Thomson scattering system at the Tokyo electron beam ion trap

A Thomson scattering system has been installed at the Tokyo electron beam ion trap for probing characteristics of the electron beam. A YVO4 green laser beam was injected antiparallel to the electron beam. The image of the Thomson scattering light from the electron beam has been observed using a charged-coupled device camera. By using a combination of interference filters, the spectral distribution of the Thomson scattering light has been measured. The Doppler shift observed for the scattered light is consistent with the beam energy. The beam radius dependence was investigated as a function of the beam energy, the beam current, and the magnetic field at the trap region. The variation of the measured beam radius against the beam current and the magnetic field were similar to those in Herrmann's prediction. The beam radius as a function of the beam energy was also similar to Herrmann's prediction but seemed to become larger at low energy. (C) 2002 American Institute of Physics.

RAMAN-SCATTERING AND SCANNING ELECTRON-TUNNELING STUDIES OF METAL LIQUID-LIKE FILMS PRODUCED FROM SILVER AND GOLD SOLS

Surface-enhanced Raman scattering (SERS) excited at several visible wavelengths and recorded using a cooled charged-coupled device detector is reported from the mobile, interfacial, liquid-like metal films (MELLFs) formed when solutions of metal complexes or pyridine in chlorocarbon solvents are mixed with aqueous sols of silver or gold. MELLF formation has not previously been reported for gold sols or for pyridine as stabilizer. Comparison of the spectra for the MELLFs formed from individual metal complexes and from 50:50 mixtures show that the spectral patterns observed for the latter are distinctive and are not generally equivalent to the sum of the spectra associated with the individual complexes, in contrast to the situation observed for sols where the individual spectra do appear to be additive. Raman scattering from both gold and silver MELLFs is readily observed at excitation wavelengths in the red, around 750 nm, but at 514 nm only that from silver films is detectable. These findings are considered in terms of particle size and absorption band intensities. A preliminary study of the film surface topography and particle size was carried out by scanning tunnelling electron microscopy (STM) of Ag MELLFs deposited on gold-coated mica substrates. Computer-processed images of the STM data show the presence on the film surface of finger-like bars, 200-400 nm long with approximately square cross-section, 40-60 nm side, together with other smaller cuboid features. The implications of these findings in relation to SERS are briefly considered.

Photometric and fundamental plane studies of galaxies

Determining the morphological parameters that describe galaxies has always been a challenging task. The studies on the correlations between different photometric as well as spectroscopic parameters of the galaxies help in understanding their structure, properties of the stars and gas which constitute the galaxy, the various physical and chemical processes which determine the properties, and galaxy formation and evolution. In the last few decades, the advent of Charge Coupled Devices (CCDs) and near infrared arrays ha\·e provided quick and reliable digitized data acquisition, in the optical and near infrared bands. This has provided an avalanche of data, which can be processed using sophisticated image analysis techniques to obtain information about the morphology of galaxies. The photometric analysis performed in this thesis involve the extraction of structural parameters of early type gala.xies imaged in the near infrared K (2.2ttm) band, obtaining correlations between these, parameters and using them to constrain the large scale properties of galaxi,~s.

Electrical transport in disordered and ordered magnetic domains under pressures and magnetic fields

Magnetic M( T, H, P) and electrical transport.( T, H, P) measurements in a strong spin-lattice-charge coupled La(0.7)Ca(0.3)MnO(3) system have been conducted. The application of H and P leads to the formation of different magnetic domain structures in the vicinity and below the polaronic-to-ferromagnetic transition temperature. The charge mobility is more sensitive to the variation of the spatial wave function overlap between Mn(3+) eg and O(2-) 2p orbitals due to the applied compacting pressure rather than the relative spin orientation between neighbouring Mn ions when the magnetic field is applied. In spite of the presence of different magnetic domain structures due to the sample history, the effect of magnetic field and pressure is less pronounced at lower temperatures on electrical transport properties.

A method for the digital image analysis of ceramic grains based on shape factor segmentation

A very simple and robust method for ceramics grains quantitative image analysis is presented. Based on the use of optimal imaging conditions for reflective light microscopy of bulk samples, a digital image processing routine was developed for shading correction, noise suppressing and contours enhancement. Image analysis was done for grains selected according to their concavities, evaluated by perimeter ratio shape factor, to avoid consider the effects of breakouts and ghost boundaries due to ceramographic preparation limitations. As an example, the method was applied for two ceramics, to compare grain size and morphology distributions. In this case, most of artefacts introduced by ceramographic preparation could be discarded due to the use of perimeter ratio exclusion range.

