http://ltl.tkk.fi/ice/Kevo/noisereview.pdf

Shot noise in mesoscopic conductors

This paper surveys experimental results concerned with secondary electron emission of surfaces bombarded by primary electrons with respect to scanning electron microscopy. The energy distribution, the angular distribution, and the yield of secondary electrons from metals and insulators are reviewed as well as the escape depth of the secondary electrons and the contribution of the backscattered electrons to the secondary electron yield. The different detectors for secondary electrons in the scanning electron microscope are described. The contrast mechanisms in the scanning electron microscope, material, topography, voltage, magnetic, and crystallographic orientation contrast based on secondary electron emission, as well as the lateral resolution, depending among other things on the spatial distribution of the emitted secondary electrons, are discussed.

Secondary electron emission in the scanning electron microscope

Attenuation lengths of low-energy electrons in solids

Femtosecond time-resolved two-photon photoemission studies of electron dynamics in metals

Field Emission Energy Distribution (FEED)

Beam-attenuation measurements were made on free-standing polycrystalline films of various thicknesses at energies between the work function and several electron volts above. The electron-electron collision mean free paths ${l}_{e}$ were determined by correction of the attenuation lengths for electron-phonon scattering lengths ${l}_{p}$ deduced from the attenuation temperature dependence. Imperfection mean free paths were negligible. The following results were obtained: for aluminum, ${l}_{e}\ensuremath{\sim}50$ \AA{} and ${l}_{p}\ensuremath{\sim}250$ \AA{} near 5 eV above the Fermi level; for gold, $45 \AA{}g{l}_{e}g15 \AA{}$ for energies between 5.5 and 10 eV; and for silver, $42 \AA{}g{l}_{e}g20 \AA{}$ for energies between 5.5 and 8 eV. In the energy range between 5.5 and 7.5 eV, it was found that ${l}_{p}\ensuremath{\sim}250$ \AA{} for gold and ${l}_{p}\ensuremath{\sim}400$ \AA{} for silver. All measured ${l}_{p}$ were only about two-thirds of the value near the Fermi level. Quinn's theory for ${l}_{e}$ in a dense free-electron gas predicts that for aluminum ${l}_{e}\ensuremath{\sim}60$ \AA{} at 5 eV. Exchange corrections in Kleinman's dielectric screening function tend to bring the value closer to the observed one. In silver and gold, considerable interaction of the beam electrons with the $d$ band occurred for which no theory is available as yet. The resulting data were compared with the energy dependence of ${l}_{e}$ deduced semiempirically by Krolikowski and Spicer from the density of states obtained from photoemission experiments. Reasonable agreement with presently available data was observed.

Slow-Electron Mean Free Paths in Aluminum, Silver, and Gold

: The mean free path for elastic scattering and for plasmon production was determined from beam attenuation measurements on films of various thicknesses. (Author)

ELECTRON MEAN FREE PATH NEAR 2 keV IN ALUMINUM

Parametric gain has been demonstrated at 30 MHz using the nonlinear inductance of Josephson point‐contact devices. SQUID‐type configurations were used to achieve degenerate‐mode negative‐resistance amplification with self‐pumping achieved via the internal Josephson oscillations. Gain as large as 11 dB was measured. The small‐signal analysis predicts parametric amplification and delineates the importance of the critical current, circuit loss, and circuit coupling efficiency.

Self-Pumped Josephson Parametric Amplification.

: The dependence and magnitude of noise currents in superconducting point contacts on dc current and voltage has been measured. The results are in good agreement with the theoretical predictions of Scalapino and Stephen. As expected, in the shot-noise limit at sufficiently high junction voltage the noise current does not vary with temperature. (Author)

Current noise in Josephson point contacts

The negative‐resistance effect recently predicted for current‐controlled highly damped Josephson junctions is experimentally demonstrated at a frequency of 9 GHz. Characteristically, the pump (or Josephson) frequency is smaller than the amplified one, and the pump mechanism is effective over a broad range of frequencies in contrast to the conventional parametric negative‐resistance effect where the pump frequency exceeds that of signal and idler and where the frequency of operation is limited to a narrow range. The broad‐band feature renders operation uncritical to tuning and bias voltage fluctuations. The fact that the junction is the element of lowest impedance in the circuit alleviates to a degree the matching problem generally encountered with Josephson contacts.

Helmut Kanter

Papers

Slow-Electron Mean Free Paths in Aluminum, Silver, and Gold

ELECTRON MEAN FREE PATH NEAR 2 keV IN ALUMINUM

Self-Pumped Josephson Parametric Amplification.

Current noise in Josephson point contacts

A novel parametric negative‐resistance effect in Josephson junctions