cvd diamond booklet
TRANSCRIPT
The CVD diamond booklet
available at: www.diamond-materials.com/download
Content
1. General properties of diamond..................................... 2
2. Optical Properties .......................................................... 4 Optical transparency.......................................................4 Absorption coefficient at 10.6 µm .................................5 Refractive index: n vs. λ ..................................................6 Refractive index: nd vs. T ................................................7 Refractive index: Thermal coefficient ............................8 X-ray absorption .............................................................9 THz dielectric properties...............................................10 Optical specifications of Diamond Materials...............11
Surface finish, optical coatings and mounting ........12
3. Thermal Properties ...................................................... 13 Thermal conductivity ....................................................13 Thermal conductivity vs. T ............................................14 Specific heat vs. T ..........................................................15 Thermal expansion........................................................16 Thermal specifications of Diamond Materials .............17
4. Mechanical Properties ................................................. 18 Vickers-Hardness ...........................................................18 Mechanical specifications of Diamond Materials ........19
5. Examples of CVD diamond applications ..................... 20
6. Useful formula ............................................................. 23 Bowing of a circular disk under pressure.....................23 Thickness requirements ................................................23
Contact Diamond Materials ............................................... 25
The CVD diamond booklet
Page 1
CVD Diamond wafers prepared by Microwave Plasma CVD: boron doped disk (blue), optical grade diamond, mechanical grade, unpolished disk
The CVD diamond booklet
Page 2
1. General properties of diamond
The most important properties of CVD diamond are the
• unsurpassed hardness
• extremely high thermal conductivity (>1800 W/mK, five times that of copper)
• broad band optical transparency
• extremely chemically inert: Not affected by any acid or other chemicals
• Graphitization only at very high temperatures (T > 700°C in an oxygen containing and 1500°C in an inert atmosphere)
The CVD diamond booklet
Page 3
*highest value of all solid materials
Property Value
Vickers hardness* 10,000 kg/mm2
Young's modulus* 1050 GPa
Poisson's ratio 0.1
Density 3.515 g/cm3
Atom density* 1.77×1023 1/cm3
Thermal expansion coefficient 1.0×10-6/K @300K
Sound velocity* 17,500 m/s
Friction coefficient 0.1
Specific heat @ 20°C 0.502 J/gK
Debye temperature* 1860±10K
Bandgap 5.45 eV
Resistivity 1013 - 1016 Ωcm
The CVD diamond booklet
Page 4
2. Optical Properties
Optical transparency
1 10 1000
10
20
30
40
50
60
70
80
Tran
smis
sio
n (
%)
Wavelength (µm)
Optical transparency of CVD diamond In the UV, Visible, IR and far IR
The spectrum has not been corrected for reflection losses
The CVD diamond booklet
Page 5
Absorption coefficient at 10.6 µm
9.0 9.5 10.0 10.5 11.00.08
0.09
0.10
0.11
0.12
0.13
0.14
Ab
sorp
tio
n c
oef
f. (
cm-1)
Wavelength (µm)
Absorption coefficient of CVD diamond as measured by laser calorimetry
The CVD diamond booklet
Page 6
Refractive index: n vs. λ
1 10 1002.35
2.40
2.45
2.50
Ref
ract
ive
ind
ex
Wavelength (µm)
The spectral variation of n is described by the Sellmeier equation:1
11063356.4
1753306.0
222
2
222
2
+−
+−
=nmxx
nmxxn
where x is the wavelength in nm
1 F. Peter, Z Phys 15, 358 (1923)
The CVD diamond booklet
Page 7
Refractive index: nd vs. T
0 200 400 600 800 1000
