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For the wafer-scale fabrication of diamond devices, the growth of diamond substrates by heteroepitaxial chemical vapor deposition is the most promising option currently available. However, the transfer of growth and also structuring processes from small homoepitaxial to larger heteroepitaxial samples is not straightforward and requires adaptation. In this study, we present an approach for the fabrication of functional microstructures including pyramids and mesas as well as more complex structures with hollow centers. The associated methods were previously demonstrated by homoepitaxial growth and are now evaluated on heteroepitaxially grown diamond films. After optimizing the growth procedures to ensure a sufficient quality of the bare diamond substrates, precursor structures for overgrowth were fabricated by e-beam lithography and plasma etching. In the overgrowth of nanopillars, a truncated pyramidal shape was achieved. The characterization with scanning electron microscopy revealed the growth of higher-index facets. Nevertheless, photoluminescence spectroscopy reveals localized doping on the sides of the microstructures. In addition, optically detected magnetic resonance reaches a contrast of 6 % of one preferred nitrogen vacancy orientation per facet and a transverse relaxation time T 2 ∗ of 96 ns. [ABSTRACT FROM AUTHOR]

Control of the charge state of the nitrogen-vacancy (NV) center is crucial because of its instability and its transitions between the negative (NV–) and neutral (NV0) NV charge states under laser irradiation In this study, we fabricated an n-i-n junction, with an i-layer sandwiched between two phosphorus-doped n-layers; then, we measured the charge state of NV centers under steady state and laser irradiation in a known band structure where the Fermi energy changes gradually. The steady-state charge state measured by a nondestructive single shot exhibited stable NV– and NV0 signals when the Fermi level was even slightly above and below the transition level, respectively. This result indicates that the charge state can be significantly stabilized through band engineering. Both charge-state populations were observed only when the Fermi level was close to the transition level. Under continuous green laser irradiation, the ratio of NV– measured by the photoluminescence spectra changed gradually with the Fermi level in the depletion layer because of the balance between excitation from the laser and the supply of charge from the band. This outcome agrees reasonably with the calculated bands. Furthermore, we measured the PL spectra of the ensemble NV centers and discovered that their charge state can be well-controlled, as in the single NV center. The charge state of the i-layer at the interface can be stabilized by depositing a thin n-layer on the surface. These results would contribute significantly to improve sensor performance. [ABSTRACT FROM AUTHOR]

Using the electronic spin of nitrogen-vacancy (NV) centers in diamond is a promising approach to realizing high-precision temperature sensors; furthermore, pulsed optically detected magnetic resonance (pulsed-ODMR) is one way to measure the temperature using these NV centers. However, pulsed-ODMR techniques such as D-Ramsey, thermal echo, or thermal Carr–Purcell–Meiboom–Gill sequences require careful calibration and strict time synchronization to control the microwave (MW) pulses, which complicates their applicability. Continuous-wave ODMR (CW-ODMR) is a more advantageous way to measure temperature with NV centers because it can be implemented simply by continuous application of a green laser and MW radiation. However, CW-ODMR has lower sensitivity than pulsed-ODMR. Therefore, it is important to improve the temperature sensitivity of CW-ODMR techniques. Herein, we thus propose and demonstrate a method for measuring temperature using CW-ODMR with a quantum spin state dressed by a radio-frequency (RF) field under a transverse magnetic field. The use of an RF field is expected to suppress the inhomogeneous broadening resulting from strain and/or electric-field variations. The experimental results confirm that the linewidth is decreased in the proposed scheme when compared to the conventional scheme. In addition, we measured the temperature sensitivity to be about 50.4 ± 3.5 mK / Hz , and this is approximately eight times better than that of the conventional scheme. [ABSTRACT FROM AUTHOR]

