Photocathode including silicon substrate with boron layer

An inspection system comprising:

• an illumination source for transmitting photons onto a sample;
• a sensor for detecting photons from the sample;
• and
• an optical system for guiding the photons from the illumination source to the sample, and from the sample to a receiving surface of the sensor,
• wherein the sensor comprises:
• a photocathode disposed adjacent to the receiving surface for emitting photoelectrons in response to said photons, the photocathode including:
• a monocrystalline silicon substrate having a first surface directed toward the optical system, and a second surface facing away from the optical system,
• a first layer consisting essentially of boron disposed directly on the second surface of the silicon substrate, and
• a second layer comprising a low work-function material disposed on the first layer;
• a detection device having a detecting surface facing the second layer, said detection device including means for detecting said photoelectrons emitted by said photocathode, and means for generating said electric signal in response to said detected photoelectrons;
• a housing operably connected between the photocathode and the detection device such that the detecting surface of the detection device is separated from the second layer of the photocathode by an intervening gap region;
• and
• means for generating an electric field between the photocathode and the detection device such that electrons emitted from the photocathode into the gap region are accelerated toward the detection device by the electric field.