Window Pattern Research Articles

Growth characteristics of GaAs nanowires obtained by selective area metal–organicvapour-phase epitaxy

GaAs nanowires were selectively grown by metal–organic vapour-phase epitaxy within aSiO2 mask window pattern fabricated on a GaAs(111)B substrate surface. The nanowires were100–3000 nm in height and 50–300 nm in diameter. The height decreased as the maskwindow diameter was increased or the growth temperature was increased from 700 to800 °C. The dependence of the nanowire height on the mask window diameter was compared witha calculation, which indicated that the height was inversely proportional to the maskwindow diameter. This suggests that the migration of growth species on the nanowire sidesurface plays a major role. Tetrahedral GaAs grew at an early stage of nanowire growthbut became hexagonal as the growth process continued. The calculated change in Gibbsfree energy for nucleation growth of the crystals indicated that tetrahedra wereenergetically more favourable than hexagons. Transmission and scanning electronmicroscopy analyses of a GaAs nanowire showed that many twins developed along the B direction, suggesting that twins had something to do with the evolution of the nanowireshape from tetrahedron to hexagon.

2001 長大スラブ軌道トンネルに適した緩衝工開口部の現地試験(S23-1 トンネルの空気力学,換気,火災(1),21世紀地球環境革命の機械工学:人・マイクロナノ・エネルギー・環境)

2001 長大スラブ軌道トンネルに適した緩衝工開口部の現地試験(S23-1 トンネルの空気力学,換気,火災(1),21世紀地球環境革命の機械工学:人・マイクロナノ・エネルギー・環境)

Therapeutic Effect and Optimal Injection Time by Human Mesenchymal Stem Cell at Spinal Cord Injury of Rat

Objective: Human mesenchymal stem cell (MSC) is known to have therapeutic effect in spinal cord injury (SCI), but the optimal therapeutic time window and survival pattern is not well known. The authors evaluated the treatment effect of MSC in the respect of injection time and survival rate in spinal cord injured rats. Methods: In experiment I, SCI is performed by New York State University (NYU) Impactor in 30 rats. Human MSCs were injected intramedullarily with 5 groups. The animals were grouped with Group 1 (injury only), Group 2 (immediate MSC injection), Group 3 (injection after 3 days), Group 4 (injection after 1 week), Group 5 (injection after 2 weeks), and Group 6 (injection after 4 weeks). The Basso Beattie Bresnahan (BBB) locomotor scale was evaluated during 8 weeks after SCI in all the animals, and then the spinal cords were stained with HE3:99-102)

Anisotropy in selective metalorganic vapor phase epitaxy of CdTe on GaAs and Si substrates

CdTe epitaxial layers are grown by metalorganic vapor phase epitaxy (MOVPE) on patterned (100) Si and (100) GaAs substrates using SiO2, Si3N4 or CaF2 masks. Selective epitaxy of CdTe can be achieved by using Si3N4 and CaF2 masks and by controlling the growth conditions during MOVPE. The selectively grown CdTe layers show strong anisotropy depending on the orientation of the window pattern on the mask, as well as on the orientation of the starting substrates. CdTe with smooth atomically flat surfaces and vertical side walls can be obtained on (100) GaAs substrates by suitably orienting the window pattern directions and optimizing the growth conditions. For the growth conditions that are suitable for the selective growth, the growth is mass-transfer limited. The lateral growth rate depends on the ratio of the window width to the mask width. Use of CaF2 allows wider temperature window for selective growth since no nucleation was observed on CaF2 even at 450°C.

Fold Defects in Aluminum Alloy A356 Lost Foam Casting

In the lost foam casting (LFC) of aluminum alloys, the expandable polystyrene (EPS) foam characteristics (foam composition, polymer processing and bead fusion) influence the formation of deleterious fold defects in the final casting. In this research, four types of EPS beads were investigated: (1) the regular EPS beads, (2) 2wt% hexabromocyclododecane and 2wt% dicumyl peroxide added to the EPS beads during the polymerization process, (3) 2wt% silicaalumina blended to EPS beads after the pre-expansion process of the beads and (4) 2wt% hexabromocyclododecane blended to EPS beads after the pre-expansion process of the beads. The density of the regular and modified EPS beads was kept constant at 25.63 kg/m3. Aluminum alloy A356 was poured at 1023 K into the window pattern. The window patterns with regular EPS beads did not fill completely and had identifiable carbon/oxide defects on the surface. The window patterns with the additives were completely filled with a few surface defects. From thermogravimetric analysis (TGA), it was found that the EPS beads with silica-alumina had a reduced onset temperature of degradation of EPS (from 634 K to 618 K) and a reduced activation energy (from 188 kJ/mol to 147 kJ/mol) relative to the regular beads. In the organic brominatedmodified EPS (both through blending and polymerization), it was found that the value of the preexponential (rate equation) was significantly increased. Through light optical microscopy (LOM) and scanning electron microscopy (SEM), it was found that the polymerization process additives increased the degree of bead fusion whereas the post pre-expansion additives decreased the degree of bead fusion. Finally, the EPS beads treated during the polymerization process produced castings with the least overall surface, subsurface and internal defects.

