|| List of recent Diamond-related patents
|Global investment grade for natural and synthetic gems used in financial investments and commercial trading and method of creating standardized baskets of gems to be used in financial and commerical products|
A process to create a fungible global standard for diamonds and gemstones. The process involves grouping diamonds in an investment standard according to their gemological, proportional, optical and light behavior characteristics.
|Supply chain architecture|
The disclosed architecture is an end-to-end supply chain audit and compliance architecture that enables users to capture pertinent supplier information throughout the entire supply chain, and conduct comprehensive risk analysis as part of due diligence compliance efforts. The architecture find particular applicability to monitoring the origin and introduction into the supply chain of conflict minerals, such as gold, diamonds, oil, etc., that have been obtained illegally or against moral and ethical standards.
|Cutting burr shank configuration|
A cutting burr that includes a pair of axially spaced diamond-shaped portions designed to be keyed into a spindle of a locking mechanism of a high speed surgical drilling instrument and adapted to fit into a single pawl thereof to lock said cutting burr in place so as to prevent axial movement thereof and provide concentric rotation of said cutting burr without any wobbling. The orientation of both portions may be identical with respect to a center plan and diamond shape in the portion at the proximal end of the shank of the cutting tool may be larger than the intermediately located diamond shape of the other portion.
An improvement over known hydraulic fracturing fluids. Boundary layer kinetic mixing material is added to components of fracturing fluid wherein kinetic mixing material is a plurality of particles wherein at least 25% of particles are several types, i.e., having surface characteristics of thin walls, three dimensional wedge-like sharp blades, points, jagged bladelike surfaces, thin blade surfaces, three-dimensional blade shapes that may have shapes similar to a “y”, “v” or “x” shape or other geometric shape, slightly curved thin walls having a shape similar to an egg shell shape, crushed hollow spheres, sharp bladelike features, 90° corners that are well defined, conglomerated protruding arms in various shapes, such as cylinders, rectangles, y-shaped particles, x-shaped particles, octagons, pentagon, triangles, and diamonds.
|System and method for determining the market price for an individual diamond|
A diamond appraisal system and method is described that allows a user select a diamond to be appraised. Based on characteristics of the appraisal diamond, comparison diamonds are selected from one or more market databases.
|Method and apparatus to fabricate vias in the gan layer of gan mmics|
The method and apparatus to fabricate vias in the gallium nitride (“gan”) layer of a gan monolithic microwave integrated circuit (“mmic”). The method and apparatus create vias in the gan layer of a gan mmic through the use of controlled laser ablation and spectroscopic analysis of sic and cvd diamond mmics.
|Method and apparatus for delivery of molecules to cells|
The present invention is concerned with a system and method for introducing a substance into cells. The system has an assembly including a plurality of elongate non-hollow nanoneedles forming a nanoneedle array or patch for delivering the substance into the cells, at least some of the nanoneedles have a non-uniform diameter with a wider upper end, a narrower lower end for penetration into the cells and a length from substantially 200 nm to 100 um.
|High energy density storage device|
A device and method for providing electrical energy storage of high specific energy density. The device contains a plurality of layers of high dielectric constant material, such as barium titanate or hexagonal barium titanate, sandwiched between electrode layers made up of a variety of possible conducting materials.
|Diamond bonded construction with improved braze joint|
Diamond bonded constructions comprise a body comprising a plurality of bonded together diamond grains with interstitial regions disposed between the grains that are substantially free of the catalyst material used to initially sinter the body. A metallic substrate is attached to the body, and a braze joint is interposed between the body and the substrate.
|Polycrystalline diamond cutting elements with engineered porosity and method for manufacturing such cutting elements|
A method for facilitating infiltration of an infiltrant material into a tsp material during re-bonding of the tsp material to a substrate, by enhancing the porosity of the tsp material near the interface with the substrate is provided. Cutting elements formed by such method and downhole tools including such cutting elements are also provided..
|Superabrasive material with protective adhesive coating and method for producing said coating|
A coating on mono- or poly-crystalline diamond or diamond-containing material includes a first adhesive layer formed directly on the diamond or diamond-containing material, the first layer including tungsten and tungsten carbide alloyed with fluorine in an amount of 0.001 to 0.12 wt % calculated on the total weight of the first layer. The coating further includes a second protective layer formed on the first layer, the second layer including at least tungsten alloyed with fluorine in an amount of 0.001 to 0.12 wt % calculated on the total weight of the second layer.
