time and the thickness of the layer.

[0128] A commercial titanium oxide (TiOx) target is used to make the first target according to the invention.

[0129] The second target, having a composition in accordance with the present invention, is manufactured from a mixture of titanium oxide and of silver particles in accordance with the techniques described hereinbelow.

[0130] The second target according to the invention is manufactured such that the Ti/Ag atomic ratio in the target is about 0.5, according to the techniques described below.

[0131] The power required to generate a plasma of the gas in the device is applied to the two cathodes. The deposition takes place under an atmosphere exclusively of argon as plasma-generating neutral gas in the housing chamber. More precisely, for all the examples that follow, the flow rate of argon injected into the chamber is 30 sccm (standard cubic centimeters per minute). The deposition time is 200 seconds for all the samples. The thickness of the layers thus obtained is from about 10 to 15 nm.

[0132] Several layers are deposited according to these same principles, varying the power applied to the two cathodes so as to obtain various dielectric matrices formed from a titanium oxide comprising silver nanoparticles present in different concentrations. Table 1 below summarizes the main parameters of the step of depositing the coating layer according to the present process.

TABLE-US-00005 TABLE 5 Power applied Power applied to target 1 to target 2 Dry Argon made of made of deposit Example (sccm) TiOx (W) TiOx-Ag (W) time E 30 100 100 200 F 30 200 100 200 G 30 300 100 200 H 30 200 0 200

[0133] Optical spectra of the samples were acquired using a spectrophotometer under the same conditions as described previously. Glass-side and layer-side transmission and reflection measurements are taken to allow an absorption spectrum to be replotted. The central positions of the absorption peaks are reported in Table 6 below.

TABLE-US-00006 TABLE 6 Absorption Example peak position E 490 nm F 440 nm G 420 nm H

[0134] The chemical composition of the colored layers according to Examples E to G were analyzed according to the same methods as described previously. The Ti/Ag mole ratio in the layers ranges between 0.7 to 1.0.

[0135] In order more precisely to characterize the nanoparticle distribution in the colored layer according to the invention, an energy-dispersive x-ray (X-EDS) analysis of samples E to G is also performed. As for Examples A to C, the distribution of the elements shows in the TiOx/Ag colored layer a higher concentration of silver nanoparticles at the center of said layer for samples E to G.

According to such a process comprising a step of co-sputtering of two targets on which the applied power may be varied, it thus becomes possible to vary without difficulty the optical properties of the layer. In particular, by increasing the power on the first TiOx target, it is possible immediately to modify the colorimetry of the layer deposited and thereby of the glazing. In particular, it becomes possible to adjust the concentration of Ag nanoparticles in the layer as a function of the desired color of the layer and of the glazing.

[0136] According to a process according to the invention, it thus ultimately becomes possible to fully control and to vary within a wide range the color of the glazing very easily and economically, without loss of production.

[0137] In particular, by simple deposition of a coating layer, it is possible via such a process according to the invention, by simple adjustment of the power applied to the two cathodes in the device according to the invention, to modify rapidly and without difficulty and over a broad range the color of the final glazing (substrate covered with the layer).

[0138] Certain particular characteristics of implementation of the target according to the invention are described below. Said target is formed from a combination of oxide of metal M (M representing all of the atoms of the elements of said group of titanium, silicon and zirconium) and of metal Me (Me representing all of the atoms of the metals of the group formed by silver, gold, platinum, copper and nickel) as described previously. The target according to the invention also preferably meets the following criteria: [0139] a homogeneous distribution of the elements M, on the one hand, and Me, on the other hand, so that no heterogeneity of dispersion of nanoparticles of Me in the matrix of oxide of M in the thin layer derived from the target is observed. This homogeneity is required both in the length and width dimensions and in the thickness of the target. The methodology and the criteria for characterizing the homogeneity of distribution are defined below. [0140] an electrical resistivity that is compatible with use in AC, RF and also DC magnetron sputtering. For this, as a guide, the resistivity of the target must be <5 .Math.cm. Values higher than this threshold may be considered, but compatibility with the DC mode will in this case not be guaranteed. [0141] a degree of porosity of less than 10%, preferentially less than 5%, so as to reduce any risk of formation of an electric arc (arcing) which may lead to local melting of the metal Me of the target.

[0142] To achieve an optimum electrical resistivity that is as low as possible, it is advantageous to make use of a formulation that is slightly sub-stoichiometric in oxygen of the oxide of the metal M when this form has an electrical resistivity below that of the corresponding oxide. Mention may be made, for example, of the compound TiO.sub.x, with x strictly less than 2. However, this degree of sub-stoichiometry is normally limited to 15% maximum, and preferentially 10% maximum, so as to limit the supply of oxygen subsequently required in the magnetron. By way of example, mention may be made for TiO.sub.x of a value of x greater than or equal to 20.85, i.e. 1.7, preferably greater than 20.9, i.e. 1.8.

