Computer Simulation and Boron Nitride
MotivationCubic boron nitride (c-BN) is of considerable interest in materials science due to its extraordinary properties, such as extreme hardness, chemical inertness, high melting temperature, wide band gap and low dielectric constant. Nowadays, thin film deposition of c-BN is successfully done by PVD methods, but the problems appearing here are manifold and the processes which are relevant for growth and stability of BN-films are hardly understood. For this reason computer simulation on atomic scale is a helpful tool for process development.
MethodsThe methods in use range from dynamical TRIM-simulations to most accurate quantum chemical codes. Full self-consistent first principles calculations, which are based on density functional theory, are done for characterization of materials properties, like elastic constants, cohesive energies and defect energies. A pseudopotential code with plane wave basis as well as a LCAO code with local and nonlocal corrections are applied. The simulation of detail processes during the thin film growth is done by Molecular Dynamics calculations, which are possible by a new interatomic potential. This empirical bond order potential was recently developed for MD-calculations of different solid BN-modifications and molecular BxNy species.
ApplicationsThe desired cubic BN modification grows typically on a hexagonal BN layer. The influence of impacting N2 and Ar projectiles is studied by MD-simulations. The left picture shows N atoms between vertically oriented BN layers , the right picture the influence of an Ar impact on horizontally oriented layers.
Computer simulation studies can be helpful to identify new configurations: Structures of two hypthetical fullerenes, B12N12 , B28N28, calculated by the empirical interatomic potential: