# Emission spectroscopy of lithium and light elements with an electron microprobe

Philippe Jonnard

► To cite this version:

Philippe Jonnard. Emission spectroscopy of lithium and light elements with an electron microprobe. International seminar on the cathodoluminescence and analysis of light elements, Bureau de Recherches Géologiques et Minières, May 2025, Orléans, France. hal-05077172

HAL Id: hal-05077172

https://hal.science/hal-05077172v1

Submitted on 21 May 2025

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# Emission spectroscopy of lithium and light elements with an electron microprobe

Philippe JONNARD

Laboratoire de Chimie Physique – Matière et Rayonnement

Sorbonne Université – CNRS

Paris, France

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

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# Measuring lithium and light elements

* Electron microprobe

X-ray emission spectroscopy induced by electrons

* Incident electrons

* Detection of X-rays

* Non-destructive

* Easy preparation of sample

* Quantification

* ...
# The Li Kα emission band

<figure><img src="image_3.png" /></figure>
# The Li Kα emission band

<figure><img src="image_4.png" /></figure>
# The Li Kα emission band

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

**Emission band**
5-20 eV wide
# The Li Kα emission band

* Lithium: atomic number Z = 3

* 2 core electrons 1s, binding energy around 55 eV

* Electron transition between valence p level toward 1s core level

* Valence electron participates to the chemical bond

* The shape and position of the emission band strongly depend on the chemical state of the emitting lithium atom

* Good, to study the electronic structure or chemistry of lithium

* No so good, to quantify: no standard for peak or height of the emission
# The Li Kα emission band – chemical sensitivity

* Calculation of x-ray emission spectra

* I(v) ∝ v³ N(E) M(E)

* v frequency (E = hν)

* N density of states

* M matrix element

* Density functional theory / WIEN2k

http://susi.theochem.tuwien.ac.at/

* Spectra alignment:
  XPS Li 1s binding energy

<figure><img src="image_6.png" /></figure>

K. Hassebi et al., X-Ray Spectrom. **52**, 330-336 (2023)

http://doi.org/10.1002/xrs.3329
# The Li Kα emission band – chemical sensitivity

* Photon energy of the maximum

<table><thead><tr><td>Li</td><td>LiAlSi2O6</td><td>LiF</td></tr></thead><tbody><tr><td>54,4 eV</td><td>55,0 eV</td><td>56,1 eV</td></tr></tbody></table>

* Area of the emission band

**Intensity**

<table><thead><tr><td>Li</td><td>LiAlSi2O6</td><td>LiF</td></tr></thead><tbody><tr><td>0,205</td><td>0,411</td><td>0,294</td></tr><tr><td>1</td><td>2,0</td><td>1,4</td></tr></tbody></table>

<figure><img src="image_7.png" /></figure>
Different spectroscopies

* Energy dispersive spectrometry (EDS)

• EDS – bolometer

• EDS – silicon drift detector, Si(Li)

- Wavelength dispersive spectrometry (WDS)

• WDS – crystal

• WDS – grating
# WDS – Crystal

* Li emission band around E = 50 eV or λ = 25 nm

* Crystal spectrometers work following the Bragg law

n λ = 2d sinθ d inter-reticular distance

θ Bragg angle (glancing, with respect to the surface)

λ / 2d < 1 is needed, therefore d > 12.5 nm

No crystal available with so large inter-reticular distances
# WDS – Crystals

* Possibility to use **pseudo-crystals**!

*Multilayers* = periodic alternation of thin films

The period (inter-reticular distance) can be adjusted to the spectral range and the angular range of the spectrometer

* [Be (12.5 nm) / Si (2 nm) / Al (14.5 nm)]x20 / Si substrate

Period d = 29 nm
# WDS – Crystals – Be/Si/Al

<figure><img src="image_8.png" /></figure>

* Reflectance measured at synchrotron (Elettra)

* Angular range of microprobe

* **High reflectance 0.3**

* Limited bandwidth, medium spectral resolution 3-4 eV

<figure><img src="image_9.png" /></figure>
# WDS – Crystals

## Issues with the windows!

* (1) Sample - spectrometer

* (2) Entrance of gaseous detector

Transmission of polypropylene, 1 µm, @ 50 eV = 1.5 10⁻⁴

Transmission of Si₃N₄, 50 nm, @ 50 eV = 0.27

CXRO, https://www.cxro.lbl.gov/

<figure><img src="image_10.png" /></figure>

<figure><img src="image_11.png" /></figure>
# WDS – Crystals – CAMECA multilayer – 5 kV

<figure><img src="image_12.png" /><figcaption>Quasi-crystal AlLiCu</figcaption></figure>

