# Kossel interferences of proton-induced X-ray emission lines to study the interfaces of thin film waveguides

Jiaping Zhang, Christopher Pendenque, Karine Le Guen, Renaud Delaunay,

Ian Vickridge, Philippe Jonnard

► To cite this version:

Jiaping Zhang, Christopher Pendenque, Karine Le Guen, Renaud Delaunay, Ian Vickridge, et al. Kossel interferences of proton-induced X-ray emission lines to study the interfaces of thin film waveguides. 3rd International Summer School on the Physical and Chemical Principles in Materials Science, Jul 2018, Nanjing, China. [hal-03932192](https://hal.science/hal-03932192)

HAL Id: hal-03932192

https://hal.science/hal-03932192

Submitted on 10 Jan 2023

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<figure><img src="image_1.png" /></figure>

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# Kossel interferences of proton-induced X-ray emission lines to study the interfaces of thin film waveguides

Jiaping Zhang<fnref n="1" />,<fnref n="2" />, Christopher Pendenque<fnref n="1" />, K. Le Guen<fnref n="1" />, Renaud Delaunay<fnref n="1" />, Ian Vickridge<fnref n="3" />, P. Jonnard<fnref n="1" />

## Introduction

While waveguide optic is ubiquitous in the visible and infrared spectral range, it is still much less developed in the X-ray regime. The X-ray waveguide can be used as spatial and coherence filters for X-ray coherent imaging [1-2]. It is usually designed and fabricated with a low density guiding layer embedded in high density cladding layers. The interfaces of the thin film waveguides play a crucial role in their service reliabilities. In this study, X-ray thin film waveguide are prepared by magnetron sputtering. The Kossel interferences of proton-induced X-ray emission lines, as a novel non-destructive way [3], is used to analyze the interfacial environment of the nanoscale thin films.

## Experimental

### Sample Preparation

We first made simulations to obtain the optimized parameters (include elements and thickness) for the thin film waveguides by using the IMD software. No interfacial roughness of thin film as well as of the Si substrate was taken into account. A series thin films waveguides were designed and prepared by magnetron sputtering, as follow

<table><thead><tr><td>Sample</td><td>Structure</td></tr></thead><tbody><tr><td>RD1</td><td>Pt (4 nm)/Fe(8 nm)/Pt(10 nm)</td></tr><tr><td>RD2</td><td>Pt(4 nm)/Fe(6 nm)/Pt (10 nm)</td></tr></tbody></table>

<figure><img src="image_2.png" /></figure>

### Proton-induced X-ray emission (PIXE)

The proton beam with energy of 1.6 MeV with ≈100 nA current generated by the Van de Graaff accelerator is used to irradiate the sample. The angle between the proton beam and the sample is 90°. With the help of energy dispersive CCD camera ANDOR iKon-M (equipped with a 1024×1024 sensor array with 13×13 µm pixels), the generated X-ray fluorescence signal is recorded.

<figure><img src="image_3.png" /></figure>

## REFERENCES

[1] Osterhoff, Markus, and Tim Salditt. "Real structure effects in x-ray waveguide optics: The influence of interfacial roughness and refractive index profile on the near-field and far-field distribution." Optics Communications 282.16 (2009): 3250-3256.

[2] Hoffmann-Urlaub, Sarah, et al. "Advances in fabrication of X-ray waveguides." Microelectronic Engineering 164 (2016): 135-138.

[3] Wu, Meiyi, et al. "Kossel interferences of proton-induced X-ray emission lines in periodic multilayers." Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 386 (2016): 39-43.

## XRR and fitting results

Compared with the ideal structures, it is seen that the deposited thickness of Pt and Fe layers is larger by about 10-20%. But the density of the bulk was chosen for the different films. If we consider that the layers have in fact a density of 90% of the bulk one, then the discrepancy could be explained. The roughness difference of Pt and Fe layers, indicating the Pt-on-Fe and Fe-on-Pt interfaces are asymmetrical.

<table><thead><tr><td>RD1</td><td>Thickness (nm)</td><td>Roughness (nm)</td></tr></thead><tbody><tr><td>Pt (top layer)</td><td>4.93</td><td>1.21</td></tr><tr><td>Fe (second layer)</td><td>9.56</td><td>1.53</td></tr><tr><td>Pt (bottom layer)</td><td>11.30</td><td>0.54</td></tr><tr><td>Si substrate</td><td></td><td>0.47</td></tr></tbody></table>

<table><thead><tr><td>RD2</td><td>Thickness (nm)</td><td>Roughness (nm)</td></tr></thead><tbody><tr><td>Pt (top layer)</td><td>4.62</td><td>0.60</td></tr><tr><td>Fe (second layer)</td><td>6.65</td><td>0.80</td></tr><tr><td>Pt (bottom layer)</td><td>11.06</td><td>0.77</td></tr><tr><td>Si substrate</td><td></td><td>0.42</td></tr></tbody></table>

<figure><img src="image_4.png" /></figure>

## PIXE-Kossel lines to study the interfaces

<figure><img src="image_5.png" /></figure>

The main features of the simulated curves are almost reproduced by the experimental ones.

## CONCLUSION AND PERSPECTIVES

1. The main features of the simulated curves are reproduced by the experimental ones. But the relative intensities of the main peaks still have obvious differences.

2. We need to refine the description of the stack so as to find a combination of thicknesses and roughnesses that satisfies both XRR and PIXE-Kossel measurements.

<footnote n="1">¹ Sorbonne University, CNRS UMR 7614, Laboratoire de Chimie Physique - Matière et Rayonnement, 4 place Jussieu, F-75252 Paris cedex 05, France</footnote>

<footnote n="2">² State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi'an 710072, China</footnote>

<footnote n="3">³ Sorbonne Université, Institut des NanoSciences de Paris, 4 place Jussieu, F-75252 Paris cedex 05, France</footnote>