Effects of the Grazing Incidence Geometry on X-ray Photon Correlation Spectroscopy Measurements

Area of Science:

• Materials Science
• Condensed Matter Physics
• Surface Science

Background:

• X-ray photon correlation spectroscopy (XPCS) is a key technique for nanoscale dynamics in bulk materials.
• Grazing incidence (GI) geometry extends XPCS to surface layer dynamics.
• GI geometry introduces signal complexities due to reflection and refraction, as described by the distorted-wave Born approximation (DWBA).

Purpose of the Study:

• To experimentally quantify the impact of reflection and refraction effects on correlation analysis in GI-XPCS.
• To compare grazing incidence transmission XPCS (GT-XPCS) and GI-XPCS for thin films with non-equilibrium dynamics.
• To provide guidelines for optimizing GI-XPCS experiments and data interpretation.

Main Methods:

• Simultaneous measurement of GT-XPCS and GI-XPCS on a thin film sample.
• Analysis within the framework of the simplified distorted-wave Born approximation (DWBA).
• Calculation of refraction effects in grazing incidence small-angle X-ray scattering (GISAXS) and transmission GISAXS (GTSAXS).

Main Results:

• Reflection and refraction effects in GI-XPCS were experimentally determined and analyzed using DWBA.
• The dominant scattering contributions along the out-of-plane scattering vector (q_z) were identified.
• Experimental conditions were proposed to minimize distortions and approach transmission XPCS behavior.
• Reduced beam exposure is achievable using GI geometry alone.

Conclusions:

• GI-XPCS can be optimized to yield dynamics measurements comparable to transmission XPCS.
• Understanding DWBA and refraction effects is crucial for accurate GI-XPCS data interpretation.
• This work facilitates reliable surface dynamics studies and reduces experimental time.