Quantum sensors based on nitrogen-vacancy (NV) centers in diamond are expected to demonstrate a wide variety of applications. For high-sensitivity quantum sensors with NV center ensembles, uniform manipulation of the electron spins of the NV centers in large volumes is required. In addition, a broad microwave frequency bandwidth for manipulating the NV centers' electron spin is necessary for vector magnetometry and measurement under a finite static magnetic field. Here, we demonstrate a broadband microwave antenna for uniform manipulation of millimeter-scale volumes of diamond quantum sensors. The simulation shows that the current is distributed at both edges of the loop coil of a single copper plate due to the skin effect. The loop coil acts like a Helmholtz coil, which realizes uniformity in the z-direction of the microwave magnetic field (B1). The plate structure has a higher mechanical stability, durability, and a larger heat capacity than the Helmholtz coil, due to its large volume. The antenna achieves a higher performance than previously reported antennae, with a maximal B1 of 4.5 G, a broad bandwidth of 287 ± 6 MHz, and a peak-to-peak variation of 9.2 % over a 3.1 mm3 cylinder volume. These performances show that the presented antenna is suitable for manipulating solid-state spin ensembles for high-sensitivity quantum sensors. [ABSTRACT FROM AUTHOR]

We investigated spin-echo coherence times T2 of negatively charged nitrogen vacancy center (NV−) ensembles in single-crystalline diamond synthesized by either the high-pressure and high-temperature and chemical vapor deposition methods. This study specifically examined the magnetic dipole–dipole interaction (DDI) from the various electronic spin baths, which are the source of T2 decoherence. Diamond samples with NV− center concentration [NV−] comparable to those of neutral substitutional nitrogen concentration [Ns0] were used for DDI estimation. Results show that the T2 of the ensemble NV− center decreased in inverse proportion to the concentration of nitrogen-related paramagnetic defects [NPM], being the sum of [Ns0], [NV−], and [NV0], which is a neutrally charged state NV center. This inversely proportional relation between T2 and [NPM] indicates that the nitrogen-related paramagnetic defects of three kinds are the main decoherence source of the ensemble NV− center in the single-crystalline diamond. We found that the DDI coefficient of NVH− center was significantly smaller than that of Ns0, the NV0 center, or the NV− center. We ascertained the DDI coefficient of the NV− center D N V − through experimentation using a linear summation of the decoherence rates of each nitrogen-related paramagnetic defect. The obtained value of 89 μs ppm for D N V − corresponds well to the value estimated from the relation between DDI coefficient and spin multiplicity. [ABSTRACT FROM AUTHOR]

The longest spin coherence times for nitrogen-vacancy (NV) centers at room temperature have been achieved in phosphorus-doped n-type diamond. However, difficulty controlling impurity incorporation and the utilization of highly toxic phosphine gas in the chemical vapor deposition (CVD) technique pose problems for the growth of n-type diamond. In the present study, n-type diamond samples were synthesized by CVD using tert-butylphosphine, which is much less toxic than phosphine. The unintentional incorporation of nitrogen was found to be suppressed by incrementally increasing the gas flow rates of H2 and CH4. It was found that the spin coherence time (T2) increased with decreasing the nitrogen concentration, which suggests that the nitrogen concentration limits the length of T2. In the sample with the lowest nitrogen concentration, T2 increased to 1.62 ± 0.10 ms. Optically detected magnetic resonance spectra indicated that all of the measured NV centers were aligned along the [111] direction. Hall measurements confirmed n-type conduction in three measured samples prepared under different growth conditions. The highest measured Hall mobility at room temperature was 422 cm2/(V s). This study provides appropriate CVD conditions for growing phosphorus-doped n-type diamond with perfectly aligned NV centers exhibiting long spin coherence times, which is important for the production of quantum diamond devices. [ABSTRACT FROM AUTHOR]

Defects introduced to synthetic type Ib diamond micrometer-size particles by electron-beam irradiation were studied by electron paramagnetic resonance and photoluminescence (PL) spectroscopy as a function of e-beam fluence and post-irradiation thermal annealing. Increasing electron-beam fluence causes a substantial reduction of the substitutional nitrogen (P1) content, accompanied by progressively higher concentrations of paramagnetic negatively charged vacancies (V−) and triplet interstitials (R1/R2). Annealing results in a drastic decrease in the V− and R1/R2 content and an increase in the negatively charged nitrogen-vacancies (NV− or W15). Analysis of PL spectra allows for identification of color centers in the irradiated diamond samples and following their evolution after annealing. These data facilitate understanding of different factors contributing to the formation of color centers in diamond and promote efforts toward controlled engineering of optical centers in fluorescent diamond particles. [ABSTRACT FROM AUTHOR]

