Introduction

CasaXPS is designed to take data from a wide range of instruments using native file formats wherever possible, convert these formats to the ISO 14976 (VAMAS) format and provide a single environment for all to process XPS, AES and SIMS data. For many analysts problem-solving using multiple techniques is common-place and while the origins of CasaXPS are clearly XPS the expansion of the system to cover AES and SIMS is both natural and desirable. In addition, XPS image processing has also become increasingly important and to fulfil the potential of the modern imaging XPS instruments, new features and algorithms have been added to CasaXPS.

Many of the features in CasaXPS require an understanding of why as well as how an operation is performed and therefore a large part of the CasaXPS manual is devoted to explaining the context for a sequence of data reduction steps. The mechanics of these steps are addressed within articles aimed at specific examples however the essential functioning of the CasaXPS options and the overall structure of the program will be presented in a reference section. The examples are necessarily wordy and to compensate to some degree the reference section will be pictorial in essence.

The remainder of the introductory sections is devoted to presenting an overview of CasaXPS.

CasaXPS and the ISO 14976 File Format (VAMAS)

CasaXPS is designed around the ISO 14976 VAMAS file format. The original authors of the VAMAS format provided a specification for maintaining experimental data such that the context as well as the intensities are recorded, thus offering a firm base for subsequent data reduction. The CasaXPS system is Windows based and can be seen as:

1. A means of visualizing the VAMAS file contents in the form of a browser.
2. A means of displaying the data in graphical format.
3. A set if dialog windows for managing the parameter fields within a VAMAS file.
4. Tools for processing and quantifying the data.

Design Philosophy

CasaXPS is a multiple document interface. That is to say, the window structure supports one or more files all open at the same time, where the files are maintained within a, so called, Experiment Frames which in turn are managed by the CasaXPS main window (Figure 1). The main window also includes a menu bar and up to three toolbars; these menus and toolbars provide access to dialog windows and display state switches.

Figure 1: The CasaXPS Main Frame showing a depth profile experiment displayed in the Active Experiment Frame.

Once data is loaded, adjustments to the display, processing, peak-fitting and reporting are performed via a set of dialog windows:

1. Page Tile Format dialog
2. Tile Display Parameters dialog
3. Quantification Parameters dialog
4. Spectrum Processing dialog
5. Element Library dialog
6. Annotation dialog
7. Image Processing dialog
8. Dynamic SIMS dialog

VAMAS Files and Experiment Frames

The native file format for CasaXPS is the ISO 14976 (VAMAS) file format, but what is more, the system is designed around the information and structure of these files; managing the data within CasaXPS is an exercise in manipulating the fields defined by the ISO standard. In addition to the primary dialog windows listed above, numerous dialog windows are used to make adjustments to the structure of these VAMAS files to ensure the data displayed in CasaXPS is representative of the experiment behind the data.

The action of all these dialog windows is closely coupled to the Experiment Frame window showing the focus high-light (Figure 1). Each open VAMAS file is displayed in an Experiment Frame, where the logical structure of the VAMAS file is visible in the right-hand-side of the Experiment Frame and selections from the set of spectra or images arrayed in the right-hand-side are displayed in the left-hand-side of the Experiment Frame. The focus Experiment Frame for the example in Figure 1 is the window with the title bar showing b-tp.exp.vms. The left-hand-side of the Experiment Frame maintains a scrolled-list of display tiles, where each tile can display one or more of the spectra or images; using Figure 1 as the example, the VAMAS file data blocks (VAMAS blocks) labelled Survey [1], Survey [5] and Survey [10] are displayed in the first tile in the left-hand-side of the Experiment Frame labelled b-tp.exp.vms. The tile for which the title section is displayed high-lighted represents the Active Tile; when more than one VAMAS blocks are displayed, the VAMAS block selected first using the array of VAMAS blocks in the right-hand-side is the Active VAMAS block. For the example shown in Figure 1, Survey [1] is the Active VAMAS block; any processing operations via the dialog windows are applied to the Active VAMAS block. Annotation is also directed onto the Active VAMAS block while tile display settings adjusted via the dialog windows or tool bar buttons is applied to the Active Tile.

