Quick X-ray Reflectivity using Monochromatic Synchrotron Radiation for Time-Resolved Applications

TL;DR

This paper introduces a novel, rapid X-ray reflectivity technique using monochromatic synchrotron radiation and a polycapillary optic, enabling in-situ, time-resolved thin-film growth analysis with high angular resolution and broad applicability.

Contribution

The authors present a new parallel XRR method compatible with monochromatic synchrotron radiation, improving speed and sample independence over previous techniques.

Findings

Achieved 100 ms time resolution during thin-film growth.

Resolved Kiessig fringes for layers 3-76 nm thick.

Demonstrated applicability with in-situ epitaxial growth data.

Abstract

We describe and demonstrate a new technique for parallel collection of x-ray reflectivity data, compatible with monochromatic synchrotron radiation and flat substrates, and apply it to the in-situ observation of thin-film growth. The method employs a polycapillary x-ray optic to produce a converging fan of radiation incident onto a sample surface, and an area detector to simultaneously collect the XRR signal over an angular range matching that of the incident fan. Factors determining the range and instrumental resolution of the technique in reciprocal space, in addition to the signal-to-background ratio, are described in detail. Our particular implementation records $\sim$5\degree{} in $2\theta$ and resolves Kiessig fringes from samples with layer thicknesses ranging from 3 to 76 nm. Finally, we illustrate the value of this approach by showing in-situ XRR data obtained with 100 ms time resolution during the growth of epitaxial \ce{La_{0.7}Sr_{0.3}MnO3} on \ce{SrTiO3} by Pulsed Laser Deposition (PLD) at the Cornell High Energy Synchrotron Source (CHESS). Compared to prior methods for parallel XRR data collection, ours is the first method that is both sample-independent and compatible with highly collimated, monochromatic radiation typical of 3rd generation synchrotron sources. Further, our technique can be readily adapted for use with laboratory-based sources.