The nitrogen-vacancy (NV) centers in diamond have been applied to scanning magnetometer probes combined with atomic force microscopy (AFM) to demonstrate nanometer-scale magnetic sensing and imaging. However, the scanning diamond NV center probe fabrication requires complicated processes including electron-beam lithography and photolithography. In this study, we introduce an alternative method to fabricate a scanning NV probe using laser cutting and focused ion beam (FIB) milling from a bulk diamond hosting an ensemble of NV centers. A few tens of micrometer-sized diamond pieces, cut by laser processing, were attached to the probe end of a quartz tuning-fork-based AFM. Then, it was fabricated into a few-micrometer-sized diamond NV center probe by using a donut-shaped milling pattern in the FIB processing to avoid damage to the diamond probe surface to degrade the NV− charged state at the tip apex. By using a home-built scanning NV magnetometer probe microscopy setup, an optically detected magnetic resonance was measured to detect stray magnetic fields demonstrating the imaging of a magnetic structure of approximately 5-μm periodicity from a magnetic tape. This study offers a method with a higher degree of probe-shape control for scanning NV probe that will broaden its application capabilities. [ABSTRACT FROM AUTHOR]

With the ability to transfer and process quantum information, large-scale quantum networks will enable a suite of fundamentally new applications, from quantum communications to distributed sensing, metrology, and computing. This Perspective reviews requirements for quantum network nodes and color centers in diamond as suitable node candidates. We give a brief overview of state-of-the-art quantum network experiments employing color centers in diamond and discuss future research directions, focusing, in particular, on the control and coherence of qubits that distribute and store entangled states, and on efficient spin–photon interfaces. We discuss a route toward large-scale integrated devices combining color centers in diamond with other photonic materials and give an outlook toward realistic future quantum network protocol implementations and applications. [ABSTRACT FROM AUTHOR]

Contemporary models that are used to search for solid-state point defects for quantum-information applications tend to focus on the defect's intrinsic properties rather than the range of conditions in which they will form. In this work, a first-principles based multi-scale device model is used to explore how the conditions (i.e., growth temperature, doping concentration, unintentional impurity concentration) influence the formation of a neutral aluminum vacancy complexed with an oxygen impurity at a neighboring nitrogen site v Al -1O N in an Si/Mg:AlN homojunction. Varying the donor (Si) concentration is predicted to lead to the greatest change in both the maximum height and shape of the (v Al -1O N ) 0 profile. The shape is found to depend on the acceptor (Mg) concentration as well, and a critical ratio between the acceptor and unintentional impurities below which the (v Al -1O N ) 0 center would not form was identified. A detailed analysis of the electrostatic potential, electric field, and defect chemistry obtained with the model was used to reveal the underlying causes of these changes. These results show the potential of varying processing parameters to manipulate the local electronic structure as a means to control the properties of point defects for quantum-information applications. [ABSTRACT FROM AUTHOR]

The application of transparent conducting oxides in electronic devices like solar cells or displays is common. By transferring this technology to quantum sensing and computing in the form of microwave conductors, it is possible to benefit from the advantages of these materials. By using indium tin oxide (ITO), it is demonstrated that at an arbitrary position below the conductor, an arbitrary elliptical microwave polarization can be produced by two independent sources. This is independent of the geometry and size of the ITO, whereby a non-resonant microwave approach can be chosen. Using single nitrogen vacancy (NV) centers in diamond in combination with a cross-like ITO structure, each NV center can be addressed with an ideal (clockwise or anticlockwise) microwave polarization. By optimizing the coupling of the microwave field to the NV centers and minimizing the conductor size, the creation of smaller devices compared to common approaches is possible. [ABSTRACT FROM AUTHOR]