|Combinational synthesis of diamond|
A combinatorial synthesis of the diamond unit cell is disclosed wherein a carbon atom free of meta-stable radical impurities reacts with cyclic hydrocarbon compounds or heterocyclic compounds whose structure is tetrahedral or nearly tetrahedral. Reactions conducted in the vapor phase and in the solid state are disclosed..
|Polycrystalline diamond construction and method of making same|
A polycrystalline diamond construction comprises diamond grains exhibiting inter-granular bonding and defining a plurality of interstitial regions, and a non-diamond phase at least partially filling a plurality of the interstitial regions to form non-diamond pools. The percentage of non-diamond phase in the total area of a cross-section of the body of polycrystalline diamond material is between around 0 to 5%, and the average nearest neighbour distance between grains of the non-diamond phase is less than around 1.3 microns in an analysed image of a cross-section through the body of polycrystalline material when analysed using an image analysis technique at a magnification of around 1000 and an image area of 1280 by 960 pixels; or is between around 5 to 10%, and the average nearest neighbour distance between grains of the non-diamond phase is less than around 1.04 microns, or is between around 10 to 15%, and the average nearest neighbour distance between grains of the non-diamond phase is less than around 1.04 microns, or is between around 15 to 30%, and the average nearest neighbour distance between grains of the non-diamond phase is less than around 0.8 microns..
|Jewellery cleaning wipe|
It is surprisingly found that when diamond particles are embedded into an alcohol wipe, the cleansing wipe that is formed is extremely useful at cleaning diamond jewellery in the home. It is also surprising that, given the abrasive nature of diamond, the diamond particles result in a satisfactory clean without causing any damage to the surface of the diamond being cleaned.
|Method of forming a thermally stable diamond cutting element|
A method for forming a diamond body includes placing a thermally stable polycrystalline diamond body and a first substrate into an enclosure, the thermally stable polycrystalline diamond body comprising a plurality of bonded diamond crystals and a plurality of interstitial regions between the bonded diamond crystals, the interstitial regions being substantially free of a catalyst material, heating the thermally stable polycrystalline diamond body and the first substrate to remove residual materials from the thermally stable polycrystalline diamond body, subjecting the thermally stable polycrystalline diamond body and the first substrate to a vacuum for evacuating such residual material, and pressing under high temperature the enclosure, the thermally stable polycrystalline diamond body and the first substrate while maintaining a vacuum in the enclosure to bond the thermally stable polycrystalline diamond body to the substrate.. .
|Standard diamond parcel certification for exchange traded funds|
Standard diamond parcels (sdps) are certified for use in exchange traded funds (etfs). Three sdp colour types, luxury, premium and privilege along with seven weight ranges simplify the complexity of diamond trading into twenty one different types of sdps.
|Systems and methods for bundling diamonds into valued groupings|
This disclosure relates to systems for bundling diamonds and determining a relative value of the diamonds within the bundle and the value of the bundle. Also described are methods for using the determined relative diamond values in diamond transactions and contracts..
|Assisted cutting balloon|
A dilation balloon is wrapped in one or more patterns with a wire or braided material having diamond abrasive or other abrasive material bonded thereto. The wire or braided material is vibrated in one or more ways to enhance the cutting action of the wire abrasive.
|Grinding tool and method for producing same|
A grinding tool, such as a cutting disc, includes a matrix, in particular a sintered metal matrix, and diamonds embedded in the matrix. At least the majority of the diamonds are each assigned at least one wear-promoting particle and/or at least one wear-inhibiting particle.
|Methods for wet chemistry polishing for improved low viscosity printing in solar cell fabrication|
A method of fabricating a solar cell is disclosed. The method includes forming a polished surface on a silicon substrate and forming a first flowable matrix in an interdigitated pattern on the polished surface, where the polished surface allows the first flowable matrix to form an interdigitated pattern comprising features of uniform thickness and width.
|Method of detecting mycobacterium tuberculosis complex by cell filtrate protein 10-loaded detonation nanodiamond|
A method of detecting mycobacterium tuberculosis complex (mtbc) in a culture media is provided, in which, the culture media containing the mtbc and a biomarker, such as cfp-10, secreted from the mtbc is provided, the culture media is filtered to obtain a filtrate, detonation nanodiamond particles are mixed with the filtrate to form biomarker-loaded detonation nanodiamond particles, and a mass spectrometry analysis process is performed on the biomarker-loaded detonation nanodiamond particles for detecting the biomarker.. .
