Investigation on Solar Absorption and Thermal Emittance of Al Films Deposited by Magnetron Sputtering

A metal layer with high reflectance is widely used as the bottom mirror of smart radiation devices. Reduced solar absorption and enhanced emittance tunability are required for smart radiation devices applied in aerospace. Thus, reducing the absorption in the metal is also necessary. Here, Al films have been prepared by direct current magnetron sputtering on the fused silica substrate. The structure, morphology, and optical properties of the films have been analyzed at various deposition temperatures and deposition times. The spectrum absorption tends to increase with the increase of surface roughness due to the agglomeration and size increase of Al particles, which has been further demonstrated by the simulated results. The optimized Al film exhibits small solar absorption of 0.14 and low emittance of 0.02, which benefits the application for smart radiation devices and solar reflectors.

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A New Solar Selective Absorbing Structure of Al-Al2O3 Cermet Composite Films by Pulsed Direct Current Magnetron Sputtering

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.53-54.349 ◽

2008 ◽

Vol 53-54 ◽

pp. 349-353 ◽

Cited By ~ 1

Author(s):

Li Wei Zhu ◽

Yu Dong Feng ◽

Y. Wang ◽

Z.M. Wang ◽

K. Zhao ◽

...

Keyword(s):

Thin Films ◽

Magnetron Sputtering ◽

Direct Current ◽

Composite Films ◽

Metal Distribution ◽

Dc Magnetron Sputtering ◽

Thermal Emittance ◽

Direct Current Magnetron Sputtering ◽

Pulsed Direct Current

Thin films composed of mixtures of metals and dielectric are being considered for use as solar selective coatings for a various applications. By controlling the metal distribution, the solar selective coatings can be designed to have the combined properties of high absorptance, and low infrared emittance. We have studied the preparation of the Al-Al2O3 cermet composite films deposited on the flexible Kapton substrate by pulsed direct current (DC) magnetron sputtering technique. The complex films include infrared reflective layers, interference absorptive layers, and anti-reflective layers. The measurements of the samples show that the spectral absorptance in the region of 0.2~2.5μm and thermal emittance in the region of 2.5~25μm were 92% and 7%, respectively.

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SEM analysis of DC magnetron sputtered beryllium films

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100106867 ◽

1988 ◽

Vol 46 ◽

pp. 960-961

Author(s):

E. F. Lindsey ◽

C. W. Price ◽

E. L. Pierce ◽

E. J. Hsieh

Keyword(s):

Fine Structure ◽

Electron Emission ◽

Secondary Electron ◽

Low Voltage ◽

Ion Beam ◽

Secondary Electron Emission ◽

Sem Analysis ◽

Fused Silica ◽

Grain Structure ◽

Silica Substrate

Columnar structures produced by DC magnetron sputtering can be altered by using RF biased sputtering or by exposing the film to nitrogen pulses during sputtering, and these techniques are being evaluated to refine the grain structure in sputtered beryllium films deposited on fused silica substrates. Beryllium is brittle, and fractures in sputtered beryllium films tend to be intergranular; therefore, a convenient technique to analyze grain structure in these films is to fracture the coated specimens and examine them in an SEM. However, fine structure in sputtered deposits is difficult to image in an SEM, and both the low density and the low secondary electron emission coefficient of beryllium seriously compound this problem. Secondary electron emission can be improved by coating beryllium with Au or Au-Pd, and coating also was required to overcome severe charging of the fused silica substrate even at low voltage. The coating structure can obliterate much of the fine structure in beryllium films, but reasonable results were obtained by using the high-resolution capability of an Hitachi S-800 SEM and either ion-beam coating with Au-Pd or carbon coating by thermal evaporation.

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