Roughness, surface roughening

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. 

In particular we would like to treat some essential effects of fluctuations where we assume that, for example, thermal fluctuations exist and are localized in space and time. The effects on large lengths and long times are then of interest where the results are independent of local details of the model assumptions and therefore will have some universal validity. In particular, the development of a rough surface during growth from an initially smooth surface, the so-called effect of kinetic roughening, can be understood on these scales [42,44]. 

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. ... 

Roughening the surface of a sphere causes the transition to a turbulent boundary layer to occur at a lower value of the Reynolds number. This explains the apparent anomaly that, at certain values of the Reynolds number, the drag will be lower for a sphere with a rough surface than for a similar sphere with a smooth surface. It is for the same reason that golf balls are made with a dimpled surface. 

Mechanical roughening can greatly increase the current density at a given potential. Current can arise on a rough surface at a potential several volts lower than that on a smooth surface. 

The situation improved with the introduction of the wheel-lock (Fig 1), which produced its own fire by mechanical action, in the early 16th century. This name was used because of the prominent wheel which was rotated to produce fire. In addition to the wheel, the mechanism consisted essentially of the cock, the mainspring, and the sear. The wheel was serrated to provide a rough surface. The cock was a clamp which held a small piece of iron pyrites. Iron pyrites is a mineral which, when rubbed against a roughened piece of metal, will produce sparks... 

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