[0143] Various embodiments of the target according to the invention are given below:

According to a first possible embodiment for producing the targets according to the invention, a technique of thermal spraying is used, and in particular of plasma spraying, which process may be performed under an atmosphere of air or of a neutral gas. The plasma torch (propellant) used may be of the DC or RF type, and the plasma-generating gases may be binary mixtures of the (A-B) type in which A=Ar or N.sub.2 and B=H.sub.2, He or N.sub.2 (the use of pure N.sub.2 being among the possible combinations), or ternary mixtures of the (A-B-C) type in which A=Ar; B=N.sub.2 or H.sub.2; C=He. The various variants of hot-cathode DC torches with stabilization of the plasma by cascade technology (with neutrodes), three-cathode DC torches, DC torches combining three plasmas converging in a nozzle, and water-stabilized plasma torches may be used as means for constructing the target.
Cold-cathode torches of thermal plasma generator type also fall within the context of the present invention. These generators generally use air as plasma-generating gas, but can also function with the binary or ternary mixtures mentioned previously.

[0144] Other thermal projection methods such as the HVOF (high-velocity oxyfuel) process or the dynamic cold spray process may also be used to produce targets according to the invention.

[0145] The mixture for feeding the spraying device may in particular be a mixture of particles of a metal chosen from the group formed by silver, gold, platinum, copper and nickel, preferably silver, in a purity of greater than 99%, preferably greater than 99.9%, preferably greater than 99.95% by weight and particles of an oxide of at least one element chosen from the group formed by titanium, silicon and zirconium, preferably the element Ti, said oxide being sub-stoichiometric in oxygen according to a molar proportion which may be up to 15%, preferentially up to 10%, so as to limit the supply of oxygen subsequently required in the magnetron during the use of the target.

[0146] According to another alternative mode, particles of an oxide of at least one element chosen from the group formed by titanium, silicon and zirconium or of an alloy formed from at least two of these metals, preferably titanium dioxide (TiO.sub.2) particles, may be mixed with a molten bath of a metal chosen from the group formed by silver, gold, platinum, copper and nickel Me, preferably a bath of silver maintained in melt form.

[0147] According to a particular mode, on contact with a bath of molten silver, the TiO.sub.2 particles reduce to TiO.sub.x. Preferably, the Ti/Ag atomic ratio in the target is less than 0.5, or even less than 0.4 or even less than 0.3. Such an alternative mode makes it possible, despite the larger amount of metal, for example of silver, to limit the losses of this metal when compared with a process for sputtering particles of oxide of a metal M and particles of a metal Me, for example of silver. For example, a powder of titanium dioxide (TiO.sub.2) particles typically with a median diameter of 75 microns, optionally dried beforehand or even preheated, can be sputtered, via a vector gas, or deposited by gravity in an ingot mold of molten silver typically at 1000 C.

[0148] Brazing may be performed so as to obtain a homogeneous mixture. The mixture is maintained and then cooled, for example via an induction device.

[0149] Targets of tubular form may be made with the aid of molds with a core.

[0150] For example, in particular for targets of complex form, including tubular forms, the molten metal may be maintained in melt form locally, for example via a laser device for which the wavelength and the parameters of the beam may be adapted to the metal employed, while concomitantly supplying in the region of the molten metal, by sputtering, via a vector gas, or by gravity deposition powder of the oxide of at least one element chosen from the group formed by titanium, silicon and zirconium or an alloy formed from at least two of these metals, preferably titanium dioxide, so as to obtain a homogeneous mixture and consequently uniform or controlled distribution of the inclusions of partially reduced metal M, preferably of TiO.sub.x, after reaction with the bath of molten metal.

[0151] To illustrate the use of this family of processes for producing the targets according to the invention, two implementation examples are illustrated below.

Implementation Example No. 1: Flat Target with Me=Ag and M=Ti

[0152] This implementation example according to the invention relates to the preparation of a flat target, formed from a combination of sub-stoichiometric titanium oxide TiO.sub.x (with x=1.95) and of silver particles, the two constituents being distributed in the microstructure homogeneously, said target being intended to be used in magnetron sputtering in AC, DC or RF mode.

