An electron emitter structure includes an electron emission layer which is arranged to have a first side and a second side, and an electron accelerating structure which is arranged on the first side of the electron emission layer. The electron emission layer has a mixture of metals so as to be atmospherically stable. The electron accelerating structure has at least one electrode which is electrically insulated from the electron accelerating structure so as to form an acceleration path which allows electrons which are released from the electron emission layer to be selectively accelerated upon generation of an adjustable electric field. The acceleration path has a length l of from 10 nm to 1 ?m.

An x-ray source for use in Phase Contrast Imaging is disclosed. In particular, the x-ray source includes a cathode array of individually controlled field-emission electron guns. The field emission guns include very small diameter tips capable of producing a narrow beam of electrons. Beams emitted from the cathode array are accelerated through an acceleration cavity and are directed to a transmission type anode, impinging on the anode to create a small spot size, typically less than five micrometers. The individually controllable electron guns can be selectively activated in patterns, which can be advantageously used in Phase Contrast Imaging.

Described here is a method for performing phase contrast imaging using an array of independently controllable x-ray sources. The array of x-ray sources can be controlled to produce a distinct spatial pattern of x-ray radiation and thus can be used to encode phase contrast signals without the need for a coded aperture. The lack of coded aperture increases the flexibility of the imaging method. For instance, because a fixed, coded aperture is not required, the angular resolution of the imaging technique can be increased as compared to coded-aperture imaging. Moreover, the lack of a radioopaque coded aperture increases the photon flux that reaches the subject, thereby increasing the attainable signal-to-noise ratio.

An emitter containing a metal boride material has an at least partly rounded tip with a radius of 1 m or less. An electric field can be applied to the emitter and an electron beam is generated from the emitter. To form the emitter, material is removed from a single crystal rod to form an emitter containing a metal boride material having a rounded tip with a radius of 1 m or less.

An emitter containing a metal boride material has an at least partly rounded tip with a radius of 1 m or less. An electric field can be applied to the emitter and an electron beam is generated from the emitter. To form the emitter, material is removed from a single crystal rod to form an emitter containing a metal boride material having a rounded tip with a radius of 1 m or less.

Method for preparing a molybdenum disulfide film used in a field emission device, including: providing a sulfur vapor; blowing the sulfur vapor into a reaction chamber having a substrate and MoO.sub.3 powder to generate a gaseous MoO.sub.x; feeding the sulfur vapor into the reaction chamber sequentially, heating the reaction chamber to a predetermined reaction temperature and maintaining for a predetermined reaction time, and then cooling the reaction chamber to a room temperature and maintaining for a second reaction time to form a molybdenum disulfide film on the surface of the substrate, in which the molybdenum disulfide film grows horizontally and then grows vertically. The method according to the present disclosure is simple and easy, and the field emission property of the MoS.sub.2 film obtained is good.

In a field emission electron source used in an electron optical device, a tip distal end portion of the field emission electron source includes a needle-shaped shunt having a diameter that is reduced toward a distal end, a substantially spherical protrusion formed at the distal end of the shunt, a coating that covers the shunt and the substantially spherical protrusion, and an opening through which a part of the substantially spherical protrusion is exposed, the shunt and the substantially spherical protrusion are formed by using first metal as a material, the coating is formed by using second metal as a material, and the second metal has a work function larger than a work function of the first metal.

In a field emission electron source used in an electron optical device, a tip distal end portion of the field emission electron source includes a needle-shaped shunt having a diameter that is reduced toward a distal end, a substantially spherical protrusion formed at the distal end of the shunt, a coating that covers the shunt and the substantially spherical protrusion, and an opening through which a part of the substantially spherical protrusion is exposed, the shunt and the substantially spherical protrusion are formed by using first metal as a material, the coating is formed by using second metal as a material, and the second metal has a work function larger than a work function of the first metal.

The cathode member for electron beam generation of the present disclosure includes: 95% by area or more of a single phase or two phases of a compound composed of iridium and cerium. A total content of one or more subcomponents of metallic iridium and an oxide of one or more elements of iridium and cerium is 5% by area or less of the cathode member.

Disclosed is a method for manufacturing a field emitter, comprising: forming a primary epitaxial layer on a substrate; forming a plurality of secondary epitaxial structures on the primary epitaxial layer; forming an emitter electrode layer and a dielectric layer between the emitter electrode layer and the plurality of secondary epitaxial structures on the primary epitaxial layer; sequentially forming a protective layer, an insulating layer, a gate electrode layer and a planarization layer which are laminated on the dielectric layer and the plurality of secondary epitaxial structures; etching the planarization layer to expose part of the gate electrode layer on the dielectric layer and part of the secondary epitaxial structure; etching and removing the protective layer, the insulating layer and the exposed part of the gate electrode layer on part of the secondary epitaxial structure so as to expose part of the secondary epitaxial structure; forming a gate connection electrode layer on the exposed gate electrode layer on the dielectric layer; forming an anode opposite to the exposed part of the secondary epitaxial structure, the anode and the exposed part of the secondary epitaxial structure having a predetermined distance from each other. Further disclosed is a field emitter.