SRIM-2008, Stopping Power and Range of Ions in Matter

A - Description of program or function: SRIM is a group of programs which calculate the stopping and range of ions (10 eV - 2 GeV/amu) into matter. TRIM (the Transport of Ions in Matter) is the most comprehensive program included. TRIM will accept complex targets made of compound materials with up to eight layers, each of different materials. It will calculate both the final 3D distribution of the ions and also all kinetic phenomena associated with the ion's energy loss: target damage, sputtering, ionization, and phonon production. All target atom cascades in the target are followed in detail. It can be used for physics of recoil cascades, physics of sputtering, the stopping of ions in compounds and stopping powers for ions in gases; This included radiation damage from neutron, electrons and photons. SRIM-2008: 2008.03: Made changes to sputtering of targets Z=13 to 21 to omit discontinuity in treatment; Added Help buttons to TRIM plots, and included additional comments; Changed ordinate units for Ion/Recoil distributions to same as for Ions. 2008.02: Added Ordinate scales to ion trajectory plots; Removed bug in calc. for gas layers within solid targets; Added Chapters 8 and 9 from SRIM textbook to SRIM Help. 2008.01: No changes to basic calculation of SRIM-2003; Many small bugs have been corrected. This version of SRIM is consistent with the new SRIM Textbook (2008). Allows changes of Ion/Energy/Angle during calculation and added to previous TRIM results. SRIM-2006: 2006.01 No changes to basic calculation of SRIM-2003. This upgrade has the following changes: (1) You can now download the complete plots showing the experimental/theoretical stopping of any ion in any elemental target. This file is large (20 Mb+) but it contains over 22,000 experimental data points reported since 1899. These plots may be accessed using the button on the SRIM-2006 initial window. (2) The Error Message 'The number of recoils has exceeded SRIM memory' has been fixed. The fix has been tested for up to 1 M recoiling atoms in a recoil cascade from a single recoil event. Typically, you run into this problem when you use heavy ions with high energies, approaching a GeV, in which a single collision can transfer a large amount of energy, and the recoiling atom may generate up to a million further recoils. If the number of recoils exceeds the current TRIM memory allocation, the above error message will pop-up and explain how to enlarge the TRIM memory to fix the problem. The number of allowed recoils can be increased using the file: /Data/SRIM.cfg. This file contains instructions on how to increase the number of allowed recoils. (3) You can now make a file EXYZ.txt which shows the position of the incident ion at discrete energy points. For example, for Bi(500 keV) you can make a file showing its position at 100 keV increments. This option is at the bottom of the new TRIM input window, along with a Help and an example. (4) You can now enter individual damage energies for each atom in each layer. Hence, silicon in crystalline silicon can have different displacement and Binding energies that silicon in a separate SiO{sub 2} layer. This improves both damage calculations and sputtering calculations. (5) The TRIM output window 'SHOW LIVE DATA' has been improved. FYI, this is a button in the TRIM window during the calculation. It is on the upper left corner. I think most people do not know it exists, but some people find it very useful for ions with large recoil cascades. They can see what is going on. There has been no changes to the calculation of stopping power or ranges. B - Methods: It uses a full quantum mechanical treatment of ion-atom collisions (this manual refers to the moving atom as an 'ion', and all target atoms as 'atoms'). This calculation is made very efficient by the use of statistical algorithms which allow the ion to make jumps between calculated collisions and then averaging the collision results over the intervening gap. During the collisions, the ion and atom have a screened Coulomb collision, including exchange and correlation interactions between the overlapping electron shells. The ion has long range interactions creating electron excitations and plasmons within the target. These are described by including a description of the target's collective electronic structure and interatomic bond structure when the calculation is setup (tables of nominal values are supplied). The charge state of the ion within the target is described using the concept of effective charge, which includes a velocity dependent charge state and long range screening due to the collective electron sea of the target.