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Gomes, Henrique Leonel

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  • Photocurrents in P3MeT Schottky barrier diodes
    Publication . Jones, G. W.; Taylor, D. M.; Gomes, Henrique L.
    The photocurrent action spectrum of a Schottky diode formed from electrodeposited poly(3-methylthiophene) is shown to follow closely the UV-visible absorption spectrum. At low forward bias, the peak photocurrent asymptotes to the expected square-root dependence on total potential, V-t, across the depletion region. At high reverse bias the superlinear dependence of the photocurrent on V-t suggests that internal photoemission from the rectifying aluminium electrode may be the dominant process.
  • Determination of deep and shallow levels in conjugated polymers by electrical methods
    Publication . Stallinga, Peter; Gomes, Henrique L.; Rost, H.; Holmes, A. B.; Harrison, M. G.; Friend, R. H.; Biscarini, F.; Taliani, C.; Jones, G. W.; Taylor, D. M.
    Conjugated organic semiconductors have been submitted to various electrical measurement techniques in order to reveal information about shallow levels and deep traps in the forbidden gap. The materials consisted of poly[2-methoxy, 5 ethyl (2' hexyloxy) paraphenylenevinylene] (MEH-PPV), poly(3-methylthiophene) (PMeT), and alpha-sexithienyl (alpha T6) and the employed techniques were IV, CV, admittance spectroscopy, TSC, capacitance and current transients. (C) 1999 Elsevier Science B.V. All rights reserved.
  • DLTS investigation of acceptor states in P3MeT Schottky barrier diodes
    Publication . Jones, G. W.; Taylor, D. M.; Gomes, Henrique L.
    Deep Level Transient Spectroscopy (DLTS) has been used to investigate hole traps in the depletion region of Schottky barrier diodes formed from electropolymerised poly(3-methylthiophene). The capacitance transients appear to be composed of a fast and a slow component. Analysis of the slower component using the ''rate window'' technique yields isochronal differential capacitance curves that depend on temperature in the manner predicted by theory.
  • Electrical study of impurity states in conjugated polymers
    Publication . Stallinga, Peter; Gomes, Henrique L.; Jones, G. W.; Taylor, D. M.
    Schottky diodes resulting from an intimate contact of aluminum on electro-deposited poly(3-methylthiopene), PMeT, have been studied by admittance spectroscopy, capacitance-voltage and current-voltage measurements, and optically-induced current transients. The loss-tangents show the existence of interface states that can be removed by vacuum annealing, also visible in the transients. Furthermore, the CV curves don't substantiate the idea of movement of the dopant ions.
  • Electrical characterization of semiconducting polymers
    Publication . Stallinga, Peter; Gomes, Henrique L.; Jones, G. W.; Taylor, D. M.
    Schottky diodes resulting from an intimate contact of aluminum on electrodeposited poly(3-methylthiopene) were studied by admittance spectroscopy, capacitance-voltage measurements and voltaic and optically-induced current and capacitance transients. The loss tangents show the existence of interface states that can be removed by vacuum annealing. Furthermore, the C-V curves contradict the idea of movement of the dopant ions.
  • Influence of fabrication conditions on the electrical behaviour of polymer Schottky diodes
    Publication . Gomes, Henrique L.; Jones, G. W.; Taylor, D. M.
    Evidence is presented which shows that anomalies in the I-V characteristics of Schottky diodes formed from electrodeposited poly(3-methylthiophene) are related to the time films are held under vacuum prior to deposition of the rectifying aluminium electrode. For short times (similar to 15 mins) a plateau appears in the forward bias characteristic which disappears leading to a significant voltage offset as the device ages or is driven into high forward bias.