Raman spectroscopic studies on bismuth nanoparticles prepared by laser ablation technique

Bi nanoparticles are prepared by means of laser ablation in Ar atmosphere (0.2-10 Torr) with KrF (248 nm) excimer laser of the power 200 mJ. The size of the Bi particles estimated by TEM measurements is in the range 3-10 nm. Raman active Eg mode shifts to a higher frequency and becomes broader for a sample prepared in a lower pressure of Ar atmosphere. However, the peak frequency and the bandwidth of A(lg) mode show almost no change with the change of the particle size. These experimental results can be well explained by a phonon confinement model of Campbell and Fauchet by taking the phonon dispersion properties that the Eg mode of the crystal has a large dependence on the wave numbers near the T point, but the A,g mode is rather independent of the phonon wave numbers. (C) 2002 Elsevier Science B.V. All rights reserved.