The effect of dense compression plasma flow on silicon surface morphology

The dense compression plasma flow action on silicon surface layers is investigated. Samples of monocrystalline silicon of (111) and (100) orientations were subjected to plasma flow processings. Values of energy absorbed by the silicon surface range from 5 to 25 J per pulse, the latter corresponding to the flow power density range 0.5·105–3·105 W/cm2. Microreliefs of sample surfaces and slices were recorded by means of high-resolution scanning microscopy. The action of the compression plasma flow on the sample results in the melting and subsequent modification of silicon material down to the depth of 6 μm. Micrographs of surface layers clearly show regular cylindrical structures that are the first of their kind ever observed. Cylindrical fragments measure 50–100 μm in length and 0.7–1.5 μm in diameter. These fragments are located on the surface of the sample at intervals of 1–2 μm with a surface density of (2–6)·106 cm−2. Possible mechanisms of cylindrical periodic structure formation are discussed. The roles of Rayleigh–Taylor instability, Kelvin–Helmholtz instability and Benard instability in transformations of molten surface layers are considered. It may be inferred that structural-phase changes in the state of silicon surface are related to the fast crystallization of molten layer accompanied by the development of various instabilities in the presence of an induced magnetic field.