BLUE-SHIFT OF PLASMA RESONANCE OF COPPER NANOCLUSTERS EMBEDDED IN LIF

Optical absorption spectroscopy is used to investigate the optical pro perties of copper nanoclusters embedded in lithium fluoride. The embed ded cluster samples exhibit quantum confinement effect with enhanced o ptical resonance at visible regions, while no obvious absorption has b een found for the copper film sandwiched between lithium fluoride. The positions of resonance peaks are blue-shifted with decreasing cluster size. In the framework of the Mie theory of surface plasmon, we have described the blueshift effect by a coated particle model, including t he contribution of d electrons to the dielectric function and the redu ced s-d screening interaction at the surface regions of the Cu cluster s.