Optical and Electrical Properties of α-Monoclinic Selenium

Citation

Caywood, John Millard (1969) Optical and Electrical Properties of α-Monoclinic Selenium. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/WWWK-4431. https://resolver.caltech.edu/CaltechETD:etd-09112002-170638

Abstract

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. The optical absorption of [alpha]-monoclinic selenium has been measured over the range in wavelength 1.15 [micron] to 0.2775 [micron]. The data show a well defined absorption edge at 2.25 eV with further structure appearing as changes in [...] at 2.85 eV and 3.75 eV. For comparison the absorption of selenium in solutions in which it is believed to exist in the same eight-membered puckered ring as in the crystal was measured. This absorption is qualitatively different from that of the crystal. The existence of surface barriers on [alpha]-monoclinic selenium crystals has been demonstrated. Photometric measurements indicate electron barrier heights of 1.05 eV and 1.3 eV, respectively, for Ga and Au contacts. The mobilities of holes and electrons have been measured by a time-of-flight technique to be about 0.2 [centimeters squared]/V-sec and 1.6 [centimeters squared]/V-sec, respectively, at room temperature. The hole mobility was found to be limited by traps 0.23 [plus/minus] .01 eV above the valence levels, while the electron mobility is an intrinsic mobility limited only by scattering. It was found that in the region of low carrier density (i.e. no space charge effects) the number of carriers which crossed the sample was determined by the interplay of the applied field (carrying carriers across the sample) and diffusion (carrying carriers into the metal contact where they relax). The dielectric constant, K, was determined to be 9.2 [plus/minus] .6 over the range 100 [kilohertz] to 100 [megahertz].

Thesis Files