The onset of magnetic reconnection in space, astrophysical and laboratory plasmas is reviewed discussing results from theory, numerical simulations and observations. After a brief introduction on magnetic reconnection and approach to the question of onset, we first discuss recent theoretical models and numerical simulations, followed by observations of reconnection and its effects in space and astrophysical plasmas from satellites and ground-based detectors, as well as measurements of reconnection in laboratory plasma experiments. Mechanisms allowing reconnection spanning from collisional resistivity to kinetic effects as well as partial ionization are described, providing a description valid over a wide range of plasma parameters, and therefore applicable in principle to many different astrophysical and laboratory environments. Finally, we summarize the implications of reconnection onset physics for plasma dynamics throughout the Universe and illustrate how capturing the dynamics correctly is important to understanding particle acceleration. The goal of this review is to give a view on the present status of this topic and future interesting investigations, offering a unified approach.

We present recent observation results of Sgr A* at millimeter obtained with VLBI arrays in Korea and Japan.

7 mm monitoring of Sgr A* is part of our AGN large project. The results at 7 epochs during 2013-2014, including high resolution maps, flux density and two-dimensional size measurements are presented. The source shows no significant variation in flux and structure related to the G2 encounter in 2014. According to recent MHD simulations by kawashima et al., flux and magnetic field energy can be expected to increase several years after the encounter; We will keep our monitoring in order to test this prediction.

Astrometric observations of Sgr A* were performed in 2015 at 7 and 3.5 millimeter simultaneously. Source-frequency phase referencing was applied and a combined ”core-shift” of Sgr A* and a nearby calibrator was measured. Future observations and analysis are necessary to determine the core-shift in each source.

For the visualization of the coronary arterial patterns in complete transposition (concordant atrioventricular and discordant ventriculoarterial connections), balloon occlusion aortography has been performed in right and left anterior oblique or in frontal and lateral views. These views, however, are often unsatisfactory because of super-imposition of the aortic sinuses. The so-called “laid-back” view is a newly developed angiographic projection in which the aortic sinuses and the intervening commissures are imaged as if they were seen from below and the front. We performed such laid-back aortography in 36 consecutive patients with an echocardiographic diagnosis of complete transposition. In 23 of 36 patients, we obtained additional aortograms in right and left anterior oblique views. For the evaluation of the diagnostic value of the laid-back view, as compared with that of the combined right and left anterior oblique views, both sets of aortograms were reviewed independently by the five reviewers who were asked to make a diagnosis and to specify their levels of confidence (“definite,” “probable,” and “possible”) for their diagnosis. Error rates were significantly lower for the laid-back aortograms than for the combined right and left aortograms (4 and 11%, respectively). An increased level of confidence was significantly associated with the laid-back aortograms. We illustrate the anatomy of various coronary arterial patterns seen by laid-back aortography.

Extended abstract of a paper presented at Microscopy and Microanalysis 2007 in Ft. Lauderdale, Florida, USA, August 5 – August 9, 2007

SrRuO3 (SRO) thin films were grown on SrTiO3 (100) substrates using the pulsed laser deposition method. The films' growth properties widely changed in response to different working oxygen partial pressures. An island growth mode was dominant for low pressures up to 10 mTorr followed by a step flow growth mode at 60 mTorr and step flow plus 2 D growth at 200 mTorr then reverting back to island growth at 300 mTorr. Significant out-of-plane strains of SRO films were observed for low growth pressures (up to 10 mTorr) but became notably reduced at 60 mTorr and continued to decrease gradually with further pressure increases. Formation of Ru vacancies occurs regardless of the working pressure values and appears to be minimized at 60 mTorr. Highest TC's were obtained in films exhibiting the step flow growth mode. The role of Ru deficiencies in relation to strain, growth mode, and magnetic properties is discussed.

