System Requirements
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Runs on Windows 95, 98, Windows2000, NT, XP
Supports European Windows Region number representation (WiNDF 7.0.48
and above)
This is a computationally hungry code and requires at least 200MB RAM.
A fast processor is very desirable.
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RBS, EBS, ERD, NRA
NDP
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The DataFurnace is designed to extract elemental
depth profiles from any ion beam analysis depth profiling technique,
namely Rutherford backscattering, non-Rutherford elastic backscattering
(EBS), forward recoil spectrometry (elastic recoil detection:
ERD/ERDA/FRS), or non-resonant nuclear reaction analysis (NRA).
In the
latter case the energy spectra are analysed: no tools
are
provided for depth profiling using beam energy scans. Cross-sections
are supplied by the user in most cases. Range foil ERD and
ToF-ERD
are both supported.
Support is provided for the correct calculation of sharp resonances in
EBS (although the straggling calculation is not completely correct in
this case).
Neutron depth profiling is also supported.
PIXE is not yet supported.
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Code validation
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The RBS code has been thoroughly validated
against the CRM (certified reference material) IRMM302/BAM-L001 by
Boudreault et al (Surf.Interface Anal. 33, 2002, 478).
EBS code has been validated by Jeynes et al
(Nucl.Instrum.Methods B161-163, 2000, 287).
ERD code has been validated in a round robin (Boudreault et al,
Nucl.Instrum.Methods, submitted)
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Documentation
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Manual for NDF (50 pages)
Manual for WiNDF (70 pages)
Full scientific review in J.Phys.D (30 pages)
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Simulation
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Of course, DataFurnace can simulate
spectra, like any other current IBA analysis program.
The simulator is very straightforward and includes a convenient
graphical user interface (WiNDF7.0.50 and above).
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Optimisation of a known structure
"Local Minimisation"
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Given an approximate structure
(depth profile) the program can optimise it.
Like all IBA optimisation programs, DataFurnace minimisation
usually requires the initial approximation to be quite good.
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Fitting spectra
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DataFurnace will fit spectra given the
analytical conditions and knowledge of the elements in the sample.
No other information is required from the user. Complex
spectra with overlapping partial spectra are solved as easily as simple
ones completely automatically, leaving the task for the analyst to
think about what information really is in the data, and how well
known the analytical conditions really are.
The analyst is - at last - relieved of the tedious business
of finding a structure that gives a plausible fit to the data.
Moreover, DataFurnace fits are typically extremely good, allowing
much more information to be extracted from the data than
by manual methods.
The code fits the spectra by selecting an appropriate layer structure.
Occam's Razor is used to minimise the number of layers:
continuous profiles are represented by discontinuous layered profiles.
This is valid since IBA spectra with limited depth resolution are
ambiguous. However, we have also permitted one element to
have an analytical depth profile, where any valid Fortran
analytical function is specified by the user and up to 10 parameters
are fitted (NDF7.8e and above). |
Data Formats
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A wide variety of formats are supported.
Our policy is to provide support for the formats of our licenced
users so that DataFurnace can be used routinely for large
datasets.
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Estimation of Uncertainty due to
spectral ambiguity
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Fitted depth profiles can be supplied
with statistically sound estimates of measurement uncertainty using Bayesian
inference methods which are natural to
the fitting algorithms used. Computation times for these are
typically
hours (in contrast to fitting times of minutes).
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Multiple spectra
Multiple detectors
Multiple techniques
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IBA spectra are very ambiguous. Analysts
reduce this ambiguity by taking multiple spectra at different beam
energy, incidence angles etc. They can also use multiple detectors
(different backscattering angles) or even multiple techniques (such as
simultaneous RBS/ERD for a complete analysis including H).
DataFurnace is designed to encourage analysts to do any or all of these
things. Various cases are handled, including spectra collected
simultaneously, and the special case of ERD spectra with overlapping
partial recoil spectra. This latter case is the cause for some
ToF-ERD data to be ignored, and is the usual case for heavy ion range
foil ERD (including analysis of H isotopes with a He beam).
