Search

Deoxyribonucleic acid (DNA) is one of the most important biomolecules that govern the genetic information of life, and recently it has attracted attention as a functional material for electronic device applications such as sensors [1]. In the application of DNA to electronic devices, it is necessary to form a flat thin film at the nanometer (nm) level for heterogeneous film stacking and patterning. We have been developing nm flat DNA thin films by laser molecular beam deposition (LMBD) method, and also fabricated a quartz crystal microbalance sensor (QCM) for volatile organic compound (VOC) detection and evaluated its VOC detection characteristics to explore the possibility of sensor applications of the DNA solid-state thin films [2].

Depending primarily on the energy resource and technology, the human civilization is classified into several generations: G1 (Hunting), G2 (Agricultural), G3 (Coal/Industrial: 18-19C), G4 (Electric/Electronic: 20C-), and G5~ (Quantum/Metaverse: IoT/AI, 21C). Recent progress in science and technology is so fast that it is providing us with not only future dreams but also fatal risks for our world by the dictators and autonomous domination of IoT/AI.

Currently, energy consumption in the planet is high, public awareness of energy consumption, environmental protection and steady progress in the deregulation of conventional energy, distributed generation systems (based on hydrogen) have attracted increased interest. Fuel cell (FC) base and high-temperature systems also have great potential in future single-source or multi-source (hybrid- HSE) applications due to their rapid technological development and numerous benefits such as well, as the appreciable efficiency, low emission (greenhouse gases) and flexible modular technology. Dynamic models for the main components of the system, namely the photovoltaic (PV) energy conversion system, fuel cells, electrolysers, electric power interconnection circuits, protective battery, storage tank of hydrogen, the gas compressors are developed. Two renewable energy modes, a photovoltaic field and a solid oxide fuel cell (SOFC) or Dynamics of proton exchange membrane fuel cells (PEMFC) with hydrogen storage system for generating part of system electrical energy is presented. Feasibility of using fuel cell (FC) for this system is evaluated by means of simulations. The electrical dynamic model, temperature change and dual layer capacity effect are considered in all simulations. Photovoltaic system (PV) output current is connected to the bus. Using a MPPT (maximum power point tracker) which is an electronic DC to DC converter that optimizes the match between the solar array and utility grid. The proposed system utilizes an electrolyser (EL) to generate hydrogen and a tank for storage. Therefore, there is no need for batteries. Moreover, the generated oxygen could be used in FC’s system and other applications. Moreover, such as the photovoltaic system, it is possible to connect fuel cell (FC) output voltage to DC bus alternatively. A controller model is presented to control flow of energy of system, hydrogen and oxygen to FC and improve transient and steady state responses of the output voltage to load disturbances. Simulations are carried out via MATLAB/SIMULINK and results show that the load tracking and output voltage are acceptable.

Desalination of seawater is needed in Algeria, as an option to secure the supply of drinking water to populations in coastal cities and meet the rapid increase of demand for water in agriculture and industry sectors. The biggest constraints of this system are its energy consumption and environmental impacts due to the discharges of brine in the natural environment. Today, more than 17,000 desalination plants worldwide produce about 72 million m3/d, while the global production capacity of drinking water is about 600 million m3/d. In Algeria, the production of desalination plants amounts to 2.3 million m3/d. Operating costs are mainly affected by the power stations, but the significant decreases in costs makes desalination increasingly competitive. Any approach aiming to generalize desalination should be viewed with caution. Indeed, the option of large-scale desalination results in the consumption of large amounts of electrical energy. Practically all the additional electricity produced in Algeria is currently thermal, the risk of a sharp increase in greenhouse gases emissions and discharges of untreated brine is great. However, options of low CO2 emissions are possible. The spinnerets of the most efficient desalination should be promoted: reverse osmosis with optimization, in combination with thermal power plants, energy recovery, and improvement of existing installations. Renewable energies (wind, solar photovoltaic, and concentrated solar power) applied to desalination are tracks for the future, even if their development is linked to issues of funding and competitiveness. Desalination is thus presented as an option for adaptation to climate change; the adoption should not intervene in substitution to other possibilities of “sustainability”, such as the rational use of water. It should moreover favor the production of drinking water for human consumption.