Integration of room temperature single electron transistor with CMOS subsystem

The single electron transistor (SET) is a charge-based device that may complement the dominant metal-oxide-semiconductor field effect transistor (MOSFET) technology. As the cost of scaling MOSFET to smaller dimensions are rising and the the basic functionality of MOSFET is encountering numerous challenges at dimensions smaller than 10nm, the SET has shown the potential to become the next generation device which operates based on the tunneling of electrons. Since the electron transfer mechanism of a SET device is based on the non-dissipative electron tunneling effect, the power consumption of a SET device is extremely low, estimated to be on the order of 10^-18J. The objectives of this research are to demonstrate technologies that would enable the mass produce of SET devices that are operational at room temperature and to integrate these devices on top of an active complementary-MOSFET (CMOS) substrate. To achieve these goals, two fabrication techniques are considered in this work. The Focus Ion Beam (FIB) technique is used to fabricate the islands and the tunnel junctions of the SET device. A Ultra-Violet (UV) light based Nano-Imprint Lithography (NIL) call Step-and-Flash- Imprint Lithography (SFIL) is used to fabricate the interconnections of the SET devices. Combining these two techniques, a full array of SET devices are fabricated on a planar substrate. Test and characterization of the SET devices has shown consistent Coulomb blockade effect, an important single electron characteristic. To realize a room temperature operational SET device that function as a logic device to work along CMOS, it is important to know the device behavior at different temperatures. Based on the theory developed for a single island SET device, a thermal analysis is carried out on the multi-island SET device and the observation of changes in Coulomb blockade effect is presented. The results show that the multi-island SET device operation highly depends on temperature. The important parameters that determine the SET operation is the effective capacitance Ceff and tunneling resistance Rt . These two parameters lead to the tunneling rate of an electron in the SET device, Γ. To obtain an accurate model for SET operation, the effects of the deviation in dimensions, the trap states in the insulation, and the background charge effect have to be taken into consideration. The theoretical and experimental evidence for these non-ideal effects are presented in this work.

TCAD for PV: a fast method for accurately modelling metal impurity evolution during solar cell processing

Coupled device and process silumation tools, collectively known as technology computer-aided design (TCAD), have been used in the integrated circuit industry for over 30 years. These tools allow researchers to quickly converge on optimized devide designs and manufacturing processes with minimal experimental expenditures. The PV industry has been slower to adopt these tools, but is quickly developing competency in using them. This paper introduces a predictive defect engineering paradigm and simulation tool, while demonstrating its effectiveness at increasing the performance and throughput of current industrial processes. the impurity-to-efficiency (I2E) simulator is a coupled process and device simulation tool that links wafer material purity, processing parameters and cell desigh to device performance. The tool has been validated with experimental data and used successfully with partners in industry. The simulator has also been deployed in a free web-accessible applet, which is available for use by the industrial and academic communities.

Mammography equipment

Mammography is one of the most technically demanding examinations in radiology, and it requires X-ray technology designed specifi cally for the task. The pathology to be imaged ranges from small (20–100 μm) high density microcalcifications to ill-defi ned low contrast masses. These must be imaged against a background of mixed densities. This makes demonstrating pathology challenging. Because of its use in asymptomatic screening, mammography must also employ as low a radiation dose as possible.

Decoherence of two Josephson charge qubits coupled via sigma(x)sigma(x)-type coupling and exposed to sigma(x) noise

Decoherence properties of two Josephson charge qubits coupled via the sigma(x)sigma(x) type are investigated. Considering the special structure of this new design, the dissipative effects arising from the circuit impedance providing the fluxes for the qubits' superconducting quantum interference device loops coupled to the sigma(x) qubit variables are considered. The results show that the overall decoherence effects are significantly strong in this qubit design. It is found that the dissipative effects are stronger in the case of coupling to two uncorrelated baths than are found in the case of one common bath.

Coherent charge and spin transfer in a quantum dot coupled to a mesoscopic ring

We study the effect of coherent charge and spin fluctuations in a mesoscopic device composed of a quantum dot and an Aharonov-Bohm ring. We show that, while the charge fluctuations suppress the persistent current algebraically as a function of the level spacing of the ring, the spin fluctuations give rise to a completely different behavior. We discuss the origin of this difference in relation to the peculiar nature of the ground state in the Kondo limit. (C) 2003 Elsevier B.V. All rights reserved.