Recent progress to overcome integration issues related with (Ba,Sr)TiO3 films are presented. Firstly, ternary barrier material, Ti0.7Al0.3N deposited by reactive sputtering is shown to have superior oxidation resistance than TiN through the test using contact string pattern where Pt is deposited as a electrode. Ti0.7Al0.3N barrier is able to keep stable contact resistance below 100Ω even under oxidizing condition where the temperature is 550°C and oxygen partial pressure is 7.6 Torr. If rapid thermal annealing is used, annealing temperature without oxidation of Ti0.7Al0.3N can be increased by about 100°C. Ti0.7Al0.3N is thought to be the promising one which can endure during post-annealing process. Secondly, electroplating technology is employed to fabricate the stack capacitor of Pt that has been known to be very difficult to etch. 500Å-thick Pt is used as a seed layer and very thick Pt is selectively grown on the seed layer by the electroplating. The Pt height can be controlled by changing the electroplating time, so we can make stack Pt over 8000Å. Thirdly, low temperature deposition process for MOCVD BST film is developed. The equivalent oxide thickness of about 3.5Å is obtained on Pt electrode when BST thickness is 150Å. BST film is deposited at 420°C and annealed at 700°C under oxidizing atmosphere. It is suggested that a new two step annealing consisting of high temperature annealing under inert atmosphere and low temperature annealing under oxidizing atmosphere is very effective to achieve the high dielectric constant and low leakage current of BST films at the same time. It is also adequate for preventing the barrier oxidation. BST film with Toxeq. of 5.2Å and low leakage current is obtained by annealing at 650°C under N2 followed by annealing at 550TC under O2. Electrical properties of BST deposited on side-wall of Pt concave capacitor is evaluated. The concave capacitor with about aspect ratio 3 shows the same capacitance and leakage current as the planar capacitor, which implies that BST composition and thickness is uniform on the side-wall. It is concluded that BST films on Pt electrode can be applied to real device.

We propose a novel fabrication method for a room temperature operating single-electron memory using the size and location controlled poly-Si island by lithographic technique and excimer laser annealing.

We have patterned tip shaped excimer laser windows and irradiated laser energy through windows for crystallizing amorphous silicon. As a result of laser energy, the poly-Si grains are growing from patterned window side so that the fine grain and isolated large poly-Si quantum dot are inherently formed by well-known ACSLG regime. The oxidation was then performed by RTP at 950 °C for 30 seconds in order to isolate quantum island and fine poly-Si grains for quantum dot. The peaks of the poly-oxide along the poly-Si grain boundaries were lowered during that oxidation and isolated the poly-Si grains and made oxide barriers.

To fabricate GaN-based optoelectronic devices successfully, a reproducible etch process with high etch rates, vertical etch profile, and damage-free surface is required. In this study, GaN etching was performed using planar inductively coupled plasmas and the effects of process parameters such as inductive power, bias voltage, pressures and, gas combination on the characteristics of the plasmas were studied using Langmuir probe, optical emission spectroscope (OES), and quadrupole mass spectrometer (QMS). Gas combinations of Cl2/Ar and Cl2/HBr were used to etch GaN. GaN etch rates increased with the increase of chlorine radical and ion energy (bias voltage), and the etch rates close to 4000 Å/min could be obtained without substrate heating over 100 °C. The addition of HBr and Ar (more than 20%) generally reduced GaN etch rates. In our experimental condition, it appears that the chemical reaction between Cl and Ga in GaN affects more significantly to GaN etching compared to physical sputtering, and it was partially confirmed by the data measured by Langmuir probe and OES. Angle resolved XP S data showed the variation of surface Ga/N ratio depending on the process parameters, which influence the formation of low resistance ohmic contact.

We have fabricated a new multi-channel polycrystalline silicon thin film transistor (ploy-Si TFT), of which structure may be more effectively hydrogenated than conventional multi-channel poly-Si TFT. The new multi-channel TFT has stripe-cuts in gate electrode so that more hydrogen radicals penetrate into the gate oxide and passivate the active poly-Si layer. After 90 min. hydrogenation of the new device, the electrical characteristics such as threshold voltage and field effect mobility are improved more than those of conventional device.

The new multi-channel poly-Si TFT, which receives more hydrogen radicals thorough gate oxide than the conventional multi-channel TFT, can be hydrogenated effectively in long channel devices. Besides the improvement of the device characteristics, our experimental results show that the dominant hydrogenation path is the diffusion though the gate oxide.

