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Paramagnetic metal complexes with tetrathiafulvalene moieties in its ligands, [CuII(EDT-sae-TTF)2] (1) and two new derivatives were investigated towards the potential application to the organic thi...

Proton beam writing (PBW) is known to be a powerful tool with unique advantages for microfabrication. In order to solve remaining problems and bring the PBW technology to a new level of applications, we propose a microfabrication system based on a PBW that makes fabrication of microstructures in an area only a centimeter large possible. We combined XY-stage control and electrostatic scanning to eliminate the area restrictions of our previous PBW system, and included a feature for importing CAD (Computer Aided Design) data which enables faster and more accurate development of complicated structures.

A simple and sensitive sub-micrometer scale method for visualization of the dose distribution of a focused proton beam (FPB) was developed, taking advantage of the formation of a bulky crosslinked structure induced by FPB irradiation of a common polymer and cross-linker, polyacrylic acid-N, N'-methylene bisacrylamide, blend film surface. The irradiated part of the film swelled as a peak, and the height of swelling increased with increasing FPB fluence. The film was used as a proton beam-sensitive polymer film by analysis of the irradiated film surface using atomic force microscopy. The method was successfully applied to confirm the FPB pattern. Typical misaligned spot shape of FPB gave clear 3-dimensional structures, and the half-solenoidal nanostructures are visualized clearly by use of crescent shaped beam.

Proton beam writing (PBW) was applied for micromachining of a PMMA mother for Ni electroforming. Proton beam focused down to about [email protected] at beam energy of 1.0-3.0MeV was used for PBW on a PMMA layer on Si or Cu substrate. Using modified techniques for developing of [email protected] thick resists exposed to PB and electroforming steps, fabrication of the Ni structures with aspect ratio up to 30 by electroforming with a [email protected] thick PMMA mother micromachined by PBW was successful. We also tried thermal imprint using a [email protected] thick Ni microstructure on Cu substrate with an aspect ratio of more than 4 on a PMMA film.

In the title compound, we made X-ray satellite reflection measurements up to 0.7 GPa and angle-dependent magnetoresistance (AMR) measurements at 1.9 GPa. The purpose of the study is to clarify (1) how large the temperature-pressure regime is for the long-range charge ordering (CO), (2) whether or not the high pressure regime for the superconductivity is really a metallic state, and (3) what the electronic properties are in the intermediate pressure regime between the long-range CO and the superconducting states. The long-range CO was found to be stable up to 0.7 GPa, and its temperature-pressure regime coincides with that expected from transport measurements. AMR at 1.9 GPa, 1.4 K and 12 T suggests the presence of Fermi surfaces consistent with band calculations based on X-ray structural analyses at room temperature and the same pressure. Raman studies by one of the authors (K.Y.) suggest the presence of metallic state in the intermediate pressure regime where the resistance shows apparently insulating properties. Discussion is made on the role of the charge-degree of freedom in causing the superconductivity.

New TTF-based ligands (TTF=tetrathiafulvalene) with Schiff base-type coordination sites have been synthesized: 4,5-bis(4-salicylideneiminophenyl)-4′,5′-ethylenedithio-TTF (1a), 4,5-bis(4-picolinideneiminophenyl)-4′,5′-ethylenedithio-TTF (1b), and 4-(2-salicylideneiminoethylthio)-5-methyl-4′,5′-ethylenedithio-TTF (Hsae-TTF). X-ray crystallography for 1a revealed that 1a has rigid structure around the coordination sites, which prevents it to form metal complexes. On the other hand, Hsae-TTF ligand has flexibility around its coordination sites due to alkyl chain spacer, and gave mononuclear complexes with Ni(II) and Cu(II) ions, [MII(saeTTF)2] (MII=Ni(II) and Cu(II)). The metal ions in [MII(saeTTF)2] have a square planar coordination structure with two TTF-based ligands, which was sandwiched by two neutral TTF moieties. The Cu(II) complex, [CuII(saeTTF)2], yielded charge transfer (CT) complexes with acceptors such as F4TCNQ, DDQ, and iodine. CT complexes with F4TCNQ and iodine were semiconductive, but that with DDQ was insulator. This is due to the difference of the degree of charge transfer; TTF moiety in F4TCNQ salt was partially oxidized but that of DDQ salt was completely oxidized. The radical cation salts of [CuII(saeTTF)2] with PF 6 ‐ anion was also obtained in 1:1 donor and anion ratio by electrocrystallization. The donor and anion ratio indicates that the oxidation state of TTF moieties in the radical salt, [CuII(saeTTF)2]PF6, was partial oxidation state.

