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1998
Conference Paper
Titel
Diamond windows for infrared and multispectral applications
Alternative
Diamantfenster für infrarote und multispektrale Anwendungen
Abstract
The low pressure deposition of polycrystalline diamond and the preparation of diamond windows at the Fraunhofer-IAF is reported. Using microwave plasma CVD, large area (2-6'' diameter) diamond wafers with thicknesses of up to 2 mm have been grown. The deposition is carried out in a novel microwave plasma system which uses an ellipsoid cavity to generate very intense, spatially extended plasmas. Several of these plasma reactors with 6 to 60 kW microwave power are presently used at the IAF. The diamond wafers are ground and polished and laser-cut to the desired dimensions. To assess the optical and thermal properties, the residual absorption in the 10 mu m range is determined by CO2 laser calorimetry, and temperature dependent and spatially resolved measurements of the thermal conductivity are performed. In addition, thermal expansion and refractive index measurements as a function of temperature are reported. Using high-purity process gases and optimized CVD conditions, diamond windows with a residual absorption at 10.6 mu m below 0. 1 cm(-1) and a thermal conductivity over 20 W/cmK have been realized. In addition, low dielectric losses of tan delta = 0.6x10(exp -4) at 140 GHz have been measured.
Author(s)