Accession Number : AD0002240
Title : BOMBARDMENT INDUCED PHOTOCONDUCTIVITY AND OPTICAL ABSORPTION IN MAGNESIUM OXIDE
Descriptive Note : Technical rept.
Corporate Author : MISSOURI UNIV-COLUMBIA DEPT OF PHYSICS
Personal Author(s) : DAY, HAROLD R
Report Date : 01 Nov 1952
Pagination or Media Count : 42
Abstract : Measurements of the spectral dependence of the optical absorption of colored MgO crystals revealed several absorption bands (2.1, 3.7, and 4.8 ev) in the visible and UV regions. The bands were superimposed upon a gradually rising tail which extended over the entire spectrum and increased to only about 20 cm (-1) at 200 millimicrons or 6.2 ev, the limit of measurement. A photoconductivity band was found at 1.2 ev. Irradiation of the crystals by 'UV caused an enhancement of the photoconductivity which reached a saturation level independent of the UV intensity; this enhancement is a measure of the density of imperfections in the crystal lattice. The direction of the displacement of the UV-activated region by an electric field indicated that the charge carriers are holes in the valence band. The enhancement of photoconductivity produced by bombardment with Van de Graaff electrons was unstable at room temperature, while that produced by neutron irradiation and the crystals was thermally unstable throughout the spectrum. Neutron irradiation also causes an increase in the level of UV saturation; the increase is stable at room temperature and indicates new lattice defects. The photoconductivity bands present after irradiation corresponded to the optical absorption bands caused by excess Mg. An estimate of the density of lattice defects can be made from the photoconductivity. An energy level model is proposed to explain the photoconductivity bands and the enhancement and saturation effects.
Descriptors : *PHOTOCONDUCTIVITY , *MAGNESIUM OXIDES , STABILITY , OPTIMIZATION , ULTRAVIOLET RADIATION , ELECTROOPTICS , MODELS , CRYSTAL LATTICES , INTENSITY , CHARGE CARRIERS , ELECTRIC FIELDS , VALENCE BANDS , RADIATION ABSORPTION , IRRADIATION , ABSORPTION SPECTRA , ENERGY LEVELS , BAND SPECTRA , NEUTRON IRRADIATION
Subject Categories : Electrooptical and Optoelectronic Devices
Distribution Statement : APPROVED FOR PUBLIC RELEASE