[0153] This flat TiO.sub.xAg target was produced by the plasma spraying process described previously after optimization of the distribution of the various materials in the plasma jet. The main steps of the process are as follows: [0154] Production of the intermediate support plate (tile) by machining, intended to be subsequently brazed on the target support. [0155] Preparation of the surface of the support plate by abrasive spraying (alumina-zirconia AZ grit 24). [0156] Deposition of a bonding underlayer by plasma spraying of a CuAl alloy (90% by mass of Cu), about 150 m thick. [0157] Premixing of TiOx and Ag powders in proportions calculated as a function of the differential yields (57.3% by mass of TiOx and 42.7% by mass of Ag). The mixture is stirred (in a Turbula mixer) systematically for 1 hour. The powders used for preparing the target are powders respectively having the following characteristics: [0158] TiO.sub.x powder: Powder of ground molten TiO.sub.x type (x=1.98) with a particle size (d.sub.50) of 75 m and a purity of 99.7% [0159] Silver powder produced by atomization of liquid metal, with a particle size (d.sub.50) of 45 m and a purity of 99.95% [0160] Construction of the TiO.sub.xAg active layer on the target by plasma spraying under the following conditions: [0161] Plasma torch of DC type with a maximum power of 60 kW, placed in a chamber under air [0162] Use of cooling jets placed under the copper support plate, and also on either side of the plasma torch, and directed toward the target to control the temperature and the stresses induced during the plasma spraying. [0163] Plasma spraying performed with the following parameters:

TABLE-US-00007 Parameters H.sub.2 Arc Spraying Material content intensity distance flow rate (%) (A) (mm) (g/min) Values used 13.4 450 120 80 [0164] Surface finishing by polishing and/or machining to obtain a roughness such that Ra<5 m

[0165] An optimized device for injecting the powder mixture allows suitable injection into the plasma without segregation of the powders in flight, making it possible to ensure homogeneous distribution of Me and of MO.

[0166] The main characteristics of the target thus produced are given below:

[0167] a. Chemical Composition: [0168] The chemical analysis of the target thus produced corresponds to an M/Me ratio of about 0.6.

[0169] b. Electrical Resistivity

TABLE-US-00008 Resistivity per unit volume <100 .Math. cm measured at 20 C. by the Van Der Pauw method (ASTM F76)

[0170] c. Me Dispersion Homogeneity in the Structure:

TABLE-US-00009 Homogeneity criteria (Max-min) on mean Standard deviation on on all of the ROIs Me content mean Me content Flat target 44% 19%

[0171] d. Microstructure and Degree of Porosity

[0172] The evaluation of the degree of porosity by image analysis, according to the method described hereinbelow, is 1%.

[0173] The microstructure of the target obtained is illustrated by the SEM image reported in FIG. 7 of a cross section thereof, which reflects the excellent homogeneity of distribution of the silver particles in the titanium oxide.

Exemplary Embodiment No. 2

[0174] rotating tubular target with Me=Ag and M=Ti This implementation example relates to a rotating tubular target, formed from a combination of sub-stoichiometric titanium oxide TiO.sub.x (with x=1.95) and of silver particles, the two constituents being distributed in the microstructure homogeneously, said target being intended to be used in magnetron sputtering in AC, DC or RF mode.

[0175] This tubular TiO.sub.xAg target is produced by the plasma spraying process after optimization of the distribution of the various materials in the plasma jet. The main steps of the process are as follows: [0176] Use of a support tube made of austenitic stainless steel, for instance X2CrNi18-9. [0177] Preparation of the surface of the support tube by abrasive spraying (alumina-zirconia AZ grit 24). [0178] Preparation of a bonding underlayer via the electric arc process (twin wire arc spraying), performed in air, bonding layer of NiAl composition (95% nickel), about 150-200 m thick. Alternatively, the wire flame spray or projection plasma (air plasma spray) processes may also be used to produce this bonding underlayer. [0179] Premixing of TiOx and Ag powders in proportions calculated as a function of the differential yields (62% by mass of TiOx and 38% by mass of Ag). The mixture is stirred (in a Turbula mixer) systematically for 1 hour. [0180] The powders used for preparing the target are powders respectively having the following characteristics: [0181] TiO.sub.x powder: Powder of ground molten TiO.sub.x type (x=1.98) with a particle size (d.sub.50) of 75 m and a purity of 99.7% [0182] Silver powder produced by atomization of liquid metal, with a particle size (d.sub.50) of 45 m and a purity of 99.95% [0183] Construction of the TiO.sub.xAg active layer on the target by plasma spraying under the following conditions: [0184] Plasma torch of DC type with a maximum power of 60 kW, placed in a chamber under air [0185] Use of cooling jets placed under the copper support plate, and also on either side of the plasma torch, and directed toward the target to control the temperature and the stresses induced during the plasma spraying. [0186] Plasma spraying performed with the following parameters:

TABLE-US-00010 Parameters H.sub.2 Arc Spraying Material content intensity distance flow rate (%) (A) (mm) (g/min) Values used 12.3 550 150 160 [0187] Surface finishing by polishing and/or machining to obtain a roughness such that Ra<5 m.