Browsing Data in a VAMAS File

The VAMAS file format is designed to maintain a set of data to include the experimental context for each acquisition sequence within the file. The most common XPS experiment might consist of a survey spectrum plus a set of high resolution spectra over narrower energy intervals, however such experiments in turn, may be part of a larger design where these experimental parameters are repeated after tilting the sample or interleaved by ion-gun etch cycles. The Active Experiment Frame in Figure 1 is representative of such an experiment. The VAMAS file b-tp.exp.vms is an ion-gun sputter depth profile and is presented in the right-hand-side of the Active Experiment Frame using the etch-time to align rows of spectra, where the columns are separated by species/transition assignments for the individual spectra. Offering the experiment in this logical array of VAMAS blocks provides a mechanism for browsing the data within a VAMAS file: using the left-hand-mouse button, one or more VAMAS blocks can be selected using the usual Windows mechanism for selecting items, for example, the Shift Key allows a range to be selected while the Control Key adds to and removes from a current selection. Once selected, a set of VAMAS block may be displayed in the left-hand-side of the Experiment Frame or represent the target for propagating processing and/or peak fitting via the Browser Actions mechanism.

Visualizing Data

The basic tool for visualizing data is the Display Tile. A Display Tile is an area within the left-hand-side of an Experiment Frame where spectra or images are displayed using the current set of display parameters. Display Tiles are arranged on the left-hand-side of the Experiment Frame in regular patterns of none overlapping rectangles. These rectangles are organised according to the settings on the Page Tile Format dialog window, where radio buttons allow various predefined tile configurations to specify the layout of the rectangles on a page, both number of and position. If the number of spectra displayed exceeds the number of tiles defined on a page, then the left-hand-side of the Experiment Frame becomes a scrolled list, where each click on the background of the scroll-bar moves the display to the next page of tiles. The concept of the Active Tile, as discussed above, is required because of the possibility of maintaining multiple Display Tiles in an Experiment Frame.

In addition to these none overlapping regular Display Tile formats, it is also possible to insert a Display Tile within an existing Display Tile using a marked rectangle and the Insert Key on the keyboard. Regardless of the location of a Display Tile, any Display Tile can become the Active Tile by simply left-clicking the mouse button with the cursor in the intended Display Tile. The title bar for the Display Tile so indicated will become high-lighted and from that point on, the Display Tile becomes the focus for processing, annotation and other dialog based operations. In particular, the Tile Display Parameter dialog window provides the means of explicitly defining the display settings for the Active Tile.

A further consequence of displaying spectra in multiple tiles is that, on printing, the tile format will be fitted to the printed page and used for hardcopy output. If a scrolled list appears in the left-hand-side of the Experiment Frame, then each page of tiles in the scrolled list will print on a separate page. Fitting the tile format to the printed page involves adjusting the dimension of the tiles and therefore before committing to paper, the Print Preview option can be used to assess the desirability of the printed display.

Processing and Reporting

One consequence of developing CasaXPS whilst interacting with users from a range of instruments is that a variety of methods for accomplishing a task are requested based on an individuals experience of existing software and so, in CasaXPS, there are often several methods for performing a task. Satisfying users with diverse backgrounds has led to the blending of analysis techniques to produce a rich toolbox within CasaXPS. It is therefore worth considering the variety of solutions on offer before settling on the one initially most comfortable. The sequence of detailed articles supplementing the reference section should be a valuable source for comparing the processing, peak-fitting and reporting option.

A central concept in CasaXPS is the Experiment Frame Browser. For example, only those VAMAS blocks selected in the right-hand-side of an Experiment Frame will be included in any quantification report generated from the Quantification Parameters dialog window. The need to make a selection before generating a quantification report stems from the fact that each VAMAS block maintains its own quantification parameters. That is to say, quantification region parameters and synthetic components are stored for each individual measurement. The reason for saving these parameters at a VAMAS block level is that individual adjustments to these parameters dependent on local conditions offers the flexibility to process complex data, while the ability to propagate common parameters to similar data provides an efficient transfer mechanism. The result is a system capable of processing simple and complex data files with similar ease.

In addition to the manual means of creating reports, automatic batch processing of data is available in CasaXPS. The batch processing mechanism allows an experiment to be defined, where the results are converted to VAMAS format, processed according to a template file, displayed in a layout previously defined via a tile format file and a consolidated report generated from a set of such experiments based on a report specification file. For applications such as quality control, batch processing not only offers massive time savings but also reduces human error from repetitive route operations.