Schematic of an array of four vacuum nano tubes (cross section, side view). The cathode (− − −) is a planar. The anode (+ + +) is a nano tip on a ﬂat electrode. The thin curved lines indicate the electric ﬁeld lines. The cathode is a conducting solid with high tensile strength, such as tungsten or steel. The ﬂat part of the anode needs to have a high tensile strength, such as steel.
The nano tip is a conducting solid with extremely high tensile strength, such as a carbon nanotube clamped to the steel electrode, or a tungsten Spindt-tip . The design of the electrodes is similar to a tunneling microscope, except that tunneling microscopes have one movable tip, whereas the vacuum tube arrays have many stationary tips. The insulating walls (dots) are solids with a high compressive strength, such as silicon oxides. The electrodes and the walls create a vacuum tube.
The electric ﬁeld is in the vacuum tube between the anode tip and the cathode.
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