skip to main content

Title: A cesium bromide photocathode excited by 405 nm radiation

In several applications, such as electron beam lithography and X-ray differential phase contrast imaging, there is a need for a free electron source with a current density at least 10 A/cm{sup 2} yet can be shaped with a resolution down to 20 nm and pulsed. Additional requirements are that the source must operate in a practical demountable vacuum (>1e-9 Torr) and be reasonably compact. In prior work, a photocathode comprising a film of CsBr on metal film on a sapphire substrate met the requirements except it was bulky because it required a beam (>10 W/cm{sup 2}) of 257 nm radiation. Here, we describe an approach using a 405 nm laser which is far less bulky. The 405 nm laser, however, is not energetic enough to create color centers in CsBr films. The key to our approach is to bombard the CsBr film with a flood beam of about 1 keV electrons prior to operation. Photoelectron efficiencies in the range of 100–1000 nA/mW were demonstrated with lifetimes exceeding 50 h between electron bombardments. We suspect that the electron bombardment creates intraband color centers whence electrons can be excited by the 405 nm photons into the conduction band and thence into the vacuum.
Authors:
; ; ;  [1] ;  [2]
  1. Electrical Engineering Department, Stanford University, Stanford, California 94305 (United States)
  2. SLAC National Accelerator Center, Menlo Park, CA 94025 (United States)
Publication Date:
OSTI Identifier:
22311064
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 105; Journal Issue: 2; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CESIUM BROMIDES; COLOR CENTERS; CURRENT DENSITY; EFFICIENCY; ELECTRON BEAMS; ELECTRON SOURCES; ELECTRONS; FILMS; KEV RANGE; LIFETIME; METALS; PHOTOCATHODES; PHOTONS; PULSES; RESOLUTION; SAPPHIRE; SUBSTRATES; X RADIATION