A model of sheath formation on a planar electrode in strongly electronegative plasmas is presented.The plasma sheath is studied by using a set of hydrodynamic equations.Spatial potential,net space charge distributions and sheath width as functions of distance are obtained.It shows that in a strongly electronegative sheath a presheath between bulk plasma and sheath hardly exist,and electrons,negative and positive ions in the sheath form a pure positive ion sheath near boundary of electrode.Density of net space charge has a sharp peak near the sheath edge.Compared with an electropositive sheath,it is found that the width of strongly electronegative sheath is much narrower,and the spatial potential within the sheath falls much faster.

Monte Carlo method is used to simulate ions in a double-layer target of Ti film on Al substrate.As high-intensity pulsed ion beam (HIPIB) irradiates on target,deposited energy results in rapid increase of surface temperature.Meanwhile high energy ions make cross mixing among atoms at film and substrate interface.Shooting ions and energy deposition influence melting or vaporization of target materials.It changes adhesion between film and substrate.It shows that cascade collision mixing is not a main process in mixing of a double-layer target by HIPIB irradiation.The most preferable ion current densities lie in a range of 100 A·cm^-2~150A·cm^-2.

A self-consistent Monte Carlo simulation method that includes charge exchange and elastic scattering is developed to calculate the energy and angle distributions of ions in cathode sheath of a DC argon gas discharge for the different pressures. Cross sections of the charge exchange and the momentum transfer that depend on the ion energy are taken into account precisely. It is found that, as the ions move towards the cathode, the high energy portions of ion energy distributions are enhanced gradually and the small-angle portions of the angle distributions increase. A strong field accelerates the ions to higher speed and ensures that more ions move along the lines of force. The self-consistent electric field spatial variation in the sheath is nonlinear.