Optical properties of amorphous Si/SiO2 superlattice

Amorphous Si/SiO2 (a-Si/SiO2) superlattices have been fabricated by the mag netron sputtering technique. The superlattice with an Si layer thickness of 1.8 nm has been characterized by transmission electron microscopy (TEM). T he result indicates that most of the regions in the Si layer consist of amo rphous phase, while regular structure appears in some local regions. This i s in agreement with the Raman scattering spectroscopy. The optical absorpti on spectrum and photoluminescence (PL) spectrum have been measured. Moreove r, the third-order optical nonlinearity chi((3)) of this superlattice has b een measured. To our knowledge, this is the first investigation of the nonl inear absorption and refractive index of an a-Si/SiO2 superlattice using th e Z-scan technique. The real and imaginary parts of chi((3)) have been foun d to be 1.316 x 10(-7) eus and -5.596 x 10(-7) eus, respectively, which are about two orders of magnitude greater than those of porous silicon. The re sults may be attractive for potential application in electro-optics devices . (C) 2000 Academic Press.