Roughening, surface

SERS. A phenomenon that certainly involves the adsorbent-adsorbate interaction is that of surface-enhanced resonance Raman spectroscopy, or SERS. The basic observation is that for pyridine adsorbed on surface-roughened silver, there is an amazing enhancement of the resonance Raman intensity (see Refs. 124—128). More recent work has involved other adsorbates and colloidal... 

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]. 

J. P. van der Eerden, A. Roos, J. M. van der Veer. Surface roughening versus surface melting on Lennard-Jones crystal surfaces. J Cryst Growth 99 11, 1990. 

N. Georgiev, A. Pavlovska, E. Bauer. Surface disordering without surface roughening. Phys Rev B 52 2878, 1995. 

I. Procaccia, M. H. Jensen, V. S. L vov, K. Sneppen, R. Zeitak. Surface roughening and the long-wavelength properties of the Kuramoto-Sivashinsky equation. Phys Rev A 45 3220, 1992. 

The essential influence of surface roughening is also present in this model. Grand canonical Monte Carlo calculations were used to generate adatom populations at various temperatures up to Chemical potentials corresponding to those in the bulk LJ crystal were used, and these produced adatom densities that increased with temperature and roughly approximated the values observed in Ising model simulations below T. ... 

The rate of mass transport is the product of these two factors, the density of atoms and the diffusion coefficient per atom, as shown in Fig. 6. Over a large temperature interval up to the mass transport coefficient is almost perfectly Arrhenius in nature. The enhanced adatom concentrations at high temperatures are offset by the lower mobility of the interacting atoms. Thus, surface roughening does not appear to cause anomalies in the... 

The attractive force (F) is dependent on the Hamaker constant and the shortest distance between the particles, z. F may be decreased by decreasing A or increasing z. Theoretically, the Hamaker constant can be decreased by decreasing the densities of the two interacting particles. Since the separation distance plays a significant role in van der Waals attraction, any means to increase this distance will reduce the attractive force and increase the ease of dispersion. Surface roughening and the use of spacer particulates can increase interparticulate separation with the improved particle dispersion. 

Unsteady-state mass transfer caused by excessively fast current or potential ramps. This is especially likely to occur in measurements involving laminar flow past elongated surfaces and in free-convection studies, in which the establishment of secondary flow patterns may require long times. A compromise between the time sufficient to reach steady-state transport and the time necessary to avoid bulk depletion and surface roughening (in metal deposition) is required, and is found most reliably by preliminary experimentation. 

Color changes and chemical degradation Surface roughening and comminution Staining, discoloration, and loss of strength... 

Figure 5.28. SEM micrographs illustrating significant surface roughening of a PI-PTFE blend exposed to subthreshold laser fluences (248 nm, 0.29 J/cm2, 16 ns pulses (FWE1M) and 100 pulses exposure) at 130 x(a) and 1500 x(b) (from D Couto et al.ls).

Most studies of metal surface roughening have been performed with He scattering because two specific features make this probe particularly suited for the study of the roughening of single crystal surfaces ... 

---