Multicomponent charge transport in electrolyte solutions

The work presented in this thesis investigates the mathematical modelling of charge transport in electrolyte solutions, within the nanoporous structures of electrochemical devices. We compare two approaches found in the literature, by developing onedimensional transport models based on the Nernst-Planck and Maxwell-Stefan equations. The development of the Nernst-Planck equations relies on the assumption that the solution is infinitely dilute. However, this is typically not the case for the electrolyte solutions found within electrochemical devices. Furthermore, ionic concentrations much higher than those of the bulk concentrations can be obtained near the electrode/electrolyte interfaces due to the development of an electric double layer. Hence, multicomponent interactions which are neglected by the Nernst-Planck equations may become important. The Maxwell-Stefan equations account for these multicomponent interactions, and thus they should provide a more accurate representation of transport in electrolyte solutions. To allow for the effects of the electric double layer in both the Nernst-Planck and Maxwell-Stefan equations, we do not assume local electroneutrality in the solution. Instead, we model the electrostatic potential as a continuously varying function, by way of Poisson’s equation. Importantly, we show that for a ternary electrolyte solution at high interfacial concentrations, the Maxwell-Stefan equations predict behaviour that is not recovered from the Nernst-Planck equations. The main difficulty in the application of the Maxwell-Stefan equations to charge transport in electrolyte solutions is knowledge of the transport parameters. In this work, we apply molecular dynamics simulations to obtain the required diffusivities, and thus we are able to incorporate microscopic behaviour into a continuum scale model. This is important due to the small size scales we are concerned with, as we are still able to retain the computational efficiency of continuum modelling. This approach provides an avenue by which the microscopic behaviour may ultimately be incorporated into a full device-scale model. The one-dimensional Maxwell-Stefan model is extended to two dimensions, representing an important first step for developing a fully-coupled interfacial charge transport model for electrochemical devices. It allows us to begin investigation into ambipolar diffusion effects, where the motion of the ions in the electrolyte is affected by the transport of electrons in the electrode. As we do not consider modelling in the solid phase in this work, this is simulated by applying a time-varying potential to one interface of our two-dimensional computational domain, thus allowing a flow field to develop in the electrolyte. Our model facilitates the observation of the transport of ions near the electrode/electrolyte interface. For the simulations considered in this work, we show that while there is some motion in the direction parallel to the interface, the interfacial coupling is not sufficient for the ions in solution to be "dragged" along the interface for long distances.

Nonvolatile multilevel data storage memory device from controlled ambipolar charge trapping mechanism

The capability of storing multi-bit information is one of the most important challenges in memory technologies. An ambipolar polymer which intrinsically has the ability to transport electrons and holes as a semiconducting layer provides an opportunity for the charge trapping layer to trap both electrons and holes efficiently. Here, we achieved large memory window and distinct multilevel data storage by utilizing the phenomena of ambipolar charge trapping mechanism. As fabricated flexible memory devices display five well-defined data levels with good endurance and retention properties showing potential application in printed electronics.

Efficient charge transfer and field-induced tunneling transport in hybrid composite device of organic semiconductor and cadmium telluride quantum dots

Temperature and photo-dependent current-voltage characteristics are investigated in thin film devices of a hybrid-composite comprising of organic semiconductor poly(3,4-ethylenedioxythiophene): polystyrenesulfonate (PEDOT: PSS) and cadmium telluride quantum dots (CdTe QDs). A detailed study of the charge injection mechanism in ITO/PEDOT: PSS-CdTe QDs/Al device exhibits a transition from direct tunneling to Fowler-Nordheim tunneling with increasing electric field due to formation of high barrier at the QD interface. In addition, the hybrid-composite exhibits a huge photoluminescence quenching compared to aboriginal CdTe QDs and high increment in photoconductivity (similar to 400%), which is attributed to the charge transfer phenomena. The effective barrier height (Phi(B) approximate to 0.68 eV) is estimated from the transition voltage and the possible origin of its variation with temperature and photo-illumination is discussed. (C) 2015 AIP Publishing LLC.

Charge symmetry in ^(13)N and ^(13)C a coupled-channel model

A set of coupled-channel differential equations based on a rotationally distorted optical potential is used to calculate the wave functions required to evaluate the gamma ray transition rate from the first excited state to the ground state in ^(13)C and ^(13)N. The bremsstrahlung differential cross section of low energy protons is also calculated and compared with existing data. The marked similarity between the potentials determined at each resonance level in both nuclei supports the hypothesis of the charge symmetry of nuclear forces by explaining the deviation of the ratios of the experimental E1 transition strengths from unity.

Device for charge- and spin-pumped current generation with temperature-induced enhancement

We have proposed a device, a superconducting-lead/quantum-dot/normal-lead system with an ac voltage applied on the gate of the quantum dot induced by a microwave, based on the one-parameter pump mechanism. It can generate a pure charge- or spin-pumped current. The direction of the charge current can be reversed by pushing the levels across the Fermi energy. A spin current arises when a magnetic field is applied on the quantum dot to split the two degenerate levels, and it can be reversed by reversing the applied magnetic field. The increase of temperature enhances these currents in certain parameter intervals and decreases them in other intervals. We can explain this interesting phenomenon in terms of the shrinkage of the superconducting gap and the concepts of photon-sideband and photon-assisted processes.