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 layer of silicon dioxide has been studied using KrF excimer laser irradiation for controlling the periodicity. It was found that KrF excimer laser irradiation can produce periodical microstructures in SiO2/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 more 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 microstructure does not change the thickness of the SiO2 layer and the crystallinity in the Si substrate. The ripple structure formation in the SiO2/Si structure is related to the thermally generated surface waves. The existence of a SiO2 layer on Si substrate can change the surface tension during the melting of the Si interface and hence control the periodicity of the ripple formation. The lateral periodicity and vertical roughness of the ripple structures are within the range required for laser microtexturing of magnetic recording media.