Conductivity of island metal films covered with organic molecules (original) (raw)
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Electric conductivity of organic films, containing nanosize metal particles
Materials Science and Engineering: C, 1999
. New materials, containing nanodispersed particles Ag, Pb, Mn, Ca, Sm, Na, CdS, ZnS in the thin polymer film have been obtained Ž . via low temperature codeposition of metal or sulphide with reactive para-xylylene monomer vapours at 100 K. Electric conductivity of the films was studied during the components co-condensation, upon sample annealing in range 80-300 K and maintaining at constant temperature. With a rise of metal nanoparticles in the polymer matrix, the conductivity tends to increase. The conductivity may be Ž . determined as a tunnel transfer of charge from one nanoparticle to another through a thin dielectric layer up to 50 nm of polymer matrix. q 1999 Elsevier Science S.A. All rights reserved.
STRUCTURE AND ELECTROLUMINESCENT PROPERTIES OF THIN TETRACENE LAYERS ON GOLD ISLAND FILMS
The molecular structure, morphology, and electrical conductivity of thin tetracene layers obtained by the thermal vacuum de-position have been studied with the help of FTIR spectroscopy and STM/STS techniques as well. It has been shown that this preparation method does not change the tetracene molecular structure. The tetracene thin layers on the atomically smooth pyrolytic graphite surface demonstrate an amorphous structure. The local current-voltage characteristics (CVC) measured for tetracene films ∼ 10 monolayers thick show a well-defined asymmetry relative to a tunnel voltage. A study of the electrical conductivity and the electrolumines-cence (EL) of a planar composite consisting of gold island films and tetracene layers has revealed that EL from submicron lumi-nescent centers is observed on a superlinear section of conduction current I–V curves. The EL intensity grows with increasing voltage and becomes maximal at the CVC saturation. It is found that the EL from the nanocomposite has a 560-nm wavelength emission maximum.
Applied Surface Science, 1998
The investigated organic compounds are derivatives of the asparagic acid. Thin films of respective compounds were deposited from dimethylformamide solutions. The temperature dependences of the electrical conductivity and Seebeck coefficient are investigated. All compounds have semiconducting properties. The values of some characteristic parameters Ž . activation energy, ratio of carrier mobilities, etc. have been determined. Using sandwich cells of the type Alrorganic Ž . compoundrAl, the static current-voltage J-U characteristics have been studied. For lower values of intensity of electric Ž 2 3 y1 . field E E E E( 6 = 10 -2 = 10 V cm , J-U characteristics are ohmic. At higher values of E E, the current density J increases faster than linear. For E E( 10 3 -10 4 V cm y1 , the obtained experimental data are in good agreement with the Richardson-Schottky law. At fields E E) 10 5 V cm y1 , the experimental points deviate more and more from Schottky characteristics in direction of larger values of J. For explanation of these behaviours, the electron transitions through and over the potential barrier at metal-organic film interface are taken into account. q 1998 Elsevier Science B.V.
Electrooptical Analysis of Effects Induced by Floating Metallic Interlayers in Organic LEDs
IEEE Transactions on Electron Devices, 2009
The aim of this paper is to investigate the electrical and optical property modifications that can be related to the presence of a nanometric metallic layer at the interface between two organic emissive materials in a stacked structure. For purposes of comparison, reference devices have also been analyzed to emphasize the increase of electrical switching and hysteresis behaviors in current-voltage plots and spectral variations in electroluminescence. In this paper, we have tried to summarize the electrical effects of the floating nanometric thin metallic layer by extracting a small number of parameters which can represent the current state of the device.
Electrochemistry at Ultrathin Organic Films at Planar Gold Electrodes
Langmuir, 1996
Electrochemical impedance measurements were performed on two different molecular assemblies that were created in order to mimic living cell membranes. In the first, a bare gold electrode surface was used as a support for Langmuir-Blodgett transfers of mono-, bi-, and multilayers of dipalmitoylphosphatidic acid. In the second, a thin polyelectrolyte film was self-assembled on the gold surface prior to the Langmuir-Blodgett transfer. A small membrane resistivity, i.e. 100-300 Ω cm 2 , was observed across the phospholipid bilayer when deposited on the polyelectrolyte surface provided the outermost layer was polyanionic. The contribution to the total membrane capacitance from one monolayer in these assemblies was 1.16 µF cm-2. Similar results for the membrane capacitance were obtained in multilayer assemblies of more than five monolayers when the support was a bare gold electrode surface, whereas thinner multilayer assemblies displayed significantly higher capacitances. Furthermore, the main contribution to the membrane resistance in the latter case was shown to originate from resistances in defect pores, through which the double-layer capacitances at the ends and inside these defects were charged.
