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High Efficiency Absorber

IP.com Disclosure Number: IPCOM000039008D
Original Publication Date: 1987-Apr-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 3 page(s) / 75K

Publishing Venue

IBM

Related People

Ahn, KY: AUTHOR [+2]

Abstract

Plasma-deposited Au/Ag and similar films, which are applied to polytetrafluoroethylene and similar films, appear to be almost totally nonreflective. One of the key problems in optical storage technology is the lifetime of the storage medium. Noble metals, such as gold and platinum, are highly desirable as recording media, but their reflectivity is too high to be used for low-power writing. This method provides controlled surface roughness by depositing certain polymer films onto substrates before depositing the desired noble metal films. The microgeometry (morphology) of the surface is such that even the highly reflecting metal films, such as gold and silver, appear almost like carbon black... thus a high efficiency absorber.

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High Efficiency Absorber

Plasma-deposited Au/Ag and similar films, which are applied to polytetrafluoroethylene and similar films, appear to be almost totally nonreflective. One of the key problems in optical storage technology is the lifetime of the storage medium. Noble metals, such as gold and platinum, are highly desirable as recording media, but their reflectivity is too high to be used for low-power writing. This method provides controlled surface roughness by depositing certain polymer films onto substrates before depositing the desired noble metal films. The microgeometry (morphology) of the surface is such that even the highly reflecting metal films, such as gold and silver, appear almost like carbon black... thus a high efficiency absorber. Such absorbers may be used not only in optical storage devices, but also as an efficient solar absorber. The results obtained and shown here were obtained for 300-Ao-thick gold films deposited onto a variety of polytetrafluoroethylene (PTFE)-like films which were deposited by plasma polymerization of C2F4 monomer gas using the following process conditions: .CE Typical Deposition Conditions for PTFE-like Films Pressure during deposition : 50 microns.

Power, RF, level : 50 watts

Active substrate area : approx. 6.4 cm diameter

Gas flow rate : 10 stcc/min. or lower

Deposition rate : 25 Ao/min. One of the most critical parameters which controls the surface texture of the deposited films is the substrate temperature. At an elevated temperature, for example, at 125oC, the film appears transparent, and the normal-incidence reflectivity is around 7%, as shown in the lowest curve of Fig. 1. When a gold film (300 Ao) is deposited onto the same PTFE film, the characteristic gold reflectivity is exhibited as shown in the middle curve, which may be compared with a gold film of a smooth glass substrate (top curve). When the substrate temperature is chosen properly, the nucleation and growth of a PTFE-like film is such that the film surface becomes highly textured, and it app...