18th European Conference on Applications of Surface and Interface Analysis
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Technical Development

Session chair: Bourke, Jay, (US)
 
Shortcut: TEC 2
Date: Wednesday, 18 September, 2019, 8:30
Room: Saal 4-5 (Plenum)
Session type: Oral

Contents

Click on an contribution to preview the abstract content.

8:30 TEC 2-01

SXES spectroscopy of Lithium Nickel Manganese Cobalt Oxide Battery cathode. (#89)

S. Matveev1

1 JEOL (Germany) GmbH, Freising, Bavaria, Germany

Content

Soft X-ray Emission Spectrometers (SXES) are analytical detectors for electron microscopes (SEM) and microprobes (EPMA) recently developed at Tohoku University (Japan) in collaboration with JEOL Ltd. SXES use diffraction gratings to project an array of X-ray wavelengths formed as a result of electron beam-sample interaction over the CCD detector, thus forming an X-ray spectrum in the energy range from 50 to 2300 eV, allowing for chemical analysis of elements starting with Li. Advantage of the SXES lays in good energy resolution (from 0.3 eV Al-L, Fermi edge of metallic aluminium), which is significantly better than that of other x-ray analytical techniques (EDS, WDS), and thus allows for chemical state analysis. Acquired spectra can be re-processed after analysis, e.g. operators can change chemical elements or adjust spectral ROIs, which is expanding sample characterisation possibilities compared to quantitative WDS analysis.

Lithium Nickel Manganese Cobalt Oxide Battery cathode (NMC) surface and cross section were analysed using JEOL SXES-ER spectrometer and EDS installed on JEOL JSM-7200F FEG SEM. SXES and EDS mapping were performed at 5 kV, 50 nA Cross section cut was performed using JEOL ion cryo cross section polisher at 4kV, -120°C, and cutting duration 8h.

SXES and EDS microanalysis allowed to determine distribution of C, O, F, Mn, Co, Ni, and Al in NMC cathode. SXES spectra were also used to identify chemical state of Ni and Co, as well as spatial distribution of oxide and metal phases in the cathode material. Careful examining of C peaks measured in the cathode binder suggests that C is present there in two bonding states C-C and C-F. Obtained results demonstrate that SXES spectroscopy allows for more detailed characterisation of NMC cathodes compared to traditional analytical methods such as EDS and WDS.

 

Keywords: SXES, Chemical state Batteries, Microanalysis
8:50 TEC 2-02

From surface to sub-surface: hard X-ray XPS (HAXPES) for analysis of deeply buried interfaces in multilayer structures (#198)

O. Renault1, C. Zborowski1, 2, E. Martinez1, G. Grenet3, S. Tougaard4

1 CEA-LETI, DPFT/SMCP, Grenoble, France
2 IMEC, Leuven, Belgium
3 INL, ECL, Ecully, France
4 Southern Denmark University, Dpt of Physics, Odense, Denmark

Content

As recalled by Kroemer in his Nobel Lecture in 2000, "the interface is the device". This statement highlights the pressing needs to implement analytical methods with improved sub-surface sensitivity enabling, e.g., the access to buried interfaces in device technology. Sub-surface sensitivity is also required in virtually all field of material science. Hard X-ray Photoelectron Spectroscopy (HAXPES), traditionally implemented with synchrotron sources, has shown to increase the information depth of XPS by a factor of ≥3, getting access to the chemistry of buried interfaces [1, 2]. Reliability is increased because invasive deprocessing (or overlayer sputtering) is no longer required and subtle changes at critical interfaces can be revealed. HAXPES recently has also become more accessible thanks to efficient hard X-ray laboratory sources. Here, we will present recent application cases of HAXPES to multilayer structures used in device technology. For example, diffusion processes may be analyzed, in a qualitative and quantitative way, over typical 25-40 nm up to 70 nm depths in Al/Ta/AlGaN systems depending on the excitation energy and on whether core-level or inelastic background is used as spectral fingerprint [1, 3]. A comparative overview of the different possibilities of HAXPES using laboratory and synchrotron-sources will be proposed.

