[SY-N6] BCA-MD-KMC hybrid simulation for long time helium plasma irradiation inducing fuzzy nanostructure on tungsten
In this paper, we developed the triple hybrid simulation method for plasma-material interaction (PMI). Although the present method is composed only of atomistic simulations, an elapse time achieved experimentally relevant time scale.
PMI occurs in the processing of semiconductors, thin film depositions, applications into nanomaterial formations, and the inside wall of magnetic confinement nuclear fusion reactors. In atomistic viewpoint, PMI is the surface reaction of a target material due to ion particles continuously injected from plasma. The PMI, which is not an exception, follows the multi-scale multi-physics mechanisms.
Moreover, an important factor in PMI is competition between an irradiation flux and the diffusion speed of the injected particles in the target material. The irradiation flux in laboratory experiments is 1020 to 1024 m-2s-1, and irradiation time is 102 s to 104 s. Although molecular dynamics (MD) is often used for PMI, the experimental irradiation time is too long for MD. Therefore, the irradiation flux was generally set 104 to 108 times of the experimental flux. However, since the diffusion speed in MD becomes realistic, the competition between the irradiation flux and the diffusion speed becomes unrealistic. Thus, the expansion of time scale is necessary for PMI simulation.
Here, the present target phenomenon is fuzzy nanostructure formation on the tungsten surface by exposure to helium plasma. Injected helium atoms agglomerated in the tungsten material, and the nanoscale helium bubbles are formed. After that, the fuzzy nanostructure of tungsten measuring several ten nanometers in width is grown on a surface. To represent the fuzzy nanostructure, we developed the BCA-MD-KMC hybrid simulation method. In this method, the injection process of helium ions is solved by binary collision approximation (BCA), the deformation process of a target material due to the pressure from the helium bubbles is solved by MD, and the diffusion process of the helium atoms in a tungsten material is solved by kinetic Monte-Carlo (KMC). In the hybrid simulation, the injection flux is kept at 1022 m-2s-1 same as an experimental flux and then the irradiation time achieved 100 s. As a result, the fuzzy nanostructure growth was successfully represented.
PMI occurs in the processing of semiconductors, thin film depositions, applications into nanomaterial formations, and the inside wall of magnetic confinement nuclear fusion reactors. In atomistic viewpoint, PMI is the surface reaction of a target material due to ion particles continuously injected from plasma. The PMI, which is not an exception, follows the multi-scale multi-physics mechanisms.
Moreover, an important factor in PMI is competition between an irradiation flux and the diffusion speed of the injected particles in the target material. The irradiation flux in laboratory experiments is 1020 to 1024 m-2s-1, and irradiation time is 102 s to 104 s. Although molecular dynamics (MD) is often used for PMI, the experimental irradiation time is too long for MD. Therefore, the irradiation flux was generally set 104 to 108 times of the experimental flux. However, since the diffusion speed in MD becomes realistic, the competition between the irradiation flux and the diffusion speed becomes unrealistic. Thus, the expansion of time scale is necessary for PMI simulation.
Here, the present target phenomenon is fuzzy nanostructure formation on the tungsten surface by exposure to helium plasma. Injected helium atoms agglomerated in the tungsten material, and the nanoscale helium bubbles are formed. After that, the fuzzy nanostructure of tungsten measuring several ten nanometers in width is grown on a surface. To represent the fuzzy nanostructure, we developed the BCA-MD-KMC hybrid simulation method. In this method, the injection process of helium ions is solved by binary collision approximation (BCA), the deformation process of a target material due to the pressure from the helium bubbles is solved by MD, and the diffusion process of the helium atoms in a tungsten material is solved by kinetic Monte-Carlo (KMC). In the hybrid simulation, the injection flux is kept at 1022 m-2s-1 same as an experimental flux and then the irradiation time achieved 100 s. As a result, the fuzzy nanostructure growth was successfully represented.