• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.9-10
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• 2010

Since the discovery of graphene by mechanical exfoliation from graphite[1], various fabrication methods are available today such as chemical exfoliation, epitaxial graphene on SiC substrates, etc. In view of industrialization, the mechanical exfoliation method may not be an option. Epitaxial graphene on SiC substrates, in this respect, is by far more practical because the method consists of conventional thermal treatments familiar to semiconductor industry. Still, the use of the SiC substrate itself, and hence the incompatibility with the Si technology, lessens the importance of this technology in its future industrialization. In this context, we have tackled the problem of forming graphene on Si substrates (GOS). Our strategy is to form an ultrathin (~80 nm) SiC layer on top of a Si substrate, and to graphitize the top SiC layers by a vacuum annealing. We have actually succeeded in forming the GOS structure [2,3,4]. Raman-scattering microscopy indicates presence of few-layer graphene (FLG) formed on our annealed SiC/Si heterostructure, with the G ($1580\;cm^{-1}$) and the G'($2700\;cm^{-1}$) bands, both related to ideal graphene, clearly observed. Presence of the D ($1350\;cm^{-1}$) band indicates presence of defects in our GOS films, whose elimination remains as a challenge in the future. To obtain qualified graphene films on Si substrate, formation of qualified SiC films is crucial in the first place, and is achieved by tuning the growth parameters into a process window[5]. With a potential for forming graphene films on large-scale Si wafers, GOS is a powerful candidate as a key technology in bringing graphene into silicon technology.

• 한국재료학회지
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• 제8권4호
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• pp.359-361
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• 1998

$SiH_{4}$를 반응물질로 사용하여 electron cyclotron resonance plasma enhanced chemical vapor deposition(ECR-PECVD)로 실리콘 기판위에 증착한 수소화 비정질 실리콘(a-Si:H)으로부터 가시 photoluminescence(PL) 가 관찰되었다. a-si:H/Si로 부터의 PL은 다공질실리콘으로부터의 PL과 유사하였다. 급속열처리에 의해 $500^{\circ}C$에서 2분간 산소분위기에서 어닐링된 시편의 수소함량은 1~2%로 줄어들었고 시편은 가시 PL을 보여주지 않았는데 이는 a-Si:H의 PL과정에서 수소가 중요한 역할을 한다는 것을 뜻한다. 증착된 a-Si:H의 두께가 증가함에 따라 PL의 세기는 감소하였다. $SiH_{4}$를 사용하여 ECR-PECVD에 의해 Si상에 증착된 a-Si:H로부터의 가시 PL은 Si과 증착된 a-Si:H막 사이에 증착이 이루어지는 동안에 형성된 수소화실리콘으로부터 나오는 것으로 추론된다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.129-129
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• 2016

Graphene, as a single layer of $sp^2$-bonded carbon atoms packed into a 2D honeycomb crystal lattice, has attracted much attention due to its outstanding properties. In order to synthesize high quality graphene, transition metals, such as nickel and copper, have been widely employed as catalysts, which needs transfer to desired substrates for various applications. However, the transfer steps are not only complicated but also inevitably induce defects, impurities, wrinkles, and cracks of graphene. Furthermore, the direct synthesis of graphene on dielectric surfaces has still been a premature field for practical applications. Therefore, cost effective and concise methods for transfer-free graphene are essentially required for commercialization. Here, we report a facile transfer-free graphene synthesis method through nickel and carbon co-deposited layer. In order to fabricate 100 nm thick NiC layer on the top of $SiO_2/Si$ substrates, DC reactive magnetron sputtering was performed at a gas pressure of 2 mTorr with various Ar : $CH_4$ gas flow ratio and the 200 W DC input power was applied to a Ni target at room temperature. Then, the sample was annealed under 200 sccm Ar flow and pressure of 1 Torr at $1000^{\circ}C$ for 4 min employing a rapid thermal annealing (RTA) equipment. During the RTA process, the carbon atoms diffused through the NiC layer and deposited on both sides of the NiC layer to form graphene upon cooling. The remained NiC layer was removed by using a 0.5 M $FeCl_3$ aqueous solution, and graphene was then directly obtained on $SiO_2/Si$ without any transfer process. In order to confirm the quality of resulted graphene layer, Raman spectroscopy was implemented. Raman mapping revealed that the resulted graphene was at high quality with low degree of $sp^3$-type structural defects. Additionally, sheet resistance and transmittance of the produced graphene were analyzed by a four-point probe method and UV-vis spectroscopy, respectively. This facile non-transfer process would consequently facilitate the future graphene research and industrial applications.