TCAM을 이용한 고성능 패턴 매치 알고리즘

수 기가비트 급의 네트워크 성능 저하 없이 모든 패킷의 페이로드를 검사하여 유해 패킷을 검출해 내기 위해서 일반 메모리보다 빠른 검색을 지원하는 TCAM을 이용한 고성능 패턴 매치 알고리즘을 제안한다. 본 논문에서 제안하는 고성능 패턴 매치 알고리즘은 페이로드내에서 m바이트의 문자열당 한 번의 TCAM 룩업을 수행하는 m-바이트 점핑 윈도우 기법을 이용하여 패킷의 페이로드당 TCAM 룩업 횟수를 줄여 페이로드 스캐닝 속도를 증가시킨다. 본 논문에서 제안한 방법과 TCAM 기반 슬라이딩 윈도우 패턴 매치 방법을 이용하여 페이로드 스캐닝 성능을 비교해 보고, 제안한 방법의 우수성을 시뮬레이션을 통해 보인다. 또한 m-바이트 점핑 윈도우 패턴 매치 알고리즘이 약 2천개의 패턴을 가지는 Snort 규칙을 이용한 시뮬레이션을 통해 9Mbit TCAM에서 10Gbps 이상의 페이로드 스캐닝 성능을 낼 수 있음을 보인다. With the increasing importance of network protection from cyber threats, it is requested to develop a multi-gigabit rate pattern matching method for protecting against malicious attacks in high-speed network. This paper devises a high-speed pattern matching algorithm with TCAM by using an m-byte jumping window pattern matching scheme. The proposed algorithm significantly reduces the number of TCAM lookups per payload by m times with the marginally enlarged TCAM size which can be implemented by cascading multiple TCAMs. Due to the reduced number of TCAM lookups, we can easily achieve multi-gigabit rate for scanning the packet payload. It is shown by simulation that for the Snort nile with 2,247 patterns, our proposed algorithm supports more than 10 Gbps rate with a 9Mbit TCAM.

Metal mask fabrication with an inkjet printer for AWG phase trimming using a photosensitive refractive index change

We report a simple method for fabricating a metal mask with wet etching designed to reduce the adjacent crosstalk of arrayed-waveguide gratings (AWGs) by using a photoinduced refractive index change. This process utilizes a commercially available inkjet printer and a copy machine, and so the resolution of the fabricated window pattern is not very high. However, the fabricated mask enables us to achieve a great reduction in adjacent crosstalk because it depends solely on a slowly varying component in the phase error distribution of an AWG.

Verification of implantable cardioverter defibrillator (ICD) interventions by nonlinear analysis of heart rate variability ? preliminary results

Conventional ICD algorithms yield approximately 10-30% of spurious interventions. Our aim was to check whether nonlinear dynamics methods might be useful in the verification of ICD interventions. We extracted 190 consecutive RR files (approximately 2000-9000 RR intervals long) from the ICDs of 70 patients (36 with coronary artery disease, 8 with hypertrophic cardiomyopathy, 19 with dilated cardiomyopathy and 7 with other diseases). The 3D phase space trajectories in delay coordinates, window pattern entropy, and algorithmic complexity of the RR intervals were examined within a 50 beat sliding window. Data were not filtered for arrhythmia and artefacts. Of the 83 recordings with appropriate interventions 79 were correctly recognised in a blind test. Two interventions were not identified in patients with fast atrial fibrillation and two in cases of complex and frequent forms of arrhythmia. There were nine spurious interventions. In all except one case (atrial fibrillation with a fast ventricular response) the analysis by nonlinear methods showed that the intervention was not necessary. All of the 98 control recordings were correctly identified in the blind test. The results show that nonlinear dynamics methods may be used to supplement the existing ICD detection algorithms to enhance the detection success rate.

Shock-induced epicardial and endocardial virtual electrodes leading to ventricular fibrillation via reentry, graded responses, and transmural activation.

