JPH1149596A - Diamond - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microwave transmission window made of CVD diamond, which shows comparatively lesser variation in dielectric constant and dielectric loss with temp., and which the rise in temp. is hardly caused. SOLUTION: The diamond electromagnetic-wave transmission window for light having wavelengths equal to or longer than those of infrared rays, has a CVD diamond layer 14 which shows the following characteristics: (i) >=3,200 mm<2> active area; and (ii) average dielectric loss throughout the active area, so as to meet any one or both of the following conditions at <=20 deg.C: the absorption coefficient at 10.6 μm is <0.1 cm<-1> ; and the dielectric loss angle at 140 GHz is <=150 μrad.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to diamond, and more particularly to diamond produced by chemical vapor deposition (hereinafter referred to as "CVD") suitable for use as an electromagnetic transmission window for long wavelengths above infrared. Such a transmission window can be used to protect the electromagnetic source or detector from environmental factors.

[0002]

2. Description of the Related Art The source or detector of electromagnetic waves is based on the presence of the atmosphere,
There is a need to protect against environmental factors such as movement relative to the atmosphere, the ingress of dust or aggressive substances. In many such applications, the properties of the window are fundamental to the design of the device, so that the performance of the device is currently severely limited by the available windows.

For example, microwave windows for the beam exit of gyrotrons and other high power microwave sources maintain the high vacuum required for operation of the device, but do not allow the high intensity microwave beam to exit the window. Is not required to be destroyed. Current gyrotrons operate in pulses rather than continuously, or
It is limited to those operated with power less than 0 kW.
This is because both relatively high dielectric loss and / or relatively low thermal conductivity in the window can result in thermal damage to the window. In the case of sapphire windows, the dielectric loss of the material is a decreasing function of the temperature down to the freezing temperature, but these conditions are expensive to maintain and create the potential for a thermal runaway catastrophe.

[0004] Other examples can be found in military imaging and target capture applications. For example, high speed missiles are currently limited by the thermal / mechanical performance of windows that protect infrared guidance devices. In addition, the moving and stopping and launch platform views and target capture windows, such as tanks, helicopters, etc., are easily damaged by aggressive materials such as dust and sand, and their size depends on the mechanical properties of the material. Limited. Apart from that, they can only show a very limited range of transmission capabilities, so that they cannot be used as multi-frequency windows for a range of sources and detectors, or are otherwise preferred choices. It is a certain thing.

Like diamond on a substrate by CVD
The method of depositing various materials is well-established at present.
It is described in detail in Yu and other literature. diamond
When depositing on a substrate, the method is generally a gas mixture.
The gas mixture is decomposed into atomic
Hydrogen or halogen (eg, F, Cl) and C, ie, carbon
Radicals containing sulfur, and other reactive substances, for example,
CHx, CFx (where x is 1-4)
Can be. In addition, such as sources for nitrogen and boron,
An oxygen-containing source may be present. Helicopter in many steps
Inert gas such as chromium, neon, or argon
It may be. For example, a typical source gas mixture is charcoal
Hydrogen Cx Yy (where x and y are each 1 to 4
Halocarbon Cx Yy Halz (where x, y and
And z are 1 to 10, respectively, or COx (where x is
1-3) and optionally the following: O
_Two, H _Two, N_Two, NH_Three, B_TwoH_FiveAnd inert gas
Including more than kind. Each gas is its natural isotope
Ratios, or the relative isotope ratios
It may be artificially adjusted, for example, hydrogen is deuterium
Or may be present as tritium, wherein carbon is¹²C also
Is¹³It may exist as C. Minutes of source gas mixture
The solution is microwave, laser, RF energy, flame, or
Is attracted by energy sources like hot filaments
The reactive gas substance thus generated
Can adhere to the body and form diamond
You.

