Raman spectroscopic study on phosphorous-doped silicon nanoparticles

The Raman spectra of films prepared from 8, 19, and 30 nm nanoparticles of silicon doped with phosphorous were measured with excitation at 514.5 nm. The observed spectra were analyzed by decomposing the observed Raman bands into three symmetric Voigt function bands, which were assigned to the Si-Si stretching modes of crystalline, boundary, and amorphous-like components. The fractions of crystalline, boundary, and amorphous-like regions were estimated from the obtained components. The obtained fractions can be explained as a sphere-like nanoparticle consisting of a crystalline core surrounded with boundary and amorphous-like shells, which is consistent with the transmission electron microscope images showing a sphere-like shape. The observed spectral shape of the 8 nm nanoparticle film showed significant changes upon light irradiation with a power density of 5.5 kW cm^-2, i.e., the amorphous-like region converted to a crystalline one. The temperature of the film under laser irradiation was estimated to be lower than 1041 8C from the anti-Stokes to the Stokes Raman bands due to the Si-Si stretching mode. The observed partial crystallization is probably induced by heating associated with light irradiation.