Proton beam writing (PBW) was applied to the fabrication of dielectrophoretic (DEP) devices equipped with high-aspect-ratio pillar arrays. With coupled use of soft lithography for micro-fluidic channels, we successfully fabricated a device equipped with SU-8 pillar arrays produced by PBW, which is covered with a poly-dimethylsiloxane (PDMS) micro-fluidic channel. For more simplified prototyping of the device, we modified a SU-8 mold for simultaneous replication of both pillar arrays and micro-fluidic channel on PDMS. Replication of pillar arrays is limited to the aspect ratio of less than three.

Proton beam writing (PBW) is one of the direct write techniques for the purpose of deep micromachining. Together with the flexibility of the direct write feature, micromachining of high-aspect-ratio structures is possible due to the straight trajectory of the MeV energy protons. However, direct writing is a low throughput process, when compared with a mask process such as UV lithography. For better productivity, coupled use of PBW with electroplating has been proposed as a method to fabricate metal microstructures for molds of imprint lithography. We demonstrate the electroplating of high-aspect-ratio Ni microstructures on PMMA micromachined by PBW.

Dielectrophoresis (DEP) is a phenomenon involving translational movement of a polarizable object toward the direction of the electric field gradient. DEP has been used for electrical trapping of food poisoning microbes such as Escherichia coli (E. coli). In this paper, we developed 3D-electric micro filters equipped with high-aspect-ratio pillar array with a height of ~15 @mm and a diameter of ~1 @mm as a part of the electric micro filter. The pillar array was fabricated using a 15 micrometer thick negative resist layer on silica substrate by proton beam writing (PBW). We analyzed a DEP force distribution around pillars in the 3D-electric micro filters. Making the most of superior features of PBW as a rapid prototyping tool, we evaluate the performance of the DEP device for trapping capability of E. coli by photoluminescence (PL) measurement for various arrangements of the pillars to achieve higher trapping efficiency of the 3D-electric micro filter.

In this paper we report fabrication of high-aspect-ratio micro-structure of Ni by electroplating, using a micro-machining technique of resists using proton beam writing (PBW) at Japan Atomic Energy Agency (JAEA). A micro-structure of 5 μm thick PMMA was fabricated by exposure using PBW at 1.7 MeV and by development. A Ni structure was then formed by electroplating on the micro-structure of PMMA. Vertical and smooth side walls observed by a scanning electron microscope (SEM) indicate that PBW can be a versatile tool for fabrication of resists and metal microstructure in combination with electroplating. The electroplated Ni structure can be used as a resolution standard, which enabled us to focus the proton beam down to 130 nm.

Structural and optical properties of silica glass induced by ion microbeam irradiation were studied using micro- photoluminescence (μ-PL) spectroscopy and atomic force microscopy (AFM). Ion microbeam irradiation was performed using microbeam lines of 3-MV single-ended or tandem accelerators with various ion species including H+, He+, B3+, C4+, N4+, O4+, and Si5+ at energies of 1.7 to 18 MeV. The beam was focused to about 1 μm and was scanned over the surface of high-purity silica glass with fluences of 1013 to 1018 ions/cm2. The μ-PL spectrum in microbeam-irradiated silica shows two peaks at 540 and 650 nm. The mapping of the two PL bands reveals the distribution of defects induced along the track of ions. The compaction was observed in the form of groove at the surface of silica glass by AFM. The depth of the surface groove increases with increasing ion fluence and saturates at about several hundreds to 900 nm, depending on irradiated ion species. The mechanisms of structural and optical modifications of silica glass are can be understood in terms of energy loss due to electronic stopping and nuclear stopping powers. Refractive index changes with an order of 10– 4 to 10− 2 were estimated by a Lorentz–Lorenz relationship from the compaction. Technological implications of these results are also to be discussed.