The dielectric properties of a material are defined by two quantities: dielectric constant (or dielectric constant) dielectric loss

[0007] These quantities are well known in the theory of the electromagnetic properties of materials and are described in many textbooks. In short: permittivity is usually measured against vacuum,
Therefore it is a number. It is a measure of a material's ability to retain a charge in an electrostatic field. In an alternating electromagnetic field, the dielectric constant is also a measure of the speed of propagation of an electromagnetic wave in a material relative to the speed in vacuum. It can also be considered as a measure of the reduction of electromagnetic waves in a material relative to vacuum. The value of the dielectric constant can, in some applications, determine the optimal thickness of the window so as to minimize reflection by making the thickness an integral multiple of half a wavelength.

[0008] Dielectric loss is a measure of the attenuation of an electromagnetic wave as it passes through a material. It is the normal deviation angle (loss angle)
Or the tangent of the angle (loss tangent), expressed in radians (generally here as microradians equivalent to 10 ⁻⁶ radians) or a number equal to the tangent, respectively. For small angles (less than 0.1 radians), these two numbers are substantially the same. The value of the dielectric loss, for example, without being subjected to excessive heating and without causing excessive attenuation of the incident wave,
Determines the window's ability to transmit high power electromagnetic waves. Its value at tropical castles also determines the emission of thermal radiation in the window as a function of temperature, which protects the heat ray detection or imaging equipment and makes it as small as possible in applications where it may be heated during use. There is a need.

[0009] Dielectric loss can be measured by both resonant cavity (ie, standing wave) and beam (ie, traveling wave) systems. Beam testing is closer to the end use, but most of the testing is performed in a resonant cavity for simplicity, but the measurements are based on the shape of the standing wave pattern formed in the material and the shape of the cavity. Has the restriction that it is different from that caused by the transition to.

The details of resonant cavity measurements are well documented in the literature [eg, Sussmann et al. (199)
4) -RS Sussman, JR Brandon, GA
Scarsbrook, CG Sweeney
ey), TJ Valentine (Valentine), AJ Whitehead (Whitehead), CJH Walt (Diamond an)
d Related Materials, 3 (1994) 303-312]. The plate under test is placed essentially at one end of the microwave cavity and its thickness is ideally set to the wavelength λ of the microwave in diamond.
Integer m times 1/4 of If there is a nodal point in the microwave on the surface in contact with the end of the resonator and if m is an even number (thickness of an integral multiple of λ / 2), then there is a nodal point on the free surface and if m is In the odd case, there is an antinode on the free surface. If the sample exhibits a significant variation in loss tangent over its thickness, the dielectric loss measured by this technique will vary depending on the orientation of the disk under test. For the purposes of the present description and claims, this measurement is acceptable as long as the dielectric loss value taken is the average of the two orientations.

[0011] Alternatively, the sample can be measured using a focused microwave beam in a manner similar to the end use of the window. In a typical application, a microwave window is inserted at a right angle of incidence into a traveling wave beam in free space. However, due to the large refractive index of diamond,
Since the reflection from both surfaces of the window is large, a standing wave is formed inside the window. In this case, the standing wave pattern is determined solely by the geometry of the window, and therefore, will differ from that which would exist if the window were tested at one end of the resonator, as described above. Please be careful. For this reason, it is preferred in principle to test the window using a beam test, but conventional testing by this method is usually ruled out due to cost and other practical issues. The beam test method is similar to the laser calorimetry method used to measure the absorption coefficient in the infrared region [e.g., Massart
(Massart) et al. (1995)-M Massert, P Union, GA Scarsbrook, R
S Sussmann, P Muys, SPIE, Vol. 2
714, pp.177-184 (1996)].

[0012]

For many applications, especially in systems involving the propagation of high power microwave radiation, it is advantageous that the permittivity and dielectric loss remain relatively invariant with temperature. If the dielectric loss increases with increasing temperature, for example, the system may undergo thermal breakdown. In applications where the thickness of the window is designed to be an integral multiple of half the wavelength to minimize reflections, the window cannot be adjusted due to variations in dielectric constant with temperature, and its transmission characteristics are limited by the thermal load of the transmitted beam. It fluctuates in applications that cause a significant rise in window temperature.