PhD P. Schweizer, CEA Marcoule (2024)

<figure><img src="image_13.png" /></figure>
# WDS – Grating

* Grating spectrometers suited to the ultra-soft x-ray range

* Grating spectrometers work following the grating law

$$n \lambda = d (\sin\alpha - \sin\beta)$$
d grating period
$\alpha$ et $\beta$ incident and detection angles
(with respect to the grating normal)

Example:

$$d = 10^{-6} \text{ m (1000 lines/mm)}$$

$$\alpha = 85^{\circ} \quad \beta = 80^{\circ}$$

$$n = 1$$

$$\lambda = 11 \text{ nm (113 eV)}$$

<figure><img src="image_14.png" /></figure>
# WDS – Grating

* Angular scanning is necessary
with periodic gratings

* Use of variable line specing (VLS) grating

Flat field spectrometer

Dispersed wavelengths focused on a line

* Linear detector or camera CCD

No scanning required

<figure><img src="image_15.png" /></figure>
# WDS – Grating – RZP

* Fresnel lens

* Fresnel zone plates

<figure><img src="image_16.png" /></figure>

<figure><img src="image_17.png" /></figure>

<figure><img src="image_18.png" /></figure>

* **Reflection zone plate (RZP) spectrometer**

Only a part of the RZP is used as a variable line spacing grating

<figure><img src="image_19.png" /></figure>
# WDS – Grating – RZP

* Spectrometer good for Li K spectral range and light elements

<figure><img src="image_20.png" /></figure>

<figure><img src="image_21.png" /><figcaption>Mg L2,3</figcaption></figure>

$\Delta E$
0.25eV

<figure><img src="image_22.png" /><figcaption>Li K</figcaption></figure>

<figure><img src="image_23.png" /><figcaption>Si L2,3</figcaption></figure>

CAMECA SX100

EPMA

Spectrometer
NOB

<figure><img src="image_24.png" /><figcaption>Emitted photon energy (eV)</figcaption></figure>
WDS – Grating – RZP

<figure><img src="image_25.png" /></figure>

<figure><img src="image_26.png" /></figure>

<figure><img src="image_27.png" /></figure>

<figure><img src="image_28.png" /></figure>

Amblygonite
Li<sub>0.75</sub>Na<sub>0.25</sub>Al(PO<sub>4</sub>)F<sub>0.75</sub>(OH)<sub>0.25</sub>

Niobate de lithium
LiNbO<sub>3</sub>
WDS – Grating – RZP

<figure><img src="image_29.png" /></figure>

<figure><img src="image_30.png" /></figure>

<figure><img src="image_31.png" /></figure>

<figure><img src="image_32.png" /></figure>

<figure><img src="image_33.png" /></figure>

Al 60% wt.
Li 17%
Cu 23%

AlLiCu Quasi-cystal

X-Ray Spectrom. **54**, 171-179 (2025)
([http://doi.org/10.1002/xrs.3447](http://doi.org/10.1002/xrs.3447))

<figure><img src="image_34.png" /></figure>

<figure><img src="image_35.png" /></figure>
WDS – Grating – RZP

<figure><img src="image_36.png" /></figure>
Conclusion

* Multilayers and windows are available for medium resolution spectroscopy of light elements

* Spectrometers are available for high-resolution spectroscopy

* Spectroscopy in the ultra-soft x-ray range is difficult:

* Low intensities

* Spectral interferences

* Emission sensitive to surface (oxidation, contamination)

* Lack of reference spectra

* Forget the “standard” way to perform quantification:

* Work with integrated intensities

* New quantification model

* Account for electronic structure
# Acknowledgments

* **ANR "Spectroscopie et quantification du lithium par microanalyse X"**

* **LCPMR**

* K. Le Guen

* K. Hassebi

* W. Aid

* R. Benbalagh

* R. Vacheresse

* V. Ilakovac

* N. Temmar

**CEA Marcoule**

* E. Brackx

* P. Schweizer

* **Sorbonne Université**

* N. Rividi

* M. Fialin

* A. Verlaguet

* G. Godard

* B. Dubacq

* **CEA Saclay**

* M.-C. Lépy

* Y. Ménesguen

* **McGill University, Canada**

* R. Gauvin

* N. Brodusch

* **IPM-RAS, Russia**

* N. Chkhalo

* V. Polkonikov

* R. Pleshkov

* **Nano Optics Berlin**

* **Greateyes**

**Merci**

<figure><img src="image_37.png" /></figure>

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SQ³LiX

spectroscopy
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of lithium by xray
microanalysis