We investigated the correlation between the luminescence properties and the surface structures of submicron silica particles prepared by the Stober method. After annealing in a non-oxidizing atmosphere, the submicron-sized silica particles show a broad photoluminescence (PL) band at 500–540 nm by excitation at an ultraviolet wavelengths (254 and 365 nm), and the one at the 600 nm by excitation an Ar + laser (488 nm). The PL appeared to result from the removal of impurities and subsequent formation of several luminescent structures on the internal surface of the primary particles by thermal annealing.

We have evaluated the irradiation effects by ion microbeam on silica glass for various ion species by means of a micro-photoluminescence technique. Defect generation and refractive index change were observed for silica at the area of 10 μm × 50 μm scanned by ion microbeam of H + , He + , N 4+ , C 4+ , O 4+ , and Si 5+ with energy from 1.7 to 18 MeV. The μ-PL spectroscopy measurements were performed along the side surface perpendicular to the microbeam irradiated surface. Based on the comparison with a result of SRIM (stopping and range of ions in matter) simulation, the defect generation mechanism was discussed in terms of the energy deposition processes due to electronic and nuclear stopping powers. We conclude that the electronic stopping power is responsible for the defect generation at the track of ions. The effect of the nuclear stopping power is also not negligibly small at the end of range.

New C60-TTF dyads with several substituents on the TTF moiety were prepared to examine the substituent effect on the intramolecular charge transfer interaction. Cast films of the dyads with long alkyl chains were obtained with high quality and characterized. In X-ray diffraction study for the cast film of the derivative with -SC16H33 groups ( 1g ), high ordered reflection peaks were observed. Analysis of the diffraction pattern revealed that 1g forms the multibilayer structure in condensed film.

Radical salts based on DODHT [(1,4-dioxane-2,3-diyldithio)dihydrotetrathiafulvalene] are semiconductors at ambient pressure, but some salts (PF6, AsF6, and BF4·H2O salts) exhibit supuerconducting transition under hydrostatic pressure. X-ray diffraction and magnetic susceptibility measurements at ambient pressure for PF6 salt revealed that the insulating phase at ambient pressure corresponds to a charge ordering (CO) state with stripe-type charge pattern. While the similar magnetic behavior was observed for BF4 salt, temperature dependence of magnetic susceptibility of AsF6 salt is quite different from those of the other salts.

A new TTP donor, Me-DH-TTP (2-methyl-5-(1,3-dithiolan-2-yliden)-1,3,4,6-tetrathiapentalene), was designed to realize a system with large on-site Coulomb repulsion as compared with the previously known bis-fused type TTP donors. Probably as a consequence, (Me-DH-TTP)2AsF6 exhibits semiconducting behavior from room temperature to liquid helium temperature. By increasing pressure, metallic behavior appears below 300 K, and with distinct metal-insulator (M-I) transition up to 2.2 GPa. This M-I transition suddenly disappears beyond 2.5 GPa, and metallic state is stabilized down to 2.6 K. We discuss the possibility of quantum critical point around 2.4 GPa.

The detailed topology of the Fermi surface of the quasi-one-dimensional conductor (DMET)2I3 was investigated by the magnetooptical measurements. A pair of planar Fermi surface which has higher corrugations of Fourier components was observed. This result seems to suggest that the metallic state of this salt is stabilized by the higher corrugations of the Fermi surface.

New organic conductor based on DODHT [(1,4-dioxane-2,3-diyldithio)dihydrotetrathiafulvalene], which gave superconducting salts under pressure, with an inorganic magnetic anion, FeCl 4 - , has been synthesized. A clear transition to an insulator was observed at 130 K in the temperature dependence of resistance, but no anomaly was seen in the magnetic susceptibility measurement in the same temperature range. Crystal structure analysis of (DODHT)2FeCl4 revealed that the salt crystallized in β″-type crystal structure similarly to the superconducting DODHT salts, and as a result intermolecular interaction is quasi one-dimensional along molecular side-by-side direction.

Ultraviolet photoelectron spectra of one of three Tm@C 82 isomers, Tm@C 82 (II), were measured with synchrotron radiation light source. The spectra resemble those of Ca@C 82 (III), which indicates that these two metallofullerenes have analogous valence electronic structures as well as the cage structures. The spectra of Tm@C 82 (II) and Ca@C 82 (III) are well reproduced by a simulated spectrum obtained with ab initio calculation based on the C 2 (no.5) cage geometry. This finding supports symmetry group determination carried out with NMR measured on Tm@C 82 (II). Because of spectral resemblance, the electronic structure of metallofullerenes seems to be determined solely by the fullerene cage and entrapped atom species.

