X-ray reflecto-interferometer based on compound refractive lenses.

S Lyatun,I Lyatun,D Zverev,P Ershov,I Snigireva,O Konovalov,A Snigirev

doi:10.1107/s1600577519007896

Abstract

An X-ray amplitude-splitting interferometer based on compound refractive lenses, which operates in the reflection mode, is proposed and realized. The idea of a reflecto-interferometer is to use a very simplified experimental setup where a focused X-ray beam reflected from parallel flat surfaces creates an interference pattern in a wide angular range. The functional capabilities of the interferometer were experimentally tested at the European Synchrotron Radiation Facility (ESRF) ID06 beamline in the X-ray energy range from 10 keV to 15 keV. The main features of the proposed approach, high spatial and temporal resolution, were demonstrated experimentally. The reflections from free-standing Si3N4 membranes, gold and resist layers were studied. Experimentally recorded interferograms are in good agreement with our simulations. The main advantages and future possible applications of the reflecto-interferometer are discussed.

Highlights

Interferometry is a well established set of methods in many fields of science and industry
X-ray reflectivity with a convergent polychromatic X-ray beam (Matsushita et al, 2013) was realized on a synchrotron but the approach we proposed with a monochromatic beam solves the problem of changing the refractive index with the wavelength
We demonstrated a new intensitydivision X-ray reflecto-interferometer based on refractive optics

Summary

Introduction

Interferometry is a well established set of methods in many fields of science and industry. There have been attempts to use a convergent monochromatic X-ray beam to measure reflectivity (Naudon et al, 1989; Niggemeier et al, 1997; Miyazaki et al, 2000) but our approach is much simpler and more flexible because of the unique properties of CRLs. For example, it is possible to perform reflectivity measurements in a wide energy range without realignment of the optical scheme and the ability to change the irradiation area of the sample (Vaughan et al, 2011). Quick X-ray reflectivity (XRR) for thin-film growth was demonstrated using polycapillary optics to produce a converging beam (Joress et al, 2018) This approach has poor spatial resolution, requirements to the sample are the same as in the classical XRR, and energy tunability is lacking. The theory of X-ray reflectometry will be briefly considered in connection with our case

Basics of X-ray reflecto-interferometry theory

Experiment

Test of a gold strip on a 500 nm Si3N4 membrane with two-dimensional CRLs

Test of a gold strip on a 1000 nm Si3N4 membrane with linear CRLs

Discussion and conclusion