The surface Cs–O activation process directly determines quantum efficiency and stability of negative-electron-affinity photocathodes. To investigate the effects of excessive Cs and O supply on activation and to explore a more effective Cs–O activation recipe, Cs–O activation experiments of GaAs(100) photocathodes are carried out based on the current-driven solid Cs and O dispensers. By a comparison of differences in activation photocurrent, quantum efficiency, and photocurrent decay, it is found that the recipe of excessive O and non-excessive Cs is not suitable for activating GaAs photocathodes, while the recipe of continuous and completely excessive Cs along with intermittent and non-excessive O can achieve the most excellent photoemission performance, including the highest quantum efficiency in the long-wave threshold region and best stability under intense light irradiation after activation. Furthermore, this improved activation recipe with the least Cs–O alternating cycles is easier to operate. Combined with density functional calculations and dipole layer model, it is found that the activation recipe of completely excessive Cs and non-excessive O can form effective dipoles to the greatest extent, and avoid the direct interaction between As atoms and O atoms to form As–O–Ga oxides on the GaAs(100) reconstructed surface. [ABSTRACT FROM AUTHOR]

We report on a method by which we can systematically extract spectroscopic information such as isotropic electron–nuclear hyperfine coupling constants from near-zero field magnetoresistance (NZFMR) spectra. The method utilizes a least squares fitting of models developed from the stochastic quantum Liouville equation. We applied our fitting algorithm to two distinct material systems: Si/SiO2 metal oxide semiconductor field effect transistors and a-Si:H metal insulator semiconductor capacitors. Our fitted results and hyperfine parameters are in reasonable agreement with existing knowledge of the defects present in the systems. Our work indicates that the NZFMR response and fitting of the NZFMR spectrum via models developed from the stochastic quantum Liouville equation could be a relatively simple yet powerful addition to the family of spin-based techniques used to explore the chemical and structural nature of point defects in semiconductor devices and insulators. [ABSTRACT FROM AUTHOR]

The scanning electron microscope (SEM) is a powerful tool for analyzing the surface of various specimens. SEM observation at low voltage, which is typically lower than the 1 kV range, is very effective for obtaining surface information of specimens. However, at the low voltage range, resolution is restricted by the brightness and energy spread of electron sources. Therefore, to improve the resolution, a bright and monochromatic electron source is indispensable. In this work, we focused on an electron gun with a negative electron affinity photocathode using p-type GaAs and Cs–O adsorbates. The resolution of a prototype SEM was improved by approximately 16% compared with a SEM using a conventional Schottky emission (SE)-type emitter at the acceleration voltage of 1 kV. In addition, results showed that the measured brightness was as high as an SE-type emitter (∼107 A/m2/sr/V) and the estimated energy spread was less than 0.2 eV, which was narrower than that of a cold field emission-type emitter. [ABSTRACT FROM AUTHOR]

We show that electrically detected magnetic resonance (EDMR), through spin dependent trap assisted tunneling (SDTT) in amorphous SiC, exhibits approximately equal amplitudes at very high (8.5 T) and very low (0.013 T) magnetic fields at room temperature. This result strongly supports an SDTT/EDMR model in which spins at two nearby sites involved in a tunneling event are coupled for a finite time in circumstances somewhat analogous to spin pair coupling in the spin dependent recombination/EDMR model of Kaplan, Solomon, and Mott (KSM) [Kaplan, Solomon, and Mott, J. Phys. Lett. 39, 51 (1978)]. Since a comparable near zero magnetic field change in resistance is also observed in these samples, our results support the idea that this magnetoresistance response is also the result of a KSM-like mechanism involving SDTT. Additionally, we observe a large enhancement in SDTT/EDMR at high field (8.5 T) for temperatures below 50 K, which suggests the potential utility of SDTT in spin based quantum computation and other spintronic applications. [ABSTRACT FROM AUTHOR]

This tutorial article provides a concise and pedagogical overview on negatively charged nitrogen-vacancy (NV) centers in diamond. The research on the NV centers has attracted enormous attention for its application to quantum sensing, encompassing the areas of not only physics and applied physics but also chemistry, biology, and life sciences. Nonetheless, its key technical aspects can be understood from the viewpoint of magnetic resonance. We focus on three facets of this ever-expanding research field, to which our viewpoint is especially relevant: microwave engineering, materials science, and magnetometry. In explaining these aspects, we provide a technical basis and up-to-date technologies for research on the NV centers. [ABSTRACT FROM AUTHOR]

