X-ray Reflectometry (XRR)

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.

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

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Example Outputs Instruments Used How XRR Works

X-ray Reflectometry Services

X-ray Reflectometry

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.

Sample Requirements

Works best on very smooth, uniform, flat samples (roughness < 2 nm)
Film thickness < 5000 nm

Example Outputs

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.

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.

Instruments Used

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

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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.