Study On The Morphology And Photoluminescence Of Porous Silicon Doped With Cerium

It is reported firstly by Canham in 1990 that porous silicon can exhibit visible photoluminescence (PL) at room temperature and explained with quantum confinement effect. Since then it has generated much interest all over the world, because achieving visible-light emission from crystalline Si has remained a difficult task due to the fundamental band-structure limitation: a small and indirect band gap, so a low efficient light emission at room temperature. The observation of visible-light emission from porous silicon has begun to revitalize silicon's role as a material for optical electronics.The dissertation firstly summarized the latest development on fabrication and characterization of porous silicon and its composite system. Especially, it reviewed the achievements on the applications and investigation of their optical properties. Then it focused on presentation of author's research work titled 'Study on the Morphology and Photoluminescence of Porous Silicon doped with Cerium'.In order to obtain new optical properties of porous silicon with doping, samples of porous silicon with high efficient light emission and stable structure should be fabricated firstly, so we started with fabricating samples of porous silicon. Through adjusting the fabricating techniques parameters such as the electrolyte concentration, current density and etching time. We obtained the best parameters and characterize the morphology by atomic force microscope. The luminescence mechanism was studied and we considered that photo-excitation occurs at inside of Si nanoparticles, and then the photo-generated carriers relax to the surface and radiatively recombine on the surface states. We proved that the red emission is correlated with Si-0 complexes through further experiment, maybe origin from some defect centers related to oxygen.Doping silicon with rare earth is one of the approaches on investigation of the silicon-based materials with high luminescent efficiency. Porous silicon has shown to be a promising host of rare earth because of large surface. The rare earth Cerium ion was doped into porous silicon matrix with electrochemical doping method and the AFM images showed surface morphology was modified. We found that the photoluminescence of porous silicon enhanced and a new peak appeared in the PL spectra. Energy transfer and new surface states created by Ce doped were used to give a proper explanation. We thought that it would bring many energy levels of new surface states. Because energy transfer occurs between these levels and that of porous silicon, so the PL of porous silicon enhanced. The new PL peak maybe correlated with new luminescence centers created by Ce doped.