0
2
4
6
8
10
12
14
16
∆nd
/nd
(10
-3)
Temperature (°C)
Variation of nd with temperature Patterson et al.2
our data measured at 633 nm wavelength
2 M.J. Patterson et al., Electrochem. Soc. Proc. 95-4, 503 (1995)
The CVD diamond booklet
Page 8
Refractive index: Thermal coefficient
-200 0 200 400 600 800
0.0
1.0
2.0
3.0
4.0
5.0
dn
/dT
(10-5
/K)
Temperature (°C)
Thermal coefficient of the refractive index
Measured by laser refraction of a diamond prism
Measured with laser interferometry Fontanella et al.3
3 J. Fontanella et al., Appl. Opt. 16, 2949 (1977)
The CVD diamond booklet
Page 9
X-ray absorption
0 10 20 30 40 501E-5
1E-4
1E-3
0.01
0.1
1
Tin
Lead
Titanium
BerylliumDiamond
Ab
sorp
tio
n C
oef
fici
ent
(1/µ
m)
Energy (keV)
X-ray absorption coefficient of various materials. Data from http://www.photcoef.com
The CVD diamond booklet
Page 10
THz dielectric properties
0.5 1.0 1.5 2.0 2.5 3.0 3.5-20
-15
-10
-5
0
5
10
15
2010 20 30 40 50 60 70 80 90 100 110
10 20 30 40 50 60 70 80 90 100 1100.0
0.5
1.0
1.5
2.0
2.5
3.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
CVD Diamond
Abs
orpt
ion
Coe
ffici
ent [
cm-1]
Frequency [THz]
Wavenumbers [cm-1]
Ref
ract
ive
Inde
x
Wavenumbers [cm-1]
data from Peter Uhd Jepsen, University of Freiburg
The CVD diamond booklet
Page 11
Optical specifications of Diamond Materials
The core competences of Diamond Materials include the manufacturing of high purity CVD diamond disks with properties approaching those of perfect natural diamond crystals.
Property Value
Transmission 225nm to far IR , > 70% @ 10µm
Refractive index 2.38 @ 10µm, 2.41 @ 500nm
Absorption coefficient ≤ 0.10 cm-1 @ 10µm
Bandgap 5.45 eV
Tensile strength (0.5mm thick)
Nucleation surface in tension 600 MPa
Growth surface in tension 400 MPa
Loss tangent (tanδ @140 GHz) < 2.0×10-5
Dielectric constant 5.7
Properties of optical grade CVD-diamond by Diamond Materials
The CVD diamond booklet
Page 12
Surface finish, optical coatings and mounting
Property Value
Dimensions
Thickness 10 - 2000 µm
Diameter up to 100 mm
Surface finish
Shape flat, spherical (convex & concave)
Roughness < 5 nm*
Flatness 1 fringe/cm*
Wedge 0 1°*
Antireflection Coatings (visible and infrared)
Spec. Transmission at 10.6 µm >98.6 %
Wavefront distortion
< 4 fringes at 633 nm over 30 mm*
Mounting
Diamond windows mounted e.g. in UHV flanges (bakeable at 250°C, vacuum tight < 10-10 mbar l/s)*
*specifications available upon request
The CVD diamond booklet
Page 13
3. Thermal Properties
Thermal conductivity
0
500
1000
1500
2000
Sap
ph
ire
Silic
on
AlN
Co
pp
er
CV
D D
iam
on
d
Ther
mal
Co
nd
uct
ivit
y (W
/mK
)
Material
The thermal conductivity of diamond in comparison to other materials
The CVD diamond booklet
Page 14
Thermal conductivity vs. T
-200 -100 0 100 200 300
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
5500
Ther
mal
Co
nd
uct
ivit
y (W
/mK
)
Temperature (°C)
Thermal conductivity of CVD diamond vs. temperature
CVD diamond Theory
Copper
The CVD diamond booklet
Page 15
Specific heat vs. T
50 100 150 200 250 300 350 400 450 5001E-5
1E-4
1E-3
0.01
0.1
1
Spec
ific
hea
t (k
J/K
gK
)
Temperature (K)
The CVD diamond booklet
Page 16
Thermal expansion
0 100 200 300 400 5000.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
Ther
mal
Exp
ansi
on
(10
-6/K
)
Temperature (°C)
Thermal expansion vs. temperature
High quality CVD diamond Medium quality CVD diamond Values recommended by Slack4
4 G.A. Slack and S.F. Bartram, J. Appl. Phys. 46, 89 (1975)
The CVD diamond booklet
Page 17
Thermal specifications of Diamond Materials
Optimized CVD-diamond as provided by Diamond Materials reaches a thermal conductivity of up to 2000 W/mK e.g. it exceeds that of copper by a factor of five. In contrast to metals, where heat is conducted by electrons, lattice vibrations are responsible for the high thermal conductivity of diamond.
