On the Properties of Hydrogen Terminated Diamond as a Photocathode
  Electron emission from the negative electron affinity (NEA) surface of hydrogen terminated, boron doped diamond in the [100] orientation is investigated using angle resolved photoemission spectroscopy (ARPES). ARPES measurements using 16 eV synchrotron and 6 eV laser light are compared and found to show a catastrophic failure of the sudden approximation. While the high energy photoemission is found to yield little information regarding the NEA, low energy laser ARPES reveals for the first time that the NEA results from a novel Franck-Condon mechanism coupling electrons in the conduction band to the vacuum. The result opens the door to development of a new class of NEA electron emitters based on this effect. 
Jonathan Rameau, John Smedley, Eric Muller, Tim Kidd and Peter Johnson
cond-mat.supr-con cond-mat.other