Influence of substrate biasing on NiC/Ti multilayer performance

Y.Y.Platonov, G.Gutman, J.R.Rodriguez, K.Parker, J.Wood

OSMIC Inc., 1788 Northwood Drive, Troy, MI 48084, USA

The application of NiC/Ti multilayers for use in neutron guides as a high
performance mirrors is plagued by poor morpholodgy [1].  Currently, neutron
reflectivity of more than 90% has been achieved beyond 2.8 times the critical
angle of a Ni mirror [2].  To increase the angle of reflection from 2.8 to 3.0
times the critical angle with a reflectivity of more than 90%, a depth graded
NiC/Ti structure of thickness 3.4 microns must be fabricated.  Unfortunately,
films with this thickness have the inherent problems associated with poor
adhesion and increasing interfacial roughness.

The influence of substrate voltage biasing on W/B4C and Mo/Si X-ray multilayer
mirror performance has been described in [3,4].  In the present work, the
biasing influence on the characteristics of NiC and Ti single films and
multilayers as prepared by magnetron sputtering techniques is considered.
Analytical methods include low and high angle XRD, RHEED and AES for
investigation of layered materials density, crystalline structure, composition
and interfacial roughness.  An optimal range of substrate bias voltage
producing the best quality layer deposition was found.  Taking into account
the results of these investigations, a depth graded NiC/Ti multilayer
structure with total thickness of 3.4 microns was prepared on a glass
substrate with dimensions 250mm x 80mm.  Results of reflectivity at
wavelengths ~ 4 angstroms are presented.


References

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   for soft X-ray imaging optics, J.X-Ray Science and Technology,
   vol.4, No.2, p.142, 1994.
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