[0188] An optimized device for injecting the powder mixture allows suitable injection into the plasma without segregation of the powders in flight, making it possible to ensure homogeneous distribution of Me (Ag) and of MOx (TiOx).

Essential Characteristics of the Target Thus Produced:

[0189] a. Chemical Composition: [0190] The chemical analysis of the target thus produced corresponds to an M/Me ratio=0.92

[0191] b. Electrical Resistivity

TABLE-US-00011 Resistivity per unit volume 28.5 .Math. cm measured at 20 C. by the Van Der Pauw method (ASTM F76)

[0192] c. Me Dispersion Homogeneity in the Structure:

TABLE-US-00012 Homogeneity criteria (max-min) on mean Standard deviation on on all of the ROIs Me content mean Me content Tubular target 42% 24%

[0193] d. Microstructure and Degree of Porosity

The evaluation of the degree of porosity by image analysis, according to the method described hereinbelow, is 1%.
The microstructure of the target obtained is illustrated by the image reported in FIG. 8 below of a cross section thereof, which reflects the excellent homogeneity of distribution of the silver.

Implementation Example No. 3: Target Formed from a TiOx Preform

[0194] According to a third embodiment of a process for manufacturing a target according to the invention not making use of thermal spraying, the targets according to the invention are prepared by the process described below via its main steps directed toward producing a target with M=Ti and Me=Ag and x=1.8 to 2.0):

[0195] 1. Preparation of a Preform of the Porous TiO.sub.x Target.

The geometry of the preforms corresponds to the geometry of the segments intended to be bonded to the support plate (backing plate), namely plates, or to the support tube (backing tube), namely sleeves (hollow cylinders).
The desired degree of porosity for the preform depends on the final targeted volume content of TiO.sub.x. If A % is the targeted volume content of silver in the target, then the preform TiO.sub.x has a degree of porosity of P %=A %.
For high porosity values, the preform may be, for example, a ceramic foam produced according to the techniques of the art. Alternatively, to achieve the desired porosity levels, recourse may optionally be made to the addition of a furtive material intended to act as a pore generator during the thermal sintering cycle, this furtive material possibly being, for example, a polymer. For porosity levels which are lower but which can be reached by standard sintering, the preform may be made by imperfect sintering of a block of pressed powder.

[0196] 2. Impregnation of Said Preform

The porous preform or ceramic foam is impregnated with liquid Ag via one of the following methods: [0197] Preheating of the preform to 1000 C. followed by pouring liquid Ag onto the preform placed in a case (mold) so as to impregnate it completely [0198] Immersion of the preform (which is itself preheated to 1000 C.) in a bath of liquid Ag followed by extraction of the preform [0199] Immersion by capillarity by placing the preform above and in contact with the bath of liquid Ag so that the Ag impregnates the preform by capillarity.

[0200] 3. Fixing to the Support:

After light machining to bring the segments made to the targeted perfect geometry, the segments prepared are fixed to the support (tube or plate) via the soft brazing methods usually used for fixing magnetron targets, for example the indium brazing technique.
This third embodiment, performed as stated here, will also make it possible to produce the target according to the invention with the characteristics corresponding to the criteria stated previously (resistivity, homogeneity of distribution of Me, porosity).
The measurement techniques for measuring the essential characteristics of the targets described previously are given below: [0201] AMethodology for Characterizing the Homogeneity of Distribution of the M Oxide and Metal Me Phases in the Structure of the Target:

[0202] The methodology for characterizing the homogeneity of distribution of the M oxide phase, on the one hand, and the metal Me phase, on the other hand, are illustrated in the particular case of a target with M=Ti and Me=Ag. The element M is introduced in the form of sub-stoichiometric titanium oxide TiO.sub.x (with x=1.95) and the element Me in the form of metallic silver particles.

[0203] It is thus a matter of characterizing the homogeneity of distribution of these two phases present.

[0204] To ensure the homogeneity of distribution of these two phases present, a sample representative of the microstructure of the target in its entirety is analyzed via an image analysis protocol which makes it possible to map the presence of Me within the microstructure of the sample. The representative sample must be sampled in a representative zone of the target, encompass the entire thickness of the target and have side dimensions of a few mm. The analysis protocol is applied on images of the microstructure of the target in cross section, images taken on the representative sample with a magnification of 200 or even, preferentially, 100 so as to cover a wider zone.

