Molecular Dynamics Study Of Adhesion In MEMS

Adhesion is an urgently vital problem in the Micro electromechanical system (MEMS). Molecular dynamics simulation (MDS) which belongs to computer simulation methods, can explain phenomena which are inscrutable by theory analysis and experiment observation. Molecular dynamics simulation is an efficient method to study the adhesion in MEMS.In order to solve the adhesion in MEMS, the adhesion between the rigid sphere and the elastic substrate with the material Au is simulated by molecular dynamics (MD), and the results are illustrated in this thesis. First the basic theories about MD are introduced. Based on these theories, the adhesion model is built and the parameters in MDS are determined. The EAM potential function is utilized to simulate the inter-atom interactions, and the Velocity-Verlet algorithm is used to solve the equation of system motion. The changes of atom configurations of Sphere-Plane model in MEMS during the loading and uploading process are studied, and the changes of the pressure distribution in contact process are discussed. The changes of contact radius with contact force and gap curve are analyzed. The relationships of the adhesive force with the gap curve and the adhesive force with the atomic layer are analyzed. The variation rule of the total energy with MD step is discussed and the variation rule of potential energy with gap curve is analyzed.The thesis uses C++ language to study adhesive contact in microcosmic field by MD. It is helpful for improving the style of MD program. The phenomena of the jump-to-contact and the neck-separation are discovered. The hysteresis between the contact process and the separate process is obtained, indicating that the adhesion affects more strongly atom configurations in separate progress. The conclusion, only the close atomic layer in the contact area affects the adhesion, is got. Atoms near the contact area show pressure and those far from the contact area show pull in the pressure contact state. The phenomena of crystal distortion and atom transfer are found in contact progress.