|Surface modified dental implant|
A dental implant provided herein includes a body including titanium or titanium alloy and a diamond-like coating on the body. The diamond-like coating has a surface kurtosis rku value of at least 1.5, a surface skewness rsk value of at least 1.2, or a combination thereof to have an increase in gingival cell adhesion to the implant in soft tissue surrounding the dental implant when a portion of the dental implant is implanted into a jaw bone..
|Siloxane coating for a display lens assembly for mobile devices|
Hard coatings are applied to a lens assembly. In an embodiment, the coated lens assembly (140) includes a first layer (106b) including siloxane; a second layer (106a) including siloxane, wherein the second layer has opposing sides and a hardness greater than the first layer; and a third layer (104) including an amorphous carbon selected from a diamond-like carbon and a diamond-like nano-composite.
|Method for growth of vertically aligned carbon nanotubes on diamond substrates|
Method of growing carbon nanotubes which are substantially vertically aligned on a diamond-based substrate via a chemical vapor deposition system utilizing an iron-based catalyst is disclosed.. .
|Head gimbal assembly with diamond-like coating (dlc) at tongue/dimple interface to reduce friction and fretting wear|
A gimbal assembly of a single or dual stage actuator is provided with a layer of diamond-like carbon (dlc) as a middle layer at a tongue/dimple interface where a dimple of a supporting loadbeam contacts a tongue on the gimbal assembly. Using the dlc at the tongue/dimple interface greatly reduces the amount of fretting wear particles formed during operation of the microactuator.
|Display for mobile device with abrasion resistant siloxane coating|
An abrasion resistant coating (206) is applied to a display (202) of a mobile device (200). In an embodiment, the coating (140) includes a first layer (106b) including siloxane; a second layer (106a) including siloxane, wherein the second layer has opposing sides and a hardness greater than the first layer; and a third layer (104) including an amorphous carbon selected from a diamond-like carbon and a diamond-like nano-composite.
|Tip for a pick tool, method of making same and pick tool comprising same|
A tip for a pick tool, comprising a polycrystalline diamond (pcd) structure joined to a substrate body. The pcd structure has a strike surface including an apex opposite a boundary with the substrate body.
|Nanocrystalline diamond three-dimensional films in patterned semiconductor substrates|
An array of through-silicon vias (tsvs) are formed in a silicone substrate. The vias can be tapered such that the diameter of the via at the surface of the substrate is larger than the diameter of the via at its bottom, with the diameter varying continuously along its depth.
|Devices including a diamond layer|
A device includes a substrate layer, a diamond layer, and a device layer. The device layer is patterned.
|Double sided sl(ge)/sapphire/lll-nitride hybrid structure|
One aspect of the present invention is a double sided hybrid crystal structure including a trigonal sapphire wafer containing a (0001) c-plane and having front and rear sides. The sapphire wafer is substantially transparent to light in the visible and infrared spectra, and also provides insulation with respect to electromagnetic radio frequency noise.
|Polycrystalline diamond drill blanks with improved carbide interface geometries|
A cutting element and a method of making the superabrasive cutter are disclosed. The cutting element has a substrate and a superabrasive layer.
|Polycrystalline compacts including diamond nanoparticles, cutting elements and earth-boring tools including such compacts, and methods of forming same|
A polycrystalline compact comprises a plurality of diamond grains of micron size, submicron size, or both, and a plurality of diamond nanoparticles disposed in interstitial spaces between the plurality of diamond grains. A method of forming a polycrystalline compact comprises combining a plurality of micron and/or submicron-sized diamond grains and a plurality of diamond nanoparticles to form a mixture and sintering the mixture in a presence of a carburized binder to form a polycrystalline hard material comprising a plurality of inter-bonded diamond grains and diamond nanoparticles.
|Cutting element with improved substrate material|
Cutting elements comprise a body and a polycrystalline diamond table disposed thereon, wherein the diamond table has a thickness of greater than about 2 mm. The body is specially formed from wc—co and has a co content of equal to or less than about 10 weight percent based on the total weight of the wc—co, a coefficient of thermal expansion that is less than about 5×10−6/° c., a palmqvist toughness greater than about 180 kg/mm, and a hardness equal to or greater than about 88 hra.
