X-ray Reflectometry

X-ray Reflectometry
Simulated XRR pattern from two different metallic thin-film layer stacks: in orange is 10 nm Au over 10 nm Al; and in blue is 10 nm Au over 10 nm Ni. These data reflect different densities in the underlayer materials (different fringe amplitudes) but an effectively identical critical angle, indicating that this value is most heavily influenced by upper, dense layers.

X-ray Reflectometry (XRR) is a non-contact, non-destructive x-ray characterization technique suitable for both amorphous and crystalline materials. It provides refined film thicknesses, densities, and interfacial roughness determinations for film stacks whose approximate chemistries and thicknesses are known.

Strengths
  • Highly sensitive to electron density perpendicular to surface: optimized for thin films
  • Works well on crystalline, amorphous, or combination film stacks
  • Nondestructive analysis
Limitations
  • Elemental composition of materials should be determined in advance
  • Advanced modeling often required to extract critical insights
  • Lateral inhomogeneities cannot be incorporated into XRR models
Base Prices
Technique Variants
Pricing Starts At
Action
X-ray Reflectometry (XRR)
$500 / Sample

Example Outputs
<p>XRR pattern from <strong>Alluxa</strong>, manufacturer of high-performance optical filters and precision thin-film coatings. Annotations indicate the types of features in a standard XRR pattern, and the sample properties they inform.</p>

XRR pattern from Alluxa, manufacturer of high-performance optical filters and precision thin-film coatings. Annotations indicate the types of features in a standard XRR pattern, and the sample properties they inform.

<p>Simulated XRR pattern from two different metallic thin-film layer stacks: in <em>orange</em> is 10 nm Au over 10 nm Al; and in <em>blue</em> is 10 nm Au over 10 nm Ni. These data reflect different densities in the underlayer materials (different fringe amplitudes) but an effectively identical critical angle, indicating that this value is most heavily influenced by upper, dense layers.</p>

Simulated XRR pattern from two different metallic thin-film layer stacks: in orange is 10 nm Au over 10 nm Al; and in blue is 10 nm Au over 10 nm Ni. These data reflect different densities in the underlayer materials (different fringe amplitudes) but an effectively identical critical angle, indicating that this value is most heavily influenced by upper, dense layers.

Sample Requirements
  • Works best on very smooth, uniform, flat samples (roughness < 2 nm)
  • Film thickness < 5000 nm
Instruments Used for XRR
Rigaku SmartLab

Rigaku SmartLab

  • Probe Voltage: 45 kV
  • Probe Current: 200 mA
  • Goniometer Minimum Step-Size: 0.0001°
  • Anton Paar Heated Stage Accessory:
    • Temperature Range: ~25 °C to 1100 °C

View Instrument Spec Sheet

How XRR Works

In X-ray reflectometry (XRR analysis) an X-Ray source supplies a high-brilliance beam of X-rays which reflect off of a flat surface at very low incident angles.

The XRR system then measures the intensity of the X-rays reflected in the specular direction (where reflected angle equal to incident angle). If the interface between layers – or between a layer and the substrate – is not perfectly sharp and smooth, the reflected intensity will deviate from that predicted by the law of Fresnel reflectivity.

The deviations of the X-ray reflectometry can then be analyzed to obtain the density profile of the interface normal to the surface and modeling can be used to determine layer thicknesses, densities, and interfacial roughnesses.

Additional Resources

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