Experimental Variables and VAMAS Files

During the course of an experiment multiple acquisition sequences may be performed leading to several sets of data related by an experimental variable. That is to say, the experimental variable is a characteristic parameter of the experiment recording, for example, position, temperature or in the more common case, ion-gun etch-times. The VAMAS file format includes these experimental parameters in each VAMAS block and, what is more, there may be more than one such experimental variable for a given experiment, therefore the VAMAS blocks allow for sets of these experimental variables to be assigned to each spectrum. CasaXPS displays the active experimental variable in the first column in the right-hand-side of the Experiment Frame (Figure 1). When multiple experimental variables are present within the VAMAS blocks, the active experimental variable can be cycled by using the Next Exp Var menu option on the Select menu shown in Figure 1. Cycling through the available experimental variables is also achieved by holding the Control Key down and pressing the F1 function key.

Figure 1 A depth profile acquired on a JEOL JPS-9200. The experimental variable in the Figure is displaying the position index rather than the etch-time. Both etch-time and position index are included in the JEOL files exported in VAMAS format.

The same VAMAS file seen in Figure 1 is also displayed in Figure 2 however the active experimental variable has been switched to Etch Time.

Saving and Restoring the Display State from File

CasaXPS maintains a processing history within each VAMAS block of a VAMAS file for saving data reduction steps however display information providing the framework for visualizing spectra from a file as a set of tiles must be saved and restored from a CasaXPS specific file type. The tile file format ASCII files (tff) includes fields for preserving a given display between sessions and also offers a means of defining a display template suitable for files of similar data for which identical presentation is required.

The left-hand-side of the Experiment Frame (Figure 2) displays a sub-sampled set of O 1s regions at regular time intervals. Displays of this nature are precisely the type of display formats which can now be saved to file. The scrolled-list of tiles as well as the current number of tiles per page may be saved to file using the options on the File menu (Figure 3), namely Save Tile Format File and Load Tile Format File. Note, these same options are also repeated on the Options menu, where similar options are available for temporarily saving and restoring a tile format within a CasaXPS session.

Figure 2

To save a tile format:

1. Prepare the scrolled list in terms of number of tiles per page and the required display for each tile in the list.
2. Select the Save Tile Format File … menu option on the File menu.
3. Using the File name field on the resulting File Dialog window enter the name of the desired tile format file. The default tile format file name will be the original VAMAS file where the .vms extension is replaced by a .tff file extension.

To restore a tile format:

1. First load a VAMAS file.
2. Select the Load Tile Format File … menu option on the File menu.
3. Select the appropriate tile format file for the given VAMAS file. If the tile format file derives from a different data file, a warning dialog window appears offering the name of the file for which the tile display was prepared.

A tile format file can be applied to other files for which the spectra appear in the same VAMAS block structure as the original file used to save the tile format. The spectra must appear in the same order with respect to VAMAS block index and the data must be equivalent to the original file.

Figure 3