|Polycrystalline diamond composite compact|
A polycrystalline diamond (pcd) composite compact element comprising a pcd structure bonded to a cemented carbide substrate, in which at least a peripheral region of the substrate comprises cemented carbide material having a mean free path (mfp) characteristic of at least about 0.1 microns and at most about 0.7 microns; and an elastic limit of at least about 1.9 gpa.. .
|Carbonate pcd and methods of making the same|
A polycrystalline diamond body, and a method for making a carbonate polycrystalline diamond body includes combining a first quantity of diamond particles with a first quantity of magnesium carbonate to form a first layer in an enclosure, the first layer having a working surface, and placing a second quantity of magnesium carbonate in the enclosure forming a second layer, the first layer and the second layer forming an assembly. A quantity of at least one of silicon or aluminum is mixed in with or placed adjacent to at least one of the first layer or the second layer.
|Carbonate pcd with a distribution of si and/or al|
A method for making a carbonate polycrystalline diamond body includes combining a first quantity of diamond with a first quantity of magnesium carbonate to form a first layer for forming a working surface, and combining a second quantity of magnesium carbonate to form a second layer adjacent to the first layer, forming an assembly. The method includes placing a quantity of silicon or aluminum in or adjacent to at least a portion of the assembly and sintering the assembly including the silicon or aluminum at high pressure and high temperature, causing the silicon or aluminum to infiltrate at least one layer of the assembly..
|Delayed diffusion of novel species from the back side of carbide|
A polycrystalline diamond compact (pdc) is fabricated using a process of delayed diffusion of a diffusion species (e.g., a metalloid) introduced from the back side of a cemented carbide further away from the diamond grit or from the flank side of the cemented carbide, as opposed to the side of the cemented carbide adjacent to the diamond grit. The process of fabricating the pdc includes depositing, in a metal container, a diamond grit, a cemented carbide, and a diffusion species, then applying a high pressure and high temperature (hpht) to the contents of the metal container wherein (1) the binder of cemented carbide diffuses across the diamond grit, and (2) the diffusion species diffuses through the cemented carbide, and then through the diamond grit, thus providing a protective coating to the diamond grains of the pdc..
|Method for manufacturing semiconductor device|
A method for manufacturing a semiconductor device is disclosed. In one aspect the method includes forming a gate stack over a substrate.
|Diamond-like carbon film and method for fabricating the same|
A diamond-like carbon film for improving an efficiency of a field emitting element is disclosed in the present invention. The abovementioned diamond-like carbon film is deposited on a substrate and uses a mixture of graphite fiber and diamond powder as its nucleation layer.
|Crystallization and bleaching of diamond-like carbon and silicon oxynitride thin films|
Optically transparent diamond-like carbon (dlc) thin films are formed using relatively low-temperature deposition conditions followed by a post-deposition bleaching step. The bleaching can include exposure of an as-deposited thin film to uv laser radiation, which reduces the concentration of defects in the film.
|Bearing apparatuses including dual material bearing surfaces|
Embodiments of the invention relate to bearing apparatuses in which one bearing surface of the bearing apparatus includes diamond, while another bearing surface includes a non-diamond superhard material (e.g., silicon carbide). For example, a bearing apparatus may include a bearing stator assembly and a bearing rotor assembly.
|Non-destructive leaching depth measurement using capacitance spectroscopy|
A method of characterizing a quality of a polycrystalline diamond compact (pdc) cutter includes obtaining a pdc cutter that includes a leached layer and an unleached layer. The unleached layer is positioned adjacent to the leached layer, and the leached layer has at least a portion of a catalyst material removed from therein.
|Aquaculture net with walls with different wire direction|
An aquaculture net (20) has one or more side walls. These side walls comprise wires (12, 14) in a wavy form with maxima and minima, wherein the maxima of one wire (12) interlock with minima of a neighboring wire (14) to form patterns of a series of diamonds.
|Cutter assemblies, disc cutters, and related methods of manufacture|
In an embodiment, a cutter assembly for use on a tunnel boring machine may include a cutter ring extending circumferentially about a central axis. The cutter ring may include a radially inner surface and a radially outer surface.
