Category Archives: FAQ

Leng model for optical constants

We have implemented (starting with object generation 4.99) the Leng oscillator which has been developed to model optical constants of semiconductors. As shown in the original article (Thin Solid Films 313-314 (1988) 132-136) it works well for crystalline silicon:


Warning: While the model works fine in the vicinity of strong spectral features (critical points in the joint density of states) it may generate non-physical n and k values in regions of small absorption.

Error messages in OLE automation

In object generation 4.97 we have implemented a new mechanism to pass error messages from SCOUT and CODE to OLE automation clients.

While it runs the OLE server (i.e. SCOUT or CODE) collects error messages in a list. We have introduced a view object (type ‘Error messages view’) to display the current list of error messages in a view.

Any OLE client (LabView, Excel, …) can retrieve information about the number of error messages, their type and text content. There is also a classification to separate critical errors and warnings. Once the OLE client has finished error handling it can clear the list in the OLE server.

New fit option

We have included a new fit option which helps to increase the speed of analysis in time critical applications: In methods which use pre-fit sets in the list of fit parameters you can now include the current fit parameter values in the pre-fit search. This eventually avoids many fit iterations if differences between consecutive measurements are small.

The new feature can be turned on or off in the dialog of fit options.

 

Thickness fits: Automatic slider range

Starting with object generation 4.77 you can generate low and high limits for fit parameters automatically when you generate them – at least for thickness values. In the fit options dialog (File/Options/Fit) you can set a percentage (lower right corner) which is used to compute the low and high limit of the available thickness range. The reference value is the thickness value at the time the new fit parameter is generated.

Note that the automatically generated range is also the range of parameter sliders that are based on fit parameters.

Note also that you can automatically generate thin film thickness values as fit parameters by drag&drop of a layer stack to the list of fit parameters in the treeview. If the list of fit parameters is shown in a view this is certainly the fastest way of generating thickness sliders.

Here is an example showing sliders with limits of +/-5% that have been generated automatically: