| IBIC Simulation Tool | Copyright (C) 2012-2013 Jacopo Forneris | http://www.dfs.unito.it/solid/IST.html This file contains the documentation for the IBIC simulation tool software. IBIC simulation tool is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. IBIC simulation tool is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with IBIC Simulation Tool. If not, see . ---------------------------------------- File contents: 1. Downloadable files, contents, installation instructions, program execution. 2. The program main window. 3. The device setup menu. 4. The simulation setup menu. 5. The irradiation setup menu. 6. Running a simulation. 7. Data export. 8. About ---------------------------------------- 1. Downloadable files, contents, installation instructions, program execution. The downloadable files for IBIC Simulation Tool software available at the developer's web page http://www.dfs.unito.it/solid/RICERCA/IBA/IST.html are listed below. In the notation X refers to version number, Y to release number: - IST_win-X_Y.exe The file consists of a self-extracting archive for Windows operating system. Double click the IST_win-X_Y.exe and define a destination folder through the menu. The program is then ready for execution. To start the program, double click the IBIC_Simulation_Tool.exe file inside the destination folder. The program has been tested on Windows XP and Windows 7. - IST_mac-X_Y.dmg The file consists of a virtual image disk for Mac OS operating systems. To install the IST, mount the disk to your drive and drag the IBIC_Simulation_Tool.app to your Applications folder. To start the program, double click the IBIC_Simulation_Tool.app file. - IST_linux-X_Y.zip The zipped folder contains the binary files execution on Linux Ubuntu/Debian environment. To install the program, unzip the file to a selected destination folder. To start the program, double click or launch from shell the executable file IBIC_Simulation_Tool.exe. The program has been tested on Ubuntu 12.04 and 13.04 versions. - IST-X_Y-QT_Sourcecode.zip The zipped folder contains the software code, developed as a QT4 project. For a user-friendly, compatible and free code development software, we reccomend to refer to http://qt-project.org. ---------------------------------------- 2. The program main window The program main window is subdivided into two different areas. On the left side, control panels, setup dialogs and menus can be accessed by the user: device setup (see 3.), simulation setup (4.), irradiation setup (5.) and simulation start/stop/resume command buttons (6.). At the program start, only "Device setup" dialog is available, as the other commands and options depend on the data defined in it. In addition, a log box is available, in which the program prints all relevant operations and their current status. Three text boxes also show a summary of the parameters setup for each dialog button. In the first box presents relevant values of mesh space step (deltax, as imported from external elecrostatics files), and evaluated time steps for electrons (deltatn) and hole (deltatp), mobility and diffusivity for electrons (mun, and Dn) and holes (mun, and Dn). The second box summarizes simulation parameters, as defined by the user in the "Simulation setup" dialog; finally, the third box displays information on the "irradiation setup" dialog, if any. On the right side, a tabbed view contains relevant plots and graphs for device setup and simulation. In the "Input", eight plots are available. In the first row from the top electric field profile and weighting potential profile are shown as imported from external input files in the "device setup" dialog. In the second row, electron an hole drift-diffusion probability profiles, evaluated as described in [1]; three horizontal lines represent the values P=0.0,0.5,1.0. Value 0.5 corrensponds to purely diffusive regime. P=0.0,1.0 represent the limit for the probabilistic interpretation: if evaluated profiles exceed these constraint, a finer mesh should be adopted for discretization. The two plots in the third row represent the vacancy density profile and the ionization profile per generated ion, as defined from input files in the "irradiation setup" and "simulation setup" dialogs, respectively. Cyan curves correspond to as-imported data; the superimposed red profiles are given by the interpolation of the profiles on the simulation mesh defined in "device setup". The first plot in the fourth row represent the carriers lifetime of charge carriers (electron: blue, hole: red line), as defined in the "device setup"; the modification to the lifetime due to irradiation as defined in "irradiation setup" is also considered. The "x scale" and "y scale" widgets allow the user to rescale the maximum value of the x- and y- axis. The last plot represent the cumulative distribution function for the ionization profile, evaluated on the simulation mesh according to the interpolated ionization profile. The cumulative distribution is used to define the generation depth of each simulated electron-hole pair in frontal IBIC geometry. In the "simulation" tab, three plots are available. The main top plot displays data from lateral