Dynamic Behavior of Sputtering of Tungsten Implanted in Carbon

Abstract

Sputtering due to the bombardment of C with 0.5–10 keV W ions is studied as a function of the W ion fluence by computer simulation. The simulation deals with the dynamic composition change in the surface layer due to implantation of the W ions, the associated collisional mixing and diffusion of the implanted W. The calculated results show a clear oscillation in the sputtering yield of the implanted W as a function of the ion fluence. There is a critical energy (∼ 1 keV) for the appearance of the oscillation, where the W emission yield, defined by the sum of the W sputtering yield and W reflection coefficient, is unity. Above the critical energy, the W sputtering yield oscillates around unity, whereas below the energy it monotonically increases towards a value dependent on the incident energy. The oscillation is caused by the dynamic change in the W depth profile, therefore, it is significantly influenced by the diffusion of the implanted W inside the C bulk. The diffusion suppresses the W sputtering and therefore the oscillation of the yield. Furthermore, for strong diffusion, only W deposition is calculated during the bombardment, whereas the transition from deposition to erosion is calculated without diffusion.

Dynamic Monte Carlo Simulation of Compositional and Topography Changes Induced by Ion Beam Irradiation

“…As shown in Ref. [5], even for high energy bombardment ( Fig. 2(b)) the flat surface is deposited by W at the early stage of irradiation (< 2 × 10 17 cm −2 ).…”

“…Furthermore, the erosion rate of a thin boron film (a-B:H) under carbon deposition was not constant with time at a fixed position and the nonuniform deposition and topographic change were observed [10]. In the designed International Thermonuclear Experimental Reactor (ITER), C and W are used as the divertor components, which results in the bombardment of C (or W) by sputtered and subsequently ionized W (or C) [5]. Therefore, the compositional and topographic changes of W and C during the operations are a critical issue in the ITER project.…”

“…The binary collision approximation method [5,6] simulates the slowing down of projectile ions penetrating into a solid material and the associated formation of recoil atom cascades. A dynamic composition change arises from the deposition of implanted ions and the collisional transport of implanted and material atoms, assuming that each N projectile ions represents a differential ion fluence, ∆Φ.…”

“…With no reflection of projectile ions, the heavy non-volatile W ion incidence on the light C material strongly changes the surface composition with increasing ion fluence. At the fluence of ∼ 10 17 cm −2 , where a steady state composition is reached, a W-C mixed material is produced at the energies of > 1 keV whereas at low energy (< 1 keV), there appears a thick deposition layer [5]. Therefore, another aim of this article is to reveal…”

Transparent, amorphous and organics-free ZnO thin films produced by chemical solution deposition at 150°C

“…The zinc-acetate-dihydrate based sol-gel route is the most common way to produce ZnO thin films by CSD [20]. Different solvents, such as a mixture of absolute ethanol and lactic acid [21], 2-propanol [22], 2-methoxyethanol [23] and modifiers (diethanolamine [24], monoethanolamine [25]) have been used in the reported processes. Many different substrates have already been used for the deposition, such as silica, soda-lime glass [26], silicon wafers [27] or KBr single crystals [28].…”