A dithiane analogue of MeDH-TTP [2-isopropylidene-5-(1,3-dithiolan-2-ylidene)-1,3,4,6-tetrathiapentalene], MeDA-TTP [2-isopropylidene-5-(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene], has been prepared, and crystal structures and electrical properties of MeDA-TTP radical salts have been investigated. Although all the salts are isostructural, conducting behavior differs between the salt with an octahedral anion and the one with a tetrahedral anion; the salts with octahedral anions are metallic, but the ClO 4 salt is semiconductive. A dithiane analogue of DODHT [(1,4-dioxane-2,3-diyldithio)dihydrotetrathiafulvalene], DADOT [2-(1,3-dithiane-2-ylidene)-4,5-(1,4-dioxane-2,3-diyldithio)-1,3-dithiole] has also been synthesized. Crystal structure of the DADOT salt is completely different from that of DODHT superconductors.

The TaF 6 and FeBr 4 salts of BDA-TTP [2,5-bis(1,3-dithian-2-ylidene)-l,3,4,6-tetrathiapentalene] have been prepared and characterized as β-(BDA-TIP) 2 TaF 6 and β-(BDA-TIP) 2 FeBr 4 , respectively. The crystal structure of β-(BDA-TTP) 2 TaF 6 is isostructural to those of the ambient-pressure superconductors β-(BDA-TTP) 2 X (X = SbF 6 , AsF 6 and PF 6 ), but this salt undergoes an Ml (metal-to-insulator) transition instead of a superconducting transition at ambient pressure. The β-(BDA-TTP) 2 FeBr 4 salt, which is isomorphous to the superconductors β-(BDA-TTP) 2 MCl 4 (M = Fe and Ga) under applied pressures, exhibits a phase transition near 170 K and antiferromagnetic ordering with the Neel temperature (T N ) of about 9.5 K at ambient pressure.

The synthesis of dihydrotetrathiafulvalene (DHTTF) donors and the preparation of their charge-transfer (CT) salts have been undertaken to develop new organic metals and superconductors. The molecular structures of methylenedithio-DHTTF (MDHT), 1,4-dioxane-2,3-diyldithio-DHTTF (DODHT), and methylmethylidenedithio-DHTTF (Me-MDHT) are secured by X-ray crystallographic analyses. These DHTTF donors provide CT salts characterized by a wide range of conducting behavior from semiconducting to metallic and superconducting. The crystal structures of CT salts from each category are described.

Monolayers of well-ordered close-packed silica nanoparticles (NPs) with a diameter of 25 nm were spontaneously formed on silicon substrates over a large area and at a high rate via a wet-coating process using a capillary coater. The effects of zeta potential, dispersion solvent, and substrate friction on the NP self-assembly induced by the solvent evaporation were investigated. Experimental results showed that the solvent and the substrate had a larger impact on the order of formed monolayers than the zeta potential did, which are discussed from the viewpoint of the Derjaguin-Landau-Verwey-Overbeek (DLVO) and non-DLVO theories. Based on the above studies, we proposed a solution to fabrication of well-ordered NP monolayers without boundary defects at the surface coverage of ∼1 via the wet-coating process.

Magneto-optical measurements of a quasi-one-dimensional (q1D) organic superconductor (DMET)2I3 has been performed by using a cavity perturbation technique. Several resonant absorption lines, which can be attributed to the q1D periodic orbit resonance (q1D POR), as well as the quite unusual high-order q1D POR coming from the corrugated Fermi surface (FS) in the interlayer direction were observed. Moreover, other harmonic resonances are also observed when the AC electric field is applied along the c*-axis. We will also show its estimated q1D FS from the data analysis where the estimated FS clearly shows why there is no spin-density-wave or charge-density-wave transition in (DMET)2I3 despite having a q1D FS.

This paper presents a simulation study for self-assembling process of colloidal particles into two-dimensional arrays due to capillary immersion force. Discrete element method is used to simulate the dynamics of colloidal particles trapped in a thin liquid film. The previous model is improved in the following two points: a modification of the screening effect of capillary immersion force and introduction of periodic boundary condition. Snapshots provided by the simulations agree well with experimental images taken by atomic force microscopy. The self-assembling process is quantified with pair correlation function and coordination number. At lower coverage, colloidal particles rapidly form small clusters that consist of several particles in the early stage. Subsequently, chain-like structures with some branches are mainly generated. On the other hand, at higher coverage, large domains of hexagonal close-packed (HCP) structures are gradually generated. The rate of the growth of HCP domains is much slower than that of the generation of the small clusters and the chain-like structures.

