Diffuse absorbing beryllium coatings produced by magnetron sputtering

Charles M. Egert; David D. Allred

doi:10.1117/12.22676

1 December 1990 Diffuse absorbing beryllium coatings produced by magnetron sputtering

Charles M. Egert, David D. Allred

Proceedings Volume 1331, Stray Radiation in Optical Systems; (1990) https://doi.org/10.1117/12.22676
Event: 34th Annual International Technical Symposium on Optical and Optoelectronic Applied Science and Engineering, 1990, San Diego, CA, United States

Abstract

Beryllium coatings with varying thicknesses and columnar grain sizes were deposited by low temperature magnetron sputtering and wet chemically etched to enhance diffuse absorption of light. After etching these coatings exhibited a matte black surface finish and low specular reflectance (below 2%) in the IR up to a critical wavelength dependent upon the original grain size of the coating. Extremely thick coatings (350 j.tm) with original grain sizes of 10 to 12 j.m were produced which exhibited specular reflectances below 0.5% up to 50 p.m wavelength and a Lambertian BRDF at 10.6 p.m averaging 4.3x103 ster1. Scanning electron micrographs are presented for etched and unetched beryllium coatings which showed the etching process produces roughness and porosity over several size scales simultaneously with the maximum size scale limited by the initial coating grain size and thickness. This technique for producing diffuse absorbing baffle materials has great versatility in choice of coating material and substrate and can be expected to provide optical system designers with a variety of material options for stray light management.

Citation Download Citation

Charles M. Egert and David D. Allred "Diffuse absorbing beryllium coatings produced by magnetron sputtering", Proc. SPIE 1331, Stray Radiation in Optical Systems, (1 December 1990); https://doi.org/10.1117/12.22676

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