<title>Peculiarities of the formation of periodic structures on silicon under millisecond laser radiation</title>

Abstract

All types of periodic structures, which are formed on semiconductor surfaces by the pulsed laser radiation with photon energy h(omega) > Eg (Eg equals gap energy), may be classified in two large groups: (1) Resonant periodic structures, which form as a result of the interaction of an incident light 'pump' wave and a surface electromagnetic wave (SEW). The period of these structures is determined by the wavelength, angle of incidence, and polarization of the incident radiation; (2) Non-resonant periodic structures, with the period which is not directly associated with the parameters of laser radiation. The orientation of these structures is, as a rule, determined by the crystallography of the irradiated surface. In the case of the laser pulse duration (tau) equals 10-6-10-9 s, the forming structures were usually of resonant type, while for non-resonant structures the pulse duration was about 10-2-10-4 s. This paper reports the results of the experiments on irradiation of silicon samples surface by the laser pulses with different types of the polarization. They indicate that the properties of non-resonant structures at several orientations of the electric field vector of the light wave Eyields with respect to some crystallographic directions on the surface depend on polarization. The peculiarity of the formation of resonant periodic structures at the large angles of incidence also is examined.