• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.08a
• /
• pp.355-355
• /
• 2012

Si (111) 기판 위에 polystyrene (PS) bead를 사용하여 만들어진 약 100 nm 나노 구멍에 GaN나노선을 molecular beam epitaxy 법으로 성장하였다. 성장 온도와 III/V 비율 변화에 대하여 성장된 GaN 나노선의 모양과 광학적 특성은 scanning electron microscopy (SEM)와 photoluminescence (PL) 등으로 조사하였으며, InN/GaN 이종접합 및 InGaN p-n 다이오드구조를 성장하여 atomic force microscopy의 tip 접촉방법으로 전기적 특성을 조사하였다. PL 측정 결과 성장온도가 높아지면 Ga 빈자리와 관계된 3.28 eV의 donor acceptor pair (DAP) 신호와 3.42 eV의 stacking faults (SF) 결함에 기인된 발광 신호세기가 감소하는 결과를 SEM으로부터 나노선 폭 및 길이는 좁아지면서 짧아지는 것을 관측하였다. 또한 nitrogen 원자양이 증가하면서 Ga 빈자리와 관련된 3.28 eV DAP 신호가 증가하는 것을 관측하였다. 이들 결과로부터 GaN 나노선의 SF 발광 신호관련 원인에 대하여 논의 하였다. AFM을 이용한 I-V 측정으로부터 성장조건 변화에 따른 GaN 나노선 및 p-n 접합 나노선의 전도 특성을 조사하여 나노선의 소자 응용에 대한 기본적인 물리특성을 규명하였다.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.333-333
• /
• 2016

현재까지 가장 높은 광전류 변환 효율을 나타내는 III-V 화합물 반도체의 다중접합 태양전지 대신 이보다 단순한 에피구조를 가진 단일셀 이종접합구조의 태양전지를 제안하였다. 이를 한국나노 기술원에서 MOCVD(Metalorganic Vapour Phase Epitaxy) 장비를 이용하여 에피구조를 성장하고 태양 전지를 제작해 그 특성을 조사하였다. 태양 전지는 서로 다른 orientation의 두 GaAs 기판에 각각 동일한 에피 구조로 성장되었다. GaAs 기판은 Si 도핑된 n-type 기판으로 (100) 표면이 <111>A 방향으로 2도 off 된 웨이퍼와 10도 off 된 웨이퍼가 사용되었다. 연구에서 시뮬레이션에 사용된 태양전지의 에피 구조는 맨 위 p-GaAs (p-contact 층), p-InAlP, p-InGaP의 광흡수층과 N-InAlGaP 층과 아래의 n-InAlP와 n-GaAs의 n-contact층으로 이루어져있다.태양전지는 $5mm{\times}5mm$의 면적을 가지고 있다. 그림 1은 전류-전압의 측정된 결과를 나타낸 그래프이다. 태양전지는 1 sun 조건하에서 probe를 이용해 측정되었다. 2도 off GaAs 기판 위에 성장시킨 태양전지에서는 3.7mA의 단락전류값이, 10도$^{\circ}$ off 인 샘플에서는 4.7mA의 단락전류값이 측정되었다. 반면에 전류-전압곡선으로부터 얻은 10도 off 인 태양전지의 직렬 저항값은 2도 off 인 태양전지의 약4배 정도로 나타났다. 이는 기판의 결정방향에 따라 태양전지의 내부 전하 transport에 차이가 있음을 나타낸다. TLM (Transmission Line Model) 방법에 의한 p-contact의 ohmic저항 측정에서도 이와 일치하는 결과를 얻었다.

• Korean Chemical Engineering Research
• /
• v.49 no.3
• /
• pp.357-360
• /
• 2011

N-doped ZnO nanofilms were prepared by plasma enhanced atomic layer deposition method. $Zn(C_{2}H_{5})_{2}$, $O_{2}$ and $N_{2}$ were used as Zn, O and N sources, respectively, for N-doped ZnO films under variation of radio frequency (rf) power from 50-300W. Structural, optical and electrical properties of as-grown ZnO films were investigated with Xray diffraction(XRD), photoluminescence(PL) and Hall-effect measurements, respectively. Nitrogen content and p-type conductivity in ZnO nanofilms increased with the rf power.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.06a
• /
• pp.110-111
• /
• 2009

상온에서 밴드갭이 2.42 eV의 에너지를 가지며 직접 에너지 밴드갭을 갖는 고감도의 광전도체로 태양전지의 광투과 물질로 각광을 받고 있으며 광전도 cell로 연구되고 있는 CdS(Cadmium sulfide)를 용액 성장법(CBD)으로 제조하여 박막의 결정립의 향상과 박막내의 결함 등을 제거하기 위해 RTP(Rapid Thermal Process)를 이용하여 열처리 분위기 $N_2$, 처리시간 10분을 기준으로 열처리온도 ($300\;^{\circ}C$, $400\;^{\circ}C$, $500\;^{\circ}C$)를 변화시키며 박막의 전기적, 광학적 특성을 조사하였다. 캐리어 밀도가 급격히 낮아지고 이동도가 증가한 $500\;^{\circ}C$에서 $1.29\times10^3\;{\Omega} m$ 비저항을 나타냈다. 가시광선 영역에서 76.28%의 투과율을 보이는 특성을 나타내었다.

