Seong-Joo Jang

Growth and characterization of single crystal ZnO thin films using inductively coupled plasma metal organic chemical vapor deposition

Zinc oxide thin films were grown on sapphire substrates by metal organic chemical vapor deposition technique. Single crystal films with flat and smooth surfaces were reproducibly obtained, with application of sample bias and O2 inductively coupled plasma (ICP). At the growth condition of 650°C, 400W ICP power, −94V bias voltage and O∕Zn ratio of 75, full width at half maximum values of room temperature photoluminescence and high-resolution x-ray diffraction were measured to be 126meV and 269arcsec, respectively. It was proposed that application of sample bias provided reactant ions with kinetic energy, which promoted formation of single crystalline films.

Microstructural investigation of low temperature chemical vapor deposited 3C-SiC/Si thin films using single-source precursors

Transmission electron microscopy (TEM) was utilized to investigate microstructures of heteroepitaxial SiC/Si films, grown from single-source precursors such as tetramethylsilane [TMS, Si(CH 3 ) 4 ], hexamethyldisilane [HMDS, Si 2 (CH 3 ) 6 ], and 1,3-disilabutane [1,3-DSB, H 3 SiCH 2 SiH 2 CH 3 ]. In the case of TMS/H 2 and HMDS/H 2 samples, SiC/Si films grown at relatively high precursor concentration and/or low temperatures showed columnar grains with a high degree of epitaxial relationship with the Si substrate. Higher quality films with larger grains were observed in the case of high temperature and/or low precursor concentration samples, although a high density of interfacial voids was observed. Samples grown from pure 1,3-DSB at a low pressure showed high quality single crystalline films with few interfacial voids. It was suggested that the microstructural behavior of these films closely resembles that of the SiC films formed during the carbonization of Si surfaces by the pyrolysis of hydrocarbons, in which the nucleation rate of the film at the initial stage plays a key role. The improvement achieved during the 1,3-DSB growth is proposed to be due to the low growth pressure and the 1 : 1 ratio of Si and C associated with this precursor.

Effects of silicon-on-insulator substrate on the residual stress within 3C-SiC/Si thin films

Single-crystalline 3C-SiC heteroepitaxial layers were grown on silicon-on-insulator (SOI) and Si wafers, to investigate effects of SOI substrates on the film quality. Residual stress measurement using a laser scan method and the Raman scattering spectroscopy indicated that internal stress within SiC films on SOI were indeed reduced, when compared with that of SiC films on Si.

Chemical-vapor-deposition growth and characterization of epitaxial 3C-SiC films on SOI substrates with thin silicon top layers

Epitaxial 3C–SiC films were grown by chemical vapor deposition on the silicon-on-insulator (SOI) substrates with 20–75-nm-thick Si top layers. A relatively low growth temperature of 1150 °C and a reduced hydrogen flow rate of 1 lpm during the precarbonization process was necessary to preserve the SOI structure and thereby obtain high-quality SiC films. The transmission electron microscopy observation of the SiC/SOI structures revealed high density of misfit dislocations in the SiC film, but no dislocation within the top Si layer. The x-ray-diffraction results did not show any significant shift of the (400) SiC peak position among the SiC/Si and the SiC/SOI samples. This strongly suggests that the Si top layer is not deformed during the SiC/SOI growth and the strain within the 3C–SiC layer is not critically affected by substituting the Si substrate with the SOI substrate, even when the Si top layer is as thin as 20 nm.

Liquid phase epitaxial growth of high quality GaAs on InP using Se‐doped GaAs buffer layer and grating‐patterned substrates

High quality GaAs layers with excellent crystal quality and surface morphology were grown on InP substrates (GaAs/InP) using liquid phase epitaxy. Thin GaAs buffer layers heavily doped with Se were utilized to prevent the substrate meltback and the InP substrates patterned with gratings to reduce the dislocation density. Double crystal x‐ray diffraction showed about 230 arcsec full width at half maximum of the (400) reflection, which represents significant improvement compared to the previously reported 350 arcsec of the GaAs/InP layer grown by chemical beam epitaxy using strained superlattice buffer layers.

Evaluation on Usefulness of Applying Body-fix to Four Dimensional Radiation Therapy

This study investigates the usefulness of body fix in 4DRT on Liver cancer trying to find tumor tissue`s volume and located variations, absorbed dose on tumor and normal tissues. Test subjects 23 patients were agreed these test. These patient`s have a 4 dimensional CT scan. We make an acquisition on patients CT image by two types -put on the body fix or not-. Average tumor volume reduced by 0.17% on GTV and 3.2% on CTV and PTV. Tumor`s variation reduces 29.8%(anterior and posterior, AP) and 5.31% (upper and lower, UL). The absorbed tumor doses under put on the body fix was a little higher(1.3%) than other. Normal tissues`(normal liver, stomach, Rt. kidney, spinal cord) absorbed dose could be reduced approximately 5%. Therefore, using body fix on 4DRT for liver cancer patient is considered effectively.

