Low energy argon ion sample preparation for HRSTEM analysis

Martina Dienstleder(1), Evelin Fisslthaler(1), Christian Gspan(1) Gerald Kothleitner(2)

Introduction

Conclusion

References/ Literature

Acknowledgements Contact

1. Graz Centre for Electron Microscopy, Steyrergasse 17, 8010 Graz, Austria 2. Institute of Electron Microscopy and Nanoanalysis, Graz University of Technology, Steyrergasse 17, 8010 Graz, Austria

The advent of fully corrected ultra-high-resolution transmission electron microscopes (TEM) enabled access to the sub-atomic scale and has become paramount for innovations in material design relevant to science and technology. Their vastly improved performance for the characterization of materials is accompanied by the need to generate high-quality samples via sophisticated and innovative sample preparation techniques. Specimen preparation [1-3] hence is the key to obtain representative insights into morphology, structure, chemistry and functionality. Even minor preparation artefacts such as thin amorphization layers, ion implantation, selective milling or re-deposition can already prevent a deeper insight to a material [4-6]. To overcome this limitations the NanoMill® instrument is a versatile tool to improve the sample quality by a post treatment of the samples with low energy argon ions.

Reduction of the amorphous layer to ~ 1,5 nm Entire removal of Ga implantation induced by FIB preparation Removal of preparation induced material re-deposition Additional milling to generate ultra thin samples for HR investigations Applicable for temperature sensitive materials by using liquid nitrogen cooling

A post treatment of FIB lamellae with the NanoMill®, adapted to the respective sample system, has proved to be very useful for the reduction and removal of FIB-induced preparation artifacts. This allows to prepare a lot of different material systems and to produce the best possible samples for HRSTEM imaging and analysis.

[1] Ayache, J., Beaunier, L., Boumendil, J., Ehret, G., & Laub, D. (2010). Sample preparation handbook for transmission electron microscopy: techniques (Vol. 2). Springer Science & Business Media. [2] G. Petzow “Metallographisches Keramographisches Plastographisches ÄTZEN” [3] L. Reimer „Elektronenmikroskopische Untersuchungs- und Präparationsmethoden (1967) [4] McCaffrey et al., (2001) Surface damage formation during ion-beam thinning of samples for transmission electron microscopy, Ultramicroscopy 87, pp. 97–104. [5] A. Barna et al., (1998) Ultramicroscopy, 70, p. 161 [6] C.-M. Park et al., (2004) Measurement of Ga implantation profiles in the sidewall and bottom of focused-ion beam-etched structures Applied Physics Letters 84, 3331; DOI: 10.1063/1.1715142

„We kindly acknowledge financial support by the Austrian Research Promotion Agency (FFG) (project 850220/859238).”

martina.dienstleder@felmi-zfe.at www.felmi-zfe.at

(1) STEM dark field image of a twin boundary; (2) FIB image of TiO2 sample (prepared with standard parameters); (3) Comparison of the implantation of Ga by EDX measurements before

and after improved preparation procedure; (4) STEM dark field image of the lamella after improved sample

preparation procedure.

NanoMill® - low energy argon ion thinning and cleaning of FIB lamellae

Fischione NanoMill®

Plasma cleaning 10 min Step 1: 10°, 900 eV, 20 min, 210 µA, 15x15 µm Step 2: -10°, 900 eV, 20 min, 210 µA, 15x15 µm Step 3: -10°, 200 eV, 20 min, 210 µA, 15x15 µm Step 4: 10°, 200 eV, 20 min, 210 µA, 15x15 µm Plasma cleaning 10 min

Si Amorphous surface layer

Ga implantation

Twin boundary

Plasma cleaning 5 min Step1: 900 eV, 10°, 5 min, 15x15µm Step2: 900 eV, -10°, 5 min, 15x15µm Step3: 500eV, -10°, 5 min, 15x15µm Step4: 500 eV, 10°, 5 min, 15x15µm Step5: 200eV, 10°, 10 min, 15x15µm Step6: 200eV, -10°, 10 min, 15x15µm Plasma cleaning 5 min

-130°C

EDX ZrO2 Pt contamination

Plasma cleaning 5 min Step 1: 10°, 900 eV, 50 min, 15x15 µm Step 2: -10°, 900 eV, 50 min, 15x15 µm Plasma cleaning 5 min

BF-DF image HAADF

Step 3: 10°, 500 eV, 15 min, 15x15 µm Step 4: -10°, 500 eV, 15 min, 15x15 µm

all samples are clean, thin and nearly artifact free

BF-DF image

HAADF

HAADF

EDX

Rutile (TiO2)

Si

SiO2

HAADF

BF-DF image

BF-DF image

FIB image

BF-DF image HAADF

FEI FIB Nova 200

Ion Type: Argon Ion Energy: 50 – 2000eV Ion Beam Point Resolution: 2µm at 900eV Stage: 360° rotation; tilt: -10° to +30°; working temperature: RT to -160°C

SiO2

Si

(1) STEM HAADF image of the Si/SiO2 FIB lamella (prepared with standard parameters); last FIB milling step: 5 kV, 70 pA, +/- 7° (2) STEM HAADF image of the lamella after post treatment with low energy argon ions

(1) STEM BF/DF and HAADF image of the with standard parameter prepared ZrO2 FIB lamella; last FIB milling step: 5kV, 70pA, +/- 5°.

(2) EDX measurement of the lamella shows a preparation induced Pt- coverage on the FIB lamella.

(3) STEM BF/DF and HAADF image of the lamella after posttreatment with low energy argon ions – the Pt- contamination was completely removed.

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