Single Crystal Plates Research Articles

A nitrogen doped low-dislocation density free-standing single crystal diamond plate fabricated by a lift-off process

A nitrogen-doped single crystal diamond plate with a low dislocation density is fabricated by chemical vapor deposition (CVD) from a high pressure high temperature synthetic type IIa seed substrate by ion implantation and lift-off processes. To avoid sub-surface damage, the seed surface was subjected to deep ion beam etching. In addition, we introduced a nitrogen flow during the CVD step to grow low-strain diamond at a relatively high growth rate. This resulted in a plate with low birefringence and a dislocation density as low as 400 cm−2, which is the lowest reported value for a lift-off plate. Reproducing this lift-off process may allow mass-production of single crystal CVD diamond plates with low dislocation density and consistent quality.

Ultrasonic two-dimensional array transducer of the single-unit type with a conductive backing of the 1–3 piezocomposite structure

A two-dimensional (2D) array transducer has been developed in this work using a new conductive backing. The 2D array transducer was designed to comprise 4,096 channels operating at the center frequency of 3.4 MHz with a fractional bandwidth over 50%. The 2D array transducer designed in this work is different from other matrix transducers in that all the active channels were installed on a single piezoelectric crystal plate as a whole unit by using the new conductive backing. The new conductive backing has a structure similar to that of 1–3 piezocomposite materials. Based on the design, an experimental prototype of the 2D array transducer was fabricated and characterized. The prototype showed good agreement with the design and excellent sensitivity uniformity over the entire channels. These results confirmed the applicability of the new conductive backing to 2D array transducers.

Ion-beam studies of synthetic single-crystal diamonds

A surface layer of polished single-crystal diamond plates with the (100) orientation, which can be applied to planar high-frequency high-power microstructures, is investigated by means of ion-beam and X-ray methods. It is demonstrated that the diamond plates are characterized by a high degree of structural perfection and a low level of surface roughness.

In Situ Domain Structure Observation and Giant Magnetoelectric Coupling for PMN‐PT/Terfenol‐D Multiferroic Composites

In situ observations of ferroelectric domain structure evolution, and magnetoelectric (ME) coupling are investigated for PMN‐28PT/Terfenol‐D (abbreviation of Pb(Mg1/3Nb2/3)O3‐28PbTiO3/Tb0.3Dy0.7Fe2) and PMN‐33PT/Terfenol‐D composites under the magnetic loadings. The composite of PMN‐33PT/Terfenol‐D shows stronger ME coupling than that in PMN‐28PT/Terfenol‐D. At a thickness of 0.10–0.12 mm for the single crystal plate, a giant magnetoelectric coefficient (αME) up to 2 V/cm·Oe is obtained for PMN‐33PT/Terfenol‐D at a static magnetic field of 200 Oe and 1 kHz of the alternating magnetic field. In situ domain structure observations reveal the domain morphology change during the applied magnetic loadings. In PMN‐28PT, the domains are of predominantly rhombohedral (R) phase and they change into monoclinic MA phase upon the magnetic loading via the strain transferred between Terfenol‐D plate and PMN‐PT single crystal. In PMN‐33PT, domains of orthorhombic (O), R, and monoclinic MC coexist and phase transitions from O to MC and further to R phase occur upon the magnetic loading. The undulation and diversity of the domain structure makes the domains more susceptible to the magnetic loading via strain transferred between Terfenol‐D plate and PMN‐PT single crystal, and consequently, a strong ME coupling in the composites.

Ce:(YLu)AlO single-crystal phosphor plates for high-brightness white LEDs/LDs with high-color rendering (Ra > 90) and temperature stability

Ce:(YLu)AlO single-crystals are investigated in detail as phosphors for high-brightness LEDs and LDs. It is demonstrated that single-crystal phosphor plates (SCPPs) present very advantageous characteristics in comparison with standard powder phosphors. On the one side, the very high quantum efficiency of the SCPPs does not decrease with the temperature increase, and on the other side, the SCPPs possess a high thermal conductivity, so that these can be efficiently cooled to avoid device overheating. The optical properties of these SCPPs are investigated from room temperature to . Ce:YAlO SCPPs are adequate for high-brightness cool white light sources. Instead, Ce:(YLu)AlO SCPPs, whose emission shifts to the green with the Lu concentration, are very promising for neutral and warm white light sources in conjunction with a red-phosphor. It is shown that these white sources exhibit a color rendering over 90 for a wide range of excitation and SCPP emission wavelengths.

