Schematic view of the CFE electron gun. Electrons are extracted from the tip by applying voltage V1 to the extractor anode. The final kinetic energy of the electrons is determined by the acceleration voltage V0 applied to the tip. IE and Ip indicate the total emission current and the probe current, respectively.
A pumping curve of the CFE gun. PG indicates the pressure reading by the ion gauge.
Typical plots of (a) W(310) and (b) W(111) CFE probe current IP under a UHV pressure range of 10−8 Pa. In the plot (a), the regions (I)–(III) represent the “stable region,” the “ever decreasing region,” and the “non-decreasing region,” respectively.
The current angular intensity I′ of the CFE current from the W(310) surface, (red) in “the initial stable region” and (black) in “the non-decreasing region.” The probe current Ip of the tip B (triangle) was less than half that of the tip A (square) for the same total emission current IE, indicating the variation of I′ depending on the tip geometry.
Normalized damping curves of CFE currents in measured pressures (PG) ranging from ∼3 × 10−8 Pa to ∼4 × 10−10 Pa. The probe and total emission currents are denoted by IP and IE, respectively.
The 50% damping time τE50 and its inverse 1/ τE50 as a function of the total emission current IE. The CFE currents were obtained under pressures (a), (b) PG of ∼2 × 10−8 Pa, (c), (d) PG of 2–3 × 10−9 Pa, and (e), (f) PG of 4–5 × 10−10 Pa, where PG indicates the pressure reading by the ion gauge.
Damping plots of a W(310) CFE probe current IP. The extraction voltage was constant while tracing the continuous CFE current. In the meantime, it was applied intermittently at the times marked by solid squares for the intermittent CFE plot.
A damping plot (raw data sheet) of a W(310) CFE probe current IP. The CFE gun had been operated for about 6 months at the measurement time, and the τ90 value was about 860 min (∼14 h).
A 30 kV STEM image of a multi-walled carbon nanotube.
Schematic drawings of the CFE current tracing experiment and CFE probe current plots (raw data sheet) when the gun valve was (a), (b) closed and (c), (d) open. PA, PB, PC, and PD indicate the pressures in the IP1, IP2, IP3, and sample chambers, respectively, in Figure 1 .
Schematic drawings of CFE current tracing experiment and the CFE probe current plots when the gun valve was open with a metal plate (a), (b) extracted from the optic axis and (c), (d) inserted on the optic axis. PA, PB, PC, and PD indicate the pressures in the IP1, IP2, IP3, and sample chambers, respectively, in Figure 1 .
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