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Diamond has a unique combination of optical, thermal,

mechanical and electronic properties that makes diamond

an ideal material for extreme applications:

 

Optical Properties

 

The excellent optical properties of diamond have been known for a long time. However, optical applications require extended discs or thin coatings not provided by natural diamond crystals. With the development of CVD techniques the situation has changed completely. 

Broadband transparency

Diamond is transparent from the UV (230 nm) to the far infrared. Only minor absorption bands resulting from two phonon absorption exist between 2.5 and 6 µm. Hence diamond is an ideal material for multispectral optical applications. 

Wide band gap

No thermal generation of charge carriers at elevated temperatures, hence no "thermal run away" as in the case of Germanium under laser irradiation. Furthermore, diamond does not become nonlinear at high radiation intensities. 

High thermal conductivity>

Absorbed energy is quickly dissipated to the edges of a diamond window where it can be removed by appropriate heat sinks and cooling techniques. 

Mechanical and chemical stability

Diamond is extremely hard, wear resistant and chemically inert. 
It is an ideal material for hostile, highly erosive atmospheres. 

 

Optical transmission spectrum of CVD diamond

 

 

Thermal Properties

 
  One of many remarkable properties of diamond is its uncompeted thermal conductivity. In contrast to metals, where conduction electrons are responsible for the high thermal conductivity, heat is conducted in electrical insulators by lattice vibrations. With a sound velocity of 17500 m/s, diamond is the material with the highest Debye temperature (2220 K), exceeding that of most other insulating materials by an order of magnitude and leading to the highest thermal conductivity of any
material at room temperature (20-25W/cmK), exceeding that of copper by a factor of five. 

 

Today, CVD diamond is used for various thermal management applications such as submounts for integrated circuits and heat spreaders for high power laser diodes.

 

 

Mechanical Properties

Diamond is known for its extreme hardness. It exhibits an exceptional wear resistance and a low coefficient of friction. These properties make CVD diamond an ideal choice for highly demanding applications such as cutting tools for non-ferrous materials, surgical knives and wear resistant coatings.

 

Thermal conductivity of CVD diamond vs. temperature. For comparison, the thermal conductivity of copper is shown in red. 

 

Dielectric Properties

CVD diamond exhibits remarkable dielectric properties including a low dielectric constant of 5.7, a loss tangent below 0.00005 at 145GHz and a high dielectric strength of 1 000 000 V/cm. In combination with the extremely high thermal conductivity, low thermal expansion coefficient and high mechanical strength CVD diamond is an ideal dielectric window material. In particular for high-power microwave tubes (Gyrotron) with power levels exceedings 1 MW edge cooled diamond windows have found tremendous interest. 

Mapping of the dielectric losses (FZK, Karlsruhe)

 

CVD Diamond booklet

 

 

  For a comprehensive summary of the properties of CVD diamond you may want to download the CVD diamond booklet provided by Diamond Materials.