• JSTS:Journal of Semiconductor Technology and Science
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• 제1권4호
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• pp.202-208
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• 2001

In Recent results suggested that doping $Ta_2O_5$ with a small amount of $TiO_2$ using standard ceramic processing techniques can increase the dielectric constant of $Ta_2O_5$ significantly. In this paper, this concept is studied using RTCVD (Rapid Thermal Chemical Vapor Deposition). Ti-doped $Ta_2O_5$ films are deposited using $TaC_{12}H_{30}O_5N$, $C_8H_{24}N_4Ti$, and $O_2$ on both Si and $NH_3$-nitrided Si substrates. An $NH_3$-based interface layer at the Si surface is used to prevent interfacial oxidation during the CVD process and post deposition annealing is performed in $H_2/O_2$ ambient to improve film quality and reduce leakage current. A sputtered TiN layer is used as a diffusion barrier between the Al gate electrode and the $TaTi_xO_y$ dielectric. XPS analyses confirm the formation of a ($Ta_2O_5)_{1-x}(TiO_2)_x$ composite oxide. A high quality $TaTi_xO_y$ gate stack with EOT (Equivalent Oxide Thickness) of $7{\AA}$ and leakage current $Jg=O.5A/textrm{cm}^2$ @ Vg=-1.0V has been achieved. We have also succeeded in forming a $TaTi_x/O_y$ composite oxide by rapid thermal oxidation of the as-deposited CVD TaTi films. The electrical properties and Jg-EOT characteristics of these composite oxides are remarkably similar to that of RTCVD $Ta_2O_5, suggesting that the dielectric constant of $Ta_2O_5$ is not affected by the addition of $TiO_2$.

• 한국진공학회지
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• 제20권5호
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• pp.339-344
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• 2011

C-plane 사파이어 기판 위에 펄스 레이저 증착법으로 증착시킨 n-type ZnO 박막에 대한 Ti/Au 금속의 Ohmic 접합특성을 TLM (transfer length method) 패턴 전극을 통하여 연구하였다. 여기서, Ti와 Au 금속박막은 전자빔 증착기와 열 증착기로 각각 35 nm와 90 nm 두께로 증착하였으며, TLM패턴은 광 리소그래피 법으로 면적이 $100{\times}100{\mu}m^2$인 전극패턴을 6~61 ${\mu}m$ 간격으로 형성하였다. Ti/Au 금속박막과 ZnO 반도체 사이의 전기적인 성질을 개선하고 응력과 계면 결함을 감소시키기 위해, 산소 가스 분위기로 $100{\sim}500^{\circ}C$ 온도에서 각각 1분간 급속열처리를 하였다. $300^{\circ}C$의 온도에서 열처리한 시료에서 $1.1{\times}10^{-4}{\Omega}{\cdot}cm^2$의 가장 낮은 비저항 값을 보였는데, 이것은 열처리 동안 티타늄 산화막 형성과정에서 ZnO 박막 표면 근처에 산소빈자리가 형성됨으로써 나타나는 전자농도의 증가가 주된 원인으로 고려되었다.

