Study On The Cu Clusters Formation Film And Amrphous Ge Induced-irradiation By Using Molecular Dynamics Simulation Method

Molecular dynamics simulation is employed to investigate the film formation of Cu cluster deposition on Si substrate at different deposition conditions of cluster size, incident energy, substrate temperature, crystallographic orientation and deposition rate in the Part I. We have set the two schenmes of potential functions to describe the atoms interaction in the simulation system, one is that the interaction of Cu-Cu is described by EAM many-body potentials, one of Si-Si using SW many-body potentials, and one of Cu-Si using LJ two-body potentials; another is that likewise interaction of Cu-Cu using EAM many-body potentials, Tersoff many-body potentials is selected to describe the interaction of Si-Si, and the Morse two-body potentials is chosen for the interation of Cu-Si. The following is the main content of the study and results:1、As just one Cu cluster bombards on the Si surface in the microprocess, the results are:(1)The two kinds potentatial we chosed can be better to describe the interactation of atoms in the Cu-Si system and give some information about the dynamics process of Cu cluster deposition on Si substrate;(2) Under the same initial conditions, the trend of transformation of kinetic energy between cluster of different sizes, morphologies and substrate atoms is the similar. And as the number of cluster atoms is decreased, it takes long time to finish the kinetic energy transformation between atoms;(3) As the increasing of incident energy, the degree of epitaxy of cluster atoms increased, and the mean height of mass center of cluster debased. The smaller cluster prefers to diffuse toward the XY plane, while the larger cluster trends to move along the incident orientation;(4)As the substrate temperature goes up, the degree of epitaxy of cluster atom increased. And the MHMC decased apparently for larger cluster;(5)On the Si(001)surface, it is easier to appear the Cu/Si(001) interface,whereas on the Si(111)surface, as the incident energy is3.0eV/atom for Cu13and Cu19, Cu/Si(001) interface just occurences,1.6eV/atom threshold energy for Cu147, it appears Cu/Si(001)interface.2、As Cu atoms deposited on the Si substrate to form thin film, results are:(1) As the incident energy increases, the surface roughness decases and surface smoother.(2) As the substrate temperature goes up, deposition film becomes smoother;(3) As the deposition rate is increased, the film surface roughness increases, and above5atoms/ps, there are some voids inside or edge of deposition film. As the deposition rate is too lower (like2atoms/ps), even though the film surface is really smooth, but it will take much more time to finish film growth. So it is not the better choice in the real simulation. In our calculation, for Cu atom depositing on the Si surface, the5atoms/ps deposition rate is considered the best value to grow Cu film;(4) Under the same initial conditions, Si(111)surface is optimal; Moreover, there are some amorphous phenomenon in the interface mixing for Cu/Si(001) and Cu/Si(111);(5)The formation film maily is face-center-cubic structure, the most of them are growth Volmer-Weber model initially, then transform the FranK-vander Merwe growth model, so the main growth model is Stranski-Krastonov model.3、As Cu clusters deposited on the Si substrate to form thin film, results are:(1) As the incident energy increases, the surface roughness of formation film decreases;(2)As the substrate temperature rises, the mixing mode of Cu/Si(001) becomes clear;(3)As the number of cluster atoms is increased, the surface roughness of formation film increases;(4) Under the same initial conditions, the film on the Si(111) become smooher than on the Si(001);(5) For the Cu cluster deposited on Si substrate, the main growth mode is the SK mode.Molcular dynamics simulation studies the Ge irradiation-induced and the voids formation in the process in the Part II. We choose two schemes of potentials to investigate the void formation in a-Ge, seperarely. One is Tersoff-ZBL potentials, another is SW-Yukawa potentials. The following is the results:(1) The energy deposition leads to void formation;(2) The simulation results prove that the formation of the voids is mainly based on a shock wave mechanism and the swelling is determined by the competing processes of the formation and growth of voids on the one hand and the shrinking and annihilation of voids on the other hand;(3) In the case of Tersoff-ZBL potential, the void appears for the fisrt incident ion irradiation. Then continuing to irradiate substrate every other120.0ps, two voids coexist in simulation system at the different positions. The substrate happened swelling in the z direction. Because of the system size, even though the number of incident atoms increased, the positions and morphologies of forming voids always change, the number of voids does not increased;(4) In the case of the SW-Yukawa potential, there is a larger void formation.(5) By topological tool analysis, we come to conclustion that the density of atoms in our simulated system after irradiation is not uniformed, near the voids the rings sizes become smaller and the number of rings is increased. It is indicated that the density of atoms around the voids becomes bigger.