A masked photocathode is provided having on a radiation transmissive support a mask pattern of a material that absorbs or reflects sensitizing radiation, particularly in the ultraviolet. In one form, the mask is formed in a process that includes at least partial oxidation of a metal layer pattern. Alternatively, a mask pattern that blocks all radiation with high reflectivity may be formed by employing a metal with a subsequent insulating layer, such as of an oxide of the metal or a separately deposited insulator, for protection from the photocathode. In another form the photoemissive layer may be deposited directly on the transmissive support and have on its surface a pattern of organic material to provide the mask for electrons on the target side of the cathode as well as to prevent any radiation reflected from the target from impinging on areas from which photoemission is not desired.