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| The following spectroscopic tools may support your spectroscopic work: | |
| DirectDF | This
is a small tool for the direct determination of
dielectric functions. It can be applied if you have
recorded a transmittance as well as a reflectance
spectrum on the same sample spot, and if, in addition,
the sample is just a thick layer of the material under
investigation. No interference fringes must appear in the
spectra, although multiply reflected partial waves are
allowed. Both spectra have to be recorded at almost
normal incidence of light. From the two input spectra and
the sample thickness (which must also be known before)
the dielectric function is computed. This method applies to thick substrates with both sides polished such as microscope slides, silicon wafers polished on both sides or KBr plates. More information can be found in the |
| KKR analysis of reflectance spectra | In
the case of 'halfspace' samples where all the radiation
that contributes to the reflectance spectrum is reflected
at just one interface one can compute the dielectric
function from the reflectance spectrum. An additional
requirement is that the reflectivity is measured over a
broad spectral range and that significant structures are
contained in the spectrum. The program makes use of the so-called Kramers-Kronig-Relation (KKR) that connects the logarithm of the measured intensity reflectance spectrum to the phase spectrum. The latter is reconstructed from the measured data. The KKR is based on the knowledge of the reflectivity for all frequencies which requires some reasonable extrapolation of the measured spectrum. This is done in a graphical way.
More information can be found in the |
| Dielectric function database | Our software products can read and write optical constants from a dielectric function database which offers many pre-defined dielectric functions in ready-to-use objects. Besides data taken from literature the database also contains useful models for certain materials. These can be used as the starting point for adaption to similar materials by parameter fitting if suitable experimental spectra have been recorded. |
| Customized PLS analysis | In
certain cases a purely statistical analysis of optical
spectra is succesful. Usually the following conditions
must be met: There is access to many 'training spectra'
taken on samples for which all parameters are known. In
addition, the observed spectral features depend on the
parameters that are to be determined optically in a
monotonous way. Then the so-called 'partial least
squares' method (PLS) may be applied eventually which
provides - after a training session - a very quick
analysis of measured spectra. The speed of the analysis
makes PLS the ideal tool for rapid online production
control. We offer customized PLS programs with user-interface, spectrometer control and report features of your choice. |
| Spectrum recording programs | For some spectrometers we have developed easy-to-use spectra recording programs which output spectra in a way suitable for our various spectrum analysis tools. A direct coupling of recording and analyzing tools can be realized by OLE automation in a quite elegant way. |
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