The study of three kinds of non-tetrathiafulvalene (TTF) donors, 2,5-bis(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene (BDA), 2,5-bis(1,3-dithiolan-2-ylidene)-1,3,4,6-tetrathiapentalene (BDH), and 2-(1,3-dithiolan-2-ylidene)-5-(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene (DHDA), which contain the bis-fused 1,3-dithiole-2-ylidene unit instead of the TTF unit as a π-electron system, has been undertaken to develop new molecular-based organic superconductors, magnetic conductors, and organic metals. The BDA donor produces the superconducting SbF 6 , AsF 6 , and PF 6 salts. The κ-(BDH) 2 FeCl 4 salt is a paramagnetic organic metal stable down to 1.5 K, whereas β-(BDA) 2 FeCl 4 exhibits metallic conducting behavior with a sharp metal-to-insulator (MI) transition (T MI = 113K), and antiferromagnetic ordering with a Neel temperature of near 8.5 K. Several salts of DHDA, a hybrid of BDA and BDH, are found to be metallic.

Several TTF-ligands with Schiff-base type coordination sites have been synthesized to develop new TTF-based metal complexes: tetradentate H2bsae-TTF [4,5-bis(2-salycylideneiminoethylthio)-TTF] and hexadentate macrocyclic-TTF. Both ligands yielded mononuclear metal complexes, [CuII(bsae-TTF)] and [MII(macrocyclic-TTF)](BF4)2 (MII = FeII, CoII, NiII, ZnII). Electrochemical measurements revealed that both the bsae-TTF and macrocyclic-TTF complexes retained the redox properties of TTF moieties. All the metal complexes with macrocyclic-TTF ligand were isostructural octahedral coordination structure. Among them, Co(II) complex showed spin-crossover behaviour above room temperature. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

An assembled compound (BEDT-TTF)2[Mn2Cl5(EtOH)] (1) consisting of two structural lattices of Mn(II)–Cl one-dimensional (1-D) chains and bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) stacking layers was synthesized by electrochemical crystallization. Compound 1 crystallized in triclinic space group P-1 (#2) with a=13.1628(5) A, b=20.3985(9) A, c=7.4966(3) A, α=98.3498(8)°, β=104.980(1)°, γ=74.602(2)°, V=1868.3(1) A3, and Z=2. The 1-D chains and the stacking layers are aligned along the c-axis of the unit cell. The 1-D chain is described as [Mn2Cl5(EtOH)]∞− in which two Mn(II) ions and four Cl− ions form a ladder-like chain with Kagome (cuboidal) sublattices, and the remaining Cl− ion and an ethanol molecule cap the edge-positioned Mn(II) ions of the chains. The BEDT-TTF molecules are packed between the Mn–Cl chains (ac-plane), the intermolecular S·S contacts of which are approximately found in the range 3.440(2)–3.599(2) A. The packing feature of BEDT-TTF molecules is very similar to that of (BEDT-TTF)2ClO4(TCE)0.5 (TCE=1,1,2-trichloroethane) (J. Am. Chem. Soc., 105, 297 (1983)). Regarding the electronic state of each BEDT-TTF molecule, Raman spectroscopic analysis and ESR study revealed the presence of half-valence BEDT-TTF molecules (charge delocalization) in 1. Magnetic measurements clearly demonstrated that the paramagnetic spins on the 1-D chain [Mn2Cl5(EtOH)]∞− arrange antiferromagnetically in the low-temperature region. Additionally, 1 exhibits metallic conductivity in the temperature range 2.0–300 K (σ=21 S cm−1 at 300 K and 1719 S cm−1 at 2.0 K), due to the contribution of the stacked BEDT-TTFs. Consequently, these peculiarities that correspond to antiferromagnetic/metallic conductivity demonstrate the “bi-functionality” of 1.

Palladium(II)- or copper(II)-catalyzed homo-coupling reaction of either trimethylstannyltetrathiafulvalene or tetrathiafulvalenylzinc chloride produces symmetrical bitetrathiafulvalenes (bi-TTFs) in good yields, whereas palladium(0)-catalyzed cross-coupling reaction of tetrathiafulvalenylzinc chloride with 4-iodotetrathiafulvalenes leads to the corresponding unsymmetrically substituted bi-TTFs in moderate-to-high yields. The X-ray analysis of bi-TTF derivatives showed planar structures, and the cyclic voltammetry suggested that bi-TTFs have good donor ability comparable to that of BEDT-TTF. The symmetrical bi-TTFs formed the corresponding CT-complexes and cation radical salts. These CT-complexes and radical salts were found to be metallic or semiconducting, reflecting the effect of stoichiometry control in the dimeric TTF system. The X-ray structures of two cation radical salts revealed a unique stacking, and the precise conducting path in BEDO-bi-TTF·ClO4 was discussed on the basis of MO calculations.

Electrical and optical properties of a potassium (K) -doped film of a hexadecyl chain-linked C 60 ( C60-C16 ) were evaluated by electric conductivity, UV-visible near-IR and Raman spectra. The conductivity of the pristine film (3×10 −7 S cm −1 ) largely increased to 0.1 S cm −1 after doping. The absorption band of C60-C16 anion was observed around 900 nm in the K-doped film. As a result of Raman spectra measurement, it was confirmed that tri- and/or tetra-anions of C60-C16 are formed in the film.

Physical properties up to 600 K are studied for (TMTSF) 2 PF 6 , (TMTTF) 2 PF 6 , (DMET) 2 I 3 , (DMET) 2 AuI 2 , (DIMET) 2 I 3 , (DIMET) 2 AuI 2 and κ-(ET) 2 Cu(NCS) 2 . It has been found that all the compounds decompose between 450 and 500 K by TG-DTA measurement. Electric resistivity and thermopower of the TMTSF and DMET salts are metallic as were expected from their temperature dependence below 300 K. The TMTTF and DIMET salts show constant thermopower, though their resistivity is metallic. This suggests that the TMTTF and DIMET salts are intrinsically non-metallic even above room temperature. Rapid decrease in resistivity found for many of the Q1D salts before their decomposition suggests the partial escape of anions and change in the carrier concentration. κ-(BEDT-TTF) 2 Cu(NCS) 2 shows hysteretic temperature dependence of the resistivity above 300 K.

A new π-electron donor, 2,5-bis(13-dithian-2-ylidene)-1,3,4,6-tetrathia-pentalene (BDA-TTP), which contains no tetrathiafulvalene (TTF) molecule, produces a series ambient-pressure superconductors β-(BDA-TTP) 2 X (X = SbF 6 - , AsF 6 - , and PF 6 - ), in which the values of intermolecular overlap integrals suggest loose donor packing motifs.

Successive metal–insulator transitions in (DIMET) 2 BF 4 were studied by chopped-light ac calorimetry and electron paramagnetic resonance (EPR) measurement. An anomaly due to the metal–insulator transitions has been clearly detected in ac calorimetry between 20 and 35 K. In contrast to other double-column salts (DMET) 2 BF 4 and (DMET) 2 ClO 4 , successive metal–insulator transitions detected in transport properties are shown to be thermodynamic phase transitions. The EPR detected an anomaly only for the lowest transition around 12 K. The properties of the metal–insulator transitions are compared among the DIMET and DMET salts having the double-column structure. A frequency-dependent step in heat capacity was detected around 110 K. The step-like anomaly is attributed to a glass transition due to freezing of the intramolecular motion of the ethylene group in the ET moiety within a DIMET molecule.

Investigations of the tetrathiafulvalene (TTF) derivatives extended by the [sgrave]-bond frameworks, such as saturated heterocycles (3–8) and alkyl groups (9), have been undertaken to explore new molecular-based organic metals. TTF donors with the periphery extended by the cis-fused dioxane ring (3) and by linkage of a dichalocogenolane or dioxane ring (4–6 or 7) produce metallic radical-cation salts. While radical-cation salts of the methylated TTF donor (9a) are semiconductive, the ClO4 and PF6 salts of the ethylated one (9b) exhibit metallic conducting behavior for compressed pellets. The crystal structure of the metallic (4)2AsF6 salt is also presented.

Heat capacity of a quasi-one-dimensional organic conductor (DIMET) 2 I 3 has been measured by chopped-light ac calorimetry below room temperature. An anomaly due to a metal-insulator transition has been clearly detected around 40 K. The magnitude of the anomaly is analyzed through comparison with other Q1D conductors. A possible SDW mechanism is suggested.

The crystal structure and the physical properties of the radical ion salts BMT-TTFI2·FeX4 (X ˭ Br, Cl) and (DMET)2FeBr4 are investigated. The structures of BMT-TTFI2·FeX4 are characterized as the sheets made of dimerized donor molecules and one-dimensional anion chains. These salts show three-dimensional Curie-Weiss behavior accompanied with antiferromagnetic transitions, with the highest Neel temperature (T N= 15 K) among the π-d interaction based magnets for the FeBr4 salt. Within a crystal of (DMET)2FeBr4, the donor molecules form one-dimensional columns, between which magnetic anion sheets are inserted. This salt is metallic down to T MI = 200 K, above which the Curie-Weiss type magnetism is described in terms of donor and anion spins, in spite of the metallic condaction of the salt. Below T MI the magnetism is governed by anion spins, and an antiferromagnetic phase transition takes place at T N=3.5 K.

Temperature dependence of the heat capacities of two organic conductors, (DMET) 2 BF 4 and (DMET) 2 ClO 4 , was measured by chopped-light ac calorimetry between 10 and 300 K. A “Mott-like” nature o...

Cast and spin coat films of C 60 derivatives with a long alkyl chain were prepared. The X-ray analysis confirmed that the cast film formed a layer structure and the spin coat film has an amorphous structure. In the photocurrent spectra of both films, a peak around 720 nm was detected, which corresponds to an absorption peak in its solution. The peak, due to the interaction between the C 60 moieties, is not observed clearly. I (photocurrent) /I (darkcurrent) of the cast film is much larger than that of the spin coat film.

$(\mathrm{DMET}{)}_{2}{\mathrm{FeBr}}_{4}$ which undergoes a metal-insulator transition at ${T}_{c}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}200\mathrm{K}$ has an alternating stacked structure of DMET donor conducting sheets and ${\mathrm{FeBr}}_{4}$ magnetic sheets. Above ${T}_{c}$ it is in a quasi-1D quarter-filled metallic state, where the Curie-Weiss type magnetism is described in terms of ${\mathrm{DMET}}^{+}$ donor spins and ${\mathrm{Fe}}^{3+}$ spins. Below ${T}_{c}$ the magnetism, governed only by ${\mathrm{Fe}}^{3+}$ spins, shows antiferromagnetic order at ${T}_{\mathrm{N}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}3.5\mathrm{K}$. The localized spin feature of $\ensuremath{\pi}$ carriers above ${T}_{c}$ , which contradicts metallic conduction, is reasonably well understood in terms of the sliding motion of a Wigner lattice state.

The electrical resistivity under hydrostatic pressure was measured for the double-column organic conductors, (DMET) 2 BF 4 , (DMET) 2 ClO 4 and (DIMET) 2 BF 4 , where DMET and DIMET are dimethyl(ethylenedithio)diselenadithiafulvalene and dimethyl(ethylenedithio)tetrathiafulvalene, respectively. Each of these conducting salts undergoes three phase transitions at and below the metal-to-semiconductor transition temperature of about 30 K at 0 kbar. The temperatures of the metal-to-insulator/semiconductor (M-I) transition and two other ones were determined and the temperature—pressure phase diagrams were constructed. It was found that the second up to 15 kbar and third transition temperatures of (DMET) 2 BF 4 and (DMET) 2 ClO 4 are almost independent of pressure. The characteristics of the phase transitions are discussed by comparing the pressure dependence of the transition temperatures with that of single-column organic conductors.

Refractive-index changes ( Δn ) in Ge-doped silica glass exposed to a KrF excimer laser were investigated by measurements of the diffraction efficiency from a grating formed using a phase mask. The Δn of 3.2 × 10 −3 was achieved for a hydrogen-treated (150 atm, 2 weeks, room temperature) sample after a KrF laser irradiation (25 Hz, 0.5 J/cm 2 /pulse, 27 kJ/cm 2 ), while the Δn obtained for a non-treated sample is less than 10 −4 . The depth profile of the Δn for the hydrogen-treated sample is limited by the distribution in the hydrogen concentration inside the sample, while it is determined by the attenuation of the ultraviolet light for the non-treated sample.