Spinel ferrite Ni0.5Zn0.3Co0.2Fe1.98O4-x nanoparticles were synthesized by co-precipitation method, and samples were realized by moulding and annealing at key temperatures (TM=800°C, 900 °C, 1050 °C, determined beforehand through shrinkage measurements) going with calcining and sintering processes. Annealing at 800 °C and 900 °C led to half-dense ceramics (porosity ∼50 vol. %), whereas bulky ferrite was obtained after annealing at 1050 °C. Elemental analysis, X-ray diffraction and ion chromatography analysis were performed. Complex dielectric permittivity (ε*) and magnetic permeability (μ*) were investigated up to 6 GHz. With increasing TM, a decreasing amount of Fe2+ was observed, going with increasing sample density. Coupled effects of the Fe2+ concentration and of the porosity, both on dielectric and magnetic properties, were chiefly investigated and discussed. The materials show almost constant permittivities (ε' =5.0, 6.0, and 14.8 for TM=800 °C, 900 °C and 1050 °C, respectively). The bulk value at f=1 GHz (ε' =14.8) can be interpreted well according to Shannon's theory. The permittivities of the half-dense ceramics are discussed on the basis of Bruggeman's Effective Medium Theory. The materials annealed at 800 °C and 900 °C show almost constant magnetic permeabilities in the frequency range from 0.2 to 1GHz (μ' =3.4 and 6.0 for TM=800 °C and 900 °C). The observed permeability behavior is typical of monodomain particles, except for the sample annealed at 1050 °C, for which domain wall contribution to μ* is suspected because of non-negligible losses at low frequency (μn =1.3-1.8 at f<0.3 GHz). This finding is supported by estimations of the upper and lower values for the critical grain size, on the basis of Brown-Van der Zaag's theory. Facing bulk ceramics, and in view of using Ni0.5Zn0.3Co0.2Fe1.98O4-x ferrite as substrate for antenna miniaturization, the electromagnetic properties of half-dense ceramics materials seem to be very competitive at frequencies beyond 0.2 GHz, and up to 0.7-0.8 GHz. [ABSTRACT FROM AUTHOR]

Organic magnetoresistance (OMAR) can be caused by either single carrier (bipolaron) or double carriers (electron-hole)-based mechanisms. In order to consider applications for OMAR, it is important to control the mechanism present in the device. In this paper, we report the effect of traps on OMAR resulting of disorder at the interface between the organic active layer with the hole injection layer [poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate): PEDOT:PSS]. It has been found that while the single carriers OMAR is enhanced by the presence of traps, the double carriers OMAR is totally removed in a sample with a high interface trap density. The reasons for these results are discussed based on the impedance spectroscopy measurements. First, the mechanism (single or double carriers) responsible of the OMAR was determined with the support of the capacitance measurement. Then, the influence of traps was discussed with the Nyquist diagrams and phase angle-frequency plots of the samples. The results suggested that with a rough interface and thus high disorder, the presence of traps enhanced the bipolaron formation. Traps also acted as recombination centers for electron-hole pairs, which prevented the double carriers OMAR in devices with a rough interface. On the other hand, with a low trap density, i.e., with a smooth surface, the single carrier OMAR decreased, and double carriers OMAR appeared. The sign of the OMAR could then be controlled by simply sweeping the bias voltage. This work demonstrated that the roughness at the interface is important for controlling OMAR and its reproducibility, and that the combination of OMAR measurement and impedance spectroscopy is helpful for clarifying the processes at the interface. [ABSTRACT FROM AUTHOR]

We predict that singly occupied carrier traps, produced by electrical stress or irradiation within organic semiconductors, can cause spin blockades and the large room-temperature magnetoresistance known as organic magnetoresistance. The blockade occurs because many singly occupied traps can only become as doubly occupied in a spin-singlet configuration. Magnetic-field effects on spin mixing during transport dramatically modify the effects of this blockade and produce magnetoresistance. We calculate the quantitative effects of these traps on organic magnetoresistance from percolation theory and find a dramatic nonlinear dependence of the saturated magnetoresistance on trap density, leading to values ~20%, within the theory's range of validity. [ABSTRACT FROM AUTHOR]

