Abstract: An embodiment includes an electron beam source system having a first electron beam source unit with a substrate having a substrate-top end and a substrate-bottom end; and a first lens coupled to the substrate-bottom end defining a first aperture and having a lens-top end and a lens-bottom end. Further embodiments comprise an electron-emission region at the substrate-bottom end and aligned with the first aperture, the electron-emission region being operable to emit one or more electrons due to one or more photons contacting the electron-emission region, which may include passing through the substrate and into the electron-emission region, wherein the electron-emission region comprises a first doped portion of the substrate.