Atomic hydrogen cleaning of InP(100) for preparation of a negative electron affinity photocathode

Atomic hydrogen cleaning is used to clean InP(100) negative electron affinity photocathodes. Reflection high-energy electron diffraction patterns of reconstructed, phosphorus-stabilized, InP(100) surfaces are obtained after cleaning at similar to 400 degrees C. These surfaces produce high quantum efficiency photocathodes (similar to 8.5%) in response to 632.8 nm light. Without atomic hydrogen cleaning, activation of InP to negative electron affinity requires heating to similar to 530 degrees C. At this high temperature, phosphorus evaporates preferentially and a rough surface is obtained. These surfaces produce low quantum efficiency photocathodes (similar to 0.1%). The use of reflection high-energy electron diffraction to measure the thickness of the deposited cesium layer during activation by correlating diffraction intensity with photoemission is demonstrated. (C) 1998 American Institute of Physics. [S0021-8979(98)08620-4]