Cvd Diamond Booklet

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


Page 1

CVD Diamond wafers prepared by Microwave Plasma CVD: boron doped disk (blue), optical grade diamond, mechanical grade, unpolished disk


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)


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


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


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


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)


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)


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)


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


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


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


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


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


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


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)


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)


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


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


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


Page 20

5. Examples of CVD diamond applications

CVD diamond window in UHV flange

Ultrasharp wear resistant diamond knive


Page 21

Flexible CVD diamond heatspreaders

CVD diamond laser windows


Page 22

CVD diamond anchor wheel

Decorative CVD diamond dial


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)


Page 24


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.

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Cvd Diamond Booklet