Surfaces chemical sputtering

Feil H, Dieleman J and Garrison B 1993 Chemical sputtering of Si related to roughness formation of a Cl-passivated Si surface J. Appi. Phys. 74 1303-9... 

Static SIMS is appropriate for obtaining information on the lateral distribution of surface chemical species. A broad, defocussed ion beam is often used in order to minimise surface damage. In dynamic SIMS sample erosion takes place quite rapidly, and depth profiles are obtained by monitoring peak intensities in the mass spectrum of sputtered ions as bombardment proceeds. 

Likewise, when Ar impinged on the surface, pure sputtering ( 2 A/min) was noted. However, when the beams were simultaneously directed at the silicon surface, a relatively large (--SS A/min.) etch rate was observed the measured rate was approximately an order of magnitude greater than the sum of the chemical and physical components. Obviously, synergistic effects due to ion bombardment are crucial to this chemical etch process. Unfortunately, the exact nature of these effects is at present undefined. 

Ion sputtering induces lattice defects and atomic mixing among surface layers. Sputtering yield is different for different chemical species. Thus the composition of a sputtered surface is not necessarily the true composition of that layer. 

Fig. 11.12. Energy dependence of the erosion yield Y(Ar+) of physical sputtering of a C H film by Ar+ ions (open symbols) and the yield Y(Ar+ H) for chemical sputtering by a simultaneous flux of Ar+ ions and H atoms (full symbols). The dash-dotted and solid lines are carbon erosion yields from TRIM.SP calculations for the sputtering of carbon by argon ions using a carbon-surface-binding energy of Esb = 0.1 eV and of EBb = 4.5 eV, respectively. The dotted line gives the absolute erosion rate by the applied flux of H atoms only...

C. Hopf, W. Jacob, A. von Keudell Ion-induced surface activation, chemical sputtering, and hydrogen release during plasma-assisted hydrocarbon film growth. J. Appl. Phys. (2005) in print... 

These results provide direct evidence that chemical reactions occur and that new chemical bonds are formed during active ion bombardment of organic surfaces. Also, the use of active ions for chemical synthesis via reaction of beams with surface species or by selective "chemical sputtering" is suggested. 

The interplay of the two phases on the PtaSnCl 11) surface has been object of an extensive study carried out by Ceelen et al. [18] who used mainly a combination of LEIS and SPA-LEED, also carrying the sample at higher temperatures than those attained in the previous studies. A wealth of temperature dependent phenomena was observed in this study concerning bulk-surface chemical equilibrium, domain size variation and phase transitions. The main conclusions that can be drawn from these combined structural and compositional studies is that the ( /3 x /3) R30° reconstruction is stabilized by the depletion of tin in the subsurface layers and that this depletion is caused by a the combination of sputtering and high temperature annealing (Fig. 3). 

Fig. 32 Effect of chemical shift of Pt 4d5/2 binding energy in Pt skin layer, prepared on a bare PtsoFeso alloy surface by sputtering deposition, onto (top) the kinetically controlled H2 oxidation current (/ <) and (bottom) the steady-state CO coverage (6co) at room temperature in 0.1 M HCIO4 solution saturated with 100 ppm CO/H2 balance [96, 98]. (Reprinted with permission from Ref. 96, Copyright 2003 by John Wiley Sons Ltd).

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