PAES approaches for thin films
surfaces and interfaces studies
Programme / Sub-programme / Module: 5/5.1/ELI-RO
ELI-NP thematic: GDE/II.2 Material science studies with positron beams
Project title / Acronym: PAES approaches for thin films surfaces and interfaces studies/ FILMSURFAPES
Contract no: 17
Project duration : 17.09.2020 - 31.08.2023
Project director: Dr. Ioan-Ovidiu Pană
Project Coordinator: National Institute for Research and Development of Isotopic and Molecular Technologies
Partner 1: National Institute for Research and Development of Materials Physics
Positron annihilation-induced Auger electron spectroscopy, when operated with low energy positron kinetic energies (below ~ 5 eV) is probably the most surface sensitive technique known to date. The origin of this fact stems in the ‚negative positron work-function of most materials or, in other words, to the fact that positrons originating from vacuum should exceed a threshold value of their kinetic energy to penetrate into the bulk of the material. As a consequence, low energy positrons do not penetrate inside most materials and, after forming some metastable positronium-like metastable states near the surface of the material, they annihilate with electrons from the very first atomic layer being a versatile method to study surfaces and interfaces in condensed matter.
The main scientific objective of the project refers to the characterization of surfaces and interfaces by using positron-induced Auger electron spectroscopy (PAES) for thin films and multilayers. It is related to and derives from objectives of Program 5 / Subprogram 5.1 (HG no. 583/2015) namely "Gamma-beam applications at ELI-NP-GDE / II.2" in material science studies with positron beams.
1. preparation by pulsed laser deposition (PLD) and primary physical characterization of thin layers of FePt (L10) with different thicknesses on MgO substrate; - preparation by PLD and characterization of ZnS / FePt (L10) / MgO multilayer systems - obtaining by two different methods (PLD and chemical vapor deposition-CVD) graphene films on MgO substrate;
2. Obtaining the necessary authorizations for the realization and operation of the existing PAES system (with a 22Na positron source) of Partner 1; obtaining and interpreting the PAES spectra as well as their correlation with the other classical measurements.
3. Elaboration of a methodology for characterization of surfaces and interfaces through PAES necessary for the further developments of the low energy positron system within ELI-RO.
4. Establishing partnerships for future collaborations in experiments with low energy positrons within ELI-NP infrastructure.
For the achievement of the above objectives the project includes 4 annual stages 2020-2023. Conceptually, the proposal contains several Tasks that do not necessarily overlap with the mentioned stages. The tasks under consideration are the following:
T1. Preparation as well as theoretical and experimental characterization of thin layers based on FePt (L10). MgO and FePt (L10) / ZnS / MgO.
T2. Complete realization of the PAES spectra measurement system and its authorization by CNCAN;
T3. Obtaining the PAES spectra for thin layers based on FePt (L10). MgO and FePt (L10) / ZnS / MgO as well as their interpretation and correlation with the other experimental data and theoretical calculations. T4. Preparation as well as theoretical and experimental characterization of thin layers based on few graphene layers on MnO substrate.
T5. Obtaining PAES spectra for graphene-based thin films deposited by PLD and CVD and interpretation of these results in correlation with theoretical calculations and other experimental determinations. Elaboration of the methodology necessary for the further development of these types of experiments within ELI-NP.
T6. Dissemination of results by publication in ISI-listed journals and communications at conferences.
17 February 2021