Thermal and stress studies of normal incidence Mo/B{sub 4}C multilayers for a 6.7 nm wavelength

Journal Article · Sun Apr 10 04:00:00 EDT 2011 · Applied Optics

DOI:https://doi.org/10.1364/AO.50.001610· OSTI ID:22036615

Barthelmess, Miriam; Bajt, Sasa

Wavelength, reflectance, and stress stability of Mo/B{sub 4}C multilayers were studied as a function of postdeposition annealing up to 900 deg. C. These multilayers are of interest as normal incidence coatings for wavelengths above the boron K-absorption edge. Mo/B{sub 4}C multilayers deposited at low sputtering pressure have high compressive stress. Zero stress can be achieved at 360 deg. C-370 deg. C, but annealing at <200 deg. C is sufficient to reduce stress by {approx}40%. This stress relaxation is accompanied with a multilayer period expansion of {approx}0.02 nm and a <0.5% decrease in normal incidence reflectivity. The multilayer period remains stable up to {approx}600 deg. C, while intrinsic stress changes from compressive to tensile. A four-layer model with amorphous molybdenum and boron carbide layers separated by amorphous layers of molybdenum borides (Mo{sub x}B{sub y}) is presented. These interlayers are present already in the as-deposited state and continue to grow with increasing temperature. Their presence lowers the optical contrast and the achievable reflectivity. However, they also increase multilayer thermal stability. At temperatures >600 deg. C, a noticeable decrease in reflectivity associated with the phase transition from amorphous to crystalline molybdenum boride is observed. This is accompanied with an increase in interface and surface roughness and a change in stress as a function of temperature.

• OSTI ID: 22036615
• Journal Information: Applied Optics, Journal Name: Applied Optics Journal Issue: 11 Vol. 50; ISSN 0003-6935; ISSN APOPAI
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ANNEALING
BORON
BORON CARBIDES
COATINGS
INTERFACES
K ABSORPTION
LAYERS
MOLYBDENUM
MOLYBDENUM BORIDES
PHASE TRANSFORMATIONS
REFLECTIVITY
ROUGHNESS
SPUTTERING
STABILITY
STRESS RELAXATION
STRESSES
SURFACES
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE 0400-1000 K
WAVELENGTHS