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A 'square' binding alignment pattern, with relatively higher energy barrier but four fully aligned orientations at four off-set angles of 0°, 90°, 180°, and 270°, has been analyzed by introducing a concept of the overlap ratio, compared to a 'rectangular' one. Both the 'square-pattern' micro-chips and the substrate with the 'square-pattern' binding sites were fabricated using one-mask micromachining process, and the self-alignment in situ observation under three different off-set orientation angles of 35°, 46°, and 90° was demonstrated using a high-speed video camera. Sequential images reveal a slow translational motion in the early stage followed by a faster rotational alignment. A novel technique has been further proposed for the conductivity evaluation by using three kinds of SAM films, i.e., C12, C18, and Terphenyl. The preliminary measurements indicate that, using the proposed novel structure, the Terphenyl film is believed to be desirable as a conductive SAM film for self-alignment of micro-chips. [ABSTRACT FROM AUTHOR]

Abstract: We have investigated structural and surface property of transparent conductive Nb-doped titanium oxides (TNO) thin film with high conductivity of 10−4 Ωcm order which were made by RF-magnetron sputtering at high deposition rates followed by an annealing in vacuum. The grain sizes of TNO evaluated by atomic force microscope were found to become larger by annealing at temperature higher than 500°C. The measured work functions of the TNO films using ultra-violet light photoelectron spectroscopy were 5.02–5.47eV, and depended on TNO grain size and on the amount of surface weakly bound oxygen that was estimated from peak area intensities of O(1s) X-ray photoelectron spectra. [ABSTRACT FROM AUTHOR]

Abstract: The formation of self-assembled monolayer and multilayer using redox-active Ru complex molecules with phosphonic acids on SiO2 surface has been examined using X-ray photoelectron spectroscopy (XPS), ellipsometry, and time of flight secondary mass-ion spectroscopy (TOF-SIMS). We found that an introduction of a Zr adlayer leads to higher surface molecular density of Ru complex SAMs on the SiO2 surface, compared to that of obtained from the direct adsorption of Ru complex monolayer on the SiO2 surface. We further tried to fabricate a multilayer film using this molecule with Zr(IV) ion acting as a chemical glue by a successive immersion process. The XPS data revealed that the molecular densities of the multilayers were also higher for the immobilization with Zr adlayer between Ru complex and SiO2 surface than those without the Zr adlayer, suggesting that Zr adlayer is effective in forming highly packed molecular layer of phosphonic acids on SiO2 surface. We found the film growth reached a saturation point after 6 layers on the SiO2 surface. The film growth saturation can be explained by a molecular domain boundary effect encountered due to the large tilt angle of the molecular layer. [Copyright &y& Elsevier]

Abstract: The frictional properties of self-assembled monolayers (SAMs) covalently bonded to silicon (Si) substrates through Si–C or Si–O–C bonds were investigated using a pin-on-plate tribometer. Four kinds of molecules with different alkyl chain lengths and different head groups were used: 1-hexadecene, 1-hexadecanol, 1-dodecene and 1-dodecanol. The SAMs with longer alkyl chains exhibited lower friction coefficients than those with shorter alkyl chains. Of the SAMs with longer alkyl chains, the SAMs with the Si–C bond of the head group exhibited lower friction coefficients, higher wear resistance and higher durability than those with the Si–O–C bond. The head group and alkyl chain length of the molecules affected the frictional properties of the modified surfaces of the SAMs. [Copyright &y& Elsevier]

This paper describes a 77-GHz three-stage driver amplifier integrated with a very compact 4-dB digital attenuator. The attenuator can provide successful suppression in the gain variation of the amplifier according to ambient temperature in practical use. In addition, the amplifier matching fashion using short stubs and series transmission lines helps suppress unwanted transducer gain and return gain in the out-of band of lower than 77 GHz. The amplifier fabricated in pseudomorphic high electron-mobility technology can deliver a gain of 17.9 dB with an input return loss of 21.0 dB and an output return loss of 22.7 dB in the 77-GHz band, while keeping lower than -16.5 dB of gain in the out-of band. Over the temperature range from -20 °C to 100 °C, the measured results show that a gain variation of less than 2.0 dB is achieved by using the attenuator, while the gain variation without the attenuator is as large as 6.0 dB. The die size is as small as 2.3 × 1.4 mm² due to the very compact attenuator of a 0.2 × 0.6 mm² occupied area. [ABSTRACT FROM AUTHOR]

