Disclosed herein is a method comprising: emitting electrons from an electron ejector in response to an incident photon; driving the electrons through a hole toward a detector configured to collect the electrons and provide an output signal representative of the incident photon; driving the electrons away from sidewalls of the hole, using an electric field.

A transmissive photocathode includes a light transmitting substrate that has a first surface on which light is incident and a second surface which emits light incident from a side of the first surface, a photoelectric conversion layer that is provided on the second surface side of the light transmitting substrate and converts the light emitted from the second surface into photoelectrons, a light transmitting conductive layer that is provided between the light transmitting substrate and the photoelectric conversion layer and is composed of a single-layered graphene, and a thermal stress alleviation layer that is provided between the photoelectric conversion layer and the light transmitting conductive layer and has light transmissivity. A thermal expansion coefficient of the thermal stress alleviation layer is smaller than a thermal expansion coefficient of the photoelectric conversion layer and larger than a thermal expansion coefficient of the graphene.

A transmissive photocathode includes a light transmitting substrate that has a first surface on which light is incident and a second surface which emits light incident from a side of the first surface, a photoelectric conversion layer that is provided on the second surface side of the light transmitting substrate and converts the light emitted from the second surface into photoelectrons, a light transmitting conductive layer that is provided between the light transmitting substrate and the photoelectric conversion layer and is composed of a single-layered graphene, and a thermal stress alleviation layer that is provided between the photoelectric conversion layer and the light transmitting conductive layer and has light transmissivity. A thermal expansion coefficient of the thermal stress alleviation layer is smaller than a thermal expansion coefficient of the photoelectric conversion layer and larger than a thermal expansion coefficient of the graphene.

A dual-spectrum photocathode capable of emitting photo-electrons into a first vacuum space includes a first photodetector array formed using a first optoelectronic material that generates photo-electrons responsive to incident electromagnetic energy in a first spectral band. The dual-spectrum photocathode also includes a second photodetector array formed using a second optoelectronic material that generates photo-electrons responsive to incident electromagnetic energy in a second spectral band that is different from the first spectral band. The first spectral band may include the visible electromagnetic spectrum between 390 nanometers and 700 nanometers and the second spectral band may include the short-wave infrared (SWIR) electromagnetic spectrum above 900 nanometers.

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 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 transmissive photocathode includes a light transmitting substrate that has a first surface on which light is incident and a second surface which emits light incident from a side of the first surface, a photoelectric conversion layer that is provided on the second surface side of the light transmitting substrate and converts the light emitted from the second surface into photoelectrons, a light transmitting conductive layer that is provided between the light transmitting substrate and the photoelectric conversion layer and is composed of a single-layered graphene, and a thermal stress alleviation layer that is provided between the photoelectric conversion layer and the light transmitting conductive layer and has light transmissivity. A thermal expansion coefficient of the thermal stress alleviation layer is smaller than a thermal expansion coefficient of the photoelectric conversion layer and larger than a thermal expansion coefficient of the graphene.

A transmissive photocathode includes a light transmitting substrate that has a first surface on which light is incident and a second surface which emits light incident from a side of the first surface, a photoelectric conversion layer that is provided on the second surface side of the light transmitting substrate and converts the light emitted from the second surface into photoelectrons, a light transmitting conductive layer that is provided between the light transmitting substrate and the photoelectric conversion layer and is composed of a single-layered graphene, and a thermal stress alleviation layer that is provided between the photoelectric conversion layer and the light transmitting conductive layer and has light transmissivity. A thermal expansion coefficient of the thermal stress alleviation layer is smaller than a thermal expansion coefficient of the photoelectric conversion layer and larger than a thermal expansion coefficient of the graphene.

A photocathode structure, which can include one or more of Cs.sub.2Te, CsKTe, CsI, CsBr, GaAs, GaN, InSb, CsKSb, or a metal, has a protective film on an exterior surface. The protective film includes one or more of ruthenium, nickel, platinum, chromium, copper, gold, silver, aluminum, or an alloy thereof. The protective film can have a thickness from 1 nm to 10 nm. The photocathode structure can be used in an electron beam tool like a scanning electron microscope.

A solar generator can include a photon-enhanced thermionic emission generator with a cathode to receive solar radiation. The photon-enhanced thermionic emission generator can include an anode that in conjunction with the cathode generates a first current and waste heat from the solar radiation. A thermoelectric generator can be thermally coupled to the anode and can convert the waste heat from the anode into a second current. A circuit can connect to the photon-enhanced thermionic emission generator and to the thermoelectric generator and can combine the first and the second currents into an output current.