Sputtering angular distribution

Once the initial and boundary conditions are specified, the classical equations of motion are integrated as in any other simulation. From the start of the trajectory, the atoms are free to move under the influence of the potential. One simply identifies reaction mechanisms and products during the dynamics. For the case of sputtering, the atomic motion is integrated until it is no longer possible for atoms and molecules to eject. The final state of ejected material above the surface is then evaluated. Properties of interest include the total yield per ion, energy and angular distributions, and the structure and... 

The helium implantation profiles, after incorporating the angular distribution for the 3.5 MeV alpha particles envisioned in a power reactor, are roughly Gaussian in shape and peaked at 1.5 to 4 pm. Calculated helium profiles show that surface deformation can occur if a critical concentration is reached. The likelihood of blistering is then determined by a competition between the accumulation of helium at a depth of several microns, and the erosion of the surface by D-T sputtering. 

Eisenmenger-Sittner C, Bergauer A. and Bangert H., (1994) Measurement of the angular distribution of sputtered neutrals in a pianar magnetron geometry, J. Vac. Sci. Technol. A 12, 536-541... 

Another technique that requires less instrumentation than those discussed above involves the analysis of the sputter deposited film from the alloy. A flat metallic plate is positioned so that it intercepts part of the sputtered flux without being resputtered by the ion beam. The sputter deposited layer should be built up for periods longer than it takes to generate a steady state surface on the sputtered alloy to insure that the sputtered film has reached a composition equal to the bulk alloy and yet be several times thicker than the analysis depth of the surface technique. If the angular distribution of the sputtered flux of A and B is not uniform, then the deposited film composition will differ at different locations. It is often assumed that the sticking coefficient of each element is identical. Of course if one element in the alloy is volatile the method will fail. 

The layout of a commercial apparatus for electron gas SNMS is depicted in Figure 2. The sample head is introduced directly into the postionizing electron gas. Particle emission from the sample surface is excited by extracting ions from the ECWR plasma by a simple ion optical arrangement in front of the sample (direct bombardment mode, DBM). Since the angular distribution of sputtered particles changes from a torus-like configuration to an over-cosine behavior when the... 

SeebSck, R.J. (1999) Simulation of the energy and angular distribution of Ar in d.c. sputtering discharges. Surf Coat. Tech., 116-119, 564-567. 

The energy and angular distributions resulting from a full isotropic collision cascade as described by the linear cascade model have been modeled nsing the Sigmund-Thompson relation (Thompson 1968 Sigmund 1969). This predicts the sputtered neutral energy distribution to scale as ... 

Sputtering under conditions that are insufficient to induce a full isotropic coUi-sion cascade can still result in measurable sputter yields. These occur also under the same processes described earlier, but with far fewer collisions involved. As a result, a more energetic sputtered population will be noted that displays a more anisotropic angular distribution. This is sometimes referred to as recoil sputtering. 

Figure 3.10 Angular distribution derived by MARLOWE of sputtered 10 eV and 50 eV Aluminum atoms from Aluminum under 17.5 KeV Ar and Cs impact at 20° with respect to the surface normal. Reprinted with permission from van der Heide and Karpusov (1998) Copyright 1998 John Wiley and Sons.

Auger signals from sputtered atoms/ions display an isotropic angular distribution. 

The angular and energy distribution of the sputtered atoms have also been extensively studied (10). The linear cascade theory predicts an isotropic angular distri-... 

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