Interband absorption of Ru studied by optical absorption of continuous thin films and small particles

Abstract

E. Anno ; T. Yamaguchi, Physical Review B, 55(7), 4783-4786, 1997. "Copyright 1997 by the American Physical Society."http://prola.aps.org/abstract/PRB/v55/i7/p4783_1 publisherFor continuous thin Ru films and Ru island films consisting of Ru particles smaller than about 320A in diameter, optical absorption has been measured in the photon energy range of 0.5-6.5 eV. Absorption, found below about 1 eV and at about 2, 3, 3.6, and 4.5-5 eV for the continuous thin films, shifted to higher energies and became weaker with decreasing particle size. This change is accompanied by lattice contraction and is similar to the lattice-contraction-induced change in interband absorption of hcp Co. Thus, the absorption is interband absorption as for hcp Co, and is due to transitions from d states into empty states above the Fermi level. The absorption at about 2, 3, and 3.6 eV shifted almost equally (0.2-0.3 eV) and disappeared at almost the same time below about 70A in diameter, indicating that d states are close to each other. The absorption at about 4.5?5 eV was still well defined at about 25A in diameter. Cu, Ni, and Pd particles have also shown such well-defined interband absorption. Thus, as for Cu, Ni, and Pd, d states are presumably in flat or parallel bands

Structural Characterization, Optical Properties, and Phase Transitions of In1–xSnx Alloy Thin Films

“…48 Experimental studies of interband absorption in noble-metal particles and transitionmetal particles showed that the energy bands of metal particles broadened with increasing lattice contraction. 49 Therefore, the peaks for interband absorption show a blue shift compared with those for the bulk material. Hence, the final movement of the absorption peaks resulting from interband transitions in the considered nanometer-sized alloys should appear as a result of competition between these two mechanisms.…”

“…The lattice constants of metal particles contract as the particle size becomes smaller because of the hydrostatic pressure coming from the particle surface stress . Experimental studies of interband absorption in noble-metal particles and transition-metal particles showed that the energy bands of metal particles broadened with increasing lattice contraction . Therefore, the peaks for interband absorption show a blue shift compared with those for the bulk material.…”

Size-dependent change in parallel band absorption of Al particles

“…1 Thus the interband absorption of clusters and small particles provides information about the optical properties based on the transitions between the bands in the transition from the atomic to the solid state. 2,3 Metal clusters and particles smaller than the wavelength of incident light show, in addition to the interband absorption, optical plasma-resonance absorption due to plasma oscillations of conduction electrons in the clusters and particles. 4 Recently, the absorption mentioned above has been studied not only for pure-metal clusters and particles, but also for bimetallic clusters such as Au n Ag n .…”

Size-dependent change in interband absorption of Pb particles: Effects of surface atoms

“…The contraction of lattice constants changes energy-band structure and thus affects interband absorption. 23 It is well established 24 -26 that lattice constants of metal particles con-tract with decreasing particle size, and it has been reported 3,4 that interband absorption of metal particles becomes weaker and then disappears with contraction of lattice constants.…”

“…Thus, by studying the interband absorption of clusters and small particles, we can obtain information about the optical properties based on the energy bands and the DOS in the transition from the atomic to solid states. [1][2][3][4] In bulk metals, the coordination number is lower for surface atoms than for bulk atoms; in the fcc lattice an atom has eight nearest neighbors at the ͑100͒ surface versus nine at the ͑111͒ and twelve in the bulk. As a result, the distribution of the DOS of the energy bands of the surface layer is narrower than that of the bulk.…”