Area cathode device for generating free electrons in a first evacuated chamber comprises a back plate; a silica glass substrate peripherally sealed to the back plate to produce a second chamber; a gas contained in the second chamber; a layer of photo-sensitive material disposed on the surface of the substrate external to the first chamber; a cathode phosphor layer disposed between the back plate and the substrate; and a pair of electrodes facing each other from opposite sides of the second chamber for energizing the gas to generate a plasma for exciting the cathode phosphor layer to generate light energy for producing electron emissions from the photo-sensitive material.