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Browsing by Author "Fridlund, Christoffer"

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  • Fridlund, Christoffer (2016)
    Ion interaction with matter plays an important role in the modern silicon based micro- and nanoindustry. Ions accelerated to significant energies are able to penetrate into materials allowing for controlled tailoring of the materials' properties. However, it is extremely important to understand the nature of these interactions, and computer modelling is by far the most suitable technique for this purpose. The models used in ion irradiation software are either based on the binary collision approximation (BCA) or molecular dynamics (MD). The first mentioned is both the oldest and the most widely used one. There are three reasons for this: the simple idea, the fast calculation speeds, and the user-friendly graphical user interfaces distributed with the codes. However, there are still some pitfalls in accuracy compared to MD. MDRANGE, an ion range MD code, developed at the Accelerator Laboratory of the University of Helsinki, combines the accuracy of MD with the speed of the BCA. If the tool is given a graphical user interface, it would become more appealing to scientists not familiar with programming. Different methods and techniques for calculating the penetration depths and ranges of kinetic ions in solids are presented in this work. They are accompanied by an overview of the mathematics allowing them to be as physically accurate as possible, over reasonable computation times. For both BCA and MD, generally, the computationally most demanding part is the calculation of the interactions between two or more particles. These interactions are handled through evaluation of potential functions developed especially for different combinations of atoms. The graphical user interface developed in this work is meant as a robust setup tool for use with MDRANGE. The separation of parameters into different panels and the main functionality of the different parts are presented in detail. It is possible to generate the three mandatory input files (,, and with the tool. Out of these three files, is the file in main focus when the application is used. In addition to the generation of the three files, there are also functions included for investigating range calculation results in real time during simulations. During the last five decades, there has been a huge development of the simulation models intended for ion irradiation processes. Even though BCA models excel in speed, they are not able to compete with MD in simulating many-body interactions for atoms with kinetic energies lower than 1 keV. MDRANGE was developed as a bridge between the two models to allow for faster MD calculations, comparable to BCA calculations, while still taking into account the many-body interactions for ions with lower speeds. With the graphical user interface, developed in this work, it will become even more appealing to scientists not familiar with programming, but still in need of an ion range calculation software.