Property Value
Thermal conductivity
@300 K > 1200 W/mK* > 1500 W/mK* > 1800 W/mK*
Thermal expansion coefficient
@300 K 1.0 +/- 0.1 × 10-6/K
@700 K 4.4 +/- 0.1 × 10-6/K
Specific heat @ 20°C 0.502 J/gK
Debye temperature 1860±10K
* various thermal grades are available upon request
The CVD diamond booklet
Page 18
4. Mechanical Properties
Vickers-Hardness
0
2000
4000
6000
8000
10000
Talc
Gyp
sum
Cal
cite
Flu
ori
te
Ap
tite
Co
run
du
m
Top
az
Qu
artz
Ort
ho
cals
e
CV
D D
iam
on
d
Vic
kers
-Har
dn
ess
(kg
/mm
2 )
Material
The CVD diamond booklet
Page 19
Mechanical specifications of Diamond Materials CVD diamond manufactured by Diamond Materials exhibits an exceptional wear resistance and a low coefficient of friction. Highly demanding applications such as cutting tools, surgical knives and wear resistant components have been demonstrated.
Property Value
Vickers hardness 10,000 kg/mm2
Young's modulus 1050 GPa
Poisson's ratio 0.1
Thermal expansion coefficient 1.0×10-6/K @300K
Tensile strength (0.5mm thick)
Nucleation surface in tension 1100 MPa
Growth surface in tension 500 MPa
Density 3.515 g/cm3
The CVD diamond booklet
Page 20
5. Examples of CVD diamond applications
CVD diamond window in UHV flange
Ultrasharp wear resistant diamond knive
The CVD diamond booklet
Page 21
Flexible CVD diamond heatspreaders
CVD diamond laser windows
The CVD diamond booklet
Page 22
CVD diamond anchor wheel
Decorative CVD diamond dial
The CVD diamond booklet
Page 23
6. Useful formulae
Bowing of a circular disk under pressure5
( )νν+
+=164
5Pr4
Swss
Swcl 64
1Pr4= )1(12 2
3
ν−= ElS
where w = central deflection (ss = simply supported, cl = clamped), E = Youngs modulus, L = thickness, P = pressure, v = Poisson ratio, r = radius
Thickness requirements6 For flat windows, the minimum thickness as determined by pressure-
induced fracture is given by
f/σsfpSDL ∆= 554.0
where L = minimum thickness, σf = mechanical strength, ∆p = pressure difference, D = diameter, Ssf = safety factor
Typically mechanical strength values are in the 2000-400 MPa range depending on thickness. As a rule of thumb the minimum thickness is 1.7 % of the free diameter (one bar pressure difference, Ssf = 4).
5 Warren C. Young, Roarks Formulas for Stress & Strain, McGraw-Hill, New York (1989) 6 C.A. Klein, SPIE 1624, 475 (1992)
The CVD diamond booklet
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The CVD diamond booklet
Page 25
Contact Diamond Materials
Contact persons: Dr. Christoph Wild Dr. Eckhard Wörner
Internet: www.diamond-materials.com
E-mail: [email protected]
Telefon: +49 (0)761 600 6554
Fax: +49 (0)761 600 6553 Address: Diamond Materials GmbH Tullastr. 72 79108 Freiburg Germany
Images © 2008 Fraunhofer IAF This booklet may be freely distributed provided that it is unaltered and that no charge is made and this copyright notice is retained.