Akinari Kasai

Structure and electronic transport of highly conductive Langmuir-Blodgett films of tridecylmethylammonium-Au(dmit)2

Electronic transport measurements are reported for Langmuir-Blodgett (LB) films of tridecylmethylammonium-Au(dmit)2 for 300-4 K. The conductivity after electrochemical oxidation is 30-50 S/cm at room temperature, increases with decreasing temperature, and begins decrease at about 200 K. The conductivity at lower temperatures is explained by two-dimensional variable range hopping (2D VRH). The thermoelectric power (S) is positive and well fitted by a linear combination of the temperature dependence of 2D VRH (Sv\proptT1/3) and that of metal (Sm\proptT). These results can be explained by a model in which highly conductive metallic regions are separated by thin weakly conductive regions. The UV/visible absorption spectra and the X-ray diffraction patterns indicate that a large structural change occurs accompanied by electrochemical oxidation.

Wavelength conversion of quadrupled Nd:YAG laser radiation to the vacuum ultraviolet by anti‐Stokes stimulated Raman scattering

Up‐converted beams of a conventional quadrupled Nd:YAG laser by anti‐Stokes Raman scattering in hydrogen are characterized as a vacuum ultraviolet light source. The beams diverge with the increase of the hydrogen pressure and also with the increase of the order of anti‐Stokes scattering. Although the profiles of anti‐Stokes beams vary from a Gaussian‐like shape to a typical ring shape, the maximum energy conversion is always obtained with a near‐Gaussian beam profile. The output energy ranges from 5.9 mJ for the first‐order anti‐Stokes wave (240 nm) to 8 μJ for the ninth‐order anti‐Stokes wave (133 nm). The energy of the sixth‐order anti‐Stokes wave (160 nm) fluctuates ±45% of the average output energy. The beam characteristics are described well by a model on the basis of phase matching between four waves related to each Raman process.

Low outgassing residual gas analyzer with a beryllium–copper‐alloy‐flanged ion source

By using a newly developed beryllium–copper (BeCu)‐alloy ConFlat flange to house the hot‐cathode ion source, a remarkable decrease in the outgassing from a quadrupole residual gas analyzer (RGA) has been achieved. The reduction in outgassing between the new BeCu‐flanged RGA and an ordinary stainless‐steel RGA of otherwise similar design was a factor of 60 or more in the 10−9 Pa total pressure range. From these results, the possibility of high accuracy residual gas analysis below 10−9 Pa is introduced.

Electronic transport in Langmuir-Blodgett films of metal-(dmit)2

Thermoelectric power in highly conductive Langmuir-Blodgett films of tridecylmethylammonium-Au(dmit)2 (σRT 30−50 Scm) was examined. The metallic nature of this material is suggested from the results of the thermoelectric power. The resistivity increased with aging, however the thermoelectric power was invariant. These results suggest that the metallic nature of the film is preserved after aging. The newly developed conductive LB films of didecyldimethylammonium-Pd(dmit)2 showed a high conductivity of 5.1 Scm at room temperature. From the temperature dependence of the conductivity, semiconductor-like transport was suggested.

Electrical Conductivity and Thermoelectric Power of Langmuir-Blodgett Films of Tridecylmethylammonium-Au(dmit)2

Thermoelectric power and electrical conductivity in Langmuir-Blodgett (LB) films of tridecylmethylammonium-Au(dmit)2 have been measured in the temperature range of 300 to 125 K. The conductivity in the lateral direction of the LB films is 30 S/cm at room temperature. The conductivity increases down to around 200 K, and decreases below that temperature. The thermoelectric power is positive and its temperature dependence shows a metallic behavior in the temperature range measured. The average value in thermoelectric power at room temperature is 20 µV/K.

HALL EFFECT OF METALLIC LANGMUIR-BLODGETT FILMS BASED ON BISETHYLENEDIOXYTETRATHIAFULVALENE COMPLEX OF DECYLTETRACYANOQUINODIMETHANE

The Hall effect of a metallic Langmuir–Blodgett film based on bisethylenedioxytetrathiafulvalene complex of decyltetracyanoquinodimethane has been investigated using a double ac Hall method. The polarity of the Hall coefficient is positive over the measuring temperature range. The carrier density is of the order of 1021 cm−3, almost independent of temperature, and the Hall mobility, of around 0.05 cm2 (V s)−1 at room temperature, is in a single activated process. The Hall results have been interpreted with an inhomogeneous structure model, and support that metallic domains are developed throughout the whole sample.

Entrapment pump: Noble gas pump for use in combination with a getter pump

A new type of minicapture pump which acts on noble gas species and operates in combination with a getter pump has been developed. We call it the “entrapment pump.” The pump is a single Penning cell (φ7×h5 mm anode) whose cathode can be heated during pumping to more than 1000 °C. After the getter pump is working, the pump cathode is activated by heating. Then, in a second step, the pump is operated by applying the high voltage and residual noble gas (argon) pumped by burial, not sputtering. Weakly buried noble gas within the pump cell is re-emitted by intentional heating. This is performed during every pumpdown following any exposure to atmospheric air and the surface of the cathode is thereby cleaned and renewed. As a result, noble gas atoms are buried in a pure metal surface when high voltage is applied and no burst of contamination species is generated from the cathode surface when the pump is initially started. The re-emission of previously pumped noble gas, acting as a gas source, is also minimized fo...

Scanning Tunneling Microscopy Study of K-(BEDT-TTF)2Cu(NCS)2 and α(BEDT-TTF)2I3

Abstract Scanning tunneling microscopy (STM) measurements were performed for bis(ethylenedithio)-tetrathiafulvalene (BEDT-TTF)-based radical salts, K-(BEDT-ITF)2CU(NCS)2 and α-(BEDT-TTF)2I3. Each STM image agreed well with the corresponding bulk structure determined by X-ray diffraction method.

Optical Absorption of KCl Single Crystals in the Spectral Region from 1.1 to 7.0 eV

The reflectivity of KCl in the region from 1.1 to 6.2 eV has no structure and increases slightly with photon energy. Moreover, it depends little on the origin of the specimen. The optical density of KCl is small and increases linearly with photon energy in the region up to 5.5 eV. In this region, the optical density is almost independent of the thickness of the specimen and is therefore attributed to absorption at the surface. At 5.5 eV, however, the optical density rises steeply and depends on the thickness. However, the value extrapolated to zero thickness connects smoothly with the optical density below 5.5 eV. In KCl, the surface levels cover the band gap of the bulk. The levels which lie more than 4.0 eV below the vacuum level are occupied by electrons, and there seems to be a continuous and homogeneous distribution of the surface level.

Highly Sensitive Precise Double AC Hall Effect Apparatus for Wide Resistance Range.

A double AC apparatus having new functions is described. So far, in a highly sensitive double AC apparatus, the false signal generation due to nonlinearity at terminal junctions of the specimen and induced emf has been a decisive drawback. In the present apparatus, which eliminates the induced emf in situ by using specially designed transformers, the false signal can be completely removed. This result enables us to measure, with high precision, the Hall emf down to a voltage level comparable to the thermal noise of the specimen. In addition, the current shunting effect by capacitances in the region of high specimen resistance is reduced by the proper arrangement of lead wire and by the bootstrapping technique. The upper limit of specimen resistance for which the Hall effect is measurable with the double AC method is extended up to 100 G Ω.