• International Journal of Oral Biology
• /
• v.35 no.3
• /
• pp.107-111
• /
• 2010

Treponema denticola is a gram-negative anaerobe that can cause periodontal disease. The adhesion of this bacterium to host tissues is considered to be the primary event in the colonization and infection of a host. Fibrinogen is generally found in damaged tissues resulting from periodontitis. The binding ability of T. denticola to fibrinogen may therefore be an important virulence factor in inducing periodontal diseases. It has been reported recently that oral spirochetes can be labeled with fluorescent fatty acids and we speculated that this labeling method could be used in an oral spirochete binding assay. The binding of several different strains of T. denticola to immobilized human fibrinogen was therefore tested using the fluorescent fatty acid labeling method. In the case of immobilized fibrinogen, the T. denticola ATCC 35405 strain showed saturable binding to immobilized fibrinogen. Indeed, all four different T. denticola strains tested in this experiment, T. denticola ATCC 35405, T. denticola ATCC 33520, T. denticola ATCC 35404 and T. denticola OTK showed binding to fibrinogen. The fluorescent fatty acid labeling method thus shows utility in binding assays for T. denticola, different strains of which can generally bind to immobilized fibrinogen.

• Journal of the Korean institute of surface engineering
• /
• v.43 no.6
• /
• pp.266-271
• /
• 2010

Ternary Mo-Cu-N films were deposited on Si wafer substrates with various copper contents by magnetron sputtering method using Mo target and Cu target in $Ar/N_2$ gaseous atmosphere. As increasing $N_2$ pressure, the microstructure of Mo-N films changed from ${\gamma}-Mo_2N$ of (111) having face-centered-cubic (FCC) structure to $\delta$-MoN of (200) having hexagonal structure. Detailed the microstructures of the Mo-Cu-N coatings were studied by X-ray diffraction, scanning electron microscopy and field emission transmission electron microscope. The results indicated that the incorporation of copper into the growing Mo-N coating led to the $Mo_2N$ and MoN crystallites were more well-distributed and refined and the copper existed in grain boundary. Ternary Mo-Cu-N films had a composite microstructure of the nanosized crystal crystalline ${\gamma}-Mo_2N$ and $\delta$-MoN surrounded by amorphous $Cu_3N$ phase.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.21 no.7
• /
• pp.660-664
• /
• 2008

Titanium nitride (TiN) thin films are widely used for hard coatings due to their superior hardness, chemical stability, low friction and good adhesion properties. In this study, we investigated the effect of DC power on the characteristics of TiN thin films deposited on Si and glass substrates by DC magnetron sputtering using TiN target. We made TiN films of 300 nm thickness with various DC powers. The structural properties of films are investigated by x-ray diffractions (XRD) and tribological properties are measured by nano-indentation, nano-scratch tester. The rms roughness was measured by atomic forced microscopy (AFM). In the result, TiN films had the smooth surface and exhibited (111) directions with the increase of DC Power. Also, especially in case of 175 W DC power, TiN film exhibited the maximum hardness about 8 GPa, and the critical load near 25.

• Journal of Korean Institute of Industrial Engineers
• /
• v.27 no.1
• /
• pp.111-117
• /
• 2001

Most of the techniques for the performance estimation of unit-load AS/RS are a static model or computer simulation. Especially, their models have been developed under the assumption that the Storage/Retrieval (S/R) machine performs either single command(SC) or dual command(DC) only. In reality, depending on the operating policy and the status of the system at a particular time, the S/R machine performs a SC or a DC, or becomes idle. In order to resolve this weak point, we propose a stochastic model for the performance estimation of unit-load ASIRS by using a M/G/1 queueing model with a single server and two queues. Server utilization, expected numbers of waiting storage and retrieval commands and mean time spent in queue and system are found.

• Journal of Korean Ophthalmic Optics Society
• /
• v.6 no.2
• /
• pp.111-114
• /
• 2001

This paper presents the influence of the additive composition on flexural strength and hardness of SiC-TiC composites materials for spectacle lens cutting materials. The materials were hot-pressed at $1800^{\circ}C$ and subsequently annealed at $1910^{\circ}C$ for 3h. The heating rate was $15^{\circ}C/min$ and the cooling rate about $25^{\circ}C/min$ in from the sintering temperature to $1300^{\circ}C$. The growth of particles of spectacle lens cutting materials was analysed by SEM and crystalline phases were discussed by x-ray diffractometry. Typical fracture toughness and hardness of materials for spectacle lens cutting were $6.1MPa{\cdot}m^{1/2}$ and 14.9 GPa, respectively.

• Journal of the Korean Vacuum Society
• /
• v.8 no.4B
• /
• pp.524-529
• /
• 1999

We deposited diamond phase carbon thin films on Si substrate by the electrolysis of methanol solution. A little amount of ammonia solution was added to increase the current density of the electrolyte. We analyzed films by XRD and SEM. The chemical change of electrolyte during the electrolysis process was characterized by FTIR. We obtained better quality diamond phase carbon films at a lower applying boltage(300V) and temperature ($40^{\circ}C$) by adding ammonia solution to methanol electrolyte. Diamond (111), (220), (311) peaks were shown distinctively in XRD graph. Addition of ammonia solution resulted in lowering the applying bias voltage to 300V and the substrate temperature to $40^{\circ}C$ still maintaining a high current density at 80mA/$\textrm{cm}^2$, which prohibited a great loss of solution from vaporization. Possible change of chemical reaction due to the addition of ammonia solution was also discussed.