Surface roughening effect

Sputter-induced Roughness. Sputtering single crystal semiconductors, in particular II-VI semiconductors, with Cs" ions results in surface roughening. There is currently no satisfactory explanation of this effect. This effect, and the corresponding reduction of the depth resolution, can be avoided by rotating the sample during the measurement. 

SIMS is inherently damaging to the sample since ion bombardment removes some material from the surface. However, other forms of damage may also occur. These include surface roughening, knock-on effects, preferential sputtering, decomposition, and implantation of source ions [49]. 

The efficient scrubberless alternative consists in using hot diluted ammonia in a specific bath with very high megasonic power. In this case, the backside surface must be protected with an oxide or nitride layer to prevent a severe silicon roughening effect from occurring. Then an HF-HCl dip enables the metallic contamination and damaged layer to be removed. HCl turns the respective zeta potentials into favorable conditions that limit the particle redeposition. 

Figure 4-22 Effect of surface roughening on the SERS of adenosine top, normal Raman spectrum middle, SERS obtained by heavy roughening bottom, SERS obtained by mild roughening. (Reproduced with permission from Ref. 45.)...

Certain roughened surfaces (Ag or Au colloids) exhibit another nice intensification of the Raman effect of 103 to 106 by exciting surface plasmons in the colloid particles this is surface-enhanced Raman, first seen by Fleischmann54, and explained by van Duyne.55 Combining resonance and surface-enhanced effects in surface-enhanced resonance Raman spectroscopy (SERRS), the Raman intensity can increase by factors as large as 1012, so that solutions of concentration down to 10 12 M can be detected. 

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