• ETRI Journal
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• 제17권4호
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• pp.13-24
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• 1996

We determine the reduced mass of heavy-hole exciton and the heavy-hole in-plane mass for a series of (In, Ga)As/GaAs strained layer quantum wells using the magnetolu-minescence measurements of the exciton ground state and the modified perturbation approach. In the theoretical calculation of the magnetoexciton ground state, the exciton reduced mass is considered as an adjustable parameter, and two variation parameters are used in the unperturbed wave function which is expressed in terms of subband wave functions in the growth axis and the product of two-dimensional hydrogen and oscillator like wave functions for the in-plane component. We take into account the energy dependence of transverse and in-plane electron masses in the twoband effective mass approximation. The electron effective mass decreases as either quantum-well width or indium composition increases, and so does the heavy-hole in-plane mass down to the value at the decoupling limit ($m_{hh,\;{\rho}}=0.11m_0$).

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.391.2-391.2
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• 2014

Solution-processible hybrid bipolar field effect transistors (HBFETs) with balanced hole and electron mobilities were fabricated using a combination of the organic p-type poly (3-hexylthiophene) (P3HT) layer and inorganic n-type ZnO material. The hole and electron mobilities were first optimized in single layer devices by using acetonitrile as a solvent additive to process the P3HT and annealing to process the ZnO layer. The highest hole mobility of the P3HT-only-devices with 5% acetonitrile was 0.15 cm2V-1s-1, while the largest electron mobility was observed in the ZnO-only-devices annealed at $200^{\circ}C$ and found to be $7.2{\times}10-2cm2V-1s-1$. The inorganic-organic HBFETs consisting of P3HT with 5% acetonitrile and ZnO layer annealed at $200^{\circ}C$ exhibited balanced hole and electron mobilities of $4.0{\times}10-2$ and $3.9{\times}10-2cm2V-1s-1$, respectively. The effect on surface morphology and crystallinity by adding acetonitrile and thermal annealing were investigated through X-ray diffraction and atomic force microscopy (AFM). Our findings indicate that techniques demonstrated herein are of great utility in improving the performance of inorganic-organic hybrid devices

• Journal of the Optical Society of Korea
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• 제20권6호
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• pp.663-668
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• 2016

In single-photon-emission computed tomography (SPECT) with a pixelated semiconductor detector (PSD), not only pinhole collimators but also parallel-hole collimators are often used in preclinical nuclear-medicine imaging systems. The purpose of this study was to evaluate and compare pinhole and parallel-hole collimators in a PSD. For that purpose, we paired a PID 350 (Ajat Oy Ltd., Finland) CdTe PSD with each of the four collimators most frequently used in preclinical nuclear medicine: (1) a pinhole collimator, and (2) low-energy high-resolution (LEHR), (3) low-energy general-purpose (LEGP), and (4) low-energy high-sensitivity (LEHS) parallel-hole collimators. The sensitivity and spatial resolution of each collimator was evaluated using a point source and a hot-rod phantom. The highest sensitivity was achieved using LEHS, followed by LEGP, LEHR, and pinhole. Also, at a source-to-collimator distance of 2 cm, the spatial resolution was 1.63, 2.05, 2.79, and 3.45 mm using pinhole, LEHR, LEGP, and LEHS, respectively. The reconstructed hot-rod phantom images showed that the pinhole collimator and the LEHR parallel-hole collimator give a fine spatial resolution for preclinical SPECT with PSD. In conclusion, we successfully compared different types of collimators for a preclinical pixelated semiconductor SPECT system.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.13-13
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• 2010

Switching an elementary excitation by injecting a single carrier would offer the exciting opportunity for the ultra-high data storage technologies. However, there has been no methodology available to investigate the interaction of low energy discrete carriers with nano-structures. In order to map out the spatial dependency of such single carrier level interactions, we developed a pulse-and-probe algorithm, combining with low temperature scanning tunneling microscopy. The new tool, which we call single carrier spectroscopy, allows us to track the interaction with the target macrostructure with tunneling carriers on a single carrier basis. Using this tool, we demonstrate that it is possible not only to locally write and erase individual bi-solitons, reliably and reversibly, but also to track of creation yields of single and multiple bi-solitons. Bi-solitons are pairs of solitons that are elementary out-of-phase excitations on anti-ferromagnetically ordered pseudo-spin system of Si dimers on Si(001)-c(42) surfaces. We found that at low energy tunneling the single bisoliton creation mechanism is not correlated with the number of carriers tunneling, but with the production of a potential hole under the tip. An electric field at the surface determines the density of the local charge density under the tip, and band-bending. However a rapid, dynamic change of a field produces a potential hole that can be filled by energetic carriers, and the amount of energy released during filling process is responsible for the creation of bi-solitons. Our model based on the field-induced local hole gives excellent explanation for bi-soliton yield behaviors. Scanning tunneling spectroscopy data supports the existence of such a potential hole. The mechanism also explains the site-dependency of bi-soliton yields, which is highest at the trough, not on the dimer rows. Our study demonstrates that we can manipulate not just single atoms and molecules, but also single pseudo-spin excitations as well.