[0205] Zones of analysis (or ROI, Region Of Interest) having the same areas (for example 100100 m.sup.2), ideally 7070 m.sup.2, and which are uniformly distributed on the analysis screen are defined (see image 1). This screen, endowed with the definitions of the ROIs thus made, will act as an analysis grille on the microstructure images taken and presented facing this grille. In order thus to cover all of the microstructure sample representative of the whole target, a succession of translations is applied to successively position a sufficient number of images facing the analysis grille. Grayscale thresholding may then be applied to detect the metal phase Me (which is lighter in optical microscopy) and to determine the content thereof per unit area. The operation is repeated on at least 10 different images, taken from the target in cross section. Thus, for each ROI, a minimum of 10 images will be analyzed, which thus makes it possible to obtain the mean of the area percentage of the Me phase per ROI and the associated standard deviations.

[0206] A target thus obtained is considered as being a sufficiently homogeneous structure according to the invention if the following conditions are met: [0207] the difference between the measured maximum content of Me phase and the measured minimum content of Me phase (counted on all of the ROIs chosen randomly) less than 50%, ideally less than 40% of the nominal contents T of Me phase (i.e. the mean content of Me observed on all the ROIs) [0208] preferably, the overall standard deviation calculated on the total number of measurements (=number of ROIsnumber of images) less than 25% of the content T.
The images obtained illustrate the positioning of the ROIs and the detection of the Me phase is performed by grayscale thresholding.
Case of a Target with Non-Homogeneous Distribution:

[0209] To evaluate the pertinence of this protocol, analyses were performed by applying this homogeneity characterization protocol on various tests of preparation of targets of MOx-Me type having very different homogeneities of distribution of Me within the MOx.

[0210] Table 7 below reports the area contents of Me (silver) per ROI and the associated standard deviations, the criteria identified above ( and standard deviations) of such targets, which make it possible to reflect the homogeneity of distribution.

TABLE-US-00013 TABLE 7 Homogeneity criteria (max-min) on mean Standard deviation on on all of the ROIs Me content mean Me content Sample Test A 69% 37% Sample Test B 121% 53% [0211] B Measurement of the Degree of Porosity

[0212] Evaluation of the degree of porosity is performed fire the standard image analysis techniques using images obtained by electron microscopy.

[0213] More precisely, the volume content of the porosities contained in the targets is determined from the measurement of the area content of these porosities by means of the stereology relationships developed by J. C. Russ, R. T Dehoff, Practical Stereology, 2nd edition, Plenum Press, New York, 1986. Consequently, this section describes the protocol for measuring the surface content of the porosities, determined on images (at magnification 100 to 500) of microstructures of cross sections (metallographic cross sections).

Evaluation of this content is performed by image analysis, the main objective which is to separate the porosities from the rest of the microstructure to be able subsequently to take measurements on the characteristics of the selected parts.

[0214] More precisely, the analysis comprises several successive steps to be applied to each representative sample of the target, which has been polished beforehand: [0215] Acquisition of the images to be analyzed using acquisition software, coupled with an optical microscope and high-resolution camera assembly. The images are preferentially taken in scale. [0216] Selection of the working zone which will define the area of the sample on which the measurements will be taken. [0217] Binarization of the image by thresholding, which consists in conserving from the initial image only the pixels whose grayscale is between two predetermined thresholds. Given that the pixels representative of the porosity are very dark, the lower level may be chosen equal to 0. It then remains to set the upper threshold value, generally interactively, by using a representative histogram of the distribution of the pixels according to their grayscale value (from 0, black, to 255, white). The conserved pixels representative of the porosity are then coded as black (0) and the others as white (1) and give a binary image. [0218] Determination of the area content of the porosities relative to the area of the pixels coded as black (0) representative of the porosity on the area of the working zone. This value can be calculated automatically by the image analysis software.
The mean porosity content finally retained according to the invention is the mean value of the porosity contents obtained on a sufficient number of microstructure images taken randomly (5 to 10 images) via the method described previously.

[0219] A cathode sputtering target for performing the present invention is formed, on the one hand, from an oxide of at least one element chosen from the group of titanium, silicon and zirconium and, on the other hand, of particles of a metal included in the group formed by silver, gold, platinum, copper and nickel or particles of an alloy formed from at least two of these metals, the M/Me atomic ratio in said target being less than 1.5, M representing all of the atoms of the elements of said group of titanium, silicon and zirconium present in said layer and Me representing all of the atoms of the metals of the group formed by silver, gold, platinum, copper and nickel present in said layer.