In an embodiment, a method includes forming a first diamond layer on a substrate and inducing a layer of graphene from the first diamond layer by heating the substrate and the first diamond layer. The method includes forming a second diamond layer on top of the layer of graphene and applying a mask to the second diamond layer. The mask includes a shape of a cathode, an anode, and one or more grids. The method further includes forming a two-dimensional cold cathode, a two-dimensional anode, and one or more two-dimensional grids by reactive-ion electron-beam etching. Each of the two-dimensional cold cathode, the two-dimensional anode, and the one or more two-dimensional grids includes a portion of the first diamond layer, the graphene layer, and the second diamond layer such that the graphene layer is positioned between the first diamond layer and the second diamond layer.

The emitter of the present invention includes a nanowire. The nanowire is formed from a hafnium carbide (HfC) single crystal, and at least an end portion of the hafnium carbide single crystal, from which electrons are to be emitted, is covered with hafnium oxide (HfO.sub.2). In the emitter, the thickness of the hafnium oxide may be 1 nm to 20 nm.

A composite carbon nanotube structure comprises a first carbon nanotube structure and a second carbon nanotube structure. The first carbon nanotube structure includes a number of first carbon nanotubes extending substantially along the same direction and joined end-to-end by van der Waals force. The second carbon nanotube structure includes a number of second carbon nanotubes extending from a surface of the first carbon nanotube structure.

A new ultra-thin high-efficiency photoelectron source utilizing a metallic photonic resonant cavity having a photonic resonant cavity with a top metallic layer with a plurality of openings, each having an average dimension less than the wavelength of the excitation photons in vacuum, a bottom metallic layer and a photoelectron emission layer of semiconductor positioned between the top metallic layer and the bottom metallic.

The emitter of the present invention includes a nanowire. The nanowire is formed from a hafnium carbide (HfC) single crystal, and at least an end portion of the hafnium carbide single crystal, from which electrons are to be emitted, is covered with hafnium oxide (HfO.sub.2). In the emitter, the thickness of the hafnium oxide may be 1 nm to 20 nm.

In an embodiment, a method includes forming a first diamond layer on a substrate and inducing a layer of graphene from the first diamond layer by heating the substrate and the first diamond layer. The method includes forming a second diamond layer on top of the layer of graphene and applying a mask to the second diamond layer. The mask includes a shape of a cathode, an anode, and one or more grids. The method further includes forming a two-dimensional cold cathode, a two-dimensional anode, and one or more two-dimensional grids by reactive-ion electron-beam etching. Each of the two-dimensional cold cathode, the two-dimensional anode, and the one or more two-dimensional grids includes a portion of the first diamond layer, the graphene layer, and the second diamond layer such that the graphene layer is positioned between the first diamond layer and the second diamond layer.

A field emission electron source includes a linear carbon nanotube structure, an insulating layer and at least one conductive ring. The linear carbon nanotube structure has a first end and a second end. The insulating layer is located on outer surface of the linear carbon nanotube structure. The first conductive ring includes a first ring face 1301 and a second ring face, an end surface of the linear carbon nanotube structure, and the first ring face are coplanar.

This invention concerns a photo-cathode for a vacuum system, wherein the photo-cathode is configured for receiving electromagnetic radiation having an incoming wavelength and for emitting electrons in response thereto. The photo-cathode comprises a conducting structure having a geometry, the geometry comprising a tip section. The tip section is adapted to provide field enhancement, , when the conducting structure is illuminated with the electromagnetic radiation, wherein is greater than about 10.sup.2. The photo-cathode further comprising a substrate, the substrate being or comprising a dielectric substrate, the substrate supporting the conducting structure.

An electron emitting construct design of an x-ray emitter device is disclosed configured to facilitate radiation in the X-ray spectrum and further relates to preventing a cold cathode from being damaged by ion bombardment in high-voltage applications. The electron beam emitted by the emitting construct is focused and accelerated by an electrical field towards an electron anode target operable to attract electron beam to an associated focal spot, wherein the generated ions are accelerated along a trajectory perpendicular to the electric field in parallel to the surface of the electron anode target. More specifically, the present invention relates to realizing a robust cold cathode to avoid ion bombardments damages in high-voltage applications, by means of setting non-emitter zone surrounded by or set between the emitter areas. The system is further configured to provide an angled target anode or a stepped target anode to further reduce the ion bombardment damage.

A package having a field emission element may include a handle layer; a buried layer stacked on the handle layer; a device layer stacked on the buried layer; an insulating layer stacked in an upper region of the device layer; a gate electrode stacked in an upper region of the insulating layer; and at least one light-emitting element disposed in a lower region of the device layer, and configured to emit light through the device layer. The insulating layer may be configured with a plurality of insulating regions separated by first separation regions, and the gate electrode may be configured with a plurality of metal regions separated by second separation regions. The device layer may be provided with protruding portions disposed to protrude between the first separation regions between the insulating regions and the second separation regions between the metal regions.