"Nanostructured surfaces"

Modeling of nano-crater formation on the material surface under the influence of high-power pulsed radiation 
L.V. Shmeleva1, A.D. Suprun1, S.M. Yezhov1
1 Department of Theoretical Physics, Faculty of Physics, Taras Shevchenko National University of Kyiv. Volodymyrska Street, 64/13, Kyiv-01601, Ukraine. 
E-mail: lshmel@univ.kiev.ua

When processing surfaces of material by concentrated energy flows, one of the important consequences of the affect on the surface of a powerful radiation pulse is the formation of nano-craters. In this case, the most interesting is the regime, when the removal of matter from the solid phase to the gas phase occurs without the formation of a melt. In this case, one can set the task about the technology of "fine" surface treatment. Exactly such a problem is considered.
The bound system of dimensionless differential equations was obtained that describes the dynamics of the formation of an axially symmetric corrosion nano-crater and the combustion of a plasma plume. In the case of weak interaction of the radiation pulse with the plasma-gas torch and its inhomogeneous atomic-molecular composition, one of the equations has the form: , and describes the dynamics of a nano-crater formation. Here  is the surface shape function,  is the time,  is the spatial radial variable,  is the pressure.
Pressure determined by the equation of the plasma-gas plume dynamics, which in this case can be reduced to the form:
.
The dimensionless factor  is determined by the given spatio-temporal shape of the pulse. This parameter actually represents the ratio of the intensity of the pulse after passage the torch to its initial intensity.
In conditions where the depth of the nano-crater is a lot of smaller than the transverse dimensions the pulse, an asymptotic analysis of this system showed that the adopted model of the surface destruction process corresponds to the real crater formation dynamics.