The irradiation of ArF excimer laser (193 nm) on Si wafer (< 1 1 1 >, n-type, arsenic-doped, 0.01 Omega cm) in SF6 atmosphere, from vacuum to 1000 mbar, creates a regular self-assembled microstructure owning to a great number of microconical spikes covered with SiF2 ( fluorosilyl) layer containing sulfur impurities. The geometry of microstructure as well as the layer thickness varies with the gas pressure and the laser parameters, particularly duration, pulse energy and the dose. In this work, the electrical properties of the layer on the microstructured silicon have been investigated based on electrical impedance spectroscopy (EIS). The measured impedance significantly changes regarding to the unirradiated samples. It was shown that the corresponding electrical conductance and the dielectric constants of the layer are strongly dependent on the gas pressure and UV dose. The layer thickness was also determined in terms of SF6 pressures. (C) 2007 Elsevier B. V. All rights reserved.