Papers by Keyword: Monocrystal Silicon

Abstract: Molecular dynamics simulations method is used on the study of material deformation in monocrystal silicon during nanomachining. Both nanoindentation and nanocutting by a diamond tool tip is investigated using LAMMPS. Characterization methods such as coordination number and labeling atoms in different layers have been adopted to study the law of transformation. As the surface atoms are tracked, their transformation law is analyzed and the formation mechanism of the cuttings and finished surface is announced. The impact crystal orientation of silicon on the machining is also studied.

Abstract: A numerical analysis was performed to investigate the temperature distribution and thermal stress field in monocrystal silicon rod in the cooling process of manufactured with Czochralski (CZ) method. The thermally-induced residual stress fields of silicon rod under different length of cool-down time conditions were obtained as well as temperature fields, respectively. All simulations were finished by using ANSYS finite element code. It showed that, maximum thermal stress was mainly appeared on rod surface, the influence of length of cool-down time on it was not remarkable, the magnitude of it was far below the critical strength of silicon throughout.

Abstract: Molecular dynamics (MD) simulation is carried out to analyze the effects of abrasive ngrain size and cut depth on monocrystal silicon grinding process. Tersoff potential is used to describe the interactions of diamond and silicon atoms. Based on classical Newtonian mechanics law, the motion equations of atoms are established and the trajectory of each atom in phase space is obtained with the aid of Velocity Verlet algorithm. Debye model is introduced to convert between kinetic energy and temperature of an atom. The grinding processes of by single grain with different size and different cut depth are investigated in atomic space. Through comparing shearing force and potential energy in the single grain grinding process, the effects of cut depth and grain size on the grinding process are discussed. From the results of MD simulation, it is revealed that when the cut depth increases, both the shearing force in silicon crystal and potential energy between the silicon atoms rise, deformation and dislocations in the silicon lattices increase. As a result, all theses lead to^more severe surface and subsurface damage. With the decreasing of grain size in the same cut-depth nanometric grinding processes, the shearing force in silicon crystal and potential energy between the silicon atoms become larger, deformation and dislocations in the silicon lattices increase.