Electrically detected magnetic resonance (EDMR) involves the electron paramagnetic resonance (EPR) study of spin dependent transport mechanisms such as spin dependent tunneling and spin dependent recombination (SDR) in solid state electronics. Conventional EPR measurements generally require strong static magnetic fields, typically 3 kG or greater, and high frequency oscillating electromagnetic fields, typically 9 GHz or higher. In this study, we directly demonstrate that, in the absence of the oscillating electromagnetic field, a very large SDR response (≈1%) can be detected at zero magnetic field with associated hyperfine interactions at extremely low magnetic fields in a silicon carbide (SiC) diode at room temperature. The zero-field SDR (ZFSDR) response that we detect is unexpected in the conventional detection scheme of SDR via EDMR. We believe that our observations provide fundamental physical understanding of other recently reported zero-field phenomena such as singlet triplet mixing in double quantum dots and low-field giant magnetoresistance in organic semiconductors. Our work provides an unambiguous demonstration that the zero-field phenomenon we observe involves SDR. Measurements reported herein indicate that extremely useful low-field SDR and ZFSDR results can be acquired simply and inexpensively in systems of technological importance. This work also suggests the potential use of this new physics in applications including absolute magnetometry with self-calibration, spin based memories, quantum computation, and inexpensive low-field EDMR spectrometers for wafer/probing stations. [ABSTRACT FROM AUTHOR]

A study of the conversion efficiency and line shape of the K-α x-ray line radiation from a planar titanium target irradiated by an ultra-short laser pulse is performed. The conversion efficiency and spectral broadening are studied as a function of laser intensity (5 × 1016-1018 W cm-2), laser pulse duration (45 fs-800 fs), and laser fluence (2 × 103-4.2 × 104 J cm-2). The K-α1 line (4510 eV) is observed to be broadened (up to ∼9 eV), predominantly towards the higher energy side and strongly depends on the laser fluence rather than on laser intensity. The reason for the spectral broadening is attributed to K-α emission in warm dense plasma. The role of hot electrons and direct laser heating on spectral broadening is outlined. In addition to this, our observations indicates that the presence of pre-plasma strongly contribute to the observed broadening through the inner-shell transitions in multiply charged titanium ions in the pre-plasma. The appropriate laser irradiation parameters to achieve high conversion efficiency and minimum spectral width of the K-α radiation are identified. The study is important, since the control of the spectral profile is of general interest for diffraction or scattering experiments in view of its potential in increasing temporal resolution. [ABSTRACT FROM AUTHOR]

A nanocomposite with a magnetic loss factor (tan δ=μ″/μ′) of less than 1% at up to 1 GHz was synthesized using self-forming core/shell nanoparticles of metal/oxide; these were concentrated to achieve a relative permeability (μ′) of more than three. The self-forming core/shell nanoparticles were synthesized by oxidation of a portion of FeCoAl nanoparticles in thermal plasma. An FeCoAl complex oxide shell of approximately 2 nm in thickness was formed on the surface of FeCo nanoparticle, which had approximately 20 nm in diameter. The core/shell nanoparticles were mixed with resin to form bulk material of millimeter-order thickness. [ABSTRACT FROM AUTHOR]

A series of shock-recovery experiments on a single crystal of silicon up to 38 GPa and characterizations of the recovered samples by x-ray diffraction analysis, Raman spectroscopy, and microscopic observations were performed for a better understanding of residual effects after shock loading by using a propellant gun. The x-ray diffraction trace of each sample revealed the absence of additional constituents including metastable phases and high-pressure phases of silicon except for 11 and 38 GPa. At 11 GPa, small amounts of metastable phases of silicon were obtained. The formation of copper silicide (Cu3Si) was confirmed in the sample shocked at 38 GPa. Considering the surface morphology revealed by microscopic observation, a thermochemical reaction through the melting of silicon resulted in the formation of Cu3Si. An additional band and the center frequency deviation of a peak were shown in the Raman spectroscopy results. The results of x-ray diffraction and Raman spectroscopy indicated that crystalline size reduction rather than the formation of metastable phases occurred. Structural deformation rather than the thermal effect caused by a shock-induced temperature rise may be responsible for the disappearance of metastable phases, which were observed in other high-pressure experiments. [ABSTRACT FROM AUTHOR]

