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Electron spectrometer in adjustable triode configuration for photo-induced field emission measurements
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View: Figures


Image of FIG. 1.
FIG. 1.

Simplified PFE scheme from metals: at high electric fields E = U/z, the work function Φ0 = Wvac − WF of electrons is reduced by the Schottky effect ΔΦSchottky = (e3E/4πɛ0)0.5and by photo excitation with hν to the effective barrier height Φeff. Relaxation of excited electrons can occur due to e−e collisions.

Image of FIG. 2.
FIG. 2.

(a) Schematic of the PFES system. The spectrometer is installed in the center of the front flange, as indicated. (b) Schematic of a 180° hemispherical sector analyzer.

Image of FIG. 3.
FIG. 3.

Photo of the cathode setup. The function of all visible parts is explained in the text.

Image of FIG. 4.
FIG. 4.

Photos of the gate support structure (a) and the shell with a conical mesh gate (b).

Image of FIG. 5.
FIG. 5.

(a) Top view on the cathode and gate in measurement position. (b) View through the quartz window onto the back of a mesh gate. The laser beam passes the spectrometer nozzle.

Image of FIG. 6.
FIG. 6.

Calculated electrostatic field distributions between a flat cathode (U = −100 V) and a hole (left) or mesh gate (U = +1000V). The mesh is approximated by five concentric rings.

Image of FIG. 7.
FIG. 7.

Schematic of the triode configuration with circuit diagram.

Image of FIG. 8.
FIG. 8.

Field emission spectra of a tungsten needle measured for the largest and smallest slits and different pass energies. Please note the calculated spectral resolution values ΔW for comparison.

Image of FIG. 9.
FIG. 9.

Temperature of the W-needle vs. emission current. Inset: spectrum at 144 ± 20 nA with Fermi-Dirac fit of the high energy tail resulting in 584 ± 31 K.

Image of FIG. 10.
FIG. 10.

Spectrum of a W needle measured at Ugate = 2800 V (Icath = 3.45 μA) for d = 2 mm and Wpass = 10 eV (ΔW = 105 meV) with exponential fit of the low energy tail. Inset: FN-plot of the integral current (voltage up- and down-swing) with linear fit.

Image of FIG. 11.
FIG. 11.

SEM images of a triangular Si-tip array (Ø = 200 μm) and a single tip.

Image of FIG. 12.
FIG. 12.

Icath vs. Ugate of 91 Si-tips measured at a gap of δ z = 450 μm without and with laser illumination. Inset: corresponding FN-plot with two linear fit regions for the initial slope.

Image of FIG. 13.
FIG. 13.

(a) Normalized FE-spectra of the array with 91 Si-tips at different currents. (b) Average resistance values of the Si tips as calculated from the spectra.

Image of FIG. 14.
FIG. 14.

Comparison of electron spectra with and without illumination: (a) measured at Icath = 0.05 μA; (b) after correction of charging at Icath = 5 μA.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Electron spectrometer in adjustable triode configuration for photo-induced field emission measurements