IBIC simulations: single ion CCE pulses, median and mean profiles. A legend check box can be selected to display data labels. The bottom-left plot displays CCE spectra of all simulated IBIC pulses, both in lateral and in frontal geometry, and displays the mean value of the plot under view. The bottom-right plot displays the time-resolved CCE rise starting from the instant of e-h pair generation. The curve points are re-evaluated as a average value at any ion simulation. The "Time-Axis widget" allows to define the maximum value of the time scale (x-axis). The slider at the bottom is selectable only in case of lateral IBIC experiments; it allows to select the generation position, at which CCE spectra and time-resolved CCE curve are displayed. The selected position is highlighted in the top plot as a vertical blue line. Notice that time-resolved average data are not shown in case that the value "All data" is selected on the slider. ---------------------------------------- 3. The device setup menu. The Device setup menu allows the user to import the electrostatics of the device from external files and to specify the charge transport properties of the material. Electrodes are assumed at x=0 and at the maximum positive value on the x-axis. Electric field and weighting potential can be imported from external files clicking on the browse buttons. A dialog will appear allowing to select the corresponding input files. Notice that the text lines displayed in the "Device setup" dialog are not sufficient to import the file: The data import has the following constraints: 0) input files should contain two columns, position and y-value (electric field or weighting potential), separated by a space or a tab. 1) profiles should be given on a regular mesh, as the software extracts the discretization conditions from the x-column (position). 2) electric field and weighting potential x-column (position) mesh should be equal, both in space step and in length. 2) position should be given in [m]. 3) electric field should be given in [V/cm], for compatibility with several closed source commercial Finite Element Method software. 4) weighting field is an adimensional function,[ ], comprised between 0 and 1. Once the import of a profile is completed, the corresponding plot should be displayed in the boxes at the right side of the menu, and a text line should indicate the values of discretization (deltax is the space step size) and lenght of the mesh (in steps). Notice that both lines should be identical in order to achieve a proper setup of the device. The user should define low field mobility [cm^2/V/s], lifetime and saturation velocity [cm/s] for both charge carriers, and temperature [K]. The drift velocity profiles are evaluated according to these expressions, and the diffusivity is evaluated throught the constant value of mobility defined by the user. The drift.diffusion probability profiles are the evaluated by the program. Notice that the temperature parameter is used only to define the carriers diffusivity, from the constant and user defined value of mobility, using the Einstein's relation. No effects on trapping/detrapping, described in other parts of the software, are related with the temperature at this stage of the software development. The OK button can be clicked only if all field in the dialog are filled, and all defined values are grater than zero. ---------------------------------------- 4. The simulation setup menu. The simulation setup dialog is selectable from the main program window when the device setup has been defined successfully. The dialog allows the user to select the relevant parameters for the IBIC simulation. First, the choice between frontal and lateral IBIC geometry should be made. The lateral IBIC option allows to define the number of generation points to be considered, the number of ions to be simulated at each generation position, and the number of electron-hole pairs representing each ion strike. No ionization profile can be selected, since the ion beam is expected to scan a cross section of the device, in which the electrostatic profiles are homogeneous with respect to the penetration depth of the ion probe. In the frontal IBIC configuration, the user can import a ionization profile directly from SRIM output files (the standard output units of measure are assumed: ([Ang],[eV/Ang/ion] . The browser dialog is the same as for the Device Setup window. On the other hand, the number of generation positions cannot be specified (it will be automatically set equal to one )as the ion probes are entering in the device always at position x=0 of the device. Equivalently, user defined input profiles on a regular mesh grid can be imported. The imported files are then interpolated to define the value on the grid chosen in the "device setup". The dead layer thickness value [um] is a feature under test, which allows to shift the generation profile in case that the ion probe does not enter in the device at position x=0, but it crosses instead a dead layer of given thickness. The value given here for the dead layer thickness is also taken into account for the import of vacancy density profiles in the "irradiation