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Molecules: chemical assumptions about
sample
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DataFurnace does not require the
analyst to have any knowledge about the sample, except which elements
are present. However, in many cases the spectra are deeply
ambiguous and the user cannot get DataFurnace to give a valid answer
(in terms of what is known about the sample) without insisting that
certain depth profiles are excluded. Various tools are provided
for this, the most important of which are:
- allowing molecules to be specified. Thus a
glass can be specified as a single logical element, for example.
The molecule can be specified in an indeterminate form such as
CuOx for
example, instead of CuO or CuO2 etc: then DataFurnace will find the
best value of x (NDFv7.8e and above).
- allowing pure layers to be specified
- allowing the substrate to be specified
- allowing minimum and maximum depths of logical elements to
be specified. So we can exclude layers we know are at the surface
from deep in the sample, or exclude the substrate from the near-surface
region.
- for one element the form of the depth profile can
be specified by a formula with up to 10 parameters which NDF will fit
(NDF7.8e and above)
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Pulse Pileup
Energy Straggle
Stopping powers
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- Simple binary pulse pileup is calculated using Jeynes et
al (Nucl.Instrum.Methods, B136-138, 1998, 1229) provided the data
format gives the run-time (allowing an average count rate to be
calculated).
- Bohr or Chu straggling calculation is incorporated.
Szilágyi's DEPTH program is supported (and can be executed
directly by NDF during the fit : NDF7.8g and above)).
- TRIM88 values are distributed. A variety of other
stopping power compilations are supported including TRIM95, SRIM2000
and Hemut Paul's heavy ion stopping powers (NDF7.7a and above).
- Konac et al (" KKKNS", NIM, 1998, B136-138,
pp.156-65) stopping powers for He in Si are available as a patch.
Molecular stopping powers are supported, and the stopping
powers for He in SiO2 of Pascual-Izarra et al (NIM, 2002,
B196, pp.209-214) are also available as a patch (NDF7.8c and above).
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Roughness
Double scattering
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Moderate roughness can be fitted (NDFv7.8c and
above). Three different models are available, but they all
assume that the beam enters and leaves the sample only once.
A double scattering calculation is implemented (NDFv7.8f and above).
This is comparable to the double scattering in Matej Meyer's
SIMNRA.
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Graphical output: publishable quality
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Graphical output with a variety of spectral
manipulation and display options is provided for evaluation of results
and preparation of reports including journal publications (OK, it's
not a general purpose plotting program so only limited options are
available!):
- Raw data, includes mass calculator for surface signals
- Fitted spectra, including fitted partial spectra
- Fitted depth profiles
- Re-plotting partial spectra on concentration vs depth scale
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Numerical output
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Comprehensive output is all in well defined
readable text files. The user can read all output into his/her
own programs at will. |
Polynomial curve fitting
"multiple scattering"
Linear depth scales
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- Polynomial fits up to fifth order on up to 6 regions of
interest of a spectrum
- A procedure is facilitated involving division of
a spectrum by a fit, fitting the result with a cubic curve and putting
the coefficients into the program. Then spectral misfits due
to multiple scattering and other effects can be corrected, allowing
the analyst to force DataFurnace to fit the data closely. This
is necessary to interpret the spectra closely, and we have shown that
this can be done validly (Barradas, Jeynes & Jackson, NIM, 1998).
- Depth scales are calculated in atoms/cm2 (proper
thin film units)
- Depth scales can be expressed in nm where the user is
facilitated to specify the density of each logical element.
Linear combinations are calculated. If the chemistry of the
sample is specified correctly and the bulk densities are valid for thin
films then the depth scale in nm calculated this way is correct.
Otherwise not. In any case there is no other way to give a
correct linear depth scale.
- Depth scales can also be expressed in nm assuming a
constant sample atom density
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Batch analysis
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Up to 99 samples can be analysed in a
single batch, with up to 16 spectra per sample. The batch runs
without user input. Typically the machine is fitting the next
sample
while the analyst is preparing the report of the fit from the last one.
Final results might be run at a slower speed overnight.
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