One material commonly used in microwave window applications is sapphire. The temperature dependence of the dielectric loss of sapphire is shown in FIG. It can be seen that both are relatively sharp functions of temperature. At room temperature, the loss angle of sapphire is close to 200 microradians (2 × 10 ^-4 radians). This value is considered unacceptably high for a gyrotron tube operating at well above 100 KW, and therefore devices have been developed for this application using cryogenically cooled window assemblies. These are actually quite complicated. There is also a risk of thermal spikes due to temperature fluctuations that cause catastrophic failure.

[0014]

SUMMARY OF THE INVENTION According to the present invention, there is provided the use of a CVD diamond layer as an electromagnetic transmission window for long wavelengths above infrared. The layer exhibits the following properties:

(1) A large active area, that is, an area through which electromagnetic waves pass is large. Active area of the CVD diamond layer is 3200 mm ^2, preferably greater than 7500 mm ^2. The active area is typically circular or oval. When a flat circle, the diameter is preferably at least 65 mm, more preferably at least 100 mm
It is. If it is flat elliptical, the major axis is at least 6
Preferably it is 5 mm, more preferably at least 100 mm. Diamonds outside the active area
It can be used for mounting purposes and will be referred to hereinafter as the "mounting area".

(2) The dielectric loss is small. The average dielectric loss of the layer over the active region satisfies one or both of the following conditions at a temperature of 20 ° C. or less: 10.6 μm;
Less than ^-1, preferably absorption coefficient less than 0.05 cm ^-1, 1
At 40 GHz, the loss angle does not exceed 150 microradians and is generally smaller, preferably less than 100 microradians.

As can be seen from the data set forth in FIG. 2, the dielectric loss of a material changes with frequency. The dielectric loss is taken as the average effective dielectric loss of the sample with a diameter (1 / e) of 1/5 to 1/3 of the active area centered on the Gaussian plane near the geometric center of the active area. Can be. The data described in FIG.
It was obtained over GHz. Of course, the measurement can be performed at another frequency, for example, in the range of 50 to 200 GHz.

Further, the layer preferably has one or more of the following characteristics: (3) The dielectric loss of the active region at 140 GHz is 20
The increase per 100 ° C. over the temperature range from 0 K to 500 K is less than 20%, and more preferably decreases with increasing temperature.

(4) The dielectric constant of the active region at 140 GHz is 100 ° C. over a temperature range of 200 K to 500 K.
The variation per rise is less than 0.5%.

(5) Large thermal conductivity. The thermal conductivity of the active region is greater than 15 W / cmK, typically 18 W / cmK.
It is larger than cmK.

(6) Large strength. The layer is capable of properly attaching the layer over the active area (and attachment area),
It has sufficient strength to perform its function for the intended use. In particular, the breaking strength over the active area is 18 m long
m, width 2 mm, thickness of the layer under consideration or 1.4 mm, whichever is smaller, measured by a three-point bending test, with the nucleation surface at 600 MPa under tension.
a and exceeds 300 MPa with the growth surface under tension. Furthermore, the Weibull modulus is
Either surface tested exceeds 8 and preferably exceeds 10, and when corrected for thickness variations in strength, may exceed 20 with the growth surface under tension.

(7) Dielectric loss under X-ray irradiation is 0.75
It does not increase more than 200% with respect to the dose rate of Gy / s, and is preferably 30% or less.

(8) The dielectric loss is uniform over the active region. The dielectric loss over the active region is sufficiently uniform that in any region larger than 1 cm in diameter it does not exceed the average limit described in (2) above by more than a factor of two.

(9) There is no localized area in the active area of the layer, the local area being sufficient for its absorption to cause significant thermal / mechanical damage of the layer locally.

