3.1.1. Covalent Interactions 1355 3.1.2. Noncovalent Interactions 1356 3.1.3. π-π Stacking 1356 3.1.4. Electrostatic Interactions 1357 3.2. In Situ Synthesis Directly on the CNT Surface 1358 3.2.1. Electrochemical Techniques 1358 3.2.2. Sol-Gel Process 1361 3.2.3. Hydrothermal and Aerosol Techniques 1363 3.2.4. Gas-Phase Deposition 1364 3.3. Comparison of Synthesis Techniques 1368 4. Properties and Potential Applications of CNT-Inorganic Hybrids 1368

Carbon Nanotube−Inorganic Hybrids

Ordered anion adlayers on metal electrode surfaces.

http://www-old.mpi-halle.mpg.de/mpi/publi/pdf/11827_14.pdf

Explanation of potential-induced degradation of the shunting type by Na decoration of stacking faults in Si solar cells

A plasma display device includes: a dielectric layer on which a plurality of through-holes of a dielectric layer is disposed in a matrix shape; upper and lower electrode layers formed at both upper and lower surfaces of the dielectric layer; upper and lower substrates disposed on the outer surface of the upper and lower electrode layers; and a third electrode layer having a plurality of third electrodes which are formed between the upper substrate and the upper electrode layer, or the lower substrate and the lower electrode layer, and are insulated from the upper and lower electrode layers. Accordingly, a plasma display device can be realized which has stability and efficiency of a micro discharge. In addition, each pixel can concurrently carry out a sustain discharge by applying an alternating voltage to upper and lower electrodes forming sustain electrodes.

Plasma Display Panel

Doped conjugated polymers can exhibit exceptionally high conductivity (>10 S cm). Here, doping refers to the formation of charge-transfer complexes (CTCs) or salts by combining appropriate pairs of donors and acceptors. Similar phenomena can be found in crystalline CTCs comprising small molecules. For several decades, the nature of charge transfer (CT) and the dimensionality of charge transport in conducting polymers and small molecule crystals have been at the focus of research. For instance, the degree of CT influences conductivity and determines whether metallic or insulating character prevails, and the strength of interchain interactions determines whether primarily 1D or 3D electronic properties prevail. In addition, disorder—on both a molecular and mesoscopic scale—has a tremendous impact on these properties. In fact, true metallic behavior of a doped conjugated polymer was demonstrated only recently by significantly improving the structural quality of thin films. Apart from the interest in fundamental phenomena occurring in such systems, recent progress in the field of organic electronics has intensified efforts toward improving the understanding of conducting polymers, as they are a key element for the successful realization of printed all-organic (opto-) electronic devices. At present, formulations of poly(ethylenedioxythiophene)/poly(styrenesulfonate) dominate applications; however, it should be interesting to develop alternative routes to conducting polymers that are not based on an aqueous dispersion and thus allow for new processing options and functionality. The most widely studied class of semiconducting polymers that can be rendered conducting upon doping (with inorganic acceptors) is based on polythiophene, which has donor character; tetrafluorotetracyanoquinodimethane (F4TCNQ) is one of the strongest known molecular electron acceptors and has been used for doping molecular organic semiconductors. However, combinations of polythiophenes and strong molecular acceptors have not yet been investigated. Here we show that mixtures of the prototypical soluble polythiophene variant poly(3-hexylthiophene) (P3HT) and F4TCNQ form CTCs with high conductivity in thin films (ca. 1 S cm). Because of the flexibility of the polymer chains and the variety of possible interchain interactions, a large number of different local conformations in P3HT/F4TCNQ CTCs can be expected, leading to large variations in the electronic structure and transport properties within a macroscopic sample. We investigated the local conformation and electronic structure of P3HT/F4TCNQ CTCs in thin films by combining X-ray absorption near edge structure (XANES) measurements with theoretical modeling using density functional theory (DFT). Most notably, we found that only one specific CTC conformation predominated, in which F4TCNQ was strongly bent out of its neutral planar form because of pronounced electron donation from P3HT chain segments. In contrast, in a related F4TCNQ/oligothiophene CT crystal, F4TCNQ remained planar because of dominant intermolecular interactions in an ordered environment. Furthermore, the energy levels of the CTC were clearly shown to be hybrids of the individual levels of the separate donor and acceptor molecules, indicating that the CT in P3HT/F4TCNQ is highly localized and does not involve significant interchain interactions. Thin films of F4TCNQ-doped P3HT prepared from solution typically exhibited a dc conductivity of 1 S cm, which corresponds to an increase in conductivity by five orders of magnitude over pristine P3HT. This increase is lower than the reported value of 30 S cm for ClO4 -doped P3HT. Interestingly, the conductivity of our P3HT/F4TCNQ films was five orders of magnitude higher than the value for dimethylquarterthiophene/F4TCNQ crystals. In these crystals intermolecular interactions are strong, whereas it was proposed that in conducting polythiophenes, conduction happens primarily along single polymer chains because of weak interchain coupling. In this communication, we relate the localized character of the CT between P3HT and F4TCNQ with the observed conductivity and explain the nature of the CT states. The XANES spectrum of neutral F4TCNQ exhibits three main spectral features: peaks A, B, and C (Fig. 1a). Using just C O M M U N IC A IO N

