Sergey I. Vasil'Ev

Electromagnetic mechanism of surface enhanced second harmonic generation by “smooth” silver electrodes and scanning tunneling microscopy

Abstract The surface of originally smooth silver electrodes is studied by means of reflected second harmonic (SH) generation and scanning tunneling microscopy after electrochemical etching of N monoatomic surface layers ( N ∼ 0minus;10). At N ∼ 1 a generation of surface enhanced, diffuse, and depolarized SH is observed, and a distinct superatomic (of the scale ∼ 10 A) granular roughness is detected on the electrode surface. The fluctuation electromagnetic mechanism is proposed to explain the surface enhancement of diffuse and depolarized SH component: the effect is interpreted as resulting from exciton of local plasmons in irregular surface structures formed in the process of etching.

Surface enhanced second harmonic generation in cold deposited silver films and scanning tunneling microscopy

Abstract The nature of surface enhancement in cold deposited silver films (CDF) is studied by means of reflected second harmonic (RSH) generation and scanning tunneling microscopy. A strong dependence of RSH radiation intensity, polarization and angular distribution on film mass thickness and temperature is observed. The surface enhancement vanishes irreversibly in CDF heated up to >220 K. Intercrystallite fractures (pores) are detected in the structure of annealed films. This residual porosity is interpreted as a result of self-diffusion healing of deeper fractures. The experimental results confirm that in CDF the surface enhancement has a ″classical ″ electromagnetic origin and is due to intercrystallite pores with sufficiently small values of the width/depth ratio. A simple theoretical model is proposed to estimate analytically the enhancement in structures such as deep narrow crevices.

STM/STS investigation of naphthacenequinone electron structure and topology of LB films

Langmuir-Blodgett (LB) films of naphthacenequinone molecules on highly oriented pyrolytic graphite (HOPG) have been investigated by scanning tunneling microscopy/spectroscopy. It is shown that naphthacenequinone molecules incorporated in LB films are capable to form stable ordered structures on the surface of HOPG substrate. The distinct peak in local density of electronic states has been detected.