D-BAND BROADENING OF NOBLE-METAL PARTICLES

For Cu particles embedded in a SiO2 matrix, the size-dependent change in the width of the d-band has been investigated in the size region from about 35 to 160 angstrom in diameter by measuring the energy position of the interband-transition absorption of Cu island films in the photon-energy region from 1.5 to 6.5 eV. This position gives the energy spacing which reflects the width of the d-band. Below about 100 angstrom in diameter, the energy spacing increased with decreasing particle size. This increase supports the d-band broadening due to lattice contractions.