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Transient photoconductivity in silver chloride at low temperatures

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Title: Transient photoconductivity in silver chloride at low temperatures
Author(s): Van Heyningen, Roger Steven
Department / Program: Physics
Discipline: Physics
Degree: Ph.D.
Genre: Dissertation
Subject(s): silver chloride Transient photoconductivity
Abstract: Primary photoconductivity in single crystals of pure AgCl has been investigated in the temperature range 6.5°K to 80°K by using low intensity monochromatic light pulses and a. sensitive electrometer. In the region of fundamental optical absorption, the photoresponse as a function of wavelength and applied electric field has been found to be strongly dependent on the condition of the illuminated surface. This behavior may be explained by a theory in which it is assumed that a thin layer near the surface has a different density of traps than the volume of the crystal. The range of electrons was found to be long in an air grown crystal, ~10^-3 cm2/volt, and relatively short in a vacuum grown crystal, ~10^-6 cm2/volt, at 80°K. In both air and vacuum grown crystals the range of holes was not measurable. At 80°K an upper limit for hole range of ~10^-8 cm2/volt was established. The yield of free electrons per absorbed photon (quantum efficiency) as a function of wavelength and temperature has 'been determined from the experiment. In all crystals the measured quantum efficiency showed structure and was high, decreasing from ~0.7 at the optical absorption edge through the first absorption peak to ~ 0.1 at 220mµ. The quantum efficiency was the same at 35°K as at 80°K and was comparable at 6. 5°K. . There was no evidence that the quantum efficiency decreased in the absorption peak with decreasing temperature. Trapping greatly reduced the electron range at low temperatures (~10^-3 cm2/volt at 80°K; ~10^-9 cm2/volt at 6.5°K). Characteristics of the most important traps can be deduced from prominent electrical glow peaks at 15°K, 36°K, and 180°K, as well as from current decay measurements and trap filling experiments at fixed temperatures. The deep, 0.55 ev, traps are present in concentrations of ~10^10 cm^-3 (air grown crystals) to ~10^13 cm^-3 (vacuum grown crystals) and have a large cross section, ~10^-12 cm2. The shallow traps are in much higher concentration.
Issue Date: 1958
Genre: Dissertation / Thesis
Type: Text
Language: English
Other Identifier(s): 6267137
Publication Status: published or submitted for publication
Rights Information: © 1958 Roger Steven Van Heyningen
Date Available in IDEALS: 2010-07-30

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