A BAND MODEL FOR SYNTHETIC DOPA-MELANIN

  • 1 January 1982
    • journal article
    • research article
    • Vol. 14  (3) , 219-222
Abstract
To determine a band model for synthetic melanin obtained by autooxidation of L-dopa, dependence of dark current on temperature in the range 298.degree.-333.degree. K was measured as well as dependence of optical absorption coefficient on wavelength in the range 250-800 nm. Up to 311 K thermal activation energy equals 0.1 eV and above 313.degree. K it equals 0.78 eV. The first value is connected with the band of localized states at the Fermi level. Optical gap, determined from optical absorption measurements is equal to 1.40 eV. The estimated value of .theta.o, assuming the value of thermal coefficient of activation energy to be .gamma. = 5 .times. 10-4 eV/K, is 2 .times. 10-6 .OMEGA.-1 cm-1 for 0.1 eV and 5 .times. 102 .OMEGA.-1 cm-1 for 0.78 eV. Density of states in the valence band is N(EV) = 8 .times. 1021/cm3 .cntdot. eV, and in the band of localized states at the Fermi level N(EF) = 3 .times. 1013/cm3 .cntdot. eV.

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