 

This work was carried out on the Nanocharacterization Platform (PFNC) of the CEA Grenoble and thanks to a collaboration with NIMS and ULVAC-PHI (Japan).

References

[1] O. Renault et al., Surf. Interface Anal. 2018 ; 50 :1158

[2] A. Regoutz, Rev. Sci. Instrum. 89, 073105 (2018)  

[3]  C. Zborowski et al., Appl. Surf. Sci. 432 (2018), 60 ; J. Appl. Phys. 124, 085115 (2018).

Keywords: sub-surface, HAXPES, inelastic background, multilayer
9:10 TEC 2-03

Chemical-state-discriminated hard X-ray photoelectron diffraction study for polar InN (#329)

Y. Yamashita1, A. Yang2, K. Kobayashi2

1 NIMS, MANA, Tuskuba, Japan
2 NIMS, SPring-8, Sayo, Japan

Content

InN has received great research attention because of the small bandgap (~ 0.7 eV) and superior electrical transport properties. As a wurtzite crystal lacks inversion symmetry along c-axis direction, In-polar and N-polar InN exhibit different properties. Therefore, investigation of near-surface structure and electronic states of polar InN films are important to fully realize their potential. Due to the element and chemical state specificity and the larger probing depth, hard X-ray photoelectron diffraction (HXPD) was used to investigate the near-surface structures of polar InN films [1].

The HXPD system consists of a monochromatic Cr Kα source (5414.7 eV), a high energy version of the VG SCIENTA R4000 10 kV analyzer with wide acceptance objective lens.The angle acceptance of the combined objective lens and the analyzer is ±35° with an angular resolution of 0.5°. The total energy resolution was 1 eV. In this study, the polar angle θ is defined to be zero for the photoemission direction normal to a sample surface. The θ-dependent sensitivity of the analyzer, was calibrated using an amorphous GeSbTe sample.

Figure 1 shows the HXPD patterns from In 3d5/2 and N 1s core levels of In-polar and N-polar InN. The patterns were different from each other and then they were compared with the simulation results using a multiple-scattering cluster model[2], which is shown in Fig.1. It was found that the near-surface structure of the In-polar InN film was close to the ideal wurtzite structure. On the other hand, on the N-polar InN film, defects-rich surface was formed. In addition, the existence of the In-polar domains was observed in the HXPD patterns.

References

[1] A. Yang, Y. Yamashita, et al., Appl. Phys. Lett. 102, 031914 (2013).

[2] T. Matsushita, et a., J. Electron Spectrosc. Relat. Phenom. 178, 195 (2010).

Figure 1

In 3d and N 1s HXPD for In-polar and N-polar InN

Keywords: HAXPES, InN, photoelectron spectroscopy
9:30 TEC 2-04

Cryogenic UHV Specimen Transfer between Independent Instruments (#360)

U. Maier1, D. von Gunten1, K. P. Rice2, R. M. Ulfig2, R. G. Passey3

1 Ferrovac GmbH, Zurich, Zürich, Switzerland
2 CAMECA Instruments Inc., Madison, Wisconsin, United States of America
3 Thermo Fisher Scientific, Hillsboro, Oregon, United States of America

Content

For most analytical methods it is a demand to control the environment of a sample to prevent its change from the native state prior to analysis. Careful control  of atmosphere, pressure and temperature is crucial for obtaining meaningful results. Very often, it is a necessity to apply complementary analytical techniques on the same specimen. New concepts are needed, to transport samples between instruments while maintaining ultra high vacuum (UHV) conditions and temperature control. Here we present a commercially available UHV transfer solution that can be implemented to an unlimited number of participating instruments.

In collaboration with the scientific community [1,2,3], Ferrovac designed and built a UHV-cryo-transfer-module (UHVCTM) and their docking stations, i.e. adaptations to a variety of instruments. The “UHV-suitcase” features a battery-driven ion pump and a non-evaporable getter (NEG) to maintain UHV- and a cold stage to maintain low-temperature conditions. Temperature and vacuum control prevent the formation of crystalline ice on the sample, which would inhibit subsequent analysis.

