IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Thin Films Thursday Sessions
       Session TF-ThP

Paper TF-ThP23
Fabrication of Diamond Photocathode of Transmissive Type

Thursday, November 1, 2001, 5:30 pm, Room 134/135

Session: Thin Film Deposition/Carbon-Containing Films Poster Session
Presenter: K. Kato, Meijo University, Japan
Authors: K. Kato, Meijo University, Japan
K. Ito, Meijo University, Japan
M. Hiramatsu, Meijo University, Japan
M. Nawata, Meijo University, Japan
C.H. Lau, University of Oxford, UK
A. Bennett, University of Oxford, UK
J. Foord, University of Oxford, UK
R. Jackman, University College London, UK
Correspondent: Click to Email
Diamond is attractive as a "visible-blind" photocathode material for UV imaging, in view of its wide band gap and optical absorption properties, electrical transport characteristics and chemical stability. Under the negative electron affinity (NEA) condition, when the photon energy is higher than the band gap, the electrons are excited to the conduction band as a result of UV absorption, transported to the surface and then escape into vacuum. In order to realise the efficient diamond photocathode, it is n ecessary to optimise the optical absorption coefficient, the electron diffusion length in the bulk, and the surface escape probability. An investigation of these parameters is the purpose of the current work. Two types of diamond photocathode have been fabricated, for conventional reflective mode (UV photons and electrons interact with the same surface) and, for the first time, the more demanding trasnsmissive mode operation (electrons emitted from the opposite surface to the incoming UV light). The efficiencies of these two designs are compared and discussed in terms of the fundamental optical and electronic properties of the diamond films. In addition, we have investigated systematically the influence of a variety of surface treatments upon the photo-emissive properties of diamond photocathode, with differing levels of hydrogenation and oxidation. As a result of oxygen surface treatment, a drastic decrease in the photocurrent was observed. The use of the alkali metals, caesium and potassium in conjunction with various oxidation treatments is therefore explored in order to stabilise high quantum photo yield.