Pulsed laser deposition has been used to grow Pt(621) thin films having a chiral orientation on SrTiO3(621) substrates. Films were deposited over a range of conditions, then characterized for their crystallinity and epitaxy using x-ray diffraction and for their surface morphologies using atomic force microscopy (AFM). Films deposited at 600 ° C grew epitaxially, but with an island growth mode. Pt deposited at 250 ° C displayed smooth surfaces but did not grow epitaxially. A three-step process wherein films were seeded at 600 ° C, deposited at 250 ° C, and postannealed was shown to result in excellent epitaxial growth and flat surface morphologies. Films grown using the three-step process exhibited excellent epitaxy, having the orientation relationship (621)pt¦¦ (621)srTiO3: [012]Pt¦¦ [012]srTiO3. When postannealed at 800 ° C, they exhibited flat surfaces (rms ≈ Å) having long terraces separated by steps running along the expected [012] direction of the SrTiO3(621) substrate. Films postannealed at 600 ° C were flatter (rms ≈ Å) with no evident step directionality. The SrTiO3(621) substrates were observed to be extremely flat (rms ≈ Å) and to have morphologically featureless surfaces, as expected for a (621) surface. The good crystalline quality of the SrTiO3 substrate surface is considered to drive the growth of the chirally oriented heteroepitaxial Pt films. Similarities and differences between Pt growth on chiral surfaces and on low-index achiral surfaces are discussed. [ABSTRACT FROM AUTHOR]

The switch-off dynamics of a 180° supertwisted nematic (STN) are explored in detail by using a convergent beam system and the fully leaky guided-mode technique. From the dynamical guided-mode data and using the Ericksen–Leslie theory, the director structure in the cell at different times during switch-off is obtained. We have studied the dynamic switch-off from different applied voltages and have found that the relaxation time is independent of the voltage. From fitting the optical data, the effective viscosities are obtained. It appears that two viscosity coefficients, γ and η1, largely control the dynamics of switch-off. From the analysis of the director tilt profile in the cell, it is found that there is no backflow-induced increased tilt at the cell center in the STN cell during the switch-off. From liquid crystal hydrodynamics, this no-backflow dynamic process in the STN cell is well explained. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Anomalously strong diffraction from a bilayer lattice of dielectric microspheres, previously reported by the authors, has been attributed to the enhancement of diffraction by specular resonance in constituent bispheres. On the basis of rigorous calculations and experiments, specular resonance from bispheres is found to be dominant even in the scattering from a cluster of several microspheres. As a consequence, a diffraction model, in which a bilayer lattice of microspheres is viewed as a two-dimensional array of bispheres, is constructed. By incorporating the specular resonance into a diffraction theory of two-dimensional lattices as a structure factor, observed diffraction behavior is explained. In the diffraction from a bilayer lattice of microspheres, the specular resonance functions as a blazing mechanism. Possible configurations and suitable parameters for efficient gratings are discussed, and a self-assembled bilayer lattice of dielectric microspheres with a diameter 1.6–3.2 times as large as the wavelength is found to be promising as a low-cost and highly efficient transmission grating. The spheres can be replaced with cylinders or lenses. Tunable diffraction devices with efficiency exceeding that of conventional gratings would be realized by microelectromechanical systems comprised of two optimally designed microlens arrays. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Using a convergent beam system and the full-leaky guided-mode technique, the dynamic relaxation in a twist nematic cell is explored on removal of an ac electrical field. From the dynamical guided-mode data, the director structure in the cell at different times during relaxation is obtained. Substantial backflow is observed during the first few milliseconds after the removal of the voltage. Detailed comparison of the experimental results with the model theory verifies the validity of the Ericksen-Leslie theory. Further, by carefully fitting the time dependent guided-mode data taken over the whole relaxation of the cell, the viscosity coefficients of the liquid crystal have been determined. [ABSTRACT FROM AUTHOR]