• 한국전기전자재료학회논문지
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• 제11권6호
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• pp.442-446
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• 1998

$\alpha$--sulfur single crystal which has orthorohmbic structure was grown using Bridgman method. The indirect optical energy band gap of this crystal are 2.65 and 2.82 eV at 10 and 300K, respectively. The wavelengths of photoluminecence(PL) peaks are 543 and 596 nm at 10k, By thermally stimulated current (TSC) method, two electron traps($D_1,D_2$) located at 0/23 and 0.43eV below the conduction band and a hole trap(A) located at 0.31 eV above the valence band are observed. PL mechanism of $\alpha$-sulfur single crystal is analyzed using the values of optical energy band gap at 10k two electron traps and a hole trap.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.201-201
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• 2010

볼로미터 제작 공정 중 One step via 공정 시 via hole 모양에 의해 정기적 연결 및 구조적 안정성에 문제를 해결하기 위하여 다른 via 식각 방식으로 공정을 진행하였으며 그에 따른 via 공정 차이에 대한 결과를 연구하였다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 1995년도 제2회 KOSCI Workshop
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• pp.105-121
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• 1995

The objective of this study is to find out the design data for gas burner with an axal and radial type nozzles. The design parameters are chosen as the stabilizer type, the jet hole size of gas nozzle, the distance between gas nozzle and stabilizer, the size of stabilizer and the hole size of stabilizer, the stabilizer type with or without air swirler, the angle of swirler. For the experimental test combustor sizing ${\phi}1.3m{\times}L4.5m$ is designed and manufactured, in which the set up of power diagram, the exhaust gas analysis, blow-off test, the flame temperature and the direct photography are performed.

• 에너지공학
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• 제24권2호
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• pp.17-21
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• 2015

다공 및 다단오리피스열을 해석할 수 컴퓨터코드를 사용하여 원자력발전소 내 공급 및 배출장치의 수축오리피스를 설계하였다. 원래 단공 오리피스가 설치되었으나 다공 오리피스 설치가 필요하여 설계 변경되었다. 오리피스 사이 거리는 충분한 압력회복거리로 유지되었다. 최소 정압은 공동현상 방지를 위하여 그 온도에 상응하는 증기압 이하로 유지되도록 설계하였다. 오리피스 설치 배관의 직경은 운전시 강성을 유지할 수 있도록 원래 크기보다 증가시켰다.

• 한국자동차공학회논문집
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• 제5권1호
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• pp.146-153
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• 1997

An experiment was conducted to figure out the atomization characteristics of a highly viscous biodiesel fuel with rice-barn oil applying and ultrasonic energy into it. A spray simulator for the droplet atomization, an ultrasonic system, and six different nozzles(3 pintle-type nozzles and 3 single hole-type nozzles) were made. To investigate effects of ultrasonic energy in a highly viscous liquid fuel, an immersion liquid method was used as a measurement method on droplet size distributions. It was found that the ultrasonic energy was effective for the atomization improvement of the rice-bran oil as a highly viscous biodiesel fuel and the factor나 such as the nozzle opening pressure, pin-edge angles, hole diameters, and collection distances affected the atomization of spray droplets.

• 한국전기전자재료학회논문지
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• 제22권6호
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• pp.512-515
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• 2009

We have fabricated blue phosphorescent organic light emitting diodes (PHOLEDs) using a 3,5'-N,N'-dicarbazole-benzene (mCP) host and iridium (III) bis[(4,6-difluorophenyl)-pyridinato-N,$C^{2'}$] picolinate (Flrpic) guest materials, The Flrpic was partially doped into the mCP host layer, for investigating recombination zone, current efficiency, and emission characteristics of the blue PHOLEDs. The recombination of electrons and holes takes place inside the mCP layer adjacent to the mCP/hole blocking layer interface. The best current efficiency was obtained in a device with an emission layer structure of mCP (10 nm)/mCP:Flrpic (20 nm, 10%). The high current efficiency in this device was attributed to the confinement of Ffrpic triplet excitons by the undoped mCP layer with high triplet energy, which blocks diffusion of Ffrpic excitons to the adjacent hole transport layer with a lower triplet energy.