Mechanical properties of deposited carbon thin films on sapphire substrates using atomic force microscopy (AFM)

In this study, the mechanical properties of nano-layered carbon thin films deposited on Al2O3 single crystal substrates with varying orientations in A (1120), M (1010), R (1102) and C (0001) planes were investigated using depth-sensing nanoindentation techniques. All of the nano-layered films were deposited by a thermionic vacuum arc (TVA). In this experiment, a high purity amorphous carbon rod was used. Single crystal Al2O3 plates were used as the substrate material. All of the substrates were a commercial product that is readily available. For the surface topography, the roughness and depth-sensing nano-hardness of the deposited films were analyzed using an Ambios Q-scope atomic force microscope. An F20 thin film measurement system was used for the determination of thickness and reflection properties of the deposited thin films. Indention depths were determined as 5nm, 10nm and 15nm. In these indentation depths, hardness values were calculated in the range of 8–25GPa.

Raman investigation of femtosecond laser-induced graphitic columns in single-crystal diamond

We report on the fabrication of graphitic columns induced in single-crystal diamond plates using 100 fs laser pulses at 800 nm wavelength. Different values of laser fluence (0.6–1.2 J/cm2) and graphitization speed (1–100 μm/s) were used for the laser treatment. A Raman investigation was performed aimed at evaluating the structural properties of the fabricated columns, showing that a lower laser fluence and a proper choice of graphitization speed may improve the degree of graphite crystallinity, and suppress the residual diamond content.

Electrical conduction in nanodomains in congruent lithium tantalate single crystal

The electrical current flow behavior was investigated for nanodomains formed in a thin congruent lithium tantalate (LiTaO3) single-crystal plate. When the nanodomains were relatively large, with diameters of about 100 nm, current flow was detected along the domain wall. However, when they were about 40 nm or smaller, the current flowed through the entire nanodomain. Schottky-like rectifying behavior was observed. Unlike the case of LiNbO3, optical illumination was not required for current conduction in LiTaO3. A clear temperature dependence of the current was found indicating that the conduction mechanism for nanodomains in LiTaO3 may involve thermally activated carrier hopping.

Акустооптические свойства стекол GexS100–x и акустооптический модулятор на их основе

The investigation of acousto-optic properties of GexS100–x glasses, which had shown that they are perspective lightsoundwire material for manufacturing of acousto-optic devices for controlling the laser radiation in the visible spectral region was performed. Taking into account the technological conditions for synthesis of glasses with optical quality the two optimal compositions, Ge30S70 and Ge25S75, were proposed for fabrication of optical-acoustic modulator. These compositions possess the high optical perfection and transmission in the spectral range of 0.4—11 μm, the moderate optical absorption of 2—3 dB/cm, their acoustic quality factor ~100 times exceeds those of quartz. The construction and main parameters of the acousto-optic modulator based on Ge30S70 and Ge25S75 glasses as lightsoundwire material and the converter is a plate of lithium niobate single crystal were described. In Bragg diversion mode the modulator has the maximum bandwidth of the modulating frequencies — 10 MHz, the diffraction efficiency — 40%, the speed — near 80 nanoseconds. It is also important to note that the effective modulation is obtained with the low power (40 mW) controlled electrical signal, which facilitates a thermal mode of the modulator and allows working without the forced cooling of the modulation element.

Evaluation for interface strength fluctuations induced by inhomogeneous grain structure of Cu line in LSI Interconnects

Local adhesion strength of the interface between Cu line and SiN cap layer in a Cu damascene interconnect structure of LSI has a significant fluctuation when evaluated with in-plane dimensions of 1×1 μm specimens, which was 4.78±1.63 J/m2. The reproducibility of the evaluation technique was investigated by evaluating the strength of the Cu/SiN interface for the specimens fabricated on a plate of Cu single crystal, where the interface strength was measured as 0.62±0.02J/m2. The relative standard deviation of interface strength distribution in LSI interconnect structure was 34% which was more than ten times larger than the value 2.5% for the specimens fabricated on the plate of Cu single crystal. The significant fluctuation of interface strength was induced clearly not by the random error of the evaluation technique, but by the inhomogeneous grain structure of Cu line with various crystal orientations and grain boundaries. By means of elastic-plastic interface crack extension simulations, it was revealed that the difference in the amount of energy dissipated in plastic deformation of Cu layer mainly leads to a significant fluctuation of the apparent strength. Plastic deformation of Cu layer plays a dominant role on the local strength of interface Cu/SiN in LSI interconnects.