Abstract: We investigated the frictional properties and the durability of self-assembled double layers using pin-on-plate methods and X-ray photoelectron spectroscopy (XPS). We found that double layers made from octadecanethiol (ODT) and mercaptohexadecanoic acid (MHA) connected via Cu ions exhibited lower frictional coefficients (approximately 0.1–0.15) than that of ODT monolayer (∼0.2). XPS measurements revealed that ratios of C(1s)/Au(4f) after friction tests were lower than that before friction but was higher than that measured on ODT monolayer, suggesting that some of ODT molecules were desorbed from the surface, i.e. formation of loosely packing molecular layers after friction. These findings suggest that the loosely packed molecular layer contributed to decrease the friction. [Copyright &y& Elsevier]

We investigated molecular arrangement change of self-assembled monolayers (SAMs) made from [1,1′:4′,1″-terphenyl]-4-thiol (TP0) on Au(1 1 1) using scanning tunneling microscopy. In an ethanol solvent, lying down phase of TP0 molecules where the conjugated rings are expected to contact directly the Au surface, were observed at the initial stage of TP0 SAM growth (at 1 min immersion). After 24 h immersion, a molecular lattice, which is similar to (√3×√3)R30° structure (perpendicular arrangement) was observed. We further investigated the molecular arrangement dependence of electrical conduction of the TP0 SAMs using conductive atomic force microscopy technique. The resistances of the TP0 SAMs were ≈104 Ω (at parallel arrangement) and ≈108 Ω (at perpendicular arrangement). The resistance of the lying down TP0 SAM was lower than that of benzylmercaptane SAM where the thickness was identical to lying down TP0 SAM. The result indicated that the direct contact of the conjugated ring to the Au surface could further reduces the tunneling resistance. [Copyright &y& Elsevier]

Presents a study which looked at the performance of V-band monolithic high electron-mobility transistor (HEMT) oscillators. Oscillation characteristics on drain bias; Functions of oscillators; Comparison of the oscillation performance of several gallium arsenide pseudomorphic high electron-mobility transistor (pHEMT) based oscillators.

A novel technique of low-energy N2 neutral beam (NB) (<10 eV) irradiation was investigated as a means of controlling the surface nitridation of self-assembled monolayers (SAMs). This low-energy process without UV photons was able to nitride the surfaces of terphenyl SAMs. Furthermore, by varying the on/off period for irradiation, a pulse-time modulated NB process could be used to control the atomic ratio of nitrogen in terphenyl molecules. Time-of-flight secondary ion mass spectra revealed that one H in the terphenyl group was substituted by a NH2 group because of irradiation by the N2 beam. The data suggested that the low-energy NB technique caused less damage to modified surfaces than the conventional plasma process did. Therefore, we believe that it is a potential damage-free process for modifying the surfaces of soft organic materials and films. [ABSTRACT FROM AUTHOR]

The thermoelectric properties of organic materials have been greatly improved very recently, but studies of organic thermoelectric device fabrication are still very limited. In this work, we report proof-of-concept studies of organic thermoelectric devices fabricated by thermal lamination at 100 °C using the benchmark p-type material poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate). A 1.54 cm 2 device shows a power output of 37 μW at a temperature difference of 50 K (a power density of 24 μW/cm 2 ), which is one of the highest values when compared with previous studies. This approach potentially enables the fabrication of high-performance, large-area organic thermoelectric devices via roll-to-roll processing at a low temperature. [ABSTRACT FROM AUTHOR]

Abstract: Methyltrimethoxysilane (MTMS)-coupled mica substrate is reportedly suitable for fixing and straightening of DNA, but 3-aminopropyltriethoxysilane (APTES)-coupled mica substrate has been found less suitable. On MTMS-coupled mica substrate, the straightness of fixed DNA was sufficient, and the adsorption of contaminants was not observed using fluorescence microscopy and atomic force microscopy. For the APTES-coupled mica substrate, however, aggregated or curved DNA and adsorption of contaminants were observed. To clarify the surface factors that are responsible for this suitability, we analyzed the surface free energies of these substrates using the extended Fowkes theory. In each of the surface free energy components, the dispersion force component in the MTMS-coupled mica substrate was lower than that in the APTES-coupled mica substrate. The ratio of the polar force component on the MTMS-coupled mica substrate was about one order of magnitude on the APTES-coupled mica substrate. In addition, the ratio of the hydrogen-bonding force component for the MTMS-coupled mica substrate was about two times larger than that of the APTES-coupled mica substrate. These results suggest that the polar force and hydrogen-bonding force components are important factors for the fixation and straightening of DNA and that the dispersion force components influence the production and adsorption of contaminants. [Copyright &y& Elsevier]