• 대한전자공학회논문지SD
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• 제42권6호
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• pp.23-30
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• 2005

본 논문에서는 다양한 에미터 금속 재료를 이용하여 산화된 다공질 폴리실리콘(Oxidized Porous Poly-Silicon) 전계방출 소자를 제조하였으며 에미터 금속의 열처리 효과가 산화된 다공질 폴리실리콘 전계방출소자의 특성에 미치는 영향을 조사하였다. 다양한 에미터 금속 중 구동전극을 가진 Pt/Ti 에미터 전극을 $300^{\circ}C$-1hr 열처리한 경우 전자방출 효율은 $V_{ps}$=12 V에서 최대 $2.98\%$의 효율을 나타내었으며, $350^{\circ}C$-1hr 열처리한 경우 $V_{ps}$=16V에서 $3.37\%$의 가장 높은 효율을 나타내었다. 이는 열처리 공정을 통해 OPPS 전계방출 소자 표면에 다수의 결정립 경계와 무수히 많은 미세한 다공질 간의 흡착성의 개선으로 인한 면 저항 감소에 의한 것을 알 수 있다. OPPS 전계 방출 소자를 디스플레이소자로 적용하기 위해 형광체 발광 특성을 조사해 본 결과, $900^{\circ}C$-50min 산화 후 Pt/Ti(5nm/2nm) 에미터 전극을 사용하여 제조된 OPPS 전계 방출 소자의 경우 15 V에서 3600 cd/$m^2$, 20 V에서 6260 cd/$m^2$의 상대적으로 높은 휘도를 나타내었다. 열처리는 Ti층과 OPPS 간의 흡착성을 개선시키고 에미터 전극에 고른 전계를 가하는 중요한 역할을 한다.

• 대한금속재료학회지
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• 제46권11호
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• pp.762-769
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• 2008

Hydrogenated amorphous silicon(a-Si : H) layers, 120 nm and 50 nm in thickness, were deposited on 200 $nm-SiO_2$/single-Si substrates by inductively coupled plasma chemical vapor deposition(ICP-CVD). Subsequently, 30 nm-Ni layers were deposited by E-beam evaporation. Finally, 30 nm-Ni/120 nm a-Si : H/200 $nm-SiO_2$/single-Si and 30 nm-Ni/50 nm a-Si:H/200 $nm-SiO_2$/single-Si were prepared. The prepared samples were annealed by rapid thermal annealing(RTA) from $200^{\circ}C$ to $500^{\circ}C$ in $50^{\circ}C$ increments for 30 minute. A four-point tester, high resolution X-ray diffraction(HRXRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and scanning probe microscopy(SPM) were used to examine the sheet resistance, phase transformation, in-plane microstructure, cross-sectional microstructure, and surface roughness, respectively. The nickel silicide on the 120 nm a-Si:H substrate showed high sheet resistance($470{\Omega}/{\Box}$) at T(temperature) < $450^{\circ}C$ and low sheet resistance ($70{\Omega}/{\Box}$) at T > $450^{\circ}C$. The high and low resistive regions contained ${\zeta}-Ni_2Si$ and NiSi, respectively. In case of microstructure showed mixed phase of nickel silicide and a-Si:H on the residual a-Si:H layer at T < $450^{\circ}C$ but no mixed phase and a residual a-Si:H layer at T > $450^{\circ}C$. The surface roughness matched the phase transformation according to the silicidation temperature. The nickel silicide on the 50 nm a-Si:H substrate had high sheet resistance(${\sim}1k{\Omega}/{\Box}$) at T < $400^{\circ}C$ and low sheet resistance ($100{\Omega}/{\Box}$) at T > $400^{\circ}C$. This was attributed to the formation of ${\delta}-Ni_2Si$ at T > $400^{\circ}C$ regardless of the siliciation temperature. An examination of the microstructure showed a region of nickel silicide at T < $400^{\circ}C$ that consisted of a mixed phase of nickel silicide and a-Si:H without a residual a-Si:H layer. The region at T > $400^{\circ}C$ showed crystalline nickel silicide without a mixed phase. The surface roughness remained constant regardless of the silicidation temperature. Our results suggest that a 50 nm a-Si:H nickel silicide layer is advantageous of the active layer of a thin film transistor(TFT) when applying a nano-thick layer with a constant sheet resistance, surface roughness, and ${\delta}-Ni_2Si$ temperatures > $400^{\circ}C$.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.88-89
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• 2013

A variety of influenza A viruses from animal hosts are continuously prevalