REFLECTANCE OF CONDUCTING POLYPYRROLE - OBSERVATION OF THE METAL-INSULATOR-TRANSITION DRIVEN BY DISORDER

被引:109
作者
LEE, KH
MENON, R
YOON, CO
HEEGER, AJ
机构
[1] Institute for Polymers and Organic Solids, University of California at Santa Barbara, Santa Barbara
关键词
D O I
10.1103/PhysRevB.52.4779
中图分类号
T [工业技术];
学科分类号
08 ;
摘要
By controlling the extent of disorder through electrochemical synthesis at reduced temperatures, conducting polypyrrole (PPy) can be obtained in t;he metallic regime, in the insulating regime, and in the critical regime of the disorder-induced metal insulator (M-I) transition. We present the results of reflectance measurements (0.002-6 eV) of PPy carried out at room temperature on the metallic side and on the insulating side of the M-I transition. While the reflectance spectra obtained from samples on both sides of the M-I transition exhibit spectral features expected for a partially filled conduction band, the electronic states near the Fermi energy (E(F)) are different in the two regimes. The data obtained from metallic samples indicate delocalized electronic wave functions in the conduction band, whereas the spectral features which characterize the insulating regime indicate that the states near E(F) are localized. Consistent with theoretical predictions for the metallic and insulating regimes, the optical conductivity sigma(omega) and the real part of the dielectric function epsilon(1)(omega) each show different frequency dependences in the far infrared. In the metallic regime sigma(omega)proportional to omega(1/2) for ($) over bar h omega<600 cm(-1) and epsilon(1)(omega)(> 0) increases rapidly as omega-->0, as described by the ''localization-modified Drude model,'' leading to the conclusion that metallic polypyrrole is a disordered metal near the M-I transition. In contrast, the insulating regime is characterized as a Fermi glass as confirmed by sigma(omega) proportional to omega(2) for ($) over bar h omega<600 cm(-1).
引用
收藏
页码:4779 / 4787
页数:9
相关论文
共 50 条
  • [11] INSULATOR-TO-METAL TRANSITION IN POLYANILINE
    GINDER, JM
    RICHTER, AF
    MACDIARMID, AG
    EPSTEIN, AJ
    [J]. SOLID STATE COMMUNICATIONS, 1987, 63 (02) : 97 - 101
  • [12] ENHANCEMENT OF THE ELECTRICAL-CONDUCTIVITY OF POLYPYRROLE FILM BY STRETCHING - INFLUENCE OF THE POLYMERIZATION CONDITIONS
    HAGIWARA, T
    HIRASAKA, M
    SATO, K
    YAMAURA, M
    [J]. SYNTHETIC METALS, 1990, 36 (02) : 241 - 252
  • [13] SOLITONS IN CONDUCTING POLYMERS
    HEEGER, AJ
    KIVELSON, S
    SCHRIEFFER, JR
    SU, WP
    [J]. REVIEWS OF MODERN PHYSICS, 1988, 60 (03) : 781 - 850
  • [14] LOGARITHMIC TEMPERATURE-DEPENDENCE OF RESISTIVITY IN HEAVILY DOPED CONDUCTING POLYMERS AT LOW-TEMPERATURE
    ISHIGURO, T
    KANEKO, H
    NOGAMI, Y
    ISHIMOTO, H
    NISHIYAMA, H
    TSUKAMOTO, J
    TAKAHASHI, A
    YAMAURA, M
    HAGIWARA, T
    SATO, K
    [J]. PHYSICAL REVIEW LETTERS, 1992, 69 (04) : 660 - 663
  • [15] UNIVERSAL SUBGAP OPTICAL CONDUCTIVITY IN QUASI-ONE-DIMENSIONAL PEIERLS SYSTEMS
    KIM, K
    MCKENZIE, RH
    WILKINS, JW
    [J]. PHYSICAL REVIEW LETTERS, 1993, 71 (24) : 4015 - 4018
  • [16] INFRARED-ACTIVE VIBRATIONAL-MODES OF HEAVILY DOPED METALLIC POLYACETYLENE
    KIM, YH
    HEEGER, AJ
    [J]. PHYSICAL REVIEW B, 1989, 40 (12): : 8393 - 8398
  • [17] DRUDE METALLIC RESPONSE OF POLYPYRROLE
    KOHLMAN, RS
    JOO, J
    WANG, YZ
    POUGET, JP
    KANEKO, H
    ISHIGURO, T
    EPSTEIN, AJ
    [J]. PHYSICAL REVIEW LETTERS, 1995, 74 (05) : 773 - 776
  • [18] REFLECTANCE SPECTRA OF POLYANILINE
    LEE, K
    HEEGER, AJ
    CAO, Y
    [J]. SYNTHETIC METALS, 1995, 72 (01) : 25 - 34
  • [19] INFRARED REFLECTANCE OF POLYPYRROLE - METAL WITH A GAP IN THE SPECTRUM OF CHARGED EXCITATIONS
    LEE, K
    REGHU, M
    YUH, EL
    SARICIFTCI, NS
    HEEGER, AJ
    [J]. SYNTHETIC METALS, 1995, 68 (03) : 287 - 291
  • [20] REFLECTANCE OF POLYANILINE PROTONATED WITH CAMPHOR SULFONIC-ACID - DISORDERED METAL ON THE METAL-INSULATOR BOUNDARY
    LEE, KH
    HEEGER, AJ
    CAO, Y
    [J]. PHYSICAL REVIEW B, 1993, 48 (20): : 14884 - 14891