All-trans oligo(para-phenylenevinylene) (OPV) methyl thiols of a two-ring phenylene-vinylene dimer and a three-ring trimer have been synthesized to prepare self-assembled monolayers (SMS) onto an Au(1 1 1) surface. The molecular level morphologies of the monolayers prepared on Au surfaces were probed by scanning tunneling microscopy (STM) or atomic force microscopy (AFM). The soluble dimer formed a highly ordered structure lying down on the Au surfaces. The molecules of trimer stand slantwise on the Au surfaces, but the structure of monolayers is less ordered. Another longer OPV methyl thioacetate, a slightly soluble four-ring tetramer, has also been synthesized. Although it was difficult for aggregative molecules of the longer OPV to self-assemble on Au, we could successfully insert the tetramer into tetradecane-1-thiol monolayers on Au surfaces by an exchange reaction. The mixture monolayer showed that the isolated tetramer was adsorbed almost vertically on the Au surfaces. [Copyright &y& Elsevier]

Oligo(para-phenylene-vinylene)-methanethiol of trimer and dimer have been synthesized to prepare monolayers onto Au(111). The trimer diluted in dichloromethane glows with a brilliant blue fluorescence when excited with UV light (365 nm). The absorption and emission spectra of the dimer diluted in CH[sub 2]Cl[sub 2] show a blue shift. The molecular level morphologies of the monolayers prepared on gold surfaces were probed by scanning tunneling microscopy or atomic force microscopy (AFM). The dimer is entire trans isomer, which formed highly ordered self-assembled monolayers (SAMs) on Au. The trimer is a mixture of cis–trans isomers, and did not form ordered monolayers on Au. However, the trimer molecules could be embedded in dodecanethiol SAM, and showed higher conductance than oligo(para-phenylene) molecules characterized using a conductive AFM. [ABSTRACT FROM AUTHOR]

Damage-free surface nitridation of terphenyl methanethiol self-assembled monolayers (TP1-SAMs) was investigated using a novel low-energy N2 neutral beam (NB) irradiation technique. When a conventional inductively coupled plasma process was used, x-ray photoelectron spectra confirmed that the TP1-SAM was quickly broken because ions or ultraviolet (UV) photons enhance the surface decomposition and molecular desorption. Conversely, with the N2 NB radiation process, which is free of ions and UV photons, there was little difference in the atomic ratios of x-ray photoelectron spectra before and after NB irradiation. These results suggest that low-damage surface modification is possible through the authors’ NB technique. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • We measured the specific contact resistance between PEDOT:PSS and metal electrodes. • Formation of PEDOT:PSS film by second solvent greatly reduced the contact resistance. • Surface treatment of the PEDOT:PSS film also decreased the contact resistance. • Increase in contact area between PEDOT:PSS and Ag particles resulted in the reduction. • This finding could help the researchers developing the printed electronics devices. Abstract The contact resistance at conducting polymer-electrode junctions could substantially affect device performance because electrical currents or signals generated in the polymer devices must be transferred in their final form through the junctions to the connected load or devices. We report here the specific contact resistance between the conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and a metal electrode as measured by a transmission line technique. Toward developing printed electronics that do not require vacuum processes, we focus on the specific contact-resistance, r c , between PEDOT:PSS films and metal pastes. Addition of a second solvent such as ethylene glycol (EG), poly-ethylene glycol (PEG), and dimethyl sulfoxide (DMSO) to PEDOT:PSS solution for film formation induced a significant reduction of r c together with an enhancement of electrical conductivity. A surface treatment using EG or DMSO on electrode areas of the film also decreased r c at the PEDOT:PSS-Ag paste junction to the value at the PEDOT:PSS-Ag junction formed by electron-beam evaporation. The mechanism of reduction of r c is discussed based on morphology of the PEDOT:PSS film. [ABSTRACT FROM AUTHOR]

We evaluated the effect of an amide compound bearing methyl groups on the properties of tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) cast films. The spontaneous electron transfer between N , N -dimethylacetamide (DMA) and the TCNQ complex is expected to change the casting condition. Then, we obtained a higher density of nanofibers in TTF-TCNQ films using DMA. The electrical conduction of TTF-TCNQ films using DMA was 58.0 S/cm, which is twice that of previously reported polycrystalline films. We measured the Seebeck coefficients of the films for their future possible use as thermoelectric materials. The Seebeck coefficient and power factor of the films prepared with DMA were 32.3 μV/K and 6.05 μW/mK 2 , respectively. [ABSTRACT FROM AUTHOR]

