Current imaging tunneling surfaces

Current Imaging Tunneling Spectroscopy of Semiconductor Surfaces... 

The Scanning Tunneling Microscope has demonstrated unique capabilities for the examination of electrode topography, the vibrational spectroscopic imaging of surface adsorbed species, and the high resolution electrochemical modification of conductive surfaces. Here we discuss recent progress in electrochemical STM. Included are a comparison of STM with other ex situ and in situ surface analytic techniques, a discussion of relevant STM design considerations, and a semi-quantitative examination of faradaic current contributions for STM at solution-covered surfaces. Applications of STM to the ex situ and in situ study of electrode surfaces are presented. 

More detailed studies of surface structure can be carried out using scanning tunneling microscopy (STM). For the use of this technique, a metal tip is scanned over the surface, and the distance from the tip to the surface is determined by the tunneling current between them. Images of surfaces with subnanometer resolution are often obtained using this method. 

In a next step the possibility to image sub-surface impurities in metal surfaces by STM has been investigated [102]. The STM images were calculated for room temperature in the Tersoff and Hamann [105] approximation to determine the tunneling current I(r, U) for a gap voltage U. The local density of states (LDOS) of the sample is expressed in n(r , z, Sp+ s) [106] at the position... 

The scanning tunneling microscope (STM) and the atomic force microscope (AFM) are very high resolution microscopes that allow scientists to obtain high resolution images of surfaces with atomic or molecular resolution. Both microscopes work by scanning a very sharp tip on a surface and measuring current (STM) or in-termolecular forces (AFM) between the tip and the surface. 

Some of the samples were annealed at 650 °C for one horn. The microscopic measurements were performed in a combined SEM/STM system based on a Leica 440 SEM operating under a vacuum of 1 x 10 Ton. The small size of the STM enabled it to be mounted on the SEM specimen holder. Mechanically sharpened Pt-Ir wires were used as probe tips for tunneling experiments. The STM was used in the conventional constant-current mode, in the current imaging tuimeling mode (CITS) and in the STM - REBIC mode. For STM-REBIC mode, two ohmic contacts were provided by small Hgin dots on the sample surface connected to Au or Pt-Ir wires. The tuimel tip was located on the region between the contacts and the current was measured at room temperature with a Keithley 428 current amplifier. 

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