In this contribution a particular attention is being given to the strategic objective for the establishment of a North Africa (NA) countries cooperation on water and clean energy superhighway as the solution to regional energy challenges, water shortages, climate change and other environmental problems arising from the current fossil-fuel heavy global energy paradigm. Advanced and technical know-how and resources of Japan, through the Sahara Solar Breeder (SSB) project, can facilitate to achieve sustainable development in the region, cooperation to accelerate and expand its research activity with ambitious quantitative targets for solutions between the growing water crisis in NA and energy resources (fossil and renewables energies (RE)). With global energy demand set to rise significantly over the next 15 years, there will be a pressing need for fresh investment in new output capacity across the entire water/energy supply chain. It is still believed and emphasized that Photovoltaic (PV) will be a significant contributor within a portfolio of energy sources in the coming 10–20 years and that SSB is providing science and technology that are poised to play a transformative role in providing clean and sustainable water/energy for the whole world. Japan's energy/water innovative strategy for NA is encouraging since problems cannot be solved by one country alone hence local, regional and global cooperation is crucial.

A high-performance spin filter tunnel junction composed of an epitaxial oxide heterostructure is reported. By independently controlling the magnetic orientations of ferromagnetic tunnel barrier and electrode layers, a tunnel magnetoresistance ratio exceeding 120% is obtained purely by the spin filtering effect. A newly introduced spin filter material, Pr0.8Ca0.2Mn1-yCoyO3, is shown to be useful for building novel multibarrier spintronic tunnel devices due to its composition-controlled magnetic hardness.

We have investigated the structural and electrical characteristics of two kinds of block co-oligomers, 5,5″-Bis(2-pyridyl)-2,2′:5′,2″-terthiophene (5A) and 2,5-Bis(2-(2′-thienyl)-pyridine-5-yl)thiophene (5B), which are composed of electron-donating thiophene and electron-withdrawing pyridine rings. At the view of building block units, the amount of the module units included in these molecules is completely equivalent to each other. X-ray diffraction patterns of 5A and 5B thin films grown on atomically flat α -Al 2 O 3 (0001) substrates indicated a high degree of orientation along the c- axis. Field-effect transistors (FETs) of 5A and 5B thin films were fabricated and evaluated without exposure to air. The FETs based on 5A active layers exhibited p -type behavior with a mobility of ~ 10 −3 cm 2 /V·s and an on–off ratio of 10 4 , while no switching behavior was observed in FETs based on 5B active layers. The lower highest occupied molecular orbital (HOMO) of 5B than that of 5A in the quantum-chemical calculation might explain these FET behaviors. Thus, HOMO, lowest unoccupied molecular orbital (LUMO) levels and FET actions of the co-oligomer molecules that consist of the same amount of building blocks can be controlled by the sequence of electron-donating and electron-withdrawing building blocks.

Energy security, economic growth and environmental protection are the national energy policy drivers of any country of the world. Scientists, governments, and industries are witnessing the long-term consequences of energy consumption and foresee catastrophic outcomes if alternative methods of energy production are not developed and utilised to meet the needs of our global economy. In recent years, PV is proposed as a competitive energy policy and a step forward to the target of sustainable development and environmental friendly energy source. In this contribution a particular attention is being given to the joint event that bring together the relevant parties, the University of Sciences and Technology of Oran (USTO), Japan International Corporation and Japan Science and Technology Agencies (JICA, JST) to develop a long-term vision and strategy to boost the ideas for the realization and the development of the Sahara Solar Breeder (SSB) project. SSB advocates the view of undertaking collaborative basic, applied and development research, as well as industrial production and technical, commercial and financial support services to implement photovoltaic solar energy systems. The strategic objective is the establishment of a Global Clean Energy Superhighway as the solution to global energy challenges, water shortages, levelling of electric power supply in the world, climate change and other environmental problems arising from the current fossil-fuel heavy global energy paradigm [1] . This project will tackle the key challenges and issues related to the field of PV putting forward the USTO perspective and promoting its R/D activities by a collaborative research plan between Japan and Algeria. This event also seeks to identify the most important challenges facing both the research and economic sectors and put forward new strategies that will identify the required skills to transform the research prospects of USTO based on the analysis and prospect of elementary processes and system design.

We have fabricated epitaxial Pr 0.8 Ca 0.2 MnO 3 (PCMO) insulator layers sandwiched between Al top electrodes and epitaxial La 0.6 Sr 0.4 MnO 3 bottom electrode layers on (LaAlO 3 ) 0.3 –(Sr 2 AlTaO 6 ) 0.7 (1 0 0) substrates. Various sizes of metal/insulator/metal device structures were formed by photolithography and Ar ion milling. Device size dependence of Al/PCMO interface resistances was well fitted by series-parallel equivalent circuit, indicating several types of different resistance components exist at the Al/PCMO interfaces. These different resistance components suggest that defects might distribute inhomogeneously at the Al/PCMO interfaces which exhibit the resistance switching.

