The following animated image shows how the graphical output from a series of simulation can be used to view the development of some process as a function of one fixed variable.
Scanning the beam accelerating voltage the images composing the simulation were automatically saved, for each simulation run. The scanned variabe was varied between 10 and 100 KeV, at 10 KeV interval.
The above image was "composed" using image processing software which joins the various frames generated by
The plotting depth (llz) specified in the experimental parameters defines the volume within which the electron trajectories are followed. When an electron exits this volume, the calculation of its trajectory and other parameters is stopped, and the electron''s energy is added to the value of energy not in the energy matrix.
Trajectory calculations for an electron can stop also due to the electron leaving the top surface of the specimen (backscattered) and also due to electrons leaving the bottom surface of the specimen (transmitted electrons).
|Among the experimental parameters there are two settings that define what to do in each case above. If either is marked, as in the figure, the program will output the information about the electron at the moment of exit from the specimen to a text file, which can be processed after the simulation has finished.
In the figure showing the out-electrons settings the option of running the simulation with a scan variable is also shown. The program will use the same experimental conditions, and vary the beam voltage from 15 kV until 30 kV, in steps of 5 kV. All selected experimental results will be saved, in files numbered consecutively.
Usually when the output electrons data is selected, it is necessary to increase the number of electrons in the simulation (depending on the number of data points, i.e. electrons, that are necessary). The figure shows experimental parameters for a large number of primary electrons, and in which data for the output electrons are stored.
|After running the simulation it is possible to select the calculation options for the electron frequency option. This option is carried out from the experimental results window, on the right hand side. The area for "Out electrons" will become enabled if data has been stored for these electrons, and relevant values can be entered there, as shown in the figure on the right.
1- shows the conditions for the calculation: this is data for transmitted electrons, in which the energy of the exit electrons is stored in column 7 of the output file. The horizontal energy axis is run for all electron energies, and the "bins" for the number of electrons transmitted in the range are 100 eV wide.
2- shows the button to be pressed to perform the calculation: the selection in this case is for transmitted data.
The calculation method described could be used for other data extraction from the exit electrons files. Each file (with .b?? or .w?? extension, where ?? are digits) has an header with information about what the columns of data mean. The following figure shows the start for a transmitted electron data file, with the data columns information.
After clicking on the TX or BS button in the out-electrons calculation options, the system will analyse the out-electron data and produce a frequency graph for the selected column using the range specified. The result of this calculation is a text file, with extension .tmp, which is produced in the same directory as the original data.
If the system has the view data option configured for excel (see the Preferences menu item) the temporary file created will be added to an excel workbook as an additional spreadsheet. This excel workbook is specific to the experiment, and includes all data produced for the specific experiment, based on the name of the experiment file. An example of a front page spreadsheet in such an excel workbook is shown in the following figure.
In the previous figure, various calculations performed for the same experiment are indicated by the arrows. If a particular result file, such as AU_43N.R03, is used, the different spreadsheets are assigned consecutive indexes. Clicking on any of the indexes will display the corresponding spreadsheet, as shown in the following figure.
In this figure the arrows indicate various data items:
|The figure on the right shows an example of an electron density graph, as it appears indicated by the arrow in the above figure. The graph is created directly from the program, and can be later modified.|