Graphene-coated scintillators for low-energy electron detection

0568413 - ÚPT 2024 RIV CZ eng A - Abstract
Lalinský, Ondřej - Průcha, Lukáš - Skoupý, R.
Graphene-coated scintillators for low-energy electron detection.
16th Multinational Congress on Microscopy, 16MCM, 04-09 September 2022, Brno, Czech Republic. Book of abstracts. Brno: Czechoslovak Microscopy Society, 2022 - (Krzyžánek, V.; Hrubanová, K.; Hozák, P.; Müllerová, I.; Šlouf, M.). s. 444-445. ISBN 978-80-11-02253-2.
[Multinational Congress on Microscopy /16./. 04.09.2022-09.09.2022, Brno]
R&D Projects: GA TA ČR(CZ) TN01000008; GA MPO(CZ) FV30271
Institutional support: RVO:68081731
Keywords : graphene * cathodoluminescence efficiency * scintillation detector * low energy
OECD category: Coating and films
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Lalinský, O., Průcha, L., Skoupý, R. Graphene-coated scintillators for low-energy electron detection. In: KRZYŽÁNEK, V., HRUBANOVÁ, K., HOZÁK, P., MÜLLEROVÁ, I., ŠLOUF, M., eds. 16th Multinational Congress on Microscopy, 16MCM, 04-09 September 2022, Brno, Czech Republic. Book of abstracts. Brno: Czechoslovak Microscopy Society, 2022, s. 444-445. ISBN 978-80-11-02253-2. Low-energy electron imaging has seen increased popularity nowadays. Such imaging has the advantage over higher-energy imaging in higher surface resolution, i.e. smaller primary beam (PB) penetration depth, and therefore less sample damage depth. However, the problem can occur especially in the detection of backscattered electrons (BSE), which are usually not accelerated compared to the secondary electrons (usually to 10 keV) and impinge on the scintillator with energy close to the energy of the PB. This is because slower BSE can cause lower
cathodoluminescence (CL) response of the detector. First, the CL efficiency (integral CL intensity divided by the energy of the incident electrons) of the scintillator generally decreases with the BSE energy. Second, slower BSE lose more of their energy or may not pass through the scintillator coating at all. It is therefore necessary to find the ideal combination of coating +
scintillator for maximum CL efficiency. Scintillators of various compositions were supplied by CRYTUR. The scintillators were grown by the Czochralski method as single-crystals. The studied coating materials were Al, Sc, Indium Tin Oxide (ITO), and graphene. Al, Sc, and ITO were prepared by magnetron sputtering. Graphene was prepared by chemical vapor deposition with methane as a precursor. The graphene was grown on the Cu foil. The graphene was then transferred with the help of PMMA onto a 5.7 mm diameter and 0.5 mm thick CRY018™ sample.
The graphene on the CRY018 was studied by Raman spectroscopy. Graphene is characterized by 2 peaks in the spectrum - G (approx. 1583 cm-1) and 2D (approx. 2660 cm-1). For a single carbon layer, the 2D peak should be at least 2× larger than the G peak, as confirmed by the Figure. To study the CL efficiency, a specialized CL apparatus located at our institute was used. The primary energy (PE) was in the range of 0.6 to 10 keV. The CL spectra were studied, from which the CL efficiency was calculated. This was plotted as a function of the PE. Fig. 2 shows the results of CRY018 sample with various coatings. The CRY018 with 50 nm Al has the highest CL efficiency for PE ≥ 5 keV. However, BSE slower than 1.9 keV cannot pass through such a coating. Graphene is the best coating for slow BSE. Such a system should be able to detect BSE up to 400 eV. Although graphene is not yet possible to deposit in large quantities on scintillators, it is certainly a very promising way to effectively dissipate charge from the scintillator surface while maintaining the maximum CL efficiency of the scintillator.
Permanent Link: https://hdl.handle.net/11104/0339730