|System and method to facilitate thermal transfer for motor drive features using diamond like carbon coating|
The present disclosure includes a motor drive that includes a rectifier module, an inverter module, drive circuitry, and a heat dissipation feature. The heat dissipation feature is at least partially coated with a diamond-like carbon material in accordance with present embodiments.
|High-precision ghz clock generation using spin states in diamond|
Techniques for obtaining a frequency standard using the crystal field splitting frequency of nitrogen vacancy center in diamond are disclosed. In certain exemplary embodiments, a microwave field is applied to the diamond and optically exciting the diamond under green light.
|Erosion and wear resistant sonoelectrochemical probe|
The present invention, in one set of embodiments, provides methods and systems for integrating conducting diamond electrodes into a high power acoustic resonator. More specifically, but not by way of limitation, in certain embodiments of the present invention, diamond electrodes may be integrated into a high power acoustic resonator to provide a robust sensing device that may provide for acoustic cleaning of the electrodes and increasing the rate of mass transport to the diamond electrodes.
|Methods of fabricating polycrystalline diamond by functionalizing diamond nanoparticles, green bodies including functionalized diamond nanoparticles, and methods of forming polycrystalline diamond cutting elements|
Method of fabricating polycrystalline diamond include functionalizing surfaces of diamond nanoparticles with fluorine, combining the functionalized diamond nanoparticles with a polymer to form a mixture, and subjecting the mixture to high pressure and high temperature (hpht) conditions to form inter-granular bonds between the diamond nanoparticles. A green body includes a plurality of diamond nanoparticles functionalized with fluorine, and a polymer material interspersed with the plurality of diamond nanoparticles.
|Downhole dual cutting reamer|
A downhole dual cutting reamer for bidirectional reaming of a wellbore with a tubular body with two cutting sections between end segments. Each cutting section has a plurality of helical blades separated by a flute, and wherein the helical blades are formed from at least two spiral angled sections connected together, with cutting components on the spiral angled sections.
|Method for manufacturing an electrodeposited diamond wire saw using patterned non-conductive materials|
The present invention relates to an electrodeposited diamond wire saw using patterned non-conductive materials in which non-conductive materials are pre-patterned along the outer circumference of a wire on which diamond grit should not be rubbed, before the diamond grit is upset, in order to efficiently improve the manufacturing process, and to a method for manufacturing same. According to one preferred embodiment of the invention, the method for manufacturing an electrodeposited diamond wire saw includes: printing a masking solution on the outer circumference of a wire in a plurality of directions when the wire is inserted for patterning; and upsetting diamond grit on the remaining regions of the outer circumference of the wire, with the exception of the patterned region..
|Expanded metal and process of making the same|
An expanded metal is provided including a plurality of integral strands defining diamond shapes, each diamond shape having a long dimension as measured from two opposing vertices and a short dimension, generally transverse to the long direction, as measured between two other opposing vertices, such that the long dimension is less than twice the short dimension.. .
|Hardfacing materials including pcd particles, earth-boring tools comprising crushed polycrystalline diamond material, and related methods|
A hardfacing material includes a metal matrix material and particles of crushed polycrystalline diamond material embedded within the metal matrix material. An earth-boring tool includes a body comprising particles of fragmented polycrystalline diamond material embedded within a metal matrix material.
|Frictional trans-epithelial tissue disruption collection apparatus and method of inducing an immune response|
In an embodiment of the invention, a frictional tissue sampling device with a head designed to be rotated without rotating off the designated site can be used to obtain tissue biopsy samples. A frictional tissue sampling device with a head designed to be rotated without rotating off the designated site can be used to obtain an epithelial tissue biopsy sample from lesions.
|O-amino benzonitrile compounds, method for preparing same and uses thereof|
It relates to an anthranilonitrile compound, and to the process for preparing the said anthranilonitrile compound, and to its use. The anthranilonitrile compound has a chemical general formula (i).
