Electron source designs are disclosed. The emitter structure, which may be silicon, has a layer on it. The layer may be graphene or a photoemissive material, such as an alkali halide. An additional layer between the emitter structure and the layer or a protective layer on the layer can be included. Methods of operation and methods of manufacturing also are disclosed.

A photocathode can include a body fabricated of a wide bandgap semiconductor material, a metal layer, and an alkali halide photocathode emitter. The body may have a thickness of less than 100 nm and the alkali halide photocathode may have a thickness less than 10 nm. The photocathode can be illuminated with a dual wavelength scheme.

A flat top laser beam is used to generate an electron beam with a photocathode that can include an alkali halide. The flat top profile can be generated using an optical array. The laser beam can be split into multiple laser beams or beamlets, each of which can have the flat top profile. A phosphor screen can be imaged to determine space charge effects or electron energy of the electron beam.

A method of forming a multi-layer structure comprising may include a step of providing a substrate, a step of depositing a protection layer, a step of depositing a thin film material, and a step of detaching. The substrate may have a low surface energy surface or a low surface energy coating or modification disposed on at least a portion of a substrate to form a low surface energy surface. The step of depositing a protection layer may be performed on at least a portion of the low surface energy surface. The step of detaching may detach the multi-layer structure from the substrate

A novel photocathode employing a conduction band barrier is described. Incorporation of a barrier optimizes a trade-off between photoelectron transport efficiency and photoelectron escape probability. The barrier energy is designed to achieve a net increase in photocathode sensitivity over a specific operational temperature range.

The invention relates to a photocathode including an input window (210) suitable for receiving a flow of incident photons, and an active layer (230), the active layer consisting of a plurality of elementary layers (2301, 2302) made of semiconductor materials having decreasing forbidden bandwidths in the direction of the flow of incident photons. The surface of the photocathode opposite the input window is structured so that each elementary layer of the active layer has its own photoelectric emission surface (2401, 2402). By choosing the semiconductor materials of the elementary layers, it is possible to obtain an image which has high sensitivity in both the visible spectrum and the near infrared.

Among various examples, one is directed to identifying one or more particular photocathode semiconductor structures via a computer-based method. The method includes calculating, for each of a plurality of semiconductor materials and via a database characterizing electronic band structures of respective semiconductor materials corresponding to the plurality of semiconductor materials, an intrinsic emittance score (e.g., using an optimistic selection of a work function) as a predictive screening metric for whether the semiconductor material may exhibit low intrinsic emittance. A subset of the semiconductor materials may be selected, wherein each of the semiconductor materials in the subset satisfies screening criteria based on the intrinsic emittance score, and photocathode brightness properties of said one or more of the semiconductor materials in the subset are characterized, thereby identifying certain semiconductor materials in the subset of the semiconductor materials with desirable photocathode brightness properties.

The invention relates to a photocathode including an input window (210) suitable for receiving a flow of incident photons, and an active layer (230), the active layer consisting of a plurality of elementary layers (2301, 2302) made of semiconductor materials having decreasing forbidden bandwidths in the direction of the flow of incident photons. The surface of the photocathode opposite the input window is structured so that each elementary layer of the active layer has its own photoelectric emission surface (2401, 2402). By choosing the semiconductor materials of the elementary layers, it is possible to obtain an image which has high sensitivity in both the visible spectrum and the near infrared.

The present invention improves sensitivity of the ultraviolet band of a photoelectric surface. A photoelectric surface includes a window material that transmits ultraviolet rays, a conductive film that is formed on the window material and has conductivity, an intermediate film 4 that is formed on the conductive film and is formed of MgF.sub.2, and a photoelectric conversion film that is formed on the intermediate film 4 and is formed of CsTe. Since the photoelectric surface includes the intermediate film 4 formed of MgF.sub.2, the sensitivity of the ultraviolet band is improved.

An electron emitter comprises a tapered-shaped emission tip having a base face and an apex opposite the base face, the emission tip consisting essentially of semiconductor material, the semiconductor material being partially doped n-type and partially doped p-type, wherein the base face is doped one of n-type or p-type and the apex is doped opposite type of the base face and a p-n junction is thereby formed at a position between the base face and the apex.