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Multilayers

TTS deals with development and production of multilayers coatings for x-ray devices, based on total reflection of  x-ray beam. TTS works in close collaboration with the Reflex s.r.o. company.

 

A multilayer is a stack of  two alternating thin layers (A,B).  First is deposited smoothing and protecting layer (usually  CNx ).  Bi-layers A+B are then deposited N times on each other. The resulting structure has a desired repetition period L = tA + tB where ti is the single layer thickness. Due to different optical indices ni of the two layers, the whole stack acts like a one-dimensional artificial Bragg reflector when exposed to an X-ray beam. Layer A usually consists of a strongly absorbing material (metal). Layer B is a spacer made of a low-density material. The properties of multilayers can be described in analogy to those of single crystals.

 

No. of layer Thickness (A) Material Density (%) Roughness (A) Periods N
1 48.9 CN 20 4.8 10 x
2 23.5 CN 99.9 3.4  
3... 28.8 Ni 92.3 4.7  
...22 30.0 C 54.4 3.4  

 

Fig.1: A  typical measured  reflectivity spectrum in semilog scale.  

         glass, Ni/C  bi-layers, N = 10, R = 30.4%, Bragg peak 0.8

 

 

No. of layer Thickness (A) Material Density (%) Roughness (A) Periods N
1 56.3 SiO2 99 1.0 25 x
2... 39.1 Si 75.3 3.8  
...51 31.2 W 107.0 1.0  

 

Fig.2: A  typical measured  reflectivity spectrum in linear scale.  

         glass, W/Si  bi-layers, N = 25, R = 73.9%, Bragg peak 0.73

 

 

Multilayer's reflectivity R depends on perfect periodicity of layers, as well as on microroughness of  substrate and all single layers in the stack. The microroughness could be in the order of a few Angstroms. TTS technology is therefore concentrated on minimum roughness of layers, too (see Tables).

 

TTS develops X-ray microfocusing objectives, too.  This technology is based on multilayer sputtering onto circular parabolic mandrel and consequent replication (replacement)  of multilayer on the inside of the hollow paraboloid via electroforming method.


TTS s.r.o.

Novodvorska 994

142 21 Praha 4

Czech republic

mailto:info@tts-co.eu