INFLUENCE OF C+-IMPLANTATION DOSE ON BLUE EMISSION AND MICROSTRUCTURES OF SI-BASED POROUS BETA-SIC

Crystal Si were implanted with different doses of C+ from 10(11) to 10(17) cm(-2) at an energy of 50 keV. beta-SiC precipitates were formed by thermal annealing at 1050 degrees C for 1 h and porous structures were prepared by electrochemical anodization. Under the excitation of ultraviolet, the samples, with C+ dose greater than or equal to 10(15) cm(-2) have intense blue emission which is stronger than the photoluminescence (PL) intensity of reference porous silicon (PS), and increases as C+ dose increases; the samples with C+ dose less than or equal to 10(14) cm(-2) show similar PL spectra to those of PS. The blue peak intensity in PL spectra is correlated with the TO phonon absorption strength of beta-SiC in infrared absorption spectra. The transmission electron microscopy study shows that the blue peak is also correlated with the microstructures. Because porous beta-SiC is nanometer in size, it is suggested that the quantum confinement effect be responsible for the blue light emission.