Atomic force microscopy and Raman spectroscopy of nanoscale Si/SiO 2 superlattices

An atomic force microscope (AFM) has been used to optimize the radio frequency (rf)/ radio frequency magnetron sputtering deposition conditions for obtaining atomically smooth, hydrogen free amorphous silicon (a-Si) and silicon dioxide (a-SiO 2 ) thin films. Superlattices composed of periodically repeating units of nanoscale (a-Si/a-SiO 2 ) units were fabricated at these optimized conditions and subsequently crystallized. The amorphous and crystallized superlattices were characterized by AFM and Raman spectroscopy. Raman spectroscopy of the superlattices was performed by enhancing the weak scattered signal and eliminating the silicon substrate signal by using either waveguiding, cross polarization or interferometric enhancement techniques. The enhanced Raman spectrum clearly indicates formation of nanocrystals after crystallization.