Effect of the hydrogen radical on the reduction of a silicon tetrachloride (SiCl4) source was studied. The hydrogen radicals were generated using a tungsten (W) filament in a generation chamber, and were remotely supplied to another reaction chamber. The density of the hydrogen radical was estimated from the optical transmittance of 600-nm-wavelength light through phosphate glass doped with tungsten oxide (WO3). Lifetime of the hydrogen radical seemed sufficiently long, and its density as supplied to the reaction chamber was estimated to be on the order of 1012 cm−3. Signal intensity of the peak corresponding to SiCl4 (m/z = 170) detected by quadrupole-mass measurement was confirmed to decrease owing to the reaction with the remotely-supplied hydrogen radical. This indicates the possibility that chemically-stable SiCl4, as one of the by-products of the Siemens process, can be reduced to produce silicon.

The effect of doping a wide range of transition metals (TMs) including V, Cr, Mn, Fe, Co, and Ni into rutile TiO2 films grown on Nb-doped TiO2(110) single-crystal substrates was investigated by photoemission spectroscopy and X-ray absorption spectroscopy. For all TM-doped TiO2 films, the Ti 2p and O 1s core levels were similarly shifted to lower binding energies with increasing film thickness and the shifts were similarly saturated at a film thickness of about 15 nm. These peak shifts could be interpreted in terms of the Fermi level shift, indicating that dopants trap excess electrons from the Ti 3d band like acceptors. The present systematic data revealed that the magnitude of the saturated Fermi level shift correlates well with the effective charge transfer energy.

We have investigated the surface magnetization anisotropy of 5 at% Co doped rutile TiO2 (1 1 0) using magnetization-induced optical second harmonic generation (MSHG) in the longitudinal Kerr configuration with an incident beam angle of 4°. The MSH intensity pattern from the Co:TiO2 without surface Co clusters showed two anisotropic lobes at the second harmonic photon energy of 2 ℏ ω = 3.13 eV . Since MSH intensity is proportional to surface magnetization, the result indicates an anisotropy of the surface magnetization of Co:rutile TiO2 (1 1 0). This confirms the possibility that 5 at% Co:rutile TiO2 (1 1 0) is a ferromagnetic dilute magnetic semiconductor at its surface, as proposed in our previous paper.

Magnetic properties of nanostructured epitaxial thin layers of a series of Co and Li co-doped NiO on MgO(1 0 0) substrate with NiO buffer layer have been investigated. Thin films were synthesized by combinatorial laser molecular beam epitaxy (CLMBE) in the continuous binary composition spread approach. Large and linear variation of x was achieved in the growth of Co x Li 0.2 Ni 0.8− x O , onto 9 mm of single substrate. Homoepitaxial growth with smooth surface morphology was confirmed by grazing incidence X-ray diffraction (GIXRD) and atomic force microscopy (AFM). Linear decrease in the band gap and optical transparency was observed with increasing cobalt concentration. The magneto-optical Kerr effect revealed a strong photon energy dependency with negative Kerr rotation for all the Co-concentrations in the film, suggesting intra-valence charge transfer (IVCT) between low spin state Co 2+ with host Ni 2+ . Ferromagnetic (FM)-like ordering was observed at low temperatures, while antiferromagnetism predominates at room temperature in the Co and Li co-doped nickel oxide epitaxial films.

We have investigated the surface magnetism of 5 at% Co-doped rutile TiO2(110) using magnetization-induced optical second harmonic generation (MSHG) in the longitudinal Kerr configuration with the incident beam angle of 4° . MSHG is observed at both 2ħω = 2.33 eV and 2ħω = 4.20 eV. MSH intensity showed a hysteresis as a function of the external magnetic field for the second harmonic photon energy of 2ħω = 4.20 eV at which the absorption length limits the MSHG origin to the surface layer of 10 nm due to the TiO2 bulk. Since 5 at% Co: TiO2(110) is judged to have no metallic Co near the top surface by XPS, the hysteresis is attributed to a carrier-induced ferromagnetism at the surface of this material. Copyright © 2008 John Wiley & Sons, Ltd.