The mechanism of ventricular fibrillation (VF) induction by T wave shocks has been attributed to reentry, propagated graded responses (PGR), and triggered activity. The limitation of recording transmembrane potential (V(m)) from only a single surface has hampered efforts to elucidate the relative role of these phenomena and their relationship to shock-induced virtual electrodes. V(m) patterns from epicardial and endocardial surfaces of isolated sheep right ventricles were recorded with two CCD cameras for monophasic (M) and biphasic (B) shocks delivered at various coupling intervals (CI) from a unipolar mesh electrode on the epicardium. VF was induced via (1) the formation of reentry following make or break excitation; (2) propagated graded responses during apparent isoelectric window; and (3) breakthrough activation patterns coincident with endocardial-to-epicardial gradients in V(m). M shocks depolarized both surfaces at long CIs and polarized epicardial and endocardial surfaces oppositely at short CIs. At intermediate CIs, postshock V(m) patterns could lead to reentry on one surface or endocardial-to-epicardial gradients resulting in breakthrough. B induced VF less than M for short and intermediate CIs due to more homogeneous end-shock V(m) patterns. However, at long CIs these homogeneous patterns resulted in more VF induction because B left the tissue closer to the V(m) threshold for propagation. Postshock activity occurred either immediately via epicardial or endocardial reentry, or after a delay caused by transmural propagation or propagated graded responses. These findings could explain the isoelectric window and focal activation patterns observed on the epicardium following VF induction shocks.

Thin-film-induced index change and channel waveguiding in epitaxial GaN films

We report on optical waveguiding in the channel region of an epitaxial GaN film defined by a SiN cladding layer of a stripe window pattern. We carried out numerical analyses on the various possible effects that might contribute to the overcompensation of the negative loading effect of a SiN cladding window. This includes the photoelastic, piezoelectric, and electro-optic effects in GaN induced by a SiN window layer. The analysis result suggests that the observed phenomenon can be ascribed to a combination of both the photoelastic and electro-optic effects, and especially that the spontaneous polarization field in undoped GaN with a low background carrier concentration might play an important role in forming a channel waveguide in the window region.

Force regulation is deficient in patients with parietal lesions: a system-analytic approach

By means of a quantitative system-analytic investigation strategy, the postural motor control of the fingers was evaluated, to characterise the possible deficit of force regulation in patients with parietal lesions. In spite of a normal response to short torque pulses, the parietal-lesion patients had difficulties in returning to the preload level after the application of an additional step torque load to fingers II–IV of their left or right hands. The control offset (measured 500 ms after step torque application) was significantly larger in the patient group. This deficit in the investigated patients with parietal lesions to compensate for step torque loads was not due to a paresis, but rather resulted from a disturbance in the generation of a sufficient counterforce against the applied step torque within an adequate time window and motor pattern. This distinct force-regulation deficit was found in patients with left- and right-sided parietal lesions.

Scattering and recoiling imaging spectrometer (SARIS)

An ultrahigh vacuum spectrometer system has been designed and constructed for obtaining spatial- and time-resolved, element-specific images of atoms that are scattered and recoiled from surfaces. A pulsed noble gas ion beam in the 1–5 keV range is used to scatter and recoil atoms from a surface. A large, position-sensitive microchannel plate detector with resistive anode encoder, that is sensitive both to ions and fast neutrals records the spatial distribution patterns of the emitted atoms. The use of time-of-flight methods allows capture of these patterns in time windows as short as 10 ns. The sensitivity of these patterns to the details of surface structure provides the basis for a scattering and recoiling imaging spectrometry (SARIS). The primary ion beam current is ∼0.1 nA/cm2, supplied in 20 ns pulses at a rate of 30 kHz, resulting in ∼5×102 ions/pulse; images with adequate statistics can be obtained in several seconds with a total ion dose of <1010 ions/cm2. The SARIS technique can provide unique, element-specific, real-space, surface structural information at a resolution of <0.1 Å on a time scale of seconds for analysis of surface composition, structure, and dynamics. Examples provided for demonstrating the capabilities of the system are 4 keV He+ and Ar+ scattering and recoiling from Pt{111} and 4 keV Kr+ scattering and recoiling from CdS{0001}.

Selective MBE growth of GaAs wire and dot structures using atomic hydrogens and their electronic properties

The selective growth of GaAs wire and dot structures by molecular beam epitaxy in the presence of atomic hydrogen was studied on a GaAs substrate with stripe and window shaped SiN x mask patterns. It was found that 20 nm ridges were successfully formed on long stripe patterns but the ridge width increased substantially when grown on short stripes of less than several μm. This is ascribed to the longitudinal migration of Ga flowing from the two ends of a stripe to its central zone. The incorporation of Si dopants into a 0.3 μm-wide wire was achieved. Negative magnetoresistance and conductance fluctuations indicative of the one-dimensional nature of electrons were observed. On a 2 x 2 μm square window pattern, a pyramidal structure with two-fold symmetry was formed, on which a GaAs dot with the lateral dimension of 100 nm was grown. Photoluminescence (PL) spectra from this dot exhibited a shoulder structure 15 meV, suggesting the filling of several discrete levels and the slow relaxation of carriers.

