증착조건에 따른 HFCVD 다이아몬드 박막의 제작 및 특성조사

권민철,박홍준 東亞大學校 1997 東亞論叢 Vol.34 No.-

We investigated the optimum condition for the deposition of high quality diamond films using HFCVD(Hot Filament Chemical Vapor Deposition) method. Deposition was carried out as the DC bias current was changed from-800mA to +500mA. The chamber pressure and the methane concentration was 20torr and 1% respectively. The deposited diamond films were examined by SEM, XRD and Raman spectroscopy. We found that it was the optimum deposition condition to apply the -100mA negative bias during the nucleation stage and then to switch into the 300mA positive bias during the growth stage in the fabrication of diamond films. In the result diamond films deposited by our optimum condition were proved to be high quality diamonds.

Ge 나노결정이 함유된 MIS 구조의 전하충전 특성

정혜정,김용,이재열,박홍준 동아대학교 기초과학연구소 2001 基礎科學硏究論文集 Vol.18 No.1

펄스레이저 증착법 (Pulsed Laser Deposition) 및 급속열처리 산화공정에 의하여 Ge 나노결정이 함유된 MIS (metal-insulator-semiconductor) 구조를 제작하였다. 이 MIS 구조의 전하충전 특성을 C-V(capacitance-voltage) 방법에 의하여 연구하였다. Ge 나노결정이 함유된 MIS 구조는 모두 강한 C-V hysteresis를 나타내어서 전하충전현상이 존재함을 확인하였다. 게이트 바이어스 sweep rate를 변화시키면서 C-V 특성을 조사한 결과 sweep rate 가 감소함에 따라 C-V 이력곡선의 폭이 감소함을 발견하였고 특히 정공충전 후 순방향의 sweep에서 측정한 C-V 곡선에 특이한 plateau 현상이 일어남을 발견하였다. 이 plateau 의 폭은 sweep rate를 감소시킴에 따라 감소하였고 높이 또한 감소하였다. 이 plateau는 Ge 나노결정에 충전되었던 정공에 의한 현상으로 해석된다. Sweep rate 와 plateau 의 높이의 상관 관계로부터 정공의 탈출시간과 관련이 있는 특성시간 τ는 약 11 초 정도로 산출되었다. The charge retention characteristics in a metal-insulator-semiconductor capacitor containing Ge nanocrystals is investigated by means of capacitance-voltage measurements with various gate bias sweep rates. The metal-insulator-semiconductor capacitor is fabricated by pulsed laser deposition and rapid thermal oxidation. The capacitance-voltage curve shows the strong hysteresis indicating charging/discharging of carriers during the gate bias sweeping. The stored charge densities evaluated from the flat band voltage shifts, show the non-dispersive carrier relaxation, which is a characteristic property for nanocrystals arranged in a layer. In addition, we observe interesting capacitance ledge during forward bias sweeping. From the trap distribution determination by Terman method, the capacitance ledge is due to an energetically localized trap at 0.33 eV +Ev. The energetic position of the trap is in agreement with the ground state hole energy level in Ge nanocrystal.

탄소 나노튜브의 전계방출 특성

이경원,김은미,권민철,김용,이재열,박홍준 동아대학교 기초과학연구소 2000 基礎科學硏究論文集 Vol.17 No.1

본 연구에서는 emitter와 collector 사이의 간격과 current density 대 electric field (J-K)특성을 초점으로 카본나노튜브의 전계방출 특성을 조사하였다. 카본 소스로 CH4, 촉매 및 희석가스로서 NH3를 사용하고 HFCVD를 이용하여 실리콘 위에 카본나노튜브를 성장하였다. 나노튜브의 지름이 20-40nm이고 길이는 15㎛이다. I-V곡선에서 onset voltage는 Vons=3.36V/㎛이고, 2.5V/㎛ 의 전기장에서 8mA/cm2이상의 높은 전류밀도 특성을 보였다. Fowler-Nordheim 그래프를 그려서 팁의 특성을 나타내는 β값을 계산하였다. We report the field emission properties of carbon nanotube, focusing on current density versus electric field (J-F) characteristics and the spacing between the emitter and collector. We grow carbon nanotubes on sillicon using hot-fillament chemical vapor deposition, using CH4 gas as the carbon source and NH3 gas as the catalyst and dilution gas. Nanotubes are distributed from 20 to 40nm in diameter and 15㎛ long. Onset field of the field emission is 3.36V/㎛ and the current density is 8mA/cm2 at an electric field of 2.5V/㎛. A Fowler-Nordheim plot was made. Field enhancement factor β is calculated.

HFCVD법을 이용하여 제작한 n-형 다이아몬드 박막의 특성 연구

김병규,황윤식,권민철,김용,이재열,박홍준 동아대학교 기초과학연구소 2000 基礎科學硏究論文集 Vol.17 No.1

HFCVD법으로 암모니아 가스를 사용하여 n-형 도핑된 다이아몬드 박막을 제작하여, 기판온도와 암모니아 가스 첨가비에 따른 박막의 morphology의 변화를 조사하였다. 증착된 시료에 대한 SEM, Raman, XRD를 이용하여 박막의 특성을 분석하고, 도핑에 따른 전계방출 특성을 측정하였다. 양질의 n-형 도핑된 다이아몬드 박막을 증착시키기 위해 기판온도와 암모니아 첨가비에 따른 최적의 증착조건을 찾을 수 있었다. We fabricate n-doped diamond thin films by hot filament chemical vapor deposition method(HFCVD) using ammonia as a doping gas and investigate the effect of the substrate temperature and the ammonia gas ratio upon the diamond film morphology. The SEM, Raman spectroscopy, and the XRD analysis are executed to characterize film morphology. Field emission property of the film is measured also. We find optimum conditions of the substrate temperature and the ammonia gas ratio to deposit high quality n-doped diamond thin films.

