Investigations of Pd clusters by the combined use of HREM, STM, high-energy spectroscopies and tunneling conductance measurements

Size dependence of core and valence binding energies in Pd nanoparticles: Interplay of quantum confinement and coordination reduction

“…7͒. 1,3,5 In addition to the positive shift in the binding energy, a change in the FWHM of the Pd valence and the core levels is observed. The 4d valence band and the outer core levels 4p and 4s show a decrease, whereas the 3s, 3p, and 3d inner core levels exhibit an increase in the FWHM, revealing a different origin of the effect responsible for the varied behavior.…”

“…The common observation in the XPS studies of metal nanoparticles reported in the literature ͑Au, Ag, Pd, Pt, Ni, Cu, and Co͒ is the positive core level shift with respect to the bulk values. [1][2][3][4][5][6][7][8][9] In a few studies, shifts in the binding energy of valence band with respect to Fermi level and narrowing of valence band spectra have also been reported. 3,7,8 Although considerable efforts have been focused on elucidating the physical origin of the observed size dependent changes, the interpretation of the observed behavior is still unclear.…”

“…It may be mentioned here that in most of the reported studies on size dependence of the electronic properties of metal ͑Au, Ag, Pd, Pt, Ni, Cu, and Co͒ at nanodimensions, the samples were prepared by evaporating a small quantity of metal onto the substrate. [1][2][3][4][5][6]9 The isolated metal islands normally have a rather broad and often not well characterized size distribution. The electronic properties were studied as a function of coverage, which is approximately mentioned as the particle size.…”

Size dependence of nanostructures: Impact of bond order deficiency

“…At low temperatures, however, the level spacings especially in a small particle may become comparable to k B T or higher, rendering them nonmetallic [12]. Because of the presence of the d K in an individual nanosolid, properties such as electron conductivity and magnetic susceptibility exhibit quantized features [504]. The resultant discreteness of energy sublevels also brings about fundamental changes in the characteristic spectral features of the nanosolids, especially those related to the valence band.…”

Electronic and geometric structure of transition-metal nanoclusters

“…In the last several years, a few groups have developed the ability to perform photoemission experiments [SI or to place the clusters on a support for microscopy [9]. While, with some notable exceptions [lo], small semiconductor nanoclusters seem likely to reflect the directional or ionic bonding present in bulk materials, little is known concerning the structural details of transition metal clusters [l].…”