According to another feature of the present invention, there is provided the use of a CVD diamond layer as an electromagnetic wave transmission window used as an electromagnetic wave transmission window of a longer wavelength than infrared light, wherein the layer has an active region, that is, an electromagnetic wave transmission window. In the region where permeation takes place, at a temperature of 20 ° C. or less, the following conditions: 10.6 μm, less than 0.02 cm ⁻¹ ,
An average dielectric loss satisfying an absorption coefficient of less than ^-1 or a loss angle of less than 50 microradians at 140 GHz, preferably less than 20 microradians;
Of course, it has an active region that optionally has one or more of the characteristics described in (3) to (9) above.

The diamond is preferably polycrystalline, but may be a single crystal grown by CVD or a highly oriented polycrystalline diamond.

According to the present invention, there is further provided an electromagnetic wave transmitting window having a diamond layer as described above.

[0028] The CVD diamond layer comprises a flat surface, a dome,
It may be of any suitable shape, such as a hemisphere, ogive, or part of an aspheric surface. The aspect ratio of the lateral diameter to the thickness is not limited. All forms may be determined in view of strength, optical properties, or aerodynamic properties.

[0029]

DETAILED DESCRIPTION OF THE INVENTION There are three general designs of windows in which the inventive CVD diamond layer for microwave transmission can be used in particular. The exact power capability of each design depends on the window's dielectric loss, its ability to remove heat escaping from the cooled edge (s) of the attached window (s), and the window temperature variations that the design can tolerate. For materials with sub-radian losses or less, the approximate power range of each general design is determined by numerical thermal modeling, taking into account the variability of other properties (such as thermal conductivity with temperature). Can be estimated. These calculations indicate that a microwave transmitting window using the CVD diamond layer of the present invention can be configured to have the following capabilities:

(I) For a simple single-hole window, the transmitted power can range from less than 200 kW to more than 5 MW average power. In this form, the cooling is
This can be achieved by an adhesive metal layer attached to the edge of the window, which layer is attached by brazing, conductive epoxy or the like. Alternatively, the joints (which need not have high thermal conductivity) can be used to form a closed path for the fluid coolant to directly contact the diamond window.

(Ii) In the case of single-hole, double-element windows, where active cooling takes place between the elements, this range can be extended to values in excess of 30 MW.

(Iii) In the case of perforated windows separated by actively cooled cooling elements, this range is 100 MW
Can be expanded up to a value exceeding. The porous structure can be incorporated in one or both of the above methods, and can have fluid cooling inside the support structure that holds the window elements in an array.

The optimal shape for microwave / single window is typically a circular Gaussian beam whose diameter is
It is characterized by a diameter whose intensity drops to 1 / e (d _C , whose window diameter D _W is d _C <D _W <6d _C , more usually 2d _C
The diameter is such that <D _W <5d _C. The main design requirements of such windows are power and power density. When the beams are pulsed, they are subject to the condition that a single pulse is not long enough to exceed the temperature limit of the material or to cause destruction by inducing thermal shock.
It becomes a time average value. The power density P _D can be specified as the total power P _T divided by the characteristic beam area,
That is, a Gaussian beam is as follows.

[0034]

(Equation 1)

In current applications, single windows are typically limited to an average power of less than 120 kW using materials such as sapphire and hexagonal boron nitride. With a duration of up to about 3 seconds, a pulsed power level of up to about 550 kW has been achieved, which is based on the low thermal duty of the window, which avoids thermal destruction. cycle).

Using the CVD diamond window of the present invention,
Much greater power can be passed through the window, allowing operation of high power microwave sources, within a microwave target volume typically used in a controlled atmosphere (eg, vacuum) (eg, each fusion reactor). Or within the material processing cell). In addition, the low absorption coefficient of diamond for infrared radiation from hot objects during processing, combined with the high thermal conductivity of diamond, results in large tolerances for heat emitted from microwave targets. become.