Synthesis of continuous composition-spread (CCS) thin films is widely recognized in combinatorial material science as a powerful technique for rapidly investigating the properties of new functional materials. However, there are very few reports of CCS organic thin films due to the fact that the thermal evaporation method with Knudsen cells, which is commonly used to fabricate organic thin films in vacuum, does not offer the necessary level of deposition rate control as, for example, does pulsed laser deposition (PLD). We have successfully fabricated organic CCS thin films of pentacene and 6,13-pentacenequinone by continuous-wave laser molecular beam epitaxy (CWL-MBE), which we developed as a new fabrication method for organic thin films. The composition-spread films were characterized systematically by ultraviolet–visible spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, atomic force microscopy, and two-probe conductivity measurements. The present work brings the advantages of high-throughput parallel synthesis and systematic characterization to the field of organic electronics, allowing for quick exploration and rapid optimization of organic functional materials and devices.

We describe the use of continuous-wave semiconductor diode laser beam as a heating source in thin film deposition system. One of the examples is heating of organic materials for sublimation to replace conventional Knudsen cell. The other is heating of the substrate to very high temperature (>1000°C) which can hardly be achieved by conventional resistive or lamp heaters. Many of the advantages come from the pin-point heating on demand that is enabled by the excellent directionality of high power laser beam.

Representing the gas, liquid, and solid phase materials on the earth under the standard conditions, CO 2 , H 2 O, and SiO 2 attract my interest for their natural abundance, chemical stability, and yet fundamental roles in energy and environmental problems. Chemical consideration is made on the utilization of these stable resources for renewable clean energy materials and processes based on a thermodynamic approximation. A general scheme is presented to compare the utilization of CO 2 , H 2 O, and SiO 2 for such purposes as CO 2 fixation into functional polymers, photosynthesis of carbohydrates from CO 2 and H 2 O, and solar silicon production from SiO 2 . Focused is CO 2 copolymerization, since it is originated from our discovery of alternating CO 2 –epoxide (oxirane) copolymer in 1968 and it has been revived by the recent industrialization of this unique bio-degradable polymer in China. New ideas of using combinatorial chemical technology and soft plasma processing for fixing CO 2 into polymers are proposed together with some preliminary experimental results.

We have used photoelectron emission microscopy (PEEM) and X-ray magnetic circular dichroism (XMCD) to study the effect of thin film thickness on the magnetic domain formation in La 0.6 Sr 0.4 MnO 3 samples that were epitaxially grown on stepped SrTiO 3 (0 0 1) substrates. The magnetic image exhibited a stripe structure elongated along the step direction, irrespective of film thickness, suggesting that uniaxial magnetic anisotropy induced by step-and-terrace structures plays an important role in the magnetic domain formation. Additional domains evolved gradually with increasing film thickness. In these domains, the direction of magnetization differed from the step direction due to biaxial magneto-crystalline anisotropy. The evolution of additional magnetic domains with increasing film thickness implies that a competition exists between the two anisotropies in LSMO films.

Photodecomposition of pentacene films grown on the atomically controlled SrTiO3(001) (STO) surfaces was investigated by atomic force microscopy. The photodecomposition was found to occur only when ...

We have performed an in situ photoemission spectroscopy (PES) of well-ordered surfaces of high-quality epitaxial La1−x Srx MnO3(LSMO) thin films to investigate the temperature-dependent changes in the electronic structure of LSMO in detail. For ferromagnetic metal LSMO with x = 0.4 , the spectral intensity of the e g states near the Fermi level ( E F ) significantly increases with decreasing temperature. This result suggests that the stabilization of ferromagnetic ordering causes the enhancement of spectral weight near E F .

Present information technologies use semiconductor devices and magnetic/optical disc. However, they are all foreseen to face fundamental limitations within a decade. Therefore, superseding devices are required for the next paradigm of high performance information technologies. This paper describes prospects for single molecule devices suitable for future information processing technologies, which are expected as the most probable candidate to supersede the present semiconductor devices. The first milestone towards the realization of single molecule devices in future electronics requires quantitative evaluation of single molecule characteristics, which inevitably needs planar nano-gap electrodes between which single molecules are sandwiched, observed their structures and measured their electrical characteristics. Nano-meter electrode pattern fabrication was achieved by electron beam lithography and metal lift-off, while planarization process requires many new technologies including chemical–mechanical polishing (CMP) and wafer bonding. The detailed planarization processing technologies are described in this paper to realize nm-planar nano-scale electrodes.

