Nanometer-resolution depth-resolved measurement of florescence-yield soft x-ray absorption spectroscopy for FeCo thin film

Abstract

We develop a fluorescence-yield depth-resolved soft x-ray absorption spectroscopy (XAS) technique, which is based on the principle that the probing depth is changed by the emission angle of the fluorescence soft x rays. Compared with the electron-yield depth-resolved XAS technique, which has been established in this decade, we can observe wider range in-depth XAS distribution up to several tens of nm. Applying this technique to a 30 ML (∼4.3 nm) FeCo thin film, we observe Fe L-edge XAS spectra at the probing depth of 0.3-6 nm and find that the film has 22 ML (∼3.1 nm) surface oxide layer while its inner layer shows metallic state. We thus successfully obtain nanometer-resolution depth-resolved XAS spectra and further expect that operando measurement under the electric and/or magnetic fields is possible.

Real-Time Observation of Surface Chemical Reactions Proceeding in the Depth Direction by Wavelength-Dispersive Soft X-ray Absorption Spectroscopy

“…Co 3 O 4 , which has the highest oxidation state, has a higher energy peak position at approximately 780 eV, corresponding to Co 2p 3/2 (L 3 edge), compared with Co and CoO, whose peak positions are at approximately 779 eV. These spectra are well-known in previous studies, − but we obtained the Co, CoO, and Co 3 O 4 data shown in Figure by using the same beamline configuration as wavelength-dispersive XAS. Therefore, the measured spectrum can be estimated by how much oxidation proceeds as fitted using these spectra by obtaining the ratio of these reference spectra.…”

“…Recently, to extend the range of applicable gas pressures, the detection of fluorescence soft X-rays has been realized by using a fluorescence X-ray imaging system, and this method enabled observation of the surface chemical reactions under a gas pressure of ca. 100 Pa. On the other hand, nondestructive depth-resolved XAS measurements, which have a resolution of less than 1 nm to analyze the depth profile of the chemical status in the near-surface region, have already been developed . However, depth-resolved analysis in real time has not been actualized as a simultaneous measurement, which can follow a chemical reaction on a material surface that proceeds in the depth direction with processing time.…”

Unveiling a Chemisorbed Crystallographically Heterogeneous Graphene/L10-FePd Interface with a Robust and Perpendicular Orbital Moment

“…The wavelength (λ) was estimated from the attenuation length ( l ) and detection angle using the following relation: λ = l sin θ d . 45 The lowest θ d was determined to be ∼0.1°. By analyzing a set of X-ray data recorded at different wavelengths, depth-resolved XAS and XMCD spectra can be obtained.…”

Measurements of Low-energy X-rays with a Detector Using a Plastic Scintillator and an MPPC

“…Si-PMs (or MPPCs [1]) have an advantage in fabricating a pixelated detector operated in a low voltage, comparing with MCPs. Observation of spin structure in a magnetic thin film is planned with the fluorescence-yield depth resolved XAS technique [2]. In this method, a two-dimension pixelated detector for soft X-ray region is much useful.…”