If reflection of the microwave beam at the window is a significant problem, this can be achieved by using plane polarized microwaves incident on the window at Brewster's angle, or by adjusting the thickness of the window to an accurate half-wavelength. It can be adjusted by making it close to an integer multiple. At normal incidence, conditions that make the thickness exactly half a wavelength result in a window that works most efficiently for only a narrow band of frequencies. One advantage of a window operating at Brewster's angle is that it works well over a very wide frequency band. This can have special applications when the window is used in a frequency adaptation device, or with multiple beams of different frequencies.

FIG. 3 schematically illustrates a cross section of a specific example of mounting a microwave window. With reference to this figure, a microwave transmission tube 10 defining a passage 12 having a circular cross section is shown. Extending across the passage 12 is a layer or sheet 14 of CVD diamond, which serves as a window for the tube. Layer 14 is a short metal cylinder or ring 16, 18
Are fixed to their opposing surfaces 14a and 14b by brazing or other methods. These rings are themselves connected to the tube 10 and form a continuous circular seal or joint.

A hollow ring 24 is provided and surrounds an end region 26 of the CVD diamond layer 14. In use, cooling fluid is introduced into the annulus through pipe 28. This cooling fluid helps extract heat from the CVD diamond layer 14.

The active area of the CVD diamond layer illustrated in the figures is circular and defined within the area marked A, ie bounded by the inner surface 30 of the tube 10. It is this region that has the properties defined above.

The illustrated embodiment is an outlet embodiment of the microwave transmission tube. For example, the window can be located across the inlet or inlet of the reactor.

In some applications for multiple bands , the high transmission properties in the infrared and / or microwave and millimeter wave bands can be effectively combined with the transmission in the visible band. Since the absorption in the visible band also depends on the presence of impurities, the materials according to the invention generally show a large transmission in the visible band. The CVD diamond layer of the present invention achieves simultaneously low dielectric losses in all of these frequency bands over a large area.

Discussion of Window Strength The window must have sufficient strength to play its protective role. In general, this means that much more stringent conditions can be applied, but must at least withstand the pressure differential across the surface at atmospheric pressure.

The strength of a brittle ceramic, such as diamond, can be characterized by its breaking strength combined with Weibull modulus to show experimental variation in this value. The exact measured intensity value depends in part on the test used, due to the statistical nature of the flaw effects. The data mentioned hereafter have been obtained using a three-point bending test on bars 18 mm long, 2 mm wide, and 0.4-1.4 mm thick.

The strength data obtained for CVD diamond grown using conditions suitable for producing the CVD diamond layer of the present invention shows that:

(A) The material strength showing the dependence on the sample thickness was 600 MPa with the nucleation surface under tension.
It tends to have a larger lower limit (at greater thickness) and a value greater than 300 MPa with the growth surface under tension.

(B) The strength is higher on the nucleation side than on the growth side.

(C) If the effect of thickness is taken into account, approximately a Weibull modulus of 11 or 23 for the growth surface.

General Method The CVD diamond layer of the present invention can be manufactured using a method having the following general characteristics.

(I) Typically 7 in a microwave reactor
A substrate with a diameter of 0 to 200 mm is introduced. The substrate is typically silicon, tungsten, molybdenum, or silicon carbide, which has been preliminarily cleaned and seeded using, for example, diamond particles (0.5-10 μm particle size).

[0051] throughout (ii) then the material is generated uniform plasma, the Ar (typically in H ₂ 0 to 20
%) To a temperature of 800-1000 ° C. with a gas mixture and a slight etching in place to further clean and condition the material surface.

Because the etching is powerful, it is particularly important at this stage that the chamber design and material selection for its components be such that the material is not transferred by the gas phase or plasma to the substrate surface.

(Iii) It is also important that the impurity content of the environment in which the CVD growth is performed is appropriately controlled. In particular, the method can include one or more of the following features.

(A) Diamond growth occurs in the presence of an atmosphere containing no added nitrogen. High purity gas is used (> 99.999% purity) and the background level of nitrogen is less than 1 ppm.

