Experiments for improving fabrication, recovery and surface-protection of Cs3Sb photocathode

Abstract We examined 1) the photocurrent from Cs 3 Sb photocathode as a function of anode voltage below 200 V, 2) the relationship between the quantum efficiency of photoemission and the conditions for fabrication by the sandwich method, 3) recovery of the photoemission by additional Cs deposition, and 4) the effects of surface protection of Cs 3 Sb photocathodes by WO 3 and Cr 2 O 3 films in the passive state. The photocurrent had a maximum at approximately 68 V except when we increased the anode voltage extraordinarily slowly. Cs 3 Sb photocathodes were fabricated by increasing the temperature of sandwiched layers of Sb, Cs and Sb deposited on the fine tips of eight cathodes at less than −12 °C. Cs 3 Sb photocathodes having higher quantum efficiency were fabricated by smoothly increasing the temperature of the layers quickly after we deposited the second Sb layer. The photocurrent from the Cs 3 Sb photocathodes was significantly higher when Cs was deposited at temperatures of 50–70 °C. Deposition of a one- to three- atomic-layer W or Cr film extended the photoemission lifetime after the layers were oxidized to WO 3 or Cr 2 O 3 in the passive state due to oxidation. The WO 3 or Cr 2 O 3 in the passive state provided more surface protection as their thickness increased.