Characterization of EUV periodic multilayers

Applied Surface Science

André

et al. 2015

We study the interface evolution of a series of periodic Co/Mo 2 C multilayers as a function of the annealing temperature up to 600°C. Different complementary techniques are implemented to get information on the phenomenon taking place at the interfaces of the stack. The periodical structure of Co/Mo 2 C multilayer is proven by Time-of-flight secondary ion mass spectrometry (ToF-SIMS) depth profiles which demonstrate the formation of an oxide layer at both air/stack and stack/substrate interfaces. From Nuclear magnetic resonance (NMR) spectra, we observed the intermixing phenomenon of Co and C atoms for the asdeposited sample, and then at annealing temperature above 300°C Co and C atoms separate from their mixed regions. Comparison of NMR results between Co/Mo 2 C and Co/C references confirms this phenomenon. This is in agreement with x-ray emission spectroscopy (XES) measurements. Furthermore the calculation of the Co-C, Co-Mo and Mo-C mixing enthalpy using Miedema's model gives a proof of the demixing of Co and C atoms present within the stacks above 300°C. From the transmission electron microscopy (TEM) analysis, we found the presence of some crystallites within the as-deposited sample as well as the mainly amorphous nature of all layers. This is confirmed using x-ray diffraction (XRD) patterns which also demonstrate the growth of crystallites induced upon annealing.

Section: X-ray Emission Spectroscopymentioning

confidence: 54%

Interface observation of heat-treated Co/Mo2C multilayers

Yuan

Applied Surface Science

André

et al. 2015

“…The studied superlattice has the following structure and aimed thicknesses: x-ray optical applications, has already been characterized [21,22]. From measurements of reflectivity in the hard x-ray and extreme UV regions, of soft x-ray magnetic resonant reflectivity, and of x-ray emission and nuclear magnetic resonance spectroscopies, it was found that the interfaces were abrupt.…”

Section: Experimental and Simulation Detailsmentioning

confidence: 99%

Spontaneous soft x-ray fluorescence from a superlattice under Kossel diffraction conditions

Jonnard

Yuan

J. Phys. B: At. Mol. Opt. Phys.

et al. 2014

The present study gives the proof of principle of a technique that is an extension of Kossel diffraction both from crystals to superlattices and toward the soft x-ray region, allowing the characterization of the interfaces within a periodic structure. We measure the intensity of the Co Lα and Mg Kα characteristic fluorescence emissions from a Mg/Co superlattice upon soft x-ray excitation. The observation is made so that the angle between the sample surface and the detection direction is scanned around the first and second Bragg peaks of the fluorescence emissions. Clear modulations of the emitted intensities are observed and well reproduced by simulations based on the reciprocity theorem and assuming a perfect stack. The present work gives evidence that such a superlattice plays the role of an optical cavity for the spontaneous emission generated within the stack. This should also be the case for stimulated emission, which when combined with pumping free electron laser, will open the road to innovative x-ray distributed feedback lasers.

“…This kind of methodology has been already used successfully for the study of nanometer periodic multilayers designed for x--ray optics, see Refs. [2][3][4][5][6] for example.…”

Section: Introductionmentioning

confidence: 99%

Study of the Au‐Cr bilayer system using X‐ray reflectivity, GDOES, and ToF‐SIMS

Jonnard

Modi

Surface & Interface Analysis

et al. 2018

We study a Au (25 nm)/Cr (10 nm) bilayer system as a model of mirror for the soft x-ray energy range. The Au and Cr thin films are a few nanometers thick and are deposited on a float glass substrate. The sample is characterized using three complementary techniques: soft x-ray reflectivity (XRR), glow discharge optical emission spectrometry (GDOES) and time of flight secondary ion mass spectroscopy (ToF-SIMS). XRR provides information about the thickness and roughness of the different layers while GDOES is used to obtain the elemental depth profile of the stack and ToF-SIMS to obtain the elemental and chemical depth profile. GDOES and ToF-SIMS have both a nanometer depth resolution. A coherent description of the bilayer stack is obtained through the combination of these techniques. It consists in five layers namely a surface contamination layer, a principal gold layer, a Au-Cr mixed layer, a Cr layer and another contamination layer at the top of the substrate.