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Title: Light quasiparticles dominate electronic transport in molecular crystal field-effect transistors

Abstract

We report on an infrared spectroscopy study of mobile holes in the accumulation layer of organic field-effect transistors based on rubrene single crystals. Our data indicate that both transport and infrared properties of these transistors at room temperature are governed by light quasiparticles in molecular orbital bands with the effective masses m[small star, filled]comparable to free electron mass. Furthermore, the m[small star, filled]values inferred from our experiments are in agreement with those determined from band structure calculations. These findings reveal no evidence for prominent polaronic effects, which is at variance with the common beliefs of polaron formation in molecular solids.

Authors:
; ; ; ; ; ;
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
Advanced Light Source Division
OSTI Identifier:
937495
Report Number(s):
LBNL-979E
Journal ID: 0031-9007
DOE Contract Number:
DE-AC02-05CH11231
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review Letters; Journal Volume: 99; Related Information: Journal Publication Date: July 6, 2007
Country of Publication:
United States
Language:
English
Subject:
75; 36; Rubrene, Infread, FET, organic, effective mass

Citation Formats

Li, Z. Q., Podzorov, V., Sai, N., Martin, Michael C., Gershenson, M. E., Di Ventra, M., and Basov, D. N.. Light quasiparticles dominate electronic transport in molecular crystal field-effect transistors. United States: N. p., 2007. Web. doi:10.1103/PhysRevLett.99.016403.
Li, Z. Q., Podzorov, V., Sai, N., Martin, Michael C., Gershenson, M. E., Di Ventra, M., & Basov, D. N.. Light quasiparticles dominate electronic transport in molecular crystal field-effect transistors. United States. doi:10.1103/PhysRevLett.99.016403.
Li, Z. Q., Podzorov, V., Sai, N., Martin, Michael C., Gershenson, M. E., Di Ventra, M., and Basov, D. N.. Thu . "Light quasiparticles dominate electronic transport in molecular crystal field-effect transistors". United States. doi:10.1103/PhysRevLett.99.016403. https://www.osti.gov/servlets/purl/937495.
@article{osti_937495,
title = {Light quasiparticles dominate electronic transport in molecular crystal field-effect transistors},
author = {Li, Z. Q. and Podzorov, V. and Sai, N. and Martin, Michael C. and Gershenson, M. E. and Di Ventra, M. and Basov, D. N.},
abstractNote = {We report on an infrared spectroscopy study of mobile holes in the accumulation layer of organic field-effect transistors based on rubrene single crystals. Our data indicate that both transport and infrared properties of these transistors at room temperature are governed by light quasiparticles in molecular orbital bands with the effective masses m[small star, filled]comparable to free electron mass. Furthermore, the m[small star, filled]values inferred from our experiments are in agreement with those determined from band structure calculations. These findings reveal no evidence for prominent polaronic effects, which is at variance with the common beliefs of polaron formation in molecular solids.},
doi = {10.1103/PhysRevLett.99.016403},
journal = {Physical Review Letters},
number = ,
volume = 99,
place = {United States},
year = {Thu Mar 01 00:00:00 EST 2007},
month = {Thu Mar 01 00:00:00 EST 2007}
}
  • We report on an infrared spectroscopy study of mobile holesin the accumulation layer of organic field effect transistors based onrubrene single crystals. Our data indicate that both transport andinfrared properties of these transistors at room temperature are governedby light quasiparticles in molecular orbital bands with the effectivemasses m* comparable to free electron mass. Furthermore, the m* valuesinferred from our experiments are in agreement with those determined fromband structure calculations. These findings reveal no evidence forprominent polaronic effects, which is at variance with the common beliefsof polaron formation in molecular solids.
  • We fabricated ZnO-nanowire (NW) field-effect transistors (FETs) coated with poly(3-hexylthiophene) (P3HT) and characterized the electron-transfer characteristics from the P3HT to the ZnO NWs. Under irradiation by laser light with a wavelength of 532 nm, photo-induced electrons were created in the P3HT and then transported to the ZnO NWs, constituting a source-drain current in the initially enhancement-mode P3HT-coated ZnO-NW FETs. As the intensity of the light increased, the current increased, and its threshold voltage shifted to the negative gate-bias direction. We estimated the photo-induced electron density and the electron-transfer characteristics, which will be helpful for understanding organic-inorganic hybrid optoelectronic devices.
  • We consider the quasiparticle c -axis conductivity in highly anisotropic layered compounds in the presence of the magnetic field parallel to the layers. We show that at low temperatures the quasiparticle interlayer conductivity depends strongly on the orientation of the in-plane magnetic field if the excitation gap has nodes on the Fermi surface. Thus measurements of the angle-dependent c -axis (out-of-plane) magnetoresistance provide information on the momentum dependence of the superconducting gap (or pseudogap) on the Fermi surface. Clean and highly anisotropic layered superconductors are the best candidates for probing the existence and location of the nodes on the Fermimore » surface. {copyright} {ital 1999} {ital The American Physical Society }« less
  • Strontium titanate (SrTiO 3, STO) is a critically important material for the study of emergent electronic phases in complex oxides, as well as for the development of applications based on their heterostructures. Despite the large body of knowledge on STO, there are still many uncertainties regarding the role of defects in the properties of STO, including their influence on ferroelectricity in bulk STO and ferromagnetism in STO-based heterostructures. In this paper, we present a detailed analysis of the decay of persistent photoconductivity in STO single crystals with defect concentrations that are relatively low but significantly affect their electronic properties. Themore » results show that photo-activated electron transport cannot be described by a superposition of the properties due to independent point defects as current models suggest but is, instead, governed by defect complexes that interact through dynamic correlations. In conclusion, these results emphasize the importance of defect correlations for activated electronic transport properties of semiconducting and insulating perovskite oxides.« less
  • The effect of light irradiation on the characteristics of organic field-effect transistors containing sexithiophene (6-T) and pentacene was examined. Organic phototransistors (OPTs) in which 6-T and pentacene were incorporated were fabricated. Their response behaviors were investigated under conditions of irradiation by either modulated or continuous ultraviolet light with various intensities. Both devices showed two distinguishable responses, i.e., fast and slow responses from photoconductive and photovoltaic effects, respectively. The fast response is mainly the result of the generation of mobile carriers by the absorption of a photon energy higher than the band gap energy of the semiconductor and, subsequently, an increasemore » in conductance via a greater flow of photogenerated mobile carriers into the channel layer. On the other hand, the slow response, which was confirmed by a light induced shift in the threshold voltage (V{sub th}) or the switch-on voltage (V{sub O}), is the result of a slow release of accumulated and trapped electrons in the semiconductor-gate dielectric interface. The V{sub O} is defined as the flatband voltage of devices. Below the V{sub O}, the channel current with the gate voltage is off current, and the channel current increases with the gate voltage above the V{sub O}. The speed of release of the accumulated charge was dependent on the type of semiconductor used. Pentacene OPTs showed a particularly long retention time. Even after storage for ten days, the shifted V{sub O} (or V{sub th}) for the pentacene OPTs by light irradiation was not restored to the original value of the fresh devices. We conclude that this long sustained V{sub th} shift renders them attractive for use in ''light-addressable nonvolatile memory devices.''.« less