General properties

Diamond fascinates us because of it's unparalleled combination of material properties, and it occupies a special position in regards to all material. Diamond has the greatest heat conductivity at room temperature of all known materials (4 - 5 times higher than the heat conductivity of copper) and, at the same time, is an excellent electrical insulator.

 

In addition, diamond is the hardest of all available materials. Besides having an extremely small friction coefficient, diamond also possesses a small thermal expansion coefficient. Diamond is resistant to all know acids and bases. Moreover, diamond is transparent from the ultraviolet to the far infrared spectral range. With a band gap of 5.45 eV, diamond belongs to the group of semiconductors in which both p- type and n- type doping is possible.

 

Despite it's outstanding material properties, diamond, for a long time, received only a small roll as a working material. The main reasons for this are, first, that diamond occurs rarely in nature and, secondly, the expense involved in the synthetic production of diamond using high pressure and temperature. A further disadvantage of diamond is the small size of a single crystal, which mainly limits the applications of these diamonds to drilling and cutting tools or abrasive grit for polishing purposes.

 

The possibility of diamond synthesis with low pressure (few mbar) and by relatively low temperature (700°C - 900°C) was discovered only at the beginning of the 1980's, and subsequently triggered an active scientific and industrial interest. For the first time it was possible to deposit diamond, as a polycrystal layer over a large area, from a gas mixture of hydrogen and another gas such as methane.

 

GFD is one of the first companies worldwide to have achieved industrial production of high quality diamond layers in a production relevant scale.

 

Properties Diamond
Lattice Constant 0,356 nm
Thermal Expansion coefficient 1,1 (10-6K)
Density 3,515 (g/cm3)
Charge Mobility (hole) 1600 cm2/(V s)
Charge Mobility (electron) 2200 cm2/(V s)
Break Through Voltage 107 V/cm
rel. Dielectric Constant 5,7
Band Gap 5,45 eV
Specific Resistance 10-3 - 1016 Ωcm
Heat Conductivity 20 W/(cm K)
Refractive 2,42
Transparency vom IR bis UV (225 nm)
Hardness 10000 (kg/mm2)
E Modulus 1140 GPa
Sound Velocity 17500 m/s