Localized Charge Transfer in a Molecularly Doped Conducting Polymer

Na-induced 3\ifmmode\times\else\texttimes\fi{}1 reconstruction on the Si(111) surface was studied using a scanning tunneling microscope and other tools. Atomic images showed that this surface consisted of Na zigzag chains separated by a missing row, which covered the bulk-terminated Si(111) 1\ifmmode\times\else\texttimes\fi{}1 substrate at the coverage of 2/3. Upon further deposition, a Na multilayer was grown following the Stranski-Krastanov mode. Tunneling I-V curves showed that the first layer of Na was insulating but the insulator-metal transition occurred in the second layer. We propose, based on the structural analysis, that this transition represents a two-dimensional Mott-Hubbard system.

Structural and electronic properties of ordered single and multiple layers of Na on the Si(111) surface.

Scanning tunneling microscopy (STM) and point-probe electrical conductivity measurements of electrochemically protonated films of the emeraldine-base form of the conducting polymer, polyaniline are reported. The conductivity varies spatially, dependent on the size (LM \m=~\ 200 to 300 angstroms) of granular metallic regions which relate directly to the inhomogeneous micromorphology of the electrodeposited films. The normalized conductivity at zero bias is observed to increase with doping, indicating an increase in states at the Fermi level. The STM electronic measurements also show regions of negative differential resistance. Negative differential resistance is observed for all samples, although more frequently on less oxidized samples.

Scanning tunneling spectroscopic evidence for granular metallic conductivity in conducting polymeric polyaniline.

Enormously high secondary electron emission yields under electric field are observed from MgO deposited on carbon nanotubes. The yields reach a value as high as 15 000 and are strongly dependent upon the bias voltage applied to the sample. The creation of the electric field across the MgO film after bombardment of primary electrons is considered as one of key features, since positive charges are generated at the surface by departure of secondary electrons. Subsequent bombarding electrons produce other secondary electrons inside the MgO film, then the liberated secondaries are accelerated towards the surface under the strong field. Under this condition, the secondary electrons gain sufficient energy to create further electrons by impact ionization. The process continues until an equilibrium avalanche is established. To elucidate the earlier explanations, the kinetic energy spectra of secondary electrons are measured by an energy analyzer at various bias voltages in MgO/carbon nanotube samples. The analysis of spectral results with the energy band diagram gives us strong evidence for the suggested mechanism.

Secondary electron emission yields from MgO deposited on carbon nanotubes

STM of the Cu(111)1 × 1 surface and its exposure to chlorine and sulfur

The absolute coverage of K on the Si(111)-3×1-K surface which was prepared by deposition of K on the 420°C Si substrate was determined, by using coaxial impact-collision ion scattering spectroscopy, to be 0.29±0.03ML. This result rules out the possibility that the 3×1-K phase is formed by K impurity stabilization claimed by several groups. Another important implication of this result is that K atoms of the 3×1 overlayer are not imaged bright in the STM.

http://iopscience.iop.org/article/10.1143/JJAP.32.L1263/pdf

Dongryul Jeon

Papers

Structural and electronic properties of ordered single and multiple layers of Na on the Si(111) surface.

Scanning tunneling spectroscopic evidence for granular metallic conductivity in conducting polymeric polyaniline.

Secondary electron emission yields from MgO deposited on carbon nanotubes

STM of the Cu(111)1 × 1 surface and its exposure to chlorine and sulfur

The absolute coverage of K on the Si(111)-3×1-K surface