The role of various interfaces in deformation and fracture behavior of two-phase TiAl-Ti3Al alloys is analyzed on the basis of the specific interfacial and surface energies determined from ab initio calculations. The propensity of twinning observed in these alloys is consistent with the low true-twin boundary energy. The strong plastic anisotropy reported in TiAl polysynthetically twinned (PST) crystals is attributed partly to the localized slip along lamellar interfaces, thus lowering the yield stress for soft orientations. Interfacial fracture energies are estimated to be the highest for the α2/γ lamellar boundary and the lowest for the 120° rotational γ/γ boundary. The fracture mode mixity plays an important role in the crack-tip plasticity by ordinary slip and true-twinning, leading to translamellar and interfacial fracture.

We have fabricated a poly-Si TFT using a novel oxidation method, which improves the surface roughness at the interface between the poly-Si layer and the gate oxide layer. Compared with the poly-Si TFTs fabricated by the conventional oxidation method, the proposed poly-Si TFT exhibits the remarkable enhancement of the electrical parameters, such as the subthreshold swing and the threshold voltage. It is observed that the proposed poly-Si TFT has a higher dielectric strength and the device characteristics are not degraded significantly after an electrical stress. The improvement of the surface roughness at oxide/poly-Si interface is found to be critical to enhance the device performance.

AlGaN/GaN heterostructures with multiple quantum wells were grown by plasmaassisted molecular beam epitaxy (PAMBE). Structural and optical properties of the heterostructures were analyzed using x-ray diffraction, cathodoldminescence, and photoluminescence. Interband transitions were clearly observed in the GaN quantum wells at both room- and liquid-helium temperatures. The efficiency of the interband recombination due to the confinement effect was greatly enhanced in the thinner quantum wells. The functional dependence of the interband peaks on the well thickness is shown to be in good agreement with the calculated positions of the quantized levels in the wells.

Ohmic contacts on p-type GaN have been investigated. High quality GaN epilayers on cplane sapphire were prepared using plasma-assisted molecular beam epitaxy that utilized an inductively coupled rf nitrogen plasma source and solid source beams. The resulting film thickness and the doping concentration of the grown samples were in the range of 0.7–1.35 μm and 1018 – 1020/cm3, respectively. The metallization consisted of high work function metal bilayers which included a combinations of 25 nm-thick Ni, Ti, Pt and/or Cr and 200 nm-thick Au on the highly p-doped GaN in a transmission line model pattern. Ohmic contacts were formed by alloying the bi-layers using rapid thermal annealing (RTA) at temperatures in the range of 300–700 °C for 1 min under nitrogen ambient. Current-voltage measurements showed that the specific contact resistance was as low as 1.2 × 10 −4 Ω–cm2 for the sample having 1.4 × 1020/cm3p-type doping concentration with a Cr/Au contact annealed at 500 °C for 1 min by RTA. Judging from the scanning Auger microscopy results and the glancing angle x-ray diffraction analysis, this resistance is attributed to Cr diffusion into the GaN layer.

p-type GaN films were grown on a (0001) sapphire substrate by the plasma-assisted molecular beam epitaxy. A low-contamination, high-power efficiency inductively coupled radio frequency plasma source was used, which was developed at the University of Illinois. Using an MBE system equipped with this plasma source, high-quality p-type GaN films were grown without post-growth treatment. X-ray rocking curve measurements for (0002) diffraction showed a full width at half maximum of less than 7 arcmin. The highest room-temperature hole concentration obtained was 1.4× 1020 cm−3, and for the same sample, the mobility was 2.5 cm2/Vs It is believed that the Mott-Anderson transition occurred in this sample resulting in a metallictype conductivity in the impurity subband. Low-temperature photoluminescence had a blue emission band and no deep-level transitions, indicating the high quality of the grown films. Uniformity of the Mg doping was confirmed by secondary ion mass spectrometry.

3C-SiC, lattice-matched with TiC, is a candidate for use in wide-bandgap semiconductor devices. Epitaxial 3C-SiC films were grown on (111) and (112) TiC substrates, and defects were characterized by analytical TEM.