setup" dialog. Beam dispersion [um] can be defined only in lateral geometry; electronic [%] noise and noise threshold filter [%] can be defined in both lateral and frontal geometry. In order to successfully complete the simulation setup, the value of #points, #ions per point, #e-h pairs per ion should be equal or greater than one. At the end of a proper simulation setup, ionization and cumulative distribution function (CDF) plots should appear in the main program window, in the case the frontal IBIC geometry has been selected. If the CDF plot does not appear, try to open again the "simulation setup" dialog. Once the "simulation setup" is completed, the IBIC software is ready for the experiment simulation. Additional and optional parameters taking into account for radiation damage effects on carriers' lifetime can be defined in the "irradiation setup". ---------------------------------------- 5. The irradiation setup menu. In this dialog, the ion-induced radiation damage effects on the carriers' lifetime can be inserted in the simulation according to the model described in [2]. This dialog can be opened only when both "device setup" and "simulation setup" have been properly configured. If "yes" is checked on the "include radiation damage" option, the user can import ion-induced vacancy density profiles from SRIM simulation output file, or equivalently from user defined profiles evaluated on a regular mesh grid. Units of measure for the profile are those defined in SRIM by defauls, i.e. ([Ang],[Vacancies/Ang/ion]). The software interpolates the curve on the regular grid defined by the input files in the "device setup" dialog. According then to the model in [2], the user can define the ion fluence, the trap-to-vacancy ratio (in [2], indicated as parameter "k"), thermal velocity and trapping cross section, both for electron and holes. Notice that these parameters are NOT connected with other values (e.g. temperature) defined in "devices setup" and "simulation setup". The pre-defined values in the dialog are just an example, and should not be regarded as reliable and tested values (you can notice a factor 5 with respect to findings in [2] in silicon). As the dialog is confirmed by clicking OK, the vacancy density plot in the main program window is updated, and the lifetime profile plot is re-evaluated according to the parameters of the model and the vacancy profile. ---------------------------------------- 6. Running a simulation. To start a simulation after setup, click "Start" button. The simulation will run; keep an ey on the progress bar in the main window program. Plots and values are automatically updated and refreshed during simulation. Notice that all buttons on the left side of the main program window are disabled during simulation to not interfere with simulation parameters and simulation configuration. Buttons will be enabled again at the end of the simulation, or when the "stop" button is pressed. In order to modify parameters or open dialog windows, please wait that the current ion has been simulated. The simulation can be resumed pressing "Resume"; the button "Start" will reset all simulated parameters and results. ---------------------------------------- 7. Data export. The "Export" button in the main window program allows to export the relevant simulation data as ASCII and .png files. By clicking the button, a dialog will appear asking to define a destination folder. A folder containing information about creation time and date will there be created containing the following files. ASCII Files: - simulation_contents.txt : file with a summary of simulation parameters, profiles and options - efield.txt : imported electric field profile - gunn.txt : imported Gunn's weighting potential profile - ndrift.txt : electron drift-diffusion probability profile - pdrift.txt : hole drift-diffusion probability profile - taun.txt : electron lifetime profile - taup.txt : hole lifetime profile - ioniz.txt : ionization profile interpolated on the simulation grid - vac.txt : vacancy profile interpolated on the simulation grid - cce_mean_profile.txt : CCE mean profile (only in lateral IBIC) - cce_median_profile.txt : CCE median profile (only in lateral IBIC) CCE spectrum (exports only the profile corresponding to the value currently displayed/selected in the main program window) - time_resolved_cce.txt : Time resolved CCE curve (exports only the profile corresponding to the value currently displayed/selected in the main program window) - cce_pulses.txt : a list of all recorded total CCE pulses along with their generation position coordinate Units of measure are the same as displayed in the main program window plots. ---------------------------------------- 8. About The popup menu contains information on copyright, license and distribution of the IBIC Simulation Tool. ---------------------------------------- References [1] P. Olivero, J. Forneris, P. Gamarra, M. Jaksic, A. Lo Giudice, C. Manfredotti, Z. Pastuovic, N. Skukan E. Vittone "Monte Carlo analysis of a lateral IBIC experiment on a 4H-SiC Schottky diode" Nucl. Instr. Meth. B, 269 (2011) 2350. [2] Ž. Pastuović, E. Vittone, I. Capan, M. Jakšic, Appl. Phys. Lett. 98 (2011) 092101.