(B) The transfer of impurities from the reactor where diamond growth takes place to the growth process should be as small as possible. Resonant microwave devices may be used to prevent the plasma from contacting the surface of the substrate (on which diamond growth occurs) and surfaces other than its fixtures. Examples of preferred chamber materials are stainless steel, aluminum and its alloys, copper, gold, and platinum.

(Iv) A large microwave power of 10 to 60 kW and a large plasma power density obtained at a large gas pressure, ie, a pressure of 50 to 400 × 10 ² Pa, are used, depending in part on the area of the substrate used. .

(V) These conditions are maintained in a controlled manner during a growth period, which can be quite long depending on the required layer thickness.

[0058]

The present invention is further illustrated by the following examples. Example 1 (i) In a microwave reactor operating at a nominal 896 MHz, a pre-cleaned tungsten substrate having a diameter of 120 mm, typically having a surface Ra of 0.2 μm,
The substrate was seeded with 2-4 μm diamond particles.

(Ii) Next, using a microwave power of about 50 kW, a plasma is formed over the entire substrate,
Using a mixture of 20 sccm of Ar in 00 sccm of H ₂ , raise it to a temperature of at least 985 ° C. at 130 Torr (171 × 10 ² Pa) and briefly etch in-situ to further etch the substrate surface. Cleaned.

(Iii) Next, CH ₄ (20 sccm) was added to the process to start the growth process, and the conditions were maintained stably during the deposition period.

(Iv) All the gases used are 99.999%
It had the above purity at the source and was further purified near the point of use to ensure that the process gas was not contaminated.

(V) When the growth period was completed, the substrate was removed from the reactor and the 120 mm CVD diamond layer was removed from the substrate. The layer had a thickness of 1.5 mm. The layer or board was then worked flat and cleaned.

(Vi) The CVD diamond layer was removed from the growth step and separated from the substrate. The surface finish of the material can be modified as appropriate for the next application. Conditions for the surface roughness, flatness and parallelism of the finished window are determined by the wavelength and the specifics of the application, and the basic correlations are well known in the optical industry. When applied in the microwave spectrum region, a surface Ra smaller than 200 nm is sufficient under a parallel condition of λ / 10 when the wavelength is on the order of mm, and can be achieved by a precision polishing method. Merged applications including IR and visible wavelengths or I
In the case of R, a controlled polishing method is used to obtain a required value.

Example 2 Using the method described in Example 1, a 120 mm diameter CVD
A diamond layer was synthesized. Samples were prepared from the disks and the dielectric loss was measured as detailed in Table 1. Table 1
Indicates the size and position of the sample and the measured dielectric loss.

[0065]

[Table 1]

The samples prepared for laser calorimetry are detailed in Table 2 below, together with the results obtained.

[0067]

[Table 2]

Example 3 Using the method described in Example 1, a 120 mm diameter CVD
A diamond layer was further synthesized. From this disk, a sample for laser calorimetry was prepared. Table 3 details these samples and the results obtained.

[0069]

[Table 3]

EXAMPLE 4 A series of disks were grown at different thicknesses in the range of 0.4-1.4 mm under the same conditions as reported in the previous example. The mechanical test sample is then transferred to the initial disk thickness (as grown).
Then, these disks were cut into a size of 18 mm in length and 2 mm in width. Next, these samples are placed under tension on the growth surface.
Alternatively, a destructive test is performed with the nucleation surface under tension, and the obtained data is shown in FIG. Thickness measurements using a micrometer on the as-grown surface are estimated to be about 10% greater than the actual thickness due to the roughness, so that the actual breaking strength is about 10% greater than the indicated value. Will grow. Table 4 gives the Weibull modulus calculated from these results. It is important to note that if the flaw size distribution is well determined and gives a large Weibull modulus, the material is very predictable for engineering applications.

