CONTROLLABLE LASER-INDUCED PERIODIC STRUCTURES AT SILICON-DIOXIDE SILICON INTERFACE BY EXCIMER-LASER IRRADIATION/

Laser-induced periodical microstructure in a Si substrate covered with a thin laver of silicon dioxide has been studied using KrF excimer la ser irradiation for controlling the periodicity. It was found that KrF excimer laser irradiation can produce periodical microstructures in S iO2/Si samples by a single pulse if the laser fluence is large enough when the SiO2 thickness is small. When the SiO2 layer is thick and mor e than one laser pulse is required. circular patterns can be observed due to the interface defects. The periodicity of the ripple structure linearly depends on the SiO2 thickness. The formation of microstructur e does not change the thickness of the SiO2 layer and the crystallinit y in the Si substrate. The ripple structure formation in the SiO2/Si s tructure is related to the thermally generated surface waves. The exis tence of a SiO2 layer on Si substrate can change the surface tension d uring the melting of the Si interface and hence control the periodicit y of the ripple formation. The lateral periodicity and vertical roughn ess of the ripple structures are within the range required for laser m icrotexturing of magnetic recording media. (C) 1996 American Institute of Physics.