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Two SiC crystals were grown using SiC source powder with different level of purity and then the effect of the purity of SiC source materials on the final electrical properties has been systematically observed. Furthermore, the variation of vanadium amount according to the growth direction of vanadium doped semi-insulated SiC single crystals has been investigated. The quality of SiC crystal grown using SiC source powder with higher purity was definitely better than SiC crystal with lower purity. SiC crystals having an average resistivity value of about 1×1010 Ωcm were successfully obtained. In the result of COREMA measurement, the use of high purity SiC powder was revealed to obtain wafers with better uniformity in resistivity value.

The present research was focused on the effect of porous graphite plate in TaC-coated crucible on crystal quality and resistivity of semi-insulating SiC crystals. Two SiC crystals grown with/without porous graphite plate in TaC-coated crucible were systematically compared. 6H-SiC polytype was obtained on both crystals regardless of porous graphite plate. The quality of SiC crystal grown using porous graphite plate placed in the TaC-coated crucible was slightly better than SiC crystal without porous graphite plate. SiC crystals having an average resistivity value of about 1×1010 Ωcm were obtained. In the result of COREMA measurement, the use of porous graphite plate tends to obtain wafers with better uniformity in resistivity value.

6-inch 4H-SiC single crystal was grown with modified hot-zone design for large diameter crystal. The simulation data confirmed reduced temperature gradient between center and edge region of growing front, and actual growth experiment exhibited that SiC crystal with good quality was obtained with modified hot-zone design without any quality degradation in edge region of bulk crystal. Based on the mapping measurement of FWHM (Full width at half maximum) value in X-ray rocking curve, the crystal quality of SiC crystals from middle and top region of grown ingot was observed to be almost identical. Furthermore, various properties of SiC crystal grown with modified hot-zone design have been systematically investigated.

The modified crucible in the top seeded solution growth (TSSG) method was proposed to get the stable growth condition and the enhanced growth rate. The temperature gradient and the distribution of dissolved carbon in the solvent were obtained by numerical approaches. Compared simulation results and experiment, we investigated the region where is the most of dissolved carbon and it is supplied to the seed through what path. The cross-sectional samples of crucibles and grown SiC crystals were systematically analyzed to investigate the effect of the crucible modification on SiC crystal growth.

The crucible design having a stepped wall was introduced for increasing the growth rate of SiC crystal without metal addition in top-seeded solution growth (TSSG) method. The numerical simulation confirmed that new crucible design to increase the solvent-crucible interface could definitely change the temperature distribution and increase the carbon concentration. The simulation result, SiC single crystals were grown with Si solvent at 1900°C using a normal crucible and a stepped crucible to investigate the effect of crucible design having a stepped wall. Grown SiC layers were analyzed using Optical microscopy and Raman spectra. The growth rate in the stepped crucible was finally 66um/h observed.

A novel emitting layer structure of white organic light-emitting diodes (WOLED) was developed using exciplex-forming two blue emitters, 2,3,4,5,6-penta(9H-carbazol-9-yl)benzonitrile (5CzCN) and tris(2-(1-(2,4-diisopropyldibenzo[b,d]furan-3-yl)-1H-imidazol-2-yl)phenyl)iridium (Ir(dbi) 3 ). The 5CzCN blue delayed fluorescence material and Ir(dbi) 3 phosphorescent emitter partially formed a red exciplex in the mixed film. Combination of blue emission from the blue emitters and red emission from the exciplex provided white emission in the blue emitting 5CzCN and Ir(dbi) 3 co-doped device. The WOLED fabricated using the blue emitting 5CzCN and Ir(dbi) 3 emitters achieved high color rendering index of 90.8 at 100 cd/m 2 . [ABSTRACT FROM AUTHOR]

Highly efficient thermally activated delayed fluorescent (TADF) emitters, 5-(2-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-5H-benzofuro[3,2-c]carbazole (oBFCzTrz), 5-(3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-5H-benzofuro[3,2-c]carbazole (mBFCzTrz), and 5-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-5H-benzofuro[3,2-c]carbazole (pBFCzTrz), were synthesized to study the effects of ortho-, meta-, and para- linkages between donor and acceptor moieties. oBFCzTrz having ortho- linked donor and acceptor moieties showed smaller singlet–triplet energy gap, shorter excited state lifetime, and higher photoluminescence quantum yield than mBFCzTrz and pBFCzTrz which are interconnected by meta- and para- positions. The TADF device using oBFCzTrz as a blue emitter exhibited high external quantum efficiency over 20%, little efficiency roll-off, and long device lifetime.