The measured strength strongly depends on the thickness. The major reason for this can be shown to be the variation in particle size with thickness and the concomitant increase in flaw size. In addition, in thicker samples, the local stress near the tip of the wound increases further away from the neutral axis, thereby decreasing the intensity measured with both the nucleation and growth surfaces under tension. . Table 4 contains the Weibull modulus calculated for the range of thicknesses used to obtain the intensity data using a function adapted to the experimentally observed variations in the intensity of the growth surface. .

[0072]

[Table 4]

Example 5 A series of samples were taken from a disk synthesized under the same conditions as described in the previous example and processed to a thickness in the range 0.3-1.2 mm. The thermal conductivity of these samples was measured using a known laser flash method and found to be greater than 18 W / cmK.

Example 6 The same conditions as those described in Example 2 were used except that the pressure was 246 × 10 ² Pa and the methane concentration was 1.4%, and the diameter was 120 mm and the thickness was 2300 μm. C
A VD diamond layer was synthesized.

The disk is 100 mm in diameter and 1827 μm in thickness
And polished on both sides. At a frequency of 170 GHz, the loss angle (microradians) was found to be 20 over the center of the disk and over most of the disk. One small area near the edge had a loss angle of about 50 microradians. The samples were tested in the microwave beam-traveling wave state.

[Brief description of the drawings]

FIG. 1 shows 145 for a CVD diamond layer of the present invention.
The variation of the dielectric loss with temperature measured at GHz is calculated as (HE
FIG. 3 is a graph shown for comparison with typical data for M IDEX-) sapphire.

FIG. 2 is a graph showing the frequency variation of dielectric loss over a range of 35-145 GHz measured at room temperature, ie, 20 ° C., in a resonant cavity for a range of samples and orientations.

FIG. 3 is a schematic sectional view of an embodiment of an outlet portion of the microwave transmission tube.

FIG. 4A is the as-grown thickness of the material and the mechanical strength data obtained in this test for rods 18 mm long and 2 mm wide with thicknesses in the range of 0.4-1.4 mm. Is a graph showing strength data obtained by setting the growth surface under tension.

FIG. 4B shows mechanical strength data obtained for the rod with the nucleation surface under tension.

[Explanation of symbols]

 Reference Signs List 10 microwave transmission tube 12 passage 14 CVD diamond window

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Ricardo Simon Sussman Surrey, Guildford, Frovisher Gardens, England 3 (72) Inventor John Robert Brandon, Hampshire, England Winchester, Michael Dover, Northbrook, Lithranan ( 72) Inventor Carlton Nigel Dodge Douglas, British Isles, Harcroft Avenue 33 (72) Inventor Charles Simon James Picrus Twickenham, Chartsey Road, Cavendish House 1 (72) Inventor Andrew John Whitehead Surrey, England , Camberley, Chelesmore Drive 60 (7 2) Inventor Christopher John Howard Wort Upsorp Drive 61, Oxen, Wantage, United Kingdom (72) Inventor Stephen Edward Co. Surrey, Working, Send, England, Boughton Hall Avenue, West England

Claims (30)