In this paper, the kinematics of mechanical and adhesional micromanipulation using a needle-shaped tool under a scanning electron microscope is analyzed. A mode diagram is derived to indicate the possible micro-object behavior for the specified operational conditions. Based on the diagram, a reasonable method for pick and place operation is proposed. The keys to successful analysis are to introduce adhesional and rolling-resistance factors into the kinematic system consisting of a sphere, a needle-shaped tool, and a substrate, and to consider the time dependence of these factors due to the electron-beam (EB) irradiation. Adhesional force and the lower limit of maximum rolling resistance are evaluated quantitatively in theoretical and experimental ways. This analysis shows that it is possible to control the fracture of either the tool-sphere or substrate-sphere interface of the system selectively by the tool-loading angle and that such a selective fracture of the interfaces enables reliable pick or place operation even under EB irradiation. Although the conventional micromanipulation was not repeatable because the technique was based on an empirically effective method, this analysis should provide us with a guideline to reliable micromanipulation. [ABSTRACT FROM AUTHOR]

Measures the adhesion mechanisms of micrometer-sized polymer particles deposited on a substrate during scanning electron microscope (SEM) observation. Increase in the adhesion forces initiated by the electron-beam irradiation; Dependence of the adhesion on the electron flux and the probe voltage.

Presents information on a study which demonstrated the effectiveness of the mechanical arrangement technique in scanning electron microscope to a photonic band study. Fabrication of two-dimensional (2D) lattices of microspheres; Measurement of oblique incidence transmission spectra; Theoretical features of photonic bands in 2D lattice of spheres; Conclusions.

Studies the undoped liquid encapsulated Czochralski grown GaAs crystals with a transition from semi-insulating to medium-resistivity behavior. Value of the Hall mobility at 300K; Anomalous temperature dependence of MuH characterized; Observation of MuH with increasing temperature for T less than 400 K.

Discusses the characteristic dependence of the Hall effect mobility on the carrier concentration in undoped n-type bulk gallium arsenide. Use of effective medium theory. Mesoscopic nonuniformities; Cellular structure of dislocations; Model calculations; Thermal activation energy.

In this report, we describe the deposition of strongly bonded hydrocarbon films (1-decanol and decanoic acid) on carbon surfaces by a vacuum vapor deposition technique. From the contact angle test and x-ray photoelectron spectroscopy measurement results, we conclude that the hydrocarbon molecules having hydroxyl or carboxyl end groups can be strongly bonded on carbon surfaces by vapor deposition. It is related to the electrostatic interaction between hydroxyl or carboxyl end groups and unsaturated electrons on carbon surfaces. The friction measurements results are also discussed. [ABSTRACT FROM AUTHOR]

In recent years, it was discovered that the current through an organic semiconductor, sandwiched between two non-magnetic electrodes, can be changed significantly by applying a small magnetic field. This surprisingly large magnetoresistance effect, often dubbed as organic magnetoresistance (OMAR), has puzzled the young field of organic spintronics during the last decade. Here, we present a detailed study on the voltage and temperature dependence of OMAR, aiming to unravel the lineshapes of the magnetic field effects and thereby gain a deeper fundamental understanding of the underlying microscopic mechanism. Using a full quantitative analysis of the lineshapes, we are able to extract all linewidth parameters and the voltage and temperature dependencies are explained with a recently proposed trion mechanism. Moreover, explicit microscopic simulations show a qualitative agreement to the experimental results. [ABSTRACT FROM AUTHOR]

An experimental study on the time resolved x-ray diffraction from laser shocked silicon crystal, carried out using a 10 TW Ti:sapphire laser system, is presented. The characteristic Kα x-ray line radiation generated by 45 fs laser produced plasmas of two different target materials (iron and copper) is used as the probe, whereas the stretched pulse of sub-nanosecond duration (pump), derived from the same laser, is used to compress the sample. The use of x-ray probe of different photon energies yields information about the strain over a greater crystal depth. The dynamics of the strain propagation is inferred by monitoring the evolution of rocking curve width of the shocked sample at different time delays between the pump and the probe pulse. The shock velocity deduced from these measurements is ∼106 cm/s, consistent with the sound velocity in bulk silicon. The maximum elastic compression observed is 0.4%, indicating a pressure of 0.8 GPa. [ABSTRACT FROM AUTHOR]