The magnetoresistance of a quasi-one-dimensional (Q1D) organic superconductor, (DMET) 2 I 3 , where DMET is dimethyl(ethylenedithio)diselenadithiafulvalene, was measured up to 30 T at 1.5 K. An electrical current was applied perpendicular to the conducting a b plane and a magnetic field is rotated in the a b plane. An anomalous hump of the magnetoresistance reported previously was observed at 7 T between -15° and 15° from the most conducting b -axis. It was found that the hump has a fine structure at higher magnetic fields with two additional sharp local minima at about ±3°. Partial disappearance of the Q1D Fermi surface at a critical angle, where a kind of quantum limit is realized, is proposed to interpret the fine structure.

Comparative study is presented for the in-plane angular effect of magnetoresistance of quasi-one-dimensional organic conductors, (DMET) 2 AuBr 2 and (TMTSF) 2 ClO 4 . The magnetoresistance for the magnetic and electrical fields parallel and perpendicular to the most conducting plane, respectively, was measured at 4.2 K and up to 7.0 T. (DMET) 2 AuBr 2 shows an anomalous hump in the field-orientation dependence of the magnetoresistance for the magnetic field nearly parallel to the most conducting axis and this is very similar to what previously reported for (DMET) 2 I 3 . Weak anomaly was detected for the magnetoresistance of (TMTSF) 2 ClO 4 in the Relaxed state, while no anomaly was observed in the SDW phase in the Quenched state. By comparing the numerical angular derivatives of the magnetoresistance, it is shown that the anomaly in the in-plane angular effect continuously develops from zero magnetic field and is closely related to the quasi-one-dimensional Fermi surface. A simple method is proposed to e...

The surface roughness and stability of S or Se-terminated GaAs(111)B has been investigated by reflection high energy electron diffraction (RHEED), Auger electron spectroscopy (AES) and atomic force microscopy (AFM). RHEED streak patterns of S-terminated GaAs(111)B surfaces turned into spot patterns with increasing heating temperature. Se-terminated surfaces, on the other hand, kept the streak pattern until 550°C heating. AES measurements showed that the roughness of the S-terminated surface increased by 400°C heating, while the Se-terminated surface was stable up to 500°C heating. AFM images of both surfaces showed that the roughness of the S-terminated surface was larger than that of the Se-terminated surface. These measurements have revealed the difference in thermal stability between the S- and Se-terminated surfaces.

The structure of ultrathin epitaxial films of layered NbSe 2 and TaSe 2 grown on Se-terminated GaAs(111) substrates was determined by grazing incidence X-ray diffraction. It was found that the crystallographic polytypes of the films were dependent on the growth temperatures. The temperature range for the growth of octahedrally coordinated TaSe 2 was different from that of the bulk. Disappearance of 3R-type portion in NbSe 2 at a high growth temperature will be favorable to fabricate superconducting ultrathin epitaxial films.

Magnetoresistance of an organic superconductor, (TMTSF) 2 PF 6 , where TMTSF is tetrameth- yltetraselenafulvalene, was measured in the spin-density-wave state for the electrical current perpendicular to the conducting a b -plane and the magnetic field within the plane. The magnetic field dependence of the magnetoresistance shows an anomalous dip at 1.2 T ( B d ). The value of B d is independent of temperature and field orientation within the a b -plane below 4.2 K and the dip anomaly is more distinct at lower temperature. Clear negative magnetoresistance appears below 4.2 K. We attempted to interpret the angular-independent dip anomaly in terms of the closed orbital motion of the carriers on the side of the Fermi tube and its disappearance at a kind of quantum limit.

Epitaxial growth of TiSe2 films on Se‐terminated GaAs(111)B substrates were carried out at different growth temperature by molecular beam epitaxy. Grown films have been investigated by reflection high energy electron diffraction, Auger electron spectroscopy, and measurements of resistivity parallel to the surface. TiSe2 epitaxial films have been obtained at various temperatures, but the optimum growth temperature was determined to be 400 °C. A charge density wave transition has been observed in the resistivity of the film grown at 400 °C, indicating that it has a good quality comparable to a bulk single crystal.