We report the transport properties of nonwoven fabric-composite thermoelectric (TE) elements impregnated with the polymer poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). The porous structure formed in the fabric after the solvent evaporation of the PEDOT:PSS solution resulted in a high thermal resistance. In addition, the polymer films covering the surface of the fibers in the fabric connected the fibers to form electrical conduction paths, resulting in isotropic electrical conductivity at high PEDOT:PSS concentrations. These two factors provided the optimum PEDOT:PSS concentration for the TE power density per PEDOT:PSS content. Optimizing the TE power density per polymer content could contribute to the low-cost fabrication of TE modules from conducting polymers. We also demonstrated that the flexible TE module fabricated from the nonwoven fabric-composite achieved a power output sufficient to power a light-emitting diode. Contact electrical resistance at polymer-electrode junctions was greatly reduced by the increase in contact area arising from the wavy surface of the fabric composite. [ABSTRACT FROM AUTHOR]

The through-plane conductivity of a film sample is critically important because it largely affects the performance of batteries, capacitors, and thermoelectric devices. In this study, we developed a modified four-probe through-plane electrical conductivity measurement method using a coaxial structure. This method is general and works for free-standing film samples. We studied different samples including a steel sheet, highly oriented pyrolytic graphite, and conducting polymers. We confirmed metallic transportation in the steel sheet and hopping transportation in graphite in the through-plane direction by conducting low temperature measurements at 100 K. In the case of a conducting polymer poly(3,4-ethylenedioxythiophene)/polystyrene sulfonate, the conductivity anisotropic ratio decreases with increasing in-plane conductivity. Temperature dependent measurements show two distinct activation energy regimes in the through-plane direction in PEDOT/PSS but almost no change in the in-plane electrical conductivity activation energy. This could be due to additional carrier paths that occur through the more disordered region (the PSS-rich region) in the through-plane direction. We also examined the Meyer–Neldel rule in PEDOT/PSS and concluded that PEDOT/PSS follows the anti-Meyer–Neldel rule, likely due to the high carrier density in the film. [ABSTRACT FROM AUTHOR]

Sequential assembly of layers containing redox-active dinuclear Ru complexes that differ in their redox potential on ITO substrates afforded a series of layered structures with different potential gradients. The Ru complexes Ru-NP and Ru-CP contain tetrapodal phosphonate anchors and bridging 2,3,5,6-tetra(2-pyridyl)pyrazine or 1,2,4,5-tetra(2-pyridyl)benzene ligands, respectively. Oxidation potentials of E 1/2 = +0.83 and +1.04 V vs. Fc + /Fc ( Ru-NP ) and E 1/2 = −0.37 and 0.09 V ( Ru-CP ) were observed for the Ru(II)-Ru(II)/Ru(II)-Ru(III) and Ru(II)-Ru(III)/Ru(III)-Ru(III) couples. As the Ru-NP and Ru-CP units contain several accessible redox-active electronic states, electron transfer (ET) blockage and mediation occurred at the Ru-NP / Ru-CP heterojunction on account of the large potential gradient. An examination of the electrochemical behavior of the multilayer diblock ITO||( Ru-CP ) n |( Ru-NP ) n ( n = 1–5) heterofilms revealed that in ITO||( Ru-CP ) 4 |( Ru-NP ) 4 , the Ru(III)-Ru(III)/Ru(III)-Ru(IV) couple is involved in the electron mediation pathway on the Ru-NP / Ru-CP heterojunction. In the case of the multilayer triblock ITO||( Ru-NP ) n |( Ru-CP ) n |( Ru-NP ) n ( n = 4) heterofilms, two catalytic peaks were observed, indicating that the inner and outer Ru-NP / Ru-CP junctions display two different catalytic ET processes. In the alternating Ru-NP / Ru-CP multilayer heterofilms, the ET mediation processes are governed by the sequence order of the Ru-NP / Ru-CP heterojunction attached to the ITO electrode. In multilayer homo- and heterofilms, the dependence of the ET distance on the layer number is discussed on the basis of potential-step chronoamperometry (PSCA) results. In the multilayer Ru-NP and Ru-CP homofilms, relatively low β values were observed, while in the multilayer heterofilms, the ET rate of the catalytic wave was not affected by the number of layers, as the energy gap between the Ru-NP / Ru-CP units is the rate-determining factor. Therefore, the molecular sequence in such multilayer heterofilms, composed of layers containing Ru-NP or Ru-CP complexes, plays an important role. [ABSTRACT FROM AUTHOR]

