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.

Single Adatom Exchange in Surfactant-Mediated Epitaxial Growth

Yi, Jae Yel,Lee, El Hang,Ko, Young Jo,Park, Seong Ju,Chang, K. J. 東亞大學校附設基礎科學硏究所 1997 基礎科學硏究論文集 Vol.14 No.1

We propose a single adatom exchange mechanism for surfactant-mediated epitaxial growth through first-principles calculations for the Si epitaxy on a si(001) surface covered by an As monolayer. The As segregation is initiated by the exchange of a Si adatom with a sublayer As site, with an activation energy of about 0.1 eV which is much lower than the value of ∼ 1.0 eV for a dimer exchange. Adatom incorporation occurs with minimum surface diffusion, giving rise to a high nucleation density of two-dimensional islands, in good agreement with experiments. [S0031-9007(96)00055-5]

Atomic structure of monatomic S B steps on clean Si(001) and Ni-contaminated Si(001)

Yi, Jae Yel,Kim, Dal Hyun,Cho, Jaewon,Lee, Sekyung,Koo, Ja Yong,Hwang, Chanyong 東亞大學校附設基礎科學硏究所 1997 基礎科學硏究論文集 Vol.14 No.1

The atomic structure at monatomic-height S B steps on clean Si(001) and a Ni-contaminated Si(001) was investigated using high-resolution scanning tunneling microscopy at room temperature. Rebonded S B steps are dominant on clean Si(001). Nonrebonded S B steps with split-off dimers are favored on the Ni-contaminated Si(001) and in the vicinity of dimer vacancies on clean Si(001). The nonrebonded step with the split-off dimer is generated by the strain due to dimer vacancies. A buckled dimer was observed in the vicinity of a kink of S B step edges on clean Si(001). [S0136-1829(96)09739-1]

Rapid Thermal Annealing Eect on Charge Storage Characteristics in MOS Capacitor with Ge Nanocrystals

Jae Kwon Kim,Hea Jeong Cheong,Hong Jun Bark,J. H. Cho,Jae-Yel Yi,Kyung Hwa Park,S. H. Bang,Yong Kim 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.III

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.

증례 : 내분비-대사 ; 융모 상피성 종양을 진단받은 환자에서 발병한 갑상선 유두암 1예

김재현 ( Jae Hyun Kim ),김송이 ( Song Yi Kim ),이미영 ( Mi Young Lee ),신장열 ( Jang Yel Shin ),신영구 ( Young Goo Shin ),정춘희 ( Choon Hee Chung ) 대한내과학회 2011 대한내과학회지 Vol.80 No.4

갑상선 암은 가장 흔한 내분비암 중 하나이다. 갑상선은 성호르몬과 β-HCG 등의 영향을 받기 때문에 β-HCG가 증가되는 임신시나 융모 상피성 질환에서 갑상선 질환의 발생이 촉진 될 수 있다고 알려져 왔다. 하지만 융모 상피성 종양 환자에서 갑상선 암이 동반된 경우는 아직까지 국내에서 보고되지 않았다. 이에 저자는 융모 상피성 종양 환자에서 갑상선 유두암이 동반된 사례를 경험하였기에 문헌고찰과 함께 보고한다. Thyroid cancer is one of the most common endocrine malignancies. It is known that thyroid cancer can develop during reproductive periods, possibly due to the effects of sex hormones and growth factors such human chorionic gonadotrophin (HCG). Some data suggest that elevated HCG levels during pregnancy or gestational trophoblastic disease can stimulate thyroid cellular proliferation and promote cancer formation; however, a case of papillary thyroid cancer accompanied by a gestational trophoblastic tumor has not been reported. Here, we report the case of a 44-year-old woman with papillary thyroid cancer during treatment for a gestational trophoblastic tumor. (Korean J Med 2011;80:464-468)

Si(100) 표면에 대한 plasma 처리 효과

조재원(Jaewon Cho),이재열(Jae-Yel Yi) 한국진공학회(ASCT) 1999 Applied Science and Convergence Technology Vol.8 No.1

여러 가지 방법의 plasma 표면 처리와 산화 공정이 SiO₂-Si(100) 계면에 미치는 물리적 영향을 angle resolved uv-photoelectron spectroscopy(ARUPS)를 이용하여 연구하였다. 표면은 ex situ 방법과 함께 in situ 수소 플라즈마를 이용하여 처리되어 졌으며, 이것은 고진공 고온 열 처리 방법과 비교되어졌다. ARUPS 빛띠 상에 나타난 산화물 가전자 띠에 대한 특징적인 peak 위치는 표면 처리 및 산화 공정 방법에 따라 이동하였다. 이러한 peak의 이동은 Si에서의 띠휨에 의한 것으로 분석되어졌다. 또한 peak 이동의 원인으로 Si-SiO₂ 계면에 형성된 결점과 표면 처리 공정에 따라 달라지는 표면 거칠기 등을 고려할 수 있었다. 여러 공정에 대한 ARUPS 결과를 비교함으로써 Si-SiO₂ 계면 결합이 표면 처리 및 산화 방법에 깊이 관련되어 있음을 결론지을 수 있었다. 산소 plasma 공정은 가장 작은 band bending을 보여주었다. The effect of different plasma surface preparation and oxidation processes for the formation of SiO₂-Si(100) interfaces was studied using angle resolved uv-photoelectron spectroscopy. The surface preparation processes included ex situ preclean as well as in situ hydrogen plasma, which were compared to the processes of UHV annealing at high temperature. The spectral position of the oxide valence band features, with respect to the Fermi level, were found to shift according to the different processes of surface preparation and oxidation. The shifts were analyzed in terms of band bending in the Si. Origins of the spectral shifts were considered to include defects at the SiO₂-Si interfaces and surface morphology(roughness) dependent on the surface preparation processes. From comparison of the ARUPS results of the various processes, it was concluded that the interface bonding of the silicon oxide-Si(100) was dependent on the oxidation process and the surface preparation. The O-plasma process showed the lowest band bending.

Electronic Structures and Magnetic Properties of Fe/Si/Fe Trilayer

Min, Byung Il,Yi, Jae Yel,Park, Jin Ho,Youn, Suk Ju 東亞大學校附設基礎科學硏究所 1997 基礎科學硏究論文集 Vol.14 No.1

Employing the LMTO band method, we have studied electronic and magnetic properties of Fe/Si/Fe trilayer in which the z-direction is chosen to be (111) direction of FeSi with B₂phase. We have also determined electronic structure of bulk FeSi, as a reference material. The ground state of FeSi is paramagnetic insulator with a band gap of 0.05 eV. Band structures of Fe/Si?/Fe with varying the thickness of the spacer layer reveal that the spacer layer is metallic, and the states along the growth direction do not disperse much reflecting a two-dimensional nature. Magnetic moment of Fe atom in the interfacial layer of Fe/Si?/Fe is reduced a lot as compared to the bulk value, suggesting a strong hybridization between Fe and Si states. The geometry of the Fermi surface indicates that the magnetic coupling period of ∼8 ML (monolayers) in Fe/Si?/Fe is explained with a short Fermi wave vector of bcc Si.