N. T. Liang

XPS studies of several high temperature superconductors: Y-Ba-Cu-O and La-Ba-Cu-O systems

Abstract Copper 2P core level X-ray photoelectron spectra on several high Tc superconductors La1.85Ba0.15CuO4, Y1.2Ba0.8CuO4−δ and Y0.4B0.6CuO4−δ oxides have been measured. The results indicate the coexistence of Cu2+ and Cu3+ in these compounds.

Surface effects on Raman scattering from Sb deposited on Ag-island films.

Surface-enhanced Raman scattering from crystal vibrational modes of a Sb film rather than from vibrational modes of individual molecules has been observed for the first time to our knowledge. A ~20x enhancement of the longitudinal-optical mode (150 cm(-1)) in the Raman spectra of crystalline Sb films deposited on silver-island films was obtained. The excitation profiles, as well as the dependence of Raman intensity on the thickness of Ag films, were studied.

Studies of quenching of SERS of Ag island film by ultra-thin Sb overlayer

Abstract The intensity of the surface enhanced Raman scattering (SERS) from PNBA deposited on a Ag island film has been found to be quenched by more than two orders of magnitude, when a Sb overlayer of thickness less than 10 A was evaporated on the Ag island film. The decrease in the Raman intensity might be due to the damping of the electromagnetic resonance by the absorbing metal overlayer. The possibility of distinguishing the electromagnetic and chemical contributions to SERS is discussed.

The conductivity transition of aggregated Bi films

Abstract By analyzing the recent experimental and theoretical results, we find that the abrupt conductivity transition of an ultrathin aggregated film of bismuth during its growth is not describable by the Anderson transition or quantum percolation, but instead can be well described by a two-dimensional continuum model of classical percolation.