Article

Optical properties and quantum efficiency of thin-film alkali halides in the far ultraviolet.

Instituto de Fisica Aplicada, Consejo Superior de Investigaciones Cientificas, Madrid, Spain.
Applied Optics (Impact Factor: 1.69). 06/2002; 41(13):2532-40. DOI: 10.1364/AO.41.002532
Source: PubMed

ABSTRACT The optical constants of thin films of CsI, KI, and KBr and the quantum efficiency (QE) of planar photocathodes made with these alkali halides in the 53.6-174.4-nm spectral range are presented. The optical constants were obtained from measurements of the reflectance as a function of incidence angle. The effect of film heating and exposure to UV irradiation on the optical properties and on the QE of the three alkali halides was investigated. KBr was found to be the most stable material for both heating and UV irradiation. KI appeared to be close to temperature stable, whereas UV exposure affected its optical constants. CsI optical constants changed after 420 K heating and after UV exposure. The changes in the optical constants were related to the QE changes, and a certain correlation between both variations was determined. However, it was also demonstrated that the QE changes cannot be explained solely by the changes in optical constants.

1 Bookmark
 · 
151 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: The absorption spectra of all the alkali halides except LiF and LiI, measured in the range 5.0 to 12.0 eV at 10°K, are presented. These data complement earlier measurements made at 80°K. Identification of excition lines involving d-like electrons is made by a comparison of the crystal absorption and the absorption spectra of rare-gas atoms. From the positions of exciton states with d-like electrons, the energy of the second conduction band at Gamma is deduced for some of the alkali halides. The results of these deductions are compared with recent calculations of the conduction-band structure of KI and KCl.
    Physical Review - PHYS REV X. 01/1967; 155(3):896-907.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Various aspects related to the quantum efficiency of the reflective and semitransparent CsI photocathodes have been investigated experimentally. The investigation explored the dependence of the quantum efficiency on the following: the thickness of the photocathode film, the gas used in the parallel-plate avalanche chamber, exposure to water vapor, and the density of the CsI film. With reflective CsI photocathodes quantum efficiencies of more than 25% at 180 nm have achieved in three different gases: CH4, C2H6, and C4H10. Our study reveals that high quantum efficiency is also achievable for the semitransparent CsI photocathodes. For a 95-Å semitransparent photocathode the quantum efficiency at 185 nm can be as high as 20%. A simple model to explain the dependence of quantum efficiency on the thickness of CsI photocathodes is suggested, which may be a useful guide for further improvement of the performance of CsI photocathodes. Also reported are UV-transmittance measurements for various materials used in our studies, such as methane, ethane, isobutane, CF4, CO2, helium, neon, air, TMAE vapor, thin CsI films, and quartz windows, all in the wavelength range 115 nm to 230 nm.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 01/1994; 343(1):135-151. · 1.14 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The escape length of electrons photoinduced from thin CsI, KI, RbI, NaI, and CsBr evaporated films was measured in the 140–180 nm photon spectral range. Theoretical model predictions of the escape length value are in fair agreement with the experimental results. They vary between 10 and 40 nm, the highest values being for CsI, RbI and CsBr. For CsI, measured and calculated ultraviolet-induced escape length values are consistent with that determined from x-ray photoemission quantum yield data. Post-evaporation annealing of the films had no major impact on the measured electron transport properties. © 1998 American Institute of Physics.
    Journal of Applied Physics 08/1998; 84(5):2890-2896. · 2.21 Impact Factor

Full-text (3 Sources)

View
4 Downloads
Available from
Sep 3, 2014

Similar Publications