Reconstruction of interfaces of periodic multilayers from X-ray reflectivity using a free-form approach

Zameshin, Andrey; Makhotkin, Igor A.; Yakunin, S. N.; Kruijs, R. W. E. van de; Yakshin, Andrey; Bijkerk, Frederik

doi:10.1107/s160057671601044x

Cited by 30 publications

(19 citation statements)

References 19 publications

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“…We would get exactly the same effect on addition of a real stoichiometric interlayer transition layer to the model. A similar kind of 'mirror-like' ambiguity is typical for the inverse problem of X-ray reflectometry (Kozhevnikov, 2003;Zameshin et al, 2016). This is easy to understand if we recall that the reflection curve is, in essence, an interferogram of waves reflected from a number of interfaces within the structure.…”

Section: Figurementioning

confidence: 81%

“…The use of modified reflection coefficients instead of the Fresnel reflections allows us to use an analytical expression for calculating and optimizing non-ideal periodic multilayer mirrors. In cases where simple modifying factors cannot be used, instead of taking into account 'real' transition regions [for example, if the size of the transition region is comparable to the thickness of the layer (Haase et al, 2016;Zameshin et al, 2016)], the profile is subdivided into sufficiently thin layers, and a full calculation (i.e. avoiding any simplifications or workarounds) by recurrence relations (Parratt, 1954) is performed.…”

Section: Introductionmentioning

confidence: 99%

“…For example, to describe multilayer periodic mirrors based on La and B, a model of linear transition layers between the materials has proven to be very useful (Andreev et al, 2009;Makhotkin et al, 2013). But Zameshin et al (2016), when comparing LaN/B and LaN/La/B structures with an La thickness of 0.3 nm, found the model of linear transition layers to be completely useless for comparison of the permittivity profiles of slightly different structures, in spite of the more or less reasonable coincidence of resonant reflection peaks. For this problem, the model-free reconstruction of the permittivity profile inside the 'unit cell', translated for a given number of periods, showed its effectiveness.…”

Section: Introductionmentioning

confidence: 99%

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Extended model for the reconstruction of periodic multilayers from extreme ultraviolet and X-ray reflectivity data

et al. 2017

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An extended model for the reconstruction of multilayer nanostructures from reflectometry data in the X-ray and extreme ultraviolet ranges is proposed. In contrast to the standard model approach, where the transitional region is defined in advance as a specific function, the transition layer is sought as a linear combination of several functions at once in the extended model. This allows one to describe a much wider class of multilayer structures with different dominant physical mechanisms for the formation of transition regions. The extended model occupies an intermediate position between the classical model approach and the so-called model-free methods. The efficiency of the described method is illustrated in detail in numerical simulations and in a real experiment on the annealing of a multilayer Mo/Be mirror.research papers

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Section: Figurementioning

confidence: 81%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Extended model for the reconstruction of periodic multilayers from extreme ultraviolet and X-ray reflectivity data

et al. 2017

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“…It often does not have a friendly user interface or documentation, and working with the program involves working with its code. Thus, in order to repeat studies of structures such as those by Kozhevnikov et al (2012), Zameshin et al (2016) and Haase et al (2016), the research team needs to follow a path of developing a suitable tool, even to implement an approach that is already known and approved.…”

Section: Introductionmentioning

confidence: 99%

Multifitting: software for the reflectometric reconstruction of multilayer nanofilms

Свечников

2020

J Appl Crystallogr

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Multifitting is a computer program designed specifically for modeling the optical properties (reflection, transmission, absorption) of multilayer films consisting of an arbitrary number of layers in a wide range of wavelengths. Multifitting allows a user to calculate the reflectometric curves for a given structure (direct problem) and to find the parameters of the films from the experimentally obtained curves (inverse problem), either manually or automatically. Key features of Multifitting are the ability to work simultaneously with an arbitrary number of experimental curves and an ergonomic graphical user interface that is designed for intensive daily use in the diagnosis of thin films. Multifitting is positioned by the author as the successor to the IMD program, which has become the standard tool in research and technology groups synthesizing and studying thin-film coatings.

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“…The densities reported in the section of the thesis on La and LaN in situ growth (which was measured using a synchrotron rather than the in-house diffractometer) made it possible to assess the porosity of individual layers. Details of the analysis of interface zones in La/B-based multilayers using GIXR have been published elsewhere [39]. The use of a synchrotron for GIXR in situ measurement is outlined in the relevant section.…”

Section: Figmentioning

confidence: 99%

Structure control of La/B multilayer systems by partial nitridation

Kuznetsov¹

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Valorisation …………………………………………………………………………………………………….………96 1.3.2 XRF X-ray fluorescence (XRF) spectrometry is used to determine the elemental composition of a sample [10]. One variant of this technique, known as total reflection X-ray fluorescence (TXRF) [11], can be used to detect nanoparticles deposited on a flat surface, for example, or to trace the positions of heavy ions in organic monolayers or thick Langmuir-Blodgett films [12-16]. The multilayer coatings used in monochromators are essential in the analysis of low intensity emittance, in the case of light elements such as Li, Be, B, C, N [10]. The latter elements have a relatively low fluorescence yield. This factor, coupled with strong absorption in the sample itself, greatly reduces the intensity of the measured signal. Accordingly, the detection of light elements with XRF is difficult without multilayer coatings. Compared to single layers, the multilayers used in energy-dispersive techniques have a higher integrated reflectivity (over the Bragg peak), which makes it possible to detect light elements. These materials make the fine-tuning of reflectivity, of the position, of the reflectionpeak wavelength and of the angle of incidence a matter of routine. For the purpose of detecting B (K emission line) at angles of incidence close to 45°, for example, La/B4C and Mo/B4C multilayers were used [17]. One XRF-based application (grazing-incidence X-ray reflectivity) involves the angular-dependent measurement of samples to give depth-profiles of selected elements and details of the density of individual layers [18]. With this technique, unlike secondary ion mass spectrometry (SIMS), XPS depthprofiling, Rutherford backscattering spectroscopy (RBS) and other methods that involve sample sputtering, the sample is not damaged by incident X-rays. It also means that the XRF yield (including angular-dependent information) can be measured inhouse (using a standard lab reflectometer with an X-ray tube), thus avoiding the need for restricted and expensive access to equipment at ion centres, synchrotrons, etc. The 1.4 Multilayers for wavelengths above 6.6 nm 1.4.1 The properties and interactions of materials Based on their optical properties (high contrast and low absorption of 6 nm light), La and B were selected [4]. However, LaB6-which is thermodynamically favourable (enthalpy of formation ΔH =-160 kJ/mol [23])-is formed in La/B multilayers [24, 25]. Chemical interactions between La and B result in the formation of interface zones between the layers in a stack, which reduces optical contrast and, as a result, reflectivity [26]. One way to limit compound formation in La/B multilayers is to intentionally deposit (or pre-deposit) the compound, instead of one (or both) of the layers. One requirement is that this compound should be thermodynamically stable, so that it will not dissolve if it interacts with the other layers in a stack. However, this can result in the formation of superfluous amounts of compound in the interface zones, which impairs optical contrast. The enthalpy...

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Reconstruction of interfaces of periodic multilayers from X-ray reflectivity using a free-form approach

Cited by 30 publications

References 19 publications

Extended model for the reconstruction of periodic multilayers from extreme ultraviolet and X-ray reflectivity data

Extended model for the reconstruction of periodic multilayers from extreme ultraviolet and X-ray reflectivity data

Multifitting: software for the reflectometric reconstruction of multilayer nanofilms

Structure control of La/B multilayer systems by partial nitridation

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