Fluctuation of Mixed s-wave and d-wave Superconductors

Bark,Hong-jun 東亞大學校 1994 東亞論叢 Vol.31 No.1

고온초전도체에 대한 s-파와 d-파 혼함 질서 매개변수의 적용을 알아보았다. Tetragonal 대칭군의 A1과 B1 표현에 각각 속하는 s-파와 d-파 상태에 대한 Ginzburg-Landau 에너지 밀도를 군이론으로 계산하였고 이 계의 요동에 기인하는 비열에 관한 식을 구하였다.

Deposition of Carbon Whiskers by Applying bias Voltage and Investigation of Their Field Emission Properties

Mincheol Kweon,Hong Jun Bark 한국물리학회 2021 New Physics: Sae Mulli Vol.71 No.5

A carbon whisker-shaped thin film, similar to a carbon tube, was fabricated, instead of conventional diamond crystal particles, by applying a bias voltage to the silicon substrate. The fabricated thin film was analyzed for shape and composition by using scanning electron microscopy and Raman spectroscopy. As the bias current was increased, the shape of the carbon whiskers tended to become thinner and longer, causing an increase in the field emission current. Additionally, an increase in the CH4 concentration and substrate temperature increased the whisker diameter. Moreover, an addition of NH3 increased the growth rate and caused the formation of sharp edges on the whiskers, resulting in a decreased operating voltage in field emission

High-Throughput Analysis of New Bone Formation and Bone Substitutes After Maxillary Sinus Floor Elevation Using Synchrotron Radiation Micro-Computed Tomography

Seo, Seung-Jun,Lim, Jae-Hong,Lee, Youngkyun,Bark, Chung Wung,Kim, Yong-Gun American Scientific Publishers 2019 Journal of Nanoscience and Nanotechnology Vol.19 No.2

Effects of Enhanced Hydrophilic Titanium Dioxide-Coated Hydroxyapatite on Bone Regeneration in Rabbit Calvarial Defects

Lee, Ji-Eun,Bark, Chung Wung,Quy, Hoang Van,Seo, Seung-Jun,Lim, Jae-Hong,Kang, Sung-A,Lee, Youngkyun,Lee, Jae-Mok,Suh, Jo-Young,Kim, Yong-Gun MDPI 2018 INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES Vol.19 No.11

<P>The regeneration of bone defects caused by periodontal disease or trauma is an important goal. Porous hydroxyapatite (HA) is an osteoconductive graft material. However, the hydrophobic properties of HA can be a disadvantage in the initial healing process. HA can be coated with TiO<SUB>2</SUB> to improve its hydrophilicity, and ultraviolet irradiation (UV) can further increase the hydrophilicity by photofunctionalization. This study was designed to evaluate the effect of 5% TiO<SUB>2</SUB>-coated HA on rabbit calvarial defects and compare it with that of photofunctionalization on new bone in the early stage. The following four study groups were established, negative control, HA, TiO<SUB>2</SUB>-coated HA, and TiO<SUB>2</SUB>-coated HA with UV. The animals were sacrificed and the defects were assessed by radiography as well as histologic and histomorphometric analyses. At 2 and 8 weeks postoperatively, the TiO<SUB>2</SUB>-coated HA with UV group and TiO<SUB>2</SUB>-coated HA group showed significantly higher percentages of new bone than the control group (<I>p</I> < 0.05). UV irradiation increased the extent of new bone formation, and there was a significant difference between the TiO<SUB>2</SUB>-coated HA group and TiO<SUB>2</SUB>-coated HA with UV group. The combination of TiO<SUB>2</SUB>/HA and UV irradiation in bone regeneration appears to induce a favorable response.</P>

Time Resolved Photoluminescence Study on Silicon Nitride/Silicon-Rich-Oxide Superlattices Grown by Using Ion-Beam Sputtering Deposition

Cha Kyuman,Kim Yong,Bark Hong Jun,Chung Tae Hun,Kang Jung Hyun,Kim Young Dae,Yi Jae-Yel 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.48 No.II

Silicon nitride/silicon-rich-oxide (SiN/SRO) superlattices were fabricated by using dual ion-beam sputtering deposition. The effect of the SiN/SRO interface on the optical properties of the Si nanocrystals precipitated in the SRO layers was investigated by means of time-resolved photoluminescence measurements. The decay times of the photoluminescence for all superlattices were in the range of 20 ns 160 ns. Such small decay times reflect the strong effect of the non-radiative recombination centers existing at the SiN/SRO interfaces. For superlattices with thinner SRO thicknesses, the decay times were smaller for all detection wavelengths due to the increasing effect of the non-radiative recombination centers.ou

Selective Formation of Si Nanocrystals by Assist Ion Beam Irradiation

Jae Kwon KIM,Yong KIM,Hong Jun BARK,Jae-Yel YI,Jung Hyun KANG,Kyu Man CHA,Tae Hun CHUNG,Young Dae KIM 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.45 No.3

The deposition of substoichiometric SiOx films is investigated by means of dual ion beam deposition with emphasis on assist ion beam irradiation effect. Linear dependence of oxygen content, x, on oxygen partial pressure is found. Preferential sputtering of Si phase over SiO2 phase during assist ion beam irradiation has the effect of increasing the oxygen content in the ion-beam exposed region. The property indicates the lateral modulation of oxygen content of SiOx film by inserting a shadow mask in the assist ion beam during deposition. The area-selective formation of Si nanocrytals is shown by photoluminescence measurements after post-deposition annealing.