The pulsed laser ablation and deposition (PLD) processes of SrTiO3 were studied as a model system for developing a technique for the growth of structurally bulk-equivalent epitaxial thin films of typical complex oxides. Deposition rate vs. laser fluence measurements showed that there is a second critical fluence value above the ablation threshold. Below the critical value, both the ablation and deposition rates are linear functions of the fluence and independent of the ablation spot area. Above the critical value, the deposition rate per unit ablation area depends strongly on the ablation spot area. Homoepitaxial SrTiO3 films possessed the exact bulk lattice constant value only when the films were grown at the critical fluence, whereas larger lattice constants were obtained if the fluence was either higher or lower. Composition analysis revealed that the enlargement of the lattice constant was related to cationic unbalance. This critical laser fluence is essential for the growth of bulk-equivalent epitaxial films, and therefore accurate measurement of laser energy and ablation area is vital for reproducible film growth.

We developed a continuous-wave infrared laser molecular beam epitaxy (CW-IR-LMBE) optimized for the fabrication of organic semiconductor films. The crystal quality of these organic thin films deposited by CW-IR-LMBE was substantially the same as those deposited by thermal evaporation. Due to the possibility of quick switching of evaporation sources, CW-IR-LMBE is especially advantageous for rapid screening of composition, thickness, and fabrication parameters in materials and device optimization based on combinatorial technology.

An X-ray diffraction study of vacuum-deposited films of thiophene–pyridine co-oligomers on a sapphire substrate indicated a perpendicular or perpendicular-like alignment of the co-oligomers on the surface of the substrate. The UV-vis peak of the vacuum-deposited films shifted to a shorter wavelength from that observed in solutions. The UV-vis data support the notion that the co-oligomer in the vacuum-deposited film assumes a twisted conformation.

Under open-air atmosphere, homogeneous non-equilibrium cold plasma was generated stably by high voltage pulsed power (0.8 kV, 20 Hz) excitation of He and O2 gases. By feeding bis(dipivaloylmethanato)zinc (DPM2Zn) into this plasma, transparent flat ZnO films about 200 nm thick were successfully deposited on glass substrates directly under the slit made into the cathode. An XRD measurement revealed that ZnO films had a polycrystalline structure oriented c-axis. By increasing the O2 gas flow rate, the grain size of the polycrystalline ZnO became larger and its crystallinity was improved.

In this paper, we report on a less than 100-nm-wide nanoscale electrode array, with which the field-effect mobilities of a single grain and a single grain boundary in organic thin films are characterized. The method of fabricating the nanoscale electrode array and the evaluation results of the pentacene thin film are described. The nanoscale electrode array was fabricated by EB lithography and a liftoff process. The pentacene thin film was deposited by molecular-beam epitaxy (MBE). The resistances of a single grain and a single grain boundary were estimated to be around 10 and 100 MΩ, respectively, and the field-effect mobility was estimated to be around 1 cm2/(V s), which is almost comparable to the highest value ever reported. These results confirm that a single crystal is essential for high performance organic thin-film transistors.

When Sr1-xBaxTiO3 (0

Epitaxial SrTiO3 (STO) thin films with high electrical properties were grown on Si using ZnS single- and SrS/MnS hetero-buffer layers. STO films on both ZnS-buffered and SrS/MnS-buffered Si showed two growth orientations, (100) and (110). The temperature dependence of the growth orientation for STO films was different for the ZnS single-buffer layer in comparison with the SrS/MnS heterobuffer layers. (100) growth of STO films on SrS/MnS-buffered Si became dominant at high temperatures about 700 ?C, while (100) growth of STO films on ZnS-buffered Si became dominant at a relatively low growth temperature of 550 ?C. STO(100) films on ZnS-buffered and SrS/MnS-buffered Si showed lattice and domain matches for epitaxial relationships with [001]ZnS?[011]STO and SrS[001]?[011]STO, respectively via 45? in-plane rotation of STO films relative to both ZnS and SrS layers. The ZnS buffer layer contained many stacking faults because of the mismatch between ZnS and Si, however, those defects were terminated at the ZnS/STO interface. In contrast, the MnS buffer was very stable against stacking defect formation. Transmission electron microscopy measurements revealed the presence of a disordered region at the ZnS/Si and MnS/Si interfaces. Auger electron spectroscopy and transmission electron microscopy results showed that a good MnS/Si interface at the initial growth stage degraded to a SiS2-x-rich phase during MnS deposition and again into a SiO2-x-rich phase during STO deposition at the high growth temperature of 700 ?C. It was also observed that STO on SrS/MnS-buffered Si showed a markedly high dielectric constant compared with that of STO on ZnS-buffered Si.