An anomalous increase in the fill factor of the current-voltage characteristic in the short-wave region of the solar spectrum for a silicon photocell containing a porous-silicon structure

The possibility of increasing the efficiency of a silicon photocell by forming a porous-silicon structure in its bulk has been proposed and studied. Photocells produced from p-type single-crystal silicon plates by the diffusion method were investigated. Porous-silicon structures were formed by photoelectric anodic etching in HF-ethanol mixture. Current density and etching time were assigned by a computer in ranges of 6–14 mA/cm2 and 10–20 s, respectively. It has been found that the porous-silicon structure located in the emitter bulk substantially improves efficiency of photocells. At wavelength λ ∼ 550 nm, an anomalously large (by five to nine times) increase in efficiency was observed.

Magnetic resonance in a Cu-Cr-S structure

A layered Cu-Cr-S structure composed of single-crystal CuCrS2 layers and thin CuCr2S4 plates embedded in them has been investigated by the magnetic resonance and scanning electron microscopy methods. The Curie temperature and saturation magnetization of the spinel phase of the investigated samples have been determined. The thickness of the CuCr2S4 layers has been estimated. The dependence of the growncrystal topology on synthesis conditions has been established. An interpretation of the anomalous behavior of the magnetostatic oscillation intensity is offered.

Implantation cochléaire sous-anesthésie locale avec sédation : étude de 13 cas

Czochralski grown Ce and Gd-doped Y3Al5O12 (Ce,Gd:YAG) single crystal demonstrated superior performance features in a new concept of white LED where it is used as thin single crystal phosphor plates (SCPPs). New SCPP-based white LED realizes epoxy resin free package, which allows to eliminate the photodegradation issue of the organic material. Optical, thermal and electrical properties of SCPPs and SCPP-based white LEDs are discussed with the powder phosphor and commercial LED reference. SCPPs showed significantly higher values and better stability under the high temperatures, irradiation and current. Quantum efficiency was found to be as high as 93%.

Amine-Functionalized Polyglycidyl Methacrylate Microsphere as a Unified Template for the Synthesis of Gold Nanoparticles and Single-Crystal Gold Plates

Amine-Functionalized Polyglycidyl Methacrylate Microsphere as a Unified Template for the Synthesis of Gold Nanoparticles and Single-Crystal Gold Plates

Oxygen-Ion Transfer between YSZ/YSZ and YSZ/LSCF under Mechanical Contact Stress

The present study concerns oxygen-ion transfer between yttria-stabilized zirconia single crystals (YSZ/YSZ) under mechanical contact stress. Two YSZ single crystal plates were piled up between platinum meshes, and contact stress was mechanically applied. The interfacial conductivity as well as the bulk conductivity was successfully measured with this setup. The interfacial conductivity is greatly influenced by the contact stress, whereas the bulk conductivity is almost independent of the stress. The interfacial conductivity was significantly increased with increasing contact stress. A similar improvement in the interfacial conductivity between YSZ and lanthanum strontium cobalt ferrite (YSZ/LSCF) was also observed.

Automatic electronic-controlled mode locking self-start in fibre lasers with non-linear polarisation evolution

The present work demonstrates a fibre-laser system with automatic electronic-controlled triggering of dissipative soliton generation mode. Passive mode locking based on the effect of non-linear polarisation evolution has been achieved through a polarisation controller containing a single low-voltage liquid crystal plate whose optimal wave delay was determined from analysis of inter-mode beat spectrum of the output radiation.