2:1 cocrystals of amino acids and li+ salts crystallize from hot water to afford water stable cationic networks based upon tetrahedral lithium cations: bilayered square grids, a lithium zeolitic metal-organic material (lizmom) and several lithium diamondoid metal-organic materials (lidmoms). The compositions may be used as a pharmaceutical for the treatment of suicidality and other disorders that require lithium to penetrate the blood brain barrier and exert therapeutic effects in the cns.
|Bearing apparatus having superhard bearing elements|
Bearing assemblies and apparatuses are disclosed. Such bearing assemblies may be employed in bearing apparatuses for use in downhole motors of a subterranean drilling system or other mechanical systems.
|Cup with twinkling light effects|
This invention provides a cup with twinkling light effects, primarily comprising an inner cup, an outer cup, and a light unit, with the lower half of the inner cup having a number of arched convex strips, and the base of which has diamond-facet of concave and convex cones. As a result, when the light unit at the base of the outer cup is activated, the effects of the arched convex strips and diamond facets cause the cup to produce numerous refractions of the light source, creating twinkling rays of light with dazzling variation..
|Methods for pre-sharpening impregnated cutting structures for bits, resulting cutting structures and drill bits so equipped|
Processes for pre-sharpening cutting structures comprising particles of superabrasive material such as diamond grit, dispersed in a metal matrix material such as cemented tungsten carbide. Matrix material may be removed from a surface of a cutting structure to a desired depth to expose superabrasive particles within the matrix material adjacent the surface, and to increase exposure of partially exposed superabrasive particles at the surface.
|Tube welding rod resistant to low stress abrasion|
A tube welding rod resistant to low stress abrasion comprises a welded tube and a filler filling the welded tube. Components of the filler comprise macrocrystalline tungsten carbide particles, cast tungsten carbide particles and/or spherical cast tungsten carbide particles undergone surface carburization treatment, mechanically ground cast tungsten carbide particles, alloy powder, and an organic binder.
|Composite polycrystalline diamond body|
In this novel pdc cutter, diamond powders of different composition and/or different grain size, are distributed, shaped, and compacted with a novel pressing tool, in multiple stages, spatially arranged into different regions of the pdc diamond body, then hpht sintered to form one pdc body with spatially varying hardness, toughness and thermal resistance.. .
|Golf club handle training aid|
A golf aid is provided. The golf aid includes a golf club handle having a grip.
|Ductile mode machining methods for hard and brittle components of plasma processing apparatuses|
A method of ductile mode machining a component of a plasma processing apparatus wherein the component is made of nonmetallic hard and brittle material wherein the method comprises single point turning the component with a diamond cutting tool causing a portion of the nonmetallic hard and brittle material to undergo a high pressure phase transformation to form a ductile phase portion of the hard and brittle material during chip formation wherein a turned surface is formed from a phase changed material and the turned surface is a grooved textured surface of phase changed material.. .
|Diamond particle mololayer heat spreaders and associated methods|
Thermally regulated semiconductor devices having reduced thermally induced defects are provided, including associated methods. Such a device can include a heat spreader having a monolayer of diamond particles within a thin metal matrix and a semiconductor material thermally coupled to the heat spreader.
|Glass substrate for information recording medium and method for manufacturing the same|
The present invention relates to a method for manufacturing a glass substrate for an information recording medium having a high level of cleanness and superior smoothness. The manufacturing method includes a step for washing a disk-shaped glass plate with an acid washing liquid, a step for removing at least part of a surface layer, which is formed on the surface of the glass plate, by performing grinding with diamond abrasion grains, and a step for washing the surface with a neutral or alkaline washing liquid..
|Microwave plasma reactors and substrates for synthetic diamond manufacture|
A microwave plasma reactor for manufacturing synthetic diamond material via chemical vapour deposition, the microwave plasma reactor comprising: a microwave generator configured to generate microwaves at a frequency f; a plasma chamber comprising a base, a top plate, and a side wall extending from said base to said top plate defining a resonance cavity for supporting a microwave resonance mode between the base and the top plate; a microwave coupling configuration for feeding microwaves from the microwave generator into the plasma chamber; a gas flow system for feeding process gases into the plasma chamber and removing them therefrom; a substrate holder disposed in the plasma chamber and comprising a supporting surface for supporting a substrate; and a substrate disposed on the supporting surface, the substrate having a growth surface on which the synthetic diamond material is to be deposited in use, wherein the substrate dimensions and location within the resonance cavity are selected to generate a localized axisymmetric ez electric field profile across the growth surface in use, the localized axisymmetric ez electric field profile comprising a substantially flat central portion bound by a ring of higher electric field, the substantially flat central portion extending over at least 60% of an area of the growth surface of the substrate and having an ez electric field variation of no more than ±10% of a central ez electric field strength, the ring of higher electric field being disposed around the central portion and having a peak ez electric field strength in a range 10% to 50% higher than the central ez electric field strength.. .