The present application discloses an array substrate comprising a first substrate, a first electrode on the first substrate, a passivation layer on a side of the first electrode distal to the first substrate, the passivation layer comprising a plurality of first vias, each of which corresponds to a different part of the first electrode, an electron emission source layer on a side of the first electrode distal to the first substrate comprising at least one electron emission source in each of the plurality of first vias, and a dielectric layer on a side of the first electrode distal to the first substrate comprising a plurality of dielectric blocks corresponding to the plurality of first vias, at least a portion of each of the plurality of dielectric blocks in each of the plurality of first vias. The at least one electron emission source comprises a first portion having a first end and a second portion having a second end. The first end is in contact with the first electrode, the first portion is within a corresponding one of the plurality of dielectric blocks. The second portion and the second end are outside the corresponding one of the plurality of dielectric blocks.

The present application discloses an array substrate comprising a first substrate, a first electrode on the first substrate, a passivation layer on a side of the first electrode distal to the first substrate, the passivation layer comprising a plurality of first vias, each of which corresponds to a different part of the first electrode, an electron emission source layer on a side of the first electrode distal to the first substrate comprising at least one electron emission source in each of the plurality of first vias, and a dielectric layer on a side of the first electrode distal to the first substrate comprising a plurality of dielectric blocks corresponding to the plurality of first vias, at least a portion of each of the plurality of dielectric blocks in each of the plurality of first vias. The at least one electron emission source comprises a first portion having a first end and a second portion having a second end. The first end is in contact with the first electrode, the first portion is within a corresponding one of the plurality of dielectric blocks. The second portion and the second end are outside the corresponding one of the plurality of dielectric blocks.

A Tera Hertz reflex klystron includes an electron emission unit, a resonant unit and an output unit. The electron emission is used to emit a plurality of electrons. The electron emission unit defines a first opening. The resonant unit comprises a resonant cavity frame. The resonant cavity frame comprises a top wall and a bottom wall and defines a resonant cavity. The top wall and the bottom wall faces with each other. The bottom wall comprises a bottom opening. The top wall comprises a top opening and at least one outputting hole. The bottom opening and the first opening are merged with each other. The output unit being configured to output Tera Hertz waves. The plurality of electrons are transferred to the output unit from the at least one outputting hole.

A driving method includes providing a field emission cathode device. The field emission cathode device includes a cathode electrode, an electron emission layer electrically connected to the cathode electrode, a first gate electrode spaced from the cathode electrode by a first dielectric layer, and a second grid electrode spaced from the first gate electrode by a second dielectric layer. The second dielectric layer has a second opening. A first voltage is supplied to the cathode electrode, a second voltage is supplied to the first gate electrode, and a third voltage is supplied to the second grid electrode, to extract electrons from the electron emission layer to a space formed by the second opening, until the electrons of the space saturate. The third voltage is greater than the second voltage, such that the electrons of the space are emitted through the second grid electrode.