Oxygen-ion transfer between yttria stabilized zirconia single crystals under mechanical contact stress

The present study concerns oxygen-ion transfer between yttria-stabilized zirconia (YSZ) single crystals under mechanical contact stress. Two YSZ single crystal plates were piled up between platinum meshes, and contact stress was mechanically applied. The interfacial conductivity as well as the bulk conductivity was successfully measured with this setup. The interfacial conductivity is greatly influenced by the contact stress, whereas the bulk conductivity is almost independent of the stress. The interfacial conductivity is significantly increased with increasing contact stress, especially from 0 to 5MPa, and is saturated around 56kΩcm2 with the stress around 40MPa. The interfacial capacitance increases with contact stress. The activation energy for the interface conductivity is equal to 105–111kJ/mol, similar to that for the bulk, and appears to change slightly with stress.

Piezoelectric-metal-magnet dc magnetoelectric sensor with high dynamic response

A dc magnetoelectric sensor capable of measuring both dc and ac magnetic fields is developed by combining a thickness-polarized 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 (PMN–PT) piezoelectric single-crystal plate, a pair of electrically connected aluminum strips, and a pair of NdFeB magnet plates in orthogonal directions. The operation of the sensor is based on the mechanical mediation of the magnetically biased Lorentz force effect in the aluminum strips due to a drive magnetic field (B3D) applied to the sensor, a dc bias magnetic field (B3B) preset by the NdFeB plates, and an ac reference electric current (I2) flowing through the aluminum strips with the transverse piezoelectric effect in the PMN–PT plate at the sensor resonance. The theoretical and experimental results confirm an ultrahigh and linear current-controlled magnetic field sensitivity of 1.7 V/T/A in broad ranges of B3D amplitude of −100 to 100 mT and B3D frequency of 0–15 kHz by using an I2 of ≤100 mA at the sensor resonance frequency of 65 kHz.

Study of spatial resolution of YAG:Ce cathodoluminescent imaging screens

The aim of this paper is to find spatial resolution of YAG:Ce single crystal cathodoluminescent imaging screens at primary electron energies in the range from 20 to 100keV using theoretical simulation as well as the experimental method. Calculations have been based on the MC model for energy distribution of excited electrons. Measurement of the spatial resolution was realized using the sharp edge projection method. As the projection object, the silicon single crystal plate with the hole made by the anisotropic etching was prepared and used. The edge of this object was examined at the magnification of up to 125,000×. For the edge projection method, the experimental system with the screen specimen cartridge and with the light-microscopic module using the magnifying objective and the CCD camera has been constructed and used. The simulated as well as experimental results have been processed and are presented in the form of line spread function (LSF). The resulted image qualities were quantified using modulation transfer function (MTF). Finally, the spatial resolutions of YAG:Ce single crystal imaging screens were determined as the number of lines per mm for the contrast of 50% and primary electron beam energies of 20, 60 and 100keV.

Carrier Recombination-Incited Substrate Vibrations after Pulsed UV-Laser Photolysis of TiO2 Thin Single-Crystal Plate and Nanoparticle Films

Photo-induced carrier generation and recombination have been regarded as important steps in understanding the photocatalytic reactions on the surfaces of semiconductors such as TiO2. During the investigation of a photocatalytic water-splitting reaction on the surface of semiconductor TiO2 (rutile) single-crystal plate and sintered-nanoparticle (anatase) films coated on a CaF2 plate, a pulsed 355 nm laser was used for band-gap excitation and a continuous-working, mid-infrared laser as the probe to trace the kinetics of the photogenerated electrons. Fast oscillations with periods of 10-50 μs were observed. We demonstrated experimentally that these oscillations are neither from the nonlinear carrier recombination dynamics nor surface chemical reactions; instead, they are caused by the thermal-induced flexural vibrations initiated by the fast carrier recombination in the light-absorbing area. The observed oscillations can be well accounted for by thermal stress-induced flexural vibrations of the substrates due to rapid charge recombination, and the observed oscillation frequencies match the flexural vibration frequencies predicted by the Kirchhoff-Love thin-plate theory. Light-interference effect caused by the beam reflecting off the surfaces of the substrate and windows, which can amplify the oscillation signals, is also discussed. Several approaches are proposed to minimize or eliminate the interference from the substrate vibration in the transient kinetic measurement when a coherent laser is used as the probe beam.