Preparation of nanometer-scale windows in SiO2 for selective epitaxial growth of Si based devices

Three methods are presented for preparation of windows in SiO2 for selective epitaxial growth of Si based devices. The window patterns are defined using e-beam lithography and the structures are grown with chemical vapour deposition or molecular beam epitaxy. One method is based on wet etching; the other two are based on reactive ion etching. The resulting window sizes and quality of epitaxial growth are evaluated using transmission electron microscopy of grown structures. Each of the techniques results in high quality selective epitaxial growth. With a new post-etching treatment in a Cl2 plasma high quality growth is demonstrated in windows as small as 46 nm.

Development of single‐layer positive resist process for electron beam direct writing technology

AbstractA single‐layer resist process using a high resistivity positive resist by solubility reversal (PSR) for electron beam direct writing is described. Conventional PSR designed for mask creation is found to have inhomogeneous dissolution characteristics due to a side effect during the stage of deprotection reaction. To overcome this problem, the efficiency of dissolution inhibition is improved by controlling the composition of base resin materials. Using an optimized base resin structure, 0.4‐μm contact window patterns were successfully delineated in a 1.6‐μm thick single‐layer with a sensitivity of 3.5 μC/cm2. The dry etching durability of a single‐layer PSR was also examined and a high level of dry etching durability for SiO2 etching was observed.

Evaluation of Pupil-Filtering in High-Numerical Aperture I-Line Lens

The pupil-filtering lens system for optical lithography experimentally evaluated in this study is based on an i-line stepper lens with a numerical aperture (NA) of 0.5, and its pupil function can be set arbitrarily to change the image characteristics. With the previously proposed super-FLEX filter, the depth of focus was three times that of the system without the filter, and the resolution for window patterns was 20% higher. Image characteristics of the filter, such as the edge-enhancing effect and the proximity effect, are discussed and were experimentally evaluated. The optical and mechanical tolerances required for this system are shown to be within ranges that are attainable in practical stepper systems.

Discrete Gabor transform

A feasible algorithm for implementing the Gabor expansion, the coefficients of which are computed by the discrete Gabor transform (DGT), is presented. For a given synthesis window and sampling pattern, computing the auxiliary biorthogonal function of the DGT is nothing more than solving a linear system. The DGT presented applies for both finite as well as infinite sequences. By exploiting the nonuniqueness of the auxiliary biorthogonal function at oversampling an orthogonal like DGT is obtained. As the discrete Fourier transform (DFT) is a discrete realization of the continuous-time Fourier transform, similarly, the DGT introduced provides a feasible vehicle to implement the useful Gabor expansion.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Loading Effects on Kinetical and Electrical Aspects of Silane‐Reduced Low‐Pressure Chemical Vapor Deposited Selective Tungsten

The growth rate of selective tungsten using tungsten hexafluoride and silane was measured in situ by measuring the time‐reflectance curve during selective deposition on a grating or contact window pattern etched in oxide on a silicon substrate. Ex situ measurements were performed by step‐height and weight‐increase measurement. The growth rate and electrical resistivity depend on the loading, i.e., the density of the growing area in a selective deposition. The difference in growth rate between extreme cases, i.e., 100% vs. 0.04% growing surface of a 3‐inch wafer for identical flow and pressure conditions can be as high as a factor of 20. The true surface kinetics were independent of the loading and can be determined quantitatively by calculating the surface partial pressures using a mathematical model. At low growing surface densities, the partial pressures at the wafer surface were approximately equal to the input partial pressures. At large loading, significant differences were calculated between surface and input conditions. The apparent order of growth rate in was 1 at low ratios and increased at a critical ratio. The order of growth rate in was −0.2 (±0.05) at ratios below 0.5 and became approximately −0.7 at higher ratios. The temperature dependence of the growth rate was small. The growth rate had a maximum at 300°C.

Evaluation of thermal comfort and indoor air quality in offices

Professor Derek Croome and his colleagues in their CIB Montreal paper present the results of an investigation into the indoor environment of a naturally ventilated office and conclude that data from laboratory tests are insufficient. A field test method is established which allows an investigation to take into account window and door opening patterns and peoples reactions to air temperature, fresh air and movement.

High-precision motion and alignment in an ion-beam proximity printing system

We measure the fluorescent alignment generated by ion bombardment of an SiO2 wafer mark scanned behind a corresponding window pattern in a silicon stencil mask. We conclude that an optimized system can align to 50 nm (mean+3σ) in less than 300 ms. Throughput is shown to be limited not by the alignment system, but by thermal loading of the mask during exposure.