Ion Beam Analysis Laboratory
Facilities:
 We have a 2MV Tandetron
from High Voltage
Engineering
Europe installed in Summer 2001 and commissioned Easter 2002 with
two beam lines
: a microbeam
line commissioned Summer 2002 and a millibeam
line commissioned Autumn 2002.
The microbeam line is equipped with a magnetic quadrupole triplet lens
and magentic scanner unit from
Oxford Microbeams Ltd capable of focussing the beam to 1micron
diameter and scanning over 2mm square.
The millibeam is equipped with a 6 movement
goniometer from Arun
Microelectronics Ltd and a sample exchange mechanism through an
airlock.
The sample holder is 150mm * 100mm. The goniometer can turn
the sample to glancing beam incidence angles and is suitable for high
resolution depth profiling and depth profiling of H (and D) using
4He ERD.
- RBS, EBS, ERD, PIXE, selected NRA
with up to 2.5 MeV H, 6MeV 4He and 1.4MeV 3He beams.
- Multi-axis channelling with a UHV 6
movement goniometer (RBS/EBS/ERD).
- Microbeam analysis of laterally
inhomogeneous samples (PIXE/RBS/NRA).
- Cold stage analysis of delicate
samples using microbeam (RBS/EBS, PIXE, NRA)
Data
Analysis:
The unique Surrey " IBA DataFurnace
" software (based on a "simulated annealing" algorithm) enables
automatic, self-consistent analysis of multiple RBS, EBS and ERD
spectra, allowing rapid and economic quantitative analysis of large
batches of complex samples. Error bars on the depth profiles
obtained (see below) are derived using Bayesian inference
techniques. These new data reduction techniques have
revolutionised ion beam analysis, making it widely available as an
industrial characterisation tool.
We offer an analysis service to industry
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Materials analysed by IBA:
Ion beam analysis can be used for many different types of thin
film samples, and here are just a few that we have looked at:
Semiconductor Materials
- Accurate determination of ion dose
for implanted samples (RBS).
- Accurate depth profiles for diffused
heterostructures (RBS).
- Silicidation kinetics (RBS).
- Annealing kinetics in implanted
single crystals from damage profiles (RBS-c).
- Light element analysis (H, C, N, O)
of amorphous group IV alloys (RBS/ERD).
Qualification and characterisation of
layered materials
- Tribological coatings such as TaC
(RBS/EBS).
- Optical multilayers (RBS).
Other Materials
- Profiles of Cl at sub-0.5% in cement
(PIXE).
- Characterisation of cement type
(PIXE).
- Major, minor and trace element
analysis of biological materials (PIXE/RBS).
- Interdiffusion of deuterium-labelled
and unlabelled polymers (NRA).
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Machine and lab developments (and
faults):
Sep 2002: 2
MV Tandetron:
energy calibration . This is a report by an Erasmus student
from
Eindhoven University, Karin Schepers. The calibration is in
section
4.1. It is a 5 point calibration using EBS (elastic
non-Rutherford
backscattering) and the three O(alpha,alpha)O resonances at 3036, 3363
and
3877 keV and the two C(alpha,alpha)C resonances at 4265 and 5820 keV.
The
result is (True terminal voltage) = (Nominal terminal voltage * 1.025).
Feb 2003: Project for NPL to accurately determine thin oxide film
thicknesses (on Si). This includes a machine energy calibration,
where we determine the temperature coefficient of the monitored
energy reading, and also a determination of the 3.036MeV
16O(alpha,alpha)16O resonance cross-sections at 5% (an appendix
shows the spectra). The calibration gives: (True terminal
voltage) = (Nominal terminal voltage)*1.027(2) where the last figure
error
is due to a temperature coefficient of 0.03%/degC
May 2003: Machine down for a day to repair overheated
filament current cables . A heatsink has been added.
May 2003: Machine down for several days - no beam. The
problem was found to be a blockage in the
charge exchange canal
June 2003: Paper submitted to the IBA-16 conference in
Albuqueque, New Mexico, "The new
Surrey
IBA Facility "
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Glossary
- RBS - Rutherford
Backscattering for depth profiles of complex thin films (up to a few
microns thick and down to a few nm depth resolution).
- EBS - Elastic (i.e.
non-Rutherford) backscattering (for better C, N, O analysis).
- ERD - Elastic Recoil
Detection (used for H analysis).
- PIXE- Particle (usually
proton) Induced X-ray Emission (ppm sensitivities).
- NRA - Nuclear Reaction
Analysis (isotope specific).
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