Preparation and study of properties of a few alkali antimonide photocathodes

A new processing technique for a few alkali antimonide photocathodes is described. This technique does not require an initial antimony layer as in the conventional techniques. Electron microscopic examination of the antimony film shows that the antimony film is affected by ambient gases, and the improvement of senistivity which results in this technique is thought to be due to the absence of it. The band gaps of the photocathodes are determined by photoconductivity measurements. The threshold energy and, hence, the electron affinity is calculated from the threshold region photoemission of these photocathodes. The activation energy of the defect levels is determined by the measurement of the electrical conductivity at a low temperature in a specially designed cryostat. Finally, the role of cesium in a multialkali photocathode is discussed, and a model of band bending which assumes a K2CsSb layer at the top is proposed. This gives the threshold energy value observed experimentally.