SUMMARY The electronic structure of fluorinated self-assembled monolayers (F-SAMs) with different chain lengths was investigated by photoelectron and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. From the measurements of the photoelectron spectra in the wide region and in the C 1s core-level region, the chemical compositions and components of the F-SAMs with different chain length were clarified. In the C K-edge NEXAFS spectra of the F-SAMs, the several spectral features were observed and the intensity of the features at 292 eV and 299 eV decreased with increasing incidence angle of the excitation photons. Based on the results of the photoelectron and NEXAFS spectral measurements, the electronic structure of four F-SAMs with different chain length is discussed. [ABSTRACT FROM AUTHOR]

A novel conducting polymer, Poly(3-methoxythiophene-2,5-diyl-co-3,4-ethylenedioxythiophene-2,5-diyl]/tosylate (P1/tos), was synthesized by oxidative in situ polymerization using Fe(tos) 3 as an oxidant. Compared with poly(3,4-ethylenedioxythiophene) (PEDOT), P1 has a deeper HOMO level and a wider energy gap as observed by ultraviolet–visible spectroscopy and photoelectron yield spectroscopy. P1/tos showed electrical conductivity of 10 S/cm and a carrier mobility of about 0.6 cm 2 /(V s), which was extracted by using ion-gel thin film transistors. The calculated carrier concentration was on the order of 10 20 cm −3 , which is lower than that of PEDOT/tos. The Seebeck coefficient of P1/tos was higher than that of PEDOT/tos. [ABSTRACT FROM AUTHOR]

Abstract: The adsorption process, molecular arrangement and protonation behavior of self-assembled monolayers (SAMs) of bipyridine thiol on Au(111) were investigated using X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM), with a view towards constructing a molecular ion sensor. When the bipyridine SAMs were immersed in a strong CF3SO3H solution for protonation of the bipyridine group, additional N(1s) XPS peaks were generated at higher binding peak positions where the origin of the peak was considered to be the N–H species. We further investigated the relationship between the immersion time for the SAMs and the probability of protonation. We observed a decrease in the probability of protonation with a longer immersion time for the SAMs. We consider that both the bipyridine molecular arrangements and the molecular density on the Au surface are crucial for controlling the probability of protonation based on the STM and XPS data. [Copyright &y& Elsevier]

For obtaining molecular devices using metal—molecule—metal junctions, it is necessary to fabricate a steady conductive bridge-structure; that is stable chemical bonds need to be established from a single conductive molecule to two facing electrodes. In the present paper, we show that the steadiness of a conductive bridge-structure depends on the molecular structure of the bridge molecule for nanogap junctions using three types of modified oligo(phenylene vinylene)s (OPVs): α,ω-bis(thioacetate) oligo-(phenylene vinylene) (OPV1), α,ω-bis(methylthioacetate) oligo(phenylene vinylene) (OPV2), and OPV2 consisting of ethoxy side chains (OPV3). We examined the change in resistance between the molecule-bridged junction and a bare junction in each of the experimental Au-OPV-Au junctions to confirm whether molecules formed steady bridges. Herein, the outcomes of whether molecules formed steady bridges were defined in terms of three types of result; successful, possible and failure. We define the ratio of the number of successful junctions to the total number of experimental junctions as successful rate. A 60% successful rate for OPV3 was higher than for the other two molecules whose successful rates were estimated to be ∼10%. We propose that conjugated molecules consisting of methylthioacetate termini and short alkoxy side chains are well suited for fabricating a steady conductive bridge-structure between two facing electrodes. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we demonstrate immobilization of two kinds of π-conjugated molecules on Au using dendrimer-based templates; one is a p-phenylene ethynylene derivative and the other is a 4,4′-bis(phenylethynyl)-2,2′-bipyridine derivative. Both molecules were bound to benzyl-ether dendrons through an alkali-labile, ester linkage to give two different generation dendrimers. The removal of the dendrons from the self-assembled monolayers of the dendrimers left the isolated π-conjugated-molecules as well as small collections of the molecules on the surfaces, which was confirmed by surface Fourier transform infrared (FT-IR) spectroscopy and scanning tunneling microscopy (STM). Insertion of the dendrimer into n-dodecanethiol monolayer instead of the direct adsorption on a bare gold gave only the isolated, single molecules on the surface after the dendrons were removed. [Copyright &y& Elsevier]

The protonation/deprotonation response of a novel bipyridine containing (phenylene-ethynylene) thiol adsorbed to a Au surface was investigated with scanning tunneling microscopy (STM). STM results show reversible changes in the average heights (~50 spots) and the height distribution arising from protonation/deprotonation. [ABSTRACT FROM AUTHOR]