[Claims] 1. The following properties: (i) an active area of at least 3200 mm ² , (ii) an average dielectric loss over the active area at a temperature of less than or equal to 20 ° C. that satisfies one or both of the following conditions: 6μ
absorption coefficient of less than 0.1 cm ^{-1 at} m, 15 at 140 GHz
Electromagnetic transmission window for long wavelengths above infrared with a CVD diamond layer exhibiting a loss angle not exceeding 0 microradians. 2. The window according to claim 1, wherein the active area has a circular diameter of at least 65 mm. 3. The window according to claim 1, wherein the active area has a diameter of at least 100 mm in a circle. 4. The active area is elliptical and at least 65
The window of claim 1 having a major axis of mm. 5. The active area is elliptical and at least 10
The window of claim 1 having a major axis of 0 mm. 6. A window according to claim 1, having a loss angle of less than 100 microradians at a frequency of 140 GHz. 7. The method according to claim 1, wherein the dielectric loss in the active region at 140 GHz is less than 20% per 100 ° C. over the temperature range from 200 K to 500 K. window. 8. The window according to claim 1, wherein the dielectric loss of the active region at 140 GHz decreases with increasing temperature. 9. The window according to claim 1, having an absorption coefficient of less than 0.05 cm ^{−1 at} 10.6 μm. 10. The dielectric loss over the active region, in any region with a diameter greater than 1 cm, exceeds the average dielectric loss according to (ii) of any one of claims 1 to 9, more than twice. 10. Not sufficiently uniform.
A window according to any one of the preceding claims. 11. The dielectric constant of the active region at 140 GHz has a variation of less than 0.5% per 100 ° C. increase over a temperature range of 200 K to 500 K.
A window according to any one of the preceding claims. 12. The window according to claim 1, wherein the active region has a thermal conductivity of more than 15 W / cmK. 13. The window according to claim 1, wherein the active region has a thermal conductivity of more than 18 W / cmK. 14. A sample having a length of 18 mm, a width of 2 mm, and a thickness of 1.4 mm or less is measured by a three-point bending test to determine that the strength of the active region is 600 MPa when the tensile strength at break is lower than the nucleation surface under tension. Exceed, 3 with growth surface under tension
14. The window according to any one of claims 1 to 13, having a strength greater than 00 MPa. 15. A dielectric loss under X-ray irradiation of 0.75 G
does not increase by more than 200% for a dose rate of y / s,
The window according to claim 1. 16. A dielectric loss under X-ray irradiation of 0.75 G
15. A window according to any one of the preceding claims, wherein the window does not increase by more than 30% for a dose rate of y / s. 17. At a temperature below 20 ° C., the following conditions:
Absorption coefficient of less than 0.02 cm ^{-1 at} 0.6 μm, 140 G
An electromagnetic transmission window for wavelengths above infrared with a CVD diamond layer having an active region with an average dielectric loss that satisfies one or both of the loss angles at 50 Hz and less than 50 microradians. 18. The method according to claim 1, wherein the active area is 0.01 at 10.6 μm.
18. The window of claim 17, having an absorption coefficient of less than 5 cm- ¹ . 19. The window of claim 17, wherein the active region has a loss angle of less than 20 microradians at 140 GHz. 20. The method according to claim 17, wherein the dielectric loss in the active region at 140 GHz is less than 20% per 100 ° C. over the temperature range from 200 K to 500 K. window. 21. A window according to any one of claims 17 to 19, wherein the dielectric loss of the active region at 140 GHz decreases with increasing temperature. 22. The method of claim 17, wherein the dielectric constant of the active region at 140 GHz varies less than 0.5% per 100 ° C. increase over the temperature range of 200 K to 500 K.
A window according to any one of the preceding claims. 23. A window according to any one of claims 17 to 22, wherein the active region has a thermal conductivity of greater than 15 W / cmK. 24. A window according to any one of claims 17 to 22, wherein the active region has a thermal conductivity of greater than 18 W / cmK. 25. A sample having a length of 18 mm, a width of 2 mm, and a thickness of 1.4 mm or less is measured by a three-point bending test to determine that the strength of the active region is 600 MPa when the tensile strength at break is lower than that of the nucleation surface. Exceed, 3 with growth surface under tension
The window according to any one of claims 17 to 24, having a strength of more than 00 MPa. 26. The dielectric loss over the active region, in any region with a diameter of more than 1 cm, does not exceed the absorption coefficient or the loss tangent limit according to claim 17 by more than twice. 26. The window according to any one of claims 17 to 25, wherein the window is uniform. 27. The window according to claim 1, wherein the diamond is a polycrystalline diamond. 28. The window according to claim 1, wherein the diamond is a single crystal or a highly oriented polycrystalline diamond. 29. A flat, dome, hemisphere, ogive,
Or one of an aspherical surface.
Windows as described in section. 30. A CVD diamond layer having the characteristics described in any one of claims 1 to 29 and used as an electromagnetic transmission window for wavelengths longer than infrared light.