Informatics tools are an important part of the high-throughput or combinatorial materials development process. Particularly for thin film studies, the rate of sample synthesis and characterization has increased to a point where the throughput of the whole materials development process is limited by the ability to process the characterization data and design new experiments. We describe in this work software tools that we have developed to solve the data management problems. In particular, we discuss the use of extensible markup language (XML) to address the problem of representing structurally varied experimental data in a data management system without having to make modifications to the core software parts whenever the materials processing or characterization tools or sample and data handling procedures change.

Bi x Y 3− x Fe 5 O 12 thin films have been grown on GGG (Gd 3 Ga 5 O 12 ) (1 1 1) substrates by the combinatorial composition-spread techniques under substrate temperature ( T sub ) ranging from 410 to 700 °C and O 2 pressure of 200 mTorr. In order to study the effect of substrates on the deposition of Bi x Y 3− x Fe 5 O 12 thin films, garnet substrates annealed at 1300 °C for 3 h were also used. Magneto-optical properties were characterized by our home-designed magneto-optical imaging system. From the maps of Faraday rotation angle θ F , it was evident that the Faraday effect appears only when T sub = 430–630 °C. θ F reaches to the maximum value (∼6°/μm, λ = 632 nm) at 500 °C, and is proportional to the Bi contents. XRD and EPMA analyses showed that Bi ions are easier to substitute for Y sites and better crystallinity is obtained for annealed substrates than for commercial ones.

We have fabricated a combinatorial nm-planar electrode array by using photolithography and chemical mechanical polishing processes for high throughput electrical evaluation of organic devices. Sub-nm precision was achieved with respect to the average level difference between each pair of electrodes and a dielectric layer. The insulating property between the electrodes is high enough to measure I–V characteristics of organic semiconductors. Bottom-contact field-effect-transistors (FETs) of pentacene were fabricated on this electrode array by use of molecular beam epitaxy. It was demonstrated that the array could be used as a pre-patterned device substrate for high throughput screening of the electrical properties of organic semiconductors.

Organic thin film transistors (O-TFTs) are attracting attentions recently for their possible application to flexible field effect transistor (FET) devices and even for candidate devices in post-silicon information systems. However, the organic thin films usually grow in a polycrystalline state, and the electrical properties are very difficult to set at an appropriate value because orientation and size of the polycrystalline grains are almost uncontrollable. Thus, it should be necessary to clarify the conduction characteristics within the single grain and between the grains through grain boundaries in order to precisely control the electrical properties of the organic thin films. This paper reports on a nano-scale electrode array, which provides a method to characterize single organic semiconductor grain, as well as to determine the single grain boundary effect on the electrical conduction. The fabrication method of the nano-scale electrode array and evaluation results are described. Single grain and single grain boundary in MBE grown pentacene thin film were detected and were measured for the first time using FET structures. The resistance of single grain was estimated to be around 10 M Ohms while that of single grain boundary to be about 100 M Ohms. This is the first experimental verification of the resistance of single grain pentacene thin film and single pentacene grain boundary.

We developed a scanning microwave microscope (SμM) designed for high-throughput electric-property screening as well as for rapid construction of electronic phase diagrams at low temperatures. As a sensor probe, we used a high-Q λ/4 coaxial cavity resonator to which a thin needle with ball-tip end was attached. The sensor module was mounted on the low-temperature XYZ stage, which allowed us to map out the change of resonance frequency and quality factor due to the local tip-sample interaction at low temperatures. From the measurements of combinatorial thin films, such as Ti 1-x Co x O 2-δ and Nd 0.9 Ca 0.1 Ba 2 Cu 3 O 7-δ (NCBCO), it was demonstrated that this SμM system has enough performance for the high-throughput characterization of sample conductance under variable temperature conditions.

