Spectroscopy Of Adsorbates Research Articles

Excited states at surfaces: Fano profiles in STM spectroscopy of adsorbates.

The Fano-Anderson model for a discrete state embedded within a continuum is revisited within the context of excitation and decay processes which lead to some manifestations of Fano lineshape profiles. The phenomenon of resonance tunneling between an STM tip and a metal surface upon which there are isolated adsorbed atoms is discussed and the relationship between the spectroscopic signature of such systems and that of the Fano profile is taken up. Recent experimental studies of Kondo systems of magnetic adsorbates such as Co and Ce adsorbed on noble metal (111) surfaces have motivated this work.

Anharmonic contribution to the temperature dependence of photoemission core-level spectroscopy of adsorbates on surfaces: Oxygen on Rh(110)

High-resolution x-ray photoelectron spectroscopy has been used to investigate the temperature behavior of the O $1s$ and O $2s$ core-level photoemission signals from the $\mathrm{O}\ensuremath{-}(2\ifmmode\times\else\texttimes\fi{}2)p2mg$ structure on Rh(110). With increasing temperature we observe a continuous shift of the photoemission peaks to lower binding energy. The width of the peaks increases with increasing temperature, as previously reported for other systems. Since the adsorption site of the O atoms is independent of temperature, the phenomenon is interpreted as due to anharmonic contributions to the potential-energy curve.

Scanning Tunneling Vibrational Spectroscopy

A new method for studying of vibronic transitions by scanning tunneling microscope (“nitraresonator electron-vibronic scanning tunneling spectroscopy of adsorbates”) is proposed. Results of experiments carried out by STM “Omicron” where electron-vibronic series of field emission resonances were observed are presented. Frequencies of the resonances correspond to ones of local vibrations of titan oxide and adsorbed hydroxil particles.

Raman spectroscopy of adsorbates on semiconductors by means of SERS effect

An application of surface enhanced Raman scattering (SERS) to the surface characterization of semiconductors is reported by evaporating an Ag island film onto the surface of the materials. The surface sensitivity of the Raman effect at the metal surface is used for the study of molecules absorbed onto the semiconductors. With this method there is enhanced Raman scattering from the surface because the discontinuous Ag layer produces large electromagnetic enhancement at each Ag particle. SERS spectra are observed from tris(bipyridine)ruthenium, Ru(bpy) 3 2+ , molecules adsorbed on Si, GaAs, InP, silver, and glass substrates onto which an Ag island film has been evaporated. The spectral differences observed between the spectra from the molecules adsorbed on the semiconductors and on the glass and silver substrates allow us to affirm that the SERS signals arise from the substrate surface and not from the Ag island film. Raman scattering cannot be detected from surfaces without the deposited Ag film because the vibrational spectra of molecules adsorbed on the surface are too weak to be detected. These results prove that by using the Ag overlayer method is should be possible to study the properties of adsorbed species on semiconductor surfaces. This suggests the possibility of utilizing the SERS effect as a new surface probe of the semiconductor surface considering that Raman spectroscopy can give detailed information about the state of chemical species on the surface.

Highly Time-Resolved Calorimetry Using Pyroelectric Thin-Film Elecrrets

The use of pyroelectric thin-film electrets for calbrimetry of transient heating processes is explored. A pyroelectric calorimeter which combines a time resolution of nanoseconds with a sensitivity of nanocalories is described. The versatility and the unique properties of this new type of device are demonstrated with several applications in the thermal analysis of thin films and spectroscopy of adsorbates. Data are presented on the thermal diffusivity of thin films and on phase transitions during optical recording. In addition, results on spectroscopy of thin films and adsorbates are reported.

High-resolution infrared spectroscopy of adsorbates on semiconductor surfaces: Hydrogen on Si(100) and Ge(100)

High-resolution infrared spectroscopy of adsorbates on semiconductor surfaces: Hydrogen on Si(100) and Ge(100)