Clinical Outcomes of Stent Thrombosis after Drug-Eluting Coronary Stent Implantation

Stent thrombosis after successful drug-eluting stent(DES) implantation has been reported in around 1% of patients in clinical trials. However, the increased risk of ST associated with DES remains a matter of concern. From 1 June 2003 to 30 June 2013, we investigated clinical characteristics, in-hospital outcomes in 10,273 patients who underwent percutaneous coronary intervention in the Heart Center of CNUH. Overall incidence of ST was 1.30% (134 patients). The incidence of ST according to the stent generations and the timing of ST (n= total, early vs. late vs. very late) were 0.79% (n =81, 26 vs. 12 vs. 43) in first-generation, 0.38% (n=39, 21 vs. 9 vs. 9) in second-generation and 0.14% (n=14, 8 vs 3 vs. 3) in third-generation, (p=0.70). The mortality from ST was significantly higher in early ST group compared to the late and very late ST groups (18.2% vs. 8.3% vs. 3.6%, p=0.042). Overall incidence of ST after DES implantation was 1.30% (134 patients). The in-hospital mortality was significantly higher in early ST group compared to the late and very late ST groups. ■ keyword :∣Drug-eluting Stents∣Stent Thrombosis∣Percutaneous Coronary Intervention∣ 접수일자 : 2013년 10월 07일 수정일자 : 2013년 11월 05일 심사완료일 : 2013년 12월 02일 교신저자 : 장성주, e-mail : sjjang@dsu.ac.kr 약물방출 관상동맥 스텐트 시술 후 스텐트 혈전증 발생 환자의 임상경과 881

Measurement and Estimation for the Clearance of Radioactive Waste with Patients of Thyroid Treatment

의료현장에서의 방사성폐기물은 방사성동위원소의 사용량의 증가와 더불어 급격히 늘어나고 있다. 특히, 갑상선 질병의 진단 및 치료용으로 사용량이 증가하고 있는 I-131 핵종의 경우 8.02 일의 짧은 반감기를 가지고 있으며, 관련 폐기물은 모두 자체처분 방법으로 처분하고 있다. 이와 관련하여 국제원자력기구(IAEA)는 개인선량(10 μSv/y) 및 집단선량(1 man-Sv/y)과 핵종별 농도 에 근거하여 각각 폐기물의 규제해제기준을 제시(IAEA Safety Series No 111-P-1.1, 1992 및 IAEA RS-G-1.7, 2004)하였다. 이 연구에서는 의료현장에서 발생하는 I-131 핵종 관련 폐기물을 사용상 종류별 로 수집 및 측정하여 방사능농도의 측정 방법 및 절차를 수립한다. 또한, 측정 결과를 바탕으로 핵종의 감쇠 유도식을 산출하고, 이것을 바탕으로 자체처분 가능일자를 산출하여 이론식의 경우와 대비하여 고찰하였다. 측정 결과를 바탕으로 유도 감쇠식을 신정하여 이론적 반감기와 유효 반감기를 비교해 본 결과, I-131 핵종 의 이론적 반감기가 유효반감기(7.72일)에 비해 긴 반감기를 가지고 있음을 확인하였다. 측정결과를 바탕으로 한 유효 반감기를 적용한다면, 현재보다 더 짧은 기간 동안 I-131 핵종 폐기물을 보관하였다가 자체처분을 할 수 있다. 이 연구 결과는 ISO 표준으로 추진할 예정이다.

The Comparison of Dose Distribution on Radiation Therapy between IMRT and VMAT in Modified Radical Mastectomy Patients

Underwent on modified radical mastectomy(MRM) and radiation therapy, it affects increasing rates of chronic morbidity, because of including chest wall and internal mammary nodes(IMNs). It causes the high absorbed dose on heart and ipsilateral lung. Thus in this study, we compared dose distributions through utilizing the intensity modulated radiation therapy(IMRT) and the volumetric modulated arc therapy(VMAT). We selected 10 breast cancer patients at random who took MRM and radiation therapy. Treatment plannings were done by using IMRT and VMAT from each patient ranging supraclavicular lymphnodes(SCL) and IMNs. After that we analysed the planning target volume(PTV)`s conformity and absorbed doses on heart and lungs. As a results, PTV conformities were indicated the same patten(p

Long-term Clinical Outcomes after Primary Percutaneous Coronary Intervention in Patients with Acute Myocardial Infarction-on the basis of 65 Years

Primary percutaneous coronary intervention (PCI) has been found to be superior, in terms of hospital mortality and long-term outcome, compared with thrombolytic therapy in patients with acute myocardial infarction (AMI). However, the clinical benefits of primary PCI have not been precisely evaluated in elderly patients.1,974 patients (Group I: n