Transcript Setup for large area low-fluence irradiations with quasi

New high resolution spectrometer
for nanometer level
elemental depth profiling
M. Laitinen, M. Rossi, P. Rahkila, H. J. Whitlow
and T. Sajavaara
Department of Physics, P.O.B 35, FIN-40014 University of Jyväskylä, Finland
email: [email protected]
The New Spectrometer:
What does it look like and how does it works ?
The new spectrometer:
How does it look like and how it works ?

In principle all sample
elements can be quantified
M. Putkonen, T. Aaltonen, M. Alnes, T. Sajavaara, O. Nilsen, and H. Fjellväg, Atomic
Time-of-Flight – Elastic Recoil Detection (ToF-ERD)

Quantitative method:

Energy from well known kinematics
Time-resolution better than E-detector resolution

Element (mass) from ToF and E signals

Scattering propability to detectors
Coulombic interaction potential

Depth information
Semi-empiric parametrization for energy loss
TOF detection efficiency
 All sample elements, also H, can be detected
Sample holder
 Can getbackwall
better only by getting more electrons out of the carbon foils
-> coating the carbon foils with Atomic Layer Deposition, ALD
Better than 98% for C
and heavier masses
~
90 % for 4He
~
10-60% for H
Measured with 1600 V MCP voltage,
3000 V mirror voltage and 200x preamplifier
Time-of-flight resolution


Timing with external 200x preamplifier, CFD and TDC
Current resolution timing resolution 300 ps for 4.5 MeV incident He ions
scattered from 1 nm Au film on Si substrate

Timing:
300 ps equals ~ 4mm for 4.4 MeV He

Upgrade:
fast preamplifiers inside the chamber
300 ps
Diamond-like carbon films

2.3 µm thick diamond-like-carbon film on Si

Measured with 9 MeV 35Cl

All isotopes can be determined for light masses

Light elements can be well quantified (N content 0.05±0.02 at.%)
First results: 8.6 nm Al2O3

Atomic layer deposited Al2O3 film on silicon (Prof. Ritala, U. of Helsinki)

Density of 2.9 g/cm3 and thickness of 8.6 nm determined with XRR (Ritala)

Elemental concentrations in the film bulk as determined with TOF ERDA
are O 60±3 at.%, Al 35±2 at.%, H 4±1 at.%. and C 0.5±0.2 at.%.
Example with high mass element

Atomic layer deposited Ru film on HF cleaned Si
(Dr. Kukli, U. of Helsinki)

Bulk density of 12 g/cm3 used in the depth profiles

Monte Carlo simulations needed for getting reliable
values for light impurities
Future improvements: New TOF-gate

ALD-coated thin C-foils for high
electron yields (coming)

Timing from backwards emitted
electrons

Position (scattering angle) from
forward emitted electrons and
delay line anode

Anodes made on PCB
Commercial MCP stacks by TECTRA
Future improvements: Gas ionization detector
TOF-E results from Paul Scherrer Institute
Incident ion 12 MeV 127I and borosilicate glass target
Nucl. Instr. and Meth. B 248 (2006) 155-162
Conclusions
 New high resolution spectrometer has been built in JYFL
 ToF-ERDA provides unique capabilities for quantitative depth
profiling of all the sample elements, including hydrogen
 Depth resolution of <2 nm at the surface has been reached in
Jyväskylä, further improvements coming within months
1st timing detector,
3 μg/cm2 C-foil
2nd timing detector,
10 μg/cm2 C-foil
Acknowledgements
Mikko Ritala, U. of Helsinki
Matti Putkonen, Beneq Oy and Aalto University
Kaupo Kukli, U. of Helsinki
TEKES-EU Regional Funds
Academy of Finland
TEKES
Accelerator based
materials physics
goup in JYFL
1st timing detector, 3 μg/cm2 C-foil
2nd timing detector, 10 μg/cm2 C-foil