In this paper, we reviewed our recent study on ultraviolet stimulated emission and lasing observed at room temperature from nano-structured ZnO thin films. The nano-structured ZnO thin films were grown on sapphire substrates using Laser-Molecular-Beam-Epitaxy (L-MBE). The thin film was consisted of regularly arrayed hexagonal nano-crystallite columns, whose facets form natural micro-cavities. These nano-crystallites confine the centre-of-mass motion of excitons. As a result of the quantum size effect, the oscillation strength of the excitons is largely enhanced, which is favored to the radiate recombination of exciton at room temperature. Excited using the frequency-tripled output of a YAG laser, the nano-structured ZnO thin film showed strong ultraviolet lasing at room temperature with a threshold as low as 24kW/cm2. At a moderate pumping intensity, the room temperature stimulated emission is associated with an exciton-exciton collision process. At higher pumping density, the excitons are dissociated, and the ultraviolet stimulated emission is dominated by an electron-hole plasma recombination process. Because of the large enhancement of oscillator strength of the excitons, the optical gain of the stimulated emission measured at room temperature reaches as high as 320 cm-1, which is an order higher than that observed in bulk ZnO crystals. In comparison with the electron-hole plasma stimulated emission in most of commercial semiconductor lasers, the excitonic stimulated emission can be realized at relatively low external pumping density. The observation of excitonic lasing effect at room temperature might be valuable in realization of practical ultraviolet semiconductor laser devices.

Epitaxial Sr(V x Cr y Ti 1-x-y )O 3 (0 < x + y ≤ 0.05) ternary composition spreads were grown on two different single crystal substrates, LaAlO 3 and Nb-doped SrTiO 3 , by use of combinatorial laser molecular beam epitaxy with a specially patterned slide masking plate. The photocatalytic activity on the composition spreads was evaluated by the photo-reduction of Ag + in an AgNO 3 aqueous solution to deposit Ag metal on the spreads. The V-doping effect was found to depend greatly on the substrate: the photodeposition of Ag was much enhanced in the composition region of SrV 0.05 Ti 0.95 O 3 only on the Nb-doped SrTiO 3 , but not on the LaAlO 3 and non-doped SrTiO 3 .

Transparent and conductive oxide (TCO) thin films of Li-doped NiO were prepared by combinatorial pulsed laser deposition technique. Composition spread approach was applied to optimize the Li concentration for achieving high conductivity and transparency in the film. Conductivity of the composition spread film was found to increase almost linearly from nearly insulating to as high as 1.41 Ω−1 cm−1 with increasing Li content along a 9 mm long film. Optical transparency was found to decrease in an equal proportion across the 40 nm thick film with a slight shift in the absorption edge.

We have designed a compact combinatorial pulsed laser deposition (PLD) chamber as a building block of a desktop laboratory for advanced materials research. Development of small-size systems for the growth and characterization of films would greatly help in interconnecting a variety of analytical tools for rapid screening of advanced materials. This PLD chamber has four special features: (1) a drum-shaped growth chamber, (2) a waterwheel-like combinatorial masking system, (3) a multi-target system having one feedthrough, and (4) a small reflection high-energy electron diffraction (RHEED) system. The performance of this system is demonstrated by the RHEED intensity oscillation during homoepitaxial growth of SrTiO 3 as well as by simultaneous fabrication of a ternary phase diagram of rare earth-doped Y 2 O 3 phosphors.

The combinatorial approach to materials synthesis was employed for the quick screening of a flux material for liquid phase-mediated epitaxy of Bi 4 Ti 3 O 12 single crystal film. A series of ternary flux libraries composed of two self-fluxes (Bi 2 O 3 and Bi 4 Ti 3 O 12 ) and an impurity flux (VO x , WO x , CuO x , BiPO x , BaO, MoO x ) were fabricated on the SrTiO 3 (0 0 1) substrates. Then, stoichiometric Bi 4 Ti 3 O 12 was grown on each one of these flux libraries at a temperature presumed to melt the flux. High-throughput characterization with the concurrent X-ray diffraction (XRD) method resulted in the discovery of a novel flux material, CuO, containing Bi 2 O 3 , for Bi 4 Ti 3 O 12 single crystal film.

Two series of π-conjugated thiophene-pyridine co-oligomers, Py-Th-(Th) m -Th-Py (Py = pyridine unit; Th = thiophene unit; 4a: m = 0; 5a: m = 1; 6a: m = 2) and Th-Py-(Th) m -Py-Th (4b: m = 0; 5b: m = 1; 6b: m = 2), have been prepared by palladium- or nickel-promoted C-C coupling reaction in high yields. The π-π * absorption peak of Py-Th-(Th) m -Th-Py (390-440 nm) is observed at a longer wavelength than that of Th-Py-(Th) m -Py-Th (345-410 nm) with the same m number. These UV-vis data are considered to reflect a charge transfer (CT) interaction between the thiophene (donor) and pyridine (acceptor) units. 4a-6a, 5b, and 6b show photoluminescence in a range of 430-540 nm and give quantum yields (Φ) of 20-40%. 4b affords a high quantum yield of Φ= 71%. A linear correlation holds between the π-π* transition energy and the inverse of the number of the aromatic units [1/(m+4)] for the 4a-6a and 4b-6b series.

