PHOTOLUMINESCENCE ENHANCEMENT OF POROUS SILICON BY ORGANIC CYANO COMPOUNDS

A pronounced photoluminescence enhancement on chemically oxidized poro us silicon was induced by a series of organic cyano compounds includin g 1,2-dicyanoethylene (CE), 1,3-dicyanobenzene (1,3-CB), 1,4-dicyanobe nzene (1,4-CB), 1-cyanonaphthalene (1-CN), and 9-cyanoanthracene (9-CA ). Photoluminescence enhancement effects were reversible for all compo unds studies in this work. A dependence of photoluminescence enhanceme nt on the steric effect and the electronic characteristics of these co mpounds and the structure of the porous silicon substrates were analyz ed in terms of the photoluminescence enhancing factors. Surface chemic al composition examined by Fourier transform infrared (FTIR) spectra d emonstrated that the surface Si-H bonds were not changed and no new lu minescent compounds were formed on porous silicon surface during adsor ption of cyano compounds. A mechanism based on induced surface states acting as radiative recombination centers by cyano compounds adsorptio n was suggested.