Simulation of carbon thin film growth

Full text: There are several unresolved questions concerning the growth of carbon thin films by physical vapor deposition, that is, from an incident beam of carbon ions or atoms. Stress is an important factor in the microstructure, adhesion and mechanical properties of these films and determines their usefulness in applications such as protective coatings for computer hard disks. In this simulation, we aim to answer the following questions regarding the origin of compressive stress in carbon films: Is shallow implantation, or 'subplantation' necessary to generate compressive stress? What is the depth of penetration of the incident ions as a function of energy? What kinds of processes occur during film growth? How much amorphisation is produced in the substrate? In order to get an accurate picture of the growth process, a semi-empirical quantum mechanical method is used which is capable of modelling the many possible hybridisations of the carbon atom. A tight binding code has been applied to study the growth of carbon films on a diamond (100) substrate. The substrate comprises 640 atoms and a further 64 atoms are added to form a film. For an incident energy of 100eV, defects were found to form in the substrate to a depth of 0.6nm. The well know [110] split interstitial defect was observed to form. The results are used to assess the relative merits of two mechanisms for stress generation, namely 'subplantation' and 'surface insertion'