Аннотация:Evolution of nanostructured surfaces under ion beam irradiation is of great interest from the point of view of understanding basic processes of ion-surface evolution as well as for controlled nanosized relief formation. For gas cluster ions, it is known that surface planarization occurs under normal ion beam incidence, and ripple formation was observed for grazing angles. At the same time, evolution of surface with preformed ordered nanostructures under cluster bombardment has not been studied well yet. We can note only experiments on multilayered porous silicon and on patterned DLC irradiation under normal beam incidence.
In this work we describe the results of experiments on cluster ion beam irradiation of patterned Si under the angles 30 and 60 degrees off-normal. The pitch-like patterns having period of 2 μm and varying depth and duty factor was formed by means of electron beam lithography. Cluster ion bombardment was performed with 10 keV Ar1000 clusters. The surface relief evolution under increasing irradiation doses was controlled with AFM and SEM. Asymmetrical structures were observed on the surface after irradiation. Duty factor and peak-to-valley height of the structures nonlinearly depend on the initial values and the dose of irradiation. Analysis of the pattern evolution properties allows to understand the role of selective sputtering, surface diffusion and sputtered matter redeposition in the process of surface relief formation under ion beam irradiation.