While typically the involved instruments are UHV systems, it is also a necessity to transfer samples from high vacuum instruments such as focused ion beam scanning electron microscopes (FIB-SEM). One of many applications for the UHVCTM is the transfer from a FIB-SEM to the atom probe tomography (APT) system [4]. Adaptation of the UHVCTM to the LEAP® 5000 was presented in 2017 [5] and is shown in Fig. 1. Together with CAMECA® and Thermo Fisher Scientific, Ferrovac has developed a Quick-LoaderTM based dock that attaches to a DualBeam chamber and enables sample transfer into the UHVCTM for subsequent transport to a LEAP® 5000. Ferrovac’s novel docking station, shown in Fig. 2, was engineered to meet all requirements for the transfer process from a DualBeam instrument. The loading-docking chamber is equipped with a quick-connector that allows for a fast and simple attachment of the UHVCTM while maintaining the functionality of the generic sample loader.

References

[1] J. N. Longchamp et al., PNAS 114(7) (2017), pp. 1474-1479

[2] L.T. Stephenson et al., PLoS ONE 13 (2018), pp. 1-13.

[3] S.S.A. Gerstl et al., Microscopy and Microanalysis 23 (2017), pp. 612–613.

[4] D.K. Schreiber et al., Ultramicroscopy 194 (2018), pp. 89-99.

[5] R.M. Ulfig et al., Microscopy and Microanalysis 23 (2017), pp. 622-623.

UHVCTM adaptation to LEAP5000
Figure 1. A) A solid model of a LEAP 5000 with the UHV Cryogenic Suitcase from Ferrovac attached. B) The suitcase cross sectioned to show the cryogenically cooled stage, integrated pump, and fast pump down load lock.
UHVCTM adaptation to FIB-SEM

Figure 2.  (a1) UHVCTM “UHV-Suitcase”, (a2) loading chamber with quick connector, (a3) transfer arm, (a4) battery driven ion pump controller, (a5) LN2 Dewar, (a6) linear sledge.
(b) Detached UHVCTM. (c) UHVCTM replaced by standard transfer arm. (d) Exposure to simulated DualBeam vacuum level and recovery of UHVCTM base pressure.

Keywords: Atom Probe Tomography, Cryo-UHV sample transport, complementary analytical methods, UHV-suitcase, Vacuum transfer module
9:50 TEC 2-05

Experimental setups for XPS measurements beyond the instrumental lateral resolution limit (#37)

U. Scheithauer1

1 ptB, Unterhaching, Bavaria, Germany

Content

The lateral resolution of an XPS instrument which is equipped with a focused X-ray beam is limited by the nominal X-ray beam diameter and the long tail intensity distribution of the X-ray beam. The figure shows the normalised integral long tail intensity from outside a certain  radius as funtion of the radius parameter measured using Pt aperatures. The long tail intensity distribution of the X-ray beam impedes to perform a measurement with good lateral resolution and low detection limits at the same time.

Two experimental setups allow examining sample structures independently which are smaller than the X-ray beam dimensions. The first method uses differential sample charging on partly non-conductive samples by low energy electron flooding. The spectra recorded at the non-conductive sample areas are shifted towards lower binding energy. That way the surface composition of conductive and non-conductive sample areas are estimated independently. The second method utilizes the rather limited dimensions of the energy analyser acceptance volume. Here only the sample is placed inside the energy analyser acceptance volume. That way signals from the illuminated sample contribute exclusively to the measured photoelectrons intensity, independent form the sample size.

References

U.Scheithauer, Quantitative Lateral Resolution of a Quantum 2000 X-ray Microprobe, Surf. Interface Anal. 40 (2008) 706-709

J.J.Boland, Voltage contrast XPS - a novel scheme for spatially resolved XPS studies, Surf. Interface Anal. 10 (1987) 149-152

quantitative lateral resolution of the X-ray beam

The X-ray beam is centred in a Pt aperture. This way only the long tail intensity distribution of the X-ray beam contributes to the signal. The graphic shows the normalised count rate as function of the aperture diameter for 4 different X-ray beam diameters.

Keywords: XPS, quantitative lateral resolution, lateral resolution enhancement, sample charging, energy analyser acceptance volume