Elastic Recoil Detection Analyis
Method
Elastic Recoil Detection Analysis (ERDA) is a physical method for the determination of the elemental composition of thin films, especially for light elements. A (heavy) ion beam, typically Cl ions, is used to bombard the sample and make collisions with sample atoms. Both the scattered ion and the sample atom (recoil atom) can be ejected from the sample in forward direction and be detected.
Schematic of an ion-atom collision
The type of particle (atomic number or mass) has to be identified and the energy of the particle has to be determined. The recoil atoms and scattered ions are detected in forward direction, requiring glancing angles of incidence and exit.
Advantages
- Quantitative determination of concentrations without the need for (matrix-matched) standards
- Especially useful for light elements, also in a heavy matrix
- Depth sensitive: depth profiles of the concentrations are obtained; depth resolution 5-20 nm
- Non-destructive, although some damage like Hydrogen loss can occur
Limitations
- Millimeter beam size, typically 2x2 mm²
- Elemental loss can occur but can also be monitored and corrected for
- Analysis depth: max. 0.5 - 0.75 µm
- Measurements in vacuum
ERDA setup at HZDR
The ERDA setup is connected to the 6MV Tandetron accelerator of the IBC (Ion Beam Center) and typically a Cl ion beam is used in the energy range of 15 - 55 MeV. The lighter elements (Z < 17, Cl) are analysed through detection of the recoiled target atoms and the heavy elements are detected and quantified through Cl forward Rutherford scattering.
Detection systems available at HZDR are (see schematic below):
- Bragg-peak gas ionization chamber (BIC) for elements B - Bi
Advantages: robust in use, good quantification. - Standard semi-conductor detector with a range foil, for the light elements H, D, T, He, Li;
is used in combination with the BIC detector. - Time-of-flight - Energy detector for elements H - Ba
Advantages: good depth resolution (~5 nm at the surface), good mass separation.
Schematic of the IBC ERDA facility
ERDA setup (2022)
Samples
Requirements for the samples:
- Sample size: minimum 5x5 mm², maximum 25 mm, optimum 10-15 mm
- Sample thickness: max. 7-8 mm, optimum ≤ 1 mm (total thickness for mounting)
- Low roughness (in nm range)
Roughness influences the quantification and the sensitivity is high because of glancing angles of incidence and exit. Note that RBS is less sensitive to roughness because the angles are more perpendicular to the sample surface.
Applications
- Analysis of B and Si in FeCoSiB films for SAW magnetic field sensors.
Aim: Develop sensitive magnetic field sensors based on surface acoustic wave (SAW) devices.
Procedure: Use magnetron sputter deposition to produce amorphous, magnetostrictive FeCoSiB films and determine chemical, structural and magnetic properties to find optimum conditions for the deposition. The Si and B concentrations in the films have been analysed with ERDA. Two different ion beam energies have been used to optimise the detection of B and Si.
ERDA depth profiles for a FeCoSiB film obtained using two energies
Notes: The sample contains a Ta capping layer, which is partially oxidised. The profiles for Fe and Ta (marked rbs) are obtained from the Cl scattering spectra. Fe and Co cannot be separated in the measurement and the depth profiles for Fe also include the Co contribution.
Thormählen, L.; Seidler, D.; Schell, V.; Munnik, F.; McCord, J.; Meyners, D.
Sputter Deposited Magnetostrictive Layers for SAW Magnetic Field Sensors
Sensors 21(2021), 8386
- Li/Si incorporation in thin films for the next generation energy storage devices.
Aim: Optimise Atomic Layer Deposition (ALD) to produce lithium containing films by combining the LiHDMS precursor with an O2 plasma.
Procedure: Study the reaction pathways of this ALD process to find the optimum parameters. Carefully combine many measurements to obtain this information. ERDA has been used to determine the composition of the produced Li-containing thin films.
ERDA depth profiles of Li and P in a SiO2 layer
Notes: rbs stands for a depth profile obtained from Cl scattering. Si depth profiles can be obtained both from recoil atoms and Cl scattering. The depth profiles for Li and H have a lower depth resolution because it is obtained with a standard detector with range foil, whereas those for the other elements are obtained by the Bragg ionization chamber.
Werbrouck, A.; Mattelaer, F.; Minjauw, M.; Nisula, M.; Julin, J. A.; Munnik, F.; Dendooven, J.; Detavernier, C.
Reaction Pathways for Atomic Layer Deposition with Lithium Hexamethyl Disilazide, Trimethyl Phosphate, and Oxygen Plasma
Journal of Physical Chemistry C 124(2020), 27829-27839
- Fluorine determination in TiAl alloys.
Problem: TiAl alloys used in turbocharger rotors are not very corrosion resistant at high temperatures.
Solution: Plasma immersion ion implantation of fluorine into TiAl alloys improves corrosion resistance.
Fluorine analysis with ERDA shows the amount of F incorporated into the alloy and this result can be used to optimise the process.
ERDA depth profile of F in a TiAl alloy
Yankov, R. A.; Kolitsch, A.; von Borany, J.; Munnik, F.; Mücklich, A.; Gemming, S.; Alexewicz, A.; Bracht, H.; Rösner, H.; Donchev, A.; Schütze, M.
Microstructural studies of fluorine-implanted titanium aluminides for enhanced environmental durability
Advanced Engineering Materials 16(2014)1, 52-59
Yankov, R. A.; Kolitsch, A.; von Borany, J.; Mücklich, A.; Munnik, F.; Donchev, A.; Schütze, M.
Surface protection of titanium and titanium-aluminum alloys against environmental degradation at elevated temperatures
Surface & Coatings Technology 206(2012), 3595-3600