The pulsed laser deposition (PLD) process was studied in detail during oxide thin film growth by constructing a sophisticated PLD chamber combined with an energy-stable excimer laser. It was revealed that the transmitting laser energy at the entrance view port decreased exponentially with deposition runs, roughly by A e−0.02x%, where A is the original transmission and x is the run number, and transmission loss could become considerable (up to 90%) in 100 deposition runs. In addition, area of the focused spot on the target was found a function of charging high voltage, which is a parameter of excimer laser operation, even through a slit forming rectangular sharp-edge beam profile. Laser energy density is one of the most important parameter governing grown film properties, and therefore accurate laser energy and spot area calibration is vital for reproducible film growth. In course of this study, the importance of spot area as well as the energy density is discussed in the view of deposition rate.

A new phosphor material, Y 1− x Tb x Ca 4 O(BO 3 ) 3 (0≤ x ≤1) film was grown on SiO 2 substrates by the combinatorial pulsed laser deposition (PLD) method, which enabled us to fabricate continuous composition spread film libraries. Photoluminescence (PL) and PL decay were measured for these film libraries to identify the optimum composition as well as to determine the luminescence mechanism. The film libraries showed strong dependence of luminescence intensities on the chemical composition of Tb ion. The optimum concentration of Tb ions in Y 1− x Tb x Ca 4 O(BO 3 ) 3 was experimentally and theoretically determined to be x =0.2–0.3.

We have studied the transport properties of thin LaTiO3 films, grown on NdGaO3 and SrTiO3 substrates. In case of films grown on NdGaO3 we see a sharp increase of film resistivity when the film thickness drops below 18 nm. This appears to correspond to a surface depletion layer in the films. We could avoid the detrimental effects of surface states by growing LaTiO3 films on SrTiO3 substrates and covering the LaTiO3 layers with a SrTiO3 cap layer. In this case we succeeded in fabricating isolated LaTiO3 layers, sandwiched between SrTiO3, that remained metallic down to 4 K. This work shows that it is feasible to use the LaTiO3/SrTiO3 system for growing metallic nanostructure arrays.

Crystalline thin films of NiO and nominally 20 at.% Li-doped NiO were deposited at room temperature by pulsed laser deposition on the lattice matched MgO (100) substrate. As-deposited films were annealed at various temperatures to promote a solid phase epitaxial growth and control the surface morphology. Films were characterized by AFM and RHEED measurements. AFM images of the NiO film annealed at 1200 °C for 30 min showed an atomically flat surface and an excellent step-terrace morphology with a step height corresponding to one unit cell of NiO over a wide range of 2 μm×2 μm. Formation of atomically smooth surface in a range of annealing temperatures is highlighted and a temperature of 1200 °C is identified as being the most suitable in the solid phase epitaxy for single crystalline growth and a smooth surface of the films deposited by PLD.

We have investigated the effect of interface states on the performance of a field-effect transistor composed of a SrTiO 3 (100) single crystal as a channel and an amorphous CaHfO 3 layer as a gate insulator. The amorphous CaHfO 3 gate insulator layer, which was grown at a pressure above 1 mTorr by pulsed laser deposition (PLD), had a breakdown field of over 5 MV/cm. The transistors deposited under “hard” ablation conditions, at a laser fluence of ∼1.2 J/cm 2 , showed a normally on conducting behavior even at zero gate bias. An annealing treatment was found to decrease the interface conductivity by filling oxygen vacancies and the annealed devices exhibited clear enhancement-type transistor action.

We have developed field-effect amorphous silicon solar cells (FESC) with comb-shaped electrodes (CSE) made of transparent conductive oxide (TCO). The FESC is based on the concept of utilizing a special window layer, in which carriers are induced by the field-effect instead of heavy impurity doping, to form a pin (or nip) junction. Pulsed laser deposition was used to fabricate a TCO CSE with a ZnO/ITO/ZnO stacked-layer structure. The FESC exhibited enhanced current output on applying a bias voltage for the field-effect. The conversion efficiency of the field-effect operation was improved by 39% compared with a FESC with a metal CSE. The fill factor was improved markedly by applying a TCO to the CSE.