Study of Some Properties of Organic Semiconductor Devices
2012
Conducting polymer PolyAniline (PANI) was implanted with 75 keV Au and 30 keV Ag ions. The projectile ranges were calculated from SRIM analysis prior to implantations; it is found to be 65 nm for Au and 32 nm for Ag. The optical absorption behaviors are remarkably different from the pristine samples due to combined effects of the defects and metal fillers. The choices behind Au and Ag are due to their strong SPR effects as well as their charge conducting property. Cross-sectional FESEM revealed buried layers of Au and Ag clusters. The difference in diffusion natures are observed for two different kinds of elements. XRD characteristics reveal evolving peaks in consequence with implantation doses. The difference in the optical absorption behavior corroborates the difference in the nature of defects created due to different elements in the two types of samples. Temperature depended DC conductivity studies carried out to investigate the charge transport properties of the composite material along with the defects. A comprehensive analysis of all the measurements reveals that the defect states created by Au and Ag implantation have different behavior which is combined effects of ion energy, doses, property of the matrix and types of implanted ions. The diffusion behavior of the defects and the implanted ion species, both seem to be responsible for the difference in the observed properties of the implanted samples. The results of this study indicate that it is possible to tailor the optical and electrical properties of the composite material by the choice of ion species, implantation energy and doses and it is a novel approach to implant noble metals into conducting polymer PANI whose optical properties are depend on the oxidation states. The details of this investigation and the plausible explanation of the observed behavior are presented in this paper.
Modification of metal/semiconductor junctions by self-assembled monolayer organic films
Microelectronic Engineering, 2009
Two new metal/molecule/semiconductor contacts, Au/n-Si/TDA/Au and Au/p-Si/ODM/Au, were fabricated to understand effect of organic compounds, tridecylamine and octadecylmercaptan self-assembled monolayer (SAM) films, on electrical charge transport properties of the metal/semiconductor junctions. The morphology of the organic monolayers deposited on Si substrates was investigated by atomic force microscopy. The molecular coverage of ODM deposited on p-Si is poorer than that of TDA on n-Si substrate. The ideality factors of the p-Si/ODM and n-Si/TDA diodes were found to be 1.66 and 1.48, respectively. The electrical results show that the tridecylamine monolayer passivated junction has a lower ideality factor. The ideality factor indicates clear dependence on two different type functional groups R-SH (Thiol) and R-NH 2 (Amin) groups and it increases with different functional groups of organic molecule. The barrier height u b value of the n-Si/TDA diode is smaller than that of p-Si/ODM diode, as a result of chain length of the SAM organic molecules. The interface state density D it values of the diodes were determined using conductance technique. The n-Si/TDA diode has the smaller interface state density according to p-Si/ODM diode. We have evaluated that the organic molecules control the electronic parameters of metal/semiconductor diodes and thus, organic modification helps to get one step closer towards to new organic assisted silicon based microelectronic devices.
The Journal of Physical Chemistry C, 2015
Monomolecular films of an Oligo(phenylene)ethynylene (OPE) derivative [2isocyano-1,3-dimethylbenzene][4-(4′-amino-phenylethynyl)-phenylethynyl]-gold, 1, containing a gold atom in the molecule backbone have been prepared by the Langmuir-Blodgett (LB) method in order to study how the electrical properties can be modulated in monolayers of OPEs by the incorporation of a gold center in their structures. UV-vis reflection spectra of Langmuir monolayers of 1 at the air-water interface reveal strong aurophilic interactions between neighbouring molecules that increase upon compression. Monolayer Langmuir-Blodgett (LB) films were readily fabricated by the transfer of Langmuir films of 1 onto solid substrates. Quartz crystal microbalance (QCM) experiments conclusively demonstrate the formation of monolayer LB films with a high surface coverage. The morphology of these films was analysed by atomic force microscopy (AFM), revealing the formation of homogeneous layers with an optimum surface pressure of transference of 6 mN•m-1. Film homogeneity and integrity was confirmed by cyclic voltammetry, with efficient blocking of gold electrodes by these well-formed monolayers of 1. The electrical properties of LB films of 1 were investigated by scanning tunnelling microscopy (STM) using a 'tip-to-contact' method. Symmetrical, sigmoidal-shaped I-V curves were observed, with analysis of the pseudolinear (Ohmic) region giving a conductance value G = 3.9 10-5 G 0 , which is relatively high for an OPE derivative and may indicate a beneficial role of metal atom incorporation within the wire-like-system.
Effects of Gold Nanoparticles on Pentacene Organic Field-Effect Transistors
Japanese Journal of Applied Physics, 2011
The effect of gold nanoparticles (NPs) on pentacene organic field-effect transistors (OFETs) was being investigated by both DC and AC methods, which are current-voltage (I-V ) measurements in steady-state and impedance spectroscopy (IS) respectively. Here poly(vinyl alcohol) (PVA) and PVA blended with Au NPs as composite are spin-coated on SiO 2 as gate-insulator for top-contact pentacene OFET. The characteristics of the device were being investigated based on the contact resistance, trapped charges, effective mobility and threshold voltage based on transfer characteristics of OFET. Results revealed that OFET with NPs exhibited larger hysteresis and higher contact resistance at high voltage region. IS measurements were performed and the fitting of results by the Maxwell-Wagner equivalent circuit showed that for device with NPs a series of capacitance and resistance which represents trapping must be introduced in order to have agreeable fitting. The fitting had helped to clarify the reason behind the higher contact resistance and bigger hysteresis which was mainly caused by the space charge field formed by the traps when Au NPs were introduced into the device. #