The design and synthesis of aggregation-induced emission (AIE) luminogens have attracted rapidly growing interest owing to the fundamental significance and diverse applications in mechanosensors, optical recording, security papers, and optoelectronic devices. In this contribution we report design and synthesis of four phenanthroimidazoles 3a–3dand explored their mechanochromic and electroluminescence properties. The phenanthroimidazoles 3a–3dwere synthesized by Suzuki coupling reaction of iodophenathroimidazoles 2a–2dhaving different end groups (H, CH3, CF3, and CN) with 4-(1,2,2-triphenylvinyl)phenylboronic acid pinacol ester in good yields. The single crystal X-ray structures of 2b, 2c, 3a, and 3dare reported and show that the multiple phenyl rings in the TPE unit adopt nonplanar orientation. Their photophysical, aggregation induced emission (AIE), mechanochromic, electrochemical, and electroluminescence properties were studied. The phenanthroimidazoles 3a–3dexhibit strong AIE. High color contrast reversible mechanochromism between blue and green color was observed for phenanthroimidazoles 3a–3d. It was found that the solid state emission and mechanochromic behavior of tetraphenylethylene substituted phenanthroimidazoles 3a–3dare functions of the end group on phenanthroimidazole. In addition to the AIE and mechnochromic behavior, 3aand 3dcompounds performed well as nondoped blue emitters in the organic light-emitting diodes by affording 3.9% and 4.0% external quantum efficiency, respectively.

In this paper, we present a power control method of relay for improving a channel estimation performance in amplify-and-forward (AF) relay networks over frequency-selective fading channel. We first analyze a channel mean-square error (MSE) by imposing a power control effect on a simple (LS) channel estimation. Then, we find that there is a trade-off between the amplitude of power control and MSE performance. Moreover, we propose the optimal and suboptimal power control methods in order to resolve such a trade-off. Finally, the superiority of the proposed channel estimation with optimal power controls is verified through numerical simulations.

Abstract: Many mobile robot navigation methods use, among others, laser scanners, ultrasonic sensors, vision cameras for detecting obstacles and following paths. However, humans use only visual (e.g. eye) information for navigation. In this paper, we propose a mobile robot control method based on machine learning algorithms which use only camera vision. To efficiently define the state of the robot from raw images, our algorithm uses image-processing and feature selection steps to choose the feature subset for a neural network and uses the output of the neural network learned through supervised learning. The output of the neural network uses the state of a reinforcement learning algorithm to learn obstacle-avoiding and path-following strategies using camera vision image. The algorithm is verified by two experiments, which are line tracking and obstacle avoidance.

Transparent electronics has been one of the key terminologies forecasting the ubiquitous technology era. Several researchers have thus extensively developed transparent oxide‐based thin‐film transistors (TFTs) on glass and plastic substrates. However, work in transparent electronics has been limited mostly to high‐voltage devices operating at more than a few tens of volts, and has mainly focused on transparent display drivers. Low‐voltage logic devices, such as transparent complementary inverters, operating in an electrically stable and photo‐stable manner, are now very necessary to practically realize transparent electronics. Electrically stable dielectrics with high strength and high capacitance must also be proposed to support this mission, and simultaneously these dielectrics must be compatible with both n‐ and p‐channel TFTs in device fabrication. Here, a nanohybrid dielectric layer that is composed of multiple units of inorganic oxide and organic self‐assembled monolayer is proposel to support a transparent complementary TFT inverter operating at 3 V.

We propose a method to reduce the contact resistivity of titanium silicide (TiSi2) on phosphorus-doped epitaxial silicon by introducing a thin Se layer at the Ti/Si interface. The Se interlayer delays transition from the C49 to the C54 phase and changes the dominant diffusing species of TiSi2formation from Si to Ti. In addition, the Se interlayer worsens the interface roughness between TiSi2/Si. The contact resistivity of the sample with the Se interlayer improves by one order of magnitude, which is significant. This improvement is attributed to the suppressed diffusion of P and low Schottky barrier height.

On page 726, Minsuk Oh and co‐workers describe the fabrication of a transparent complementary thin‐film transistor inverter with a ZnO top gate and bottom gate of pentacene channels. Twelve nanometer‐thin organic–inorganic hybrid dielectric layers with high capacitance are adopted to allow the ZnO and pentacene transistors to operate under only 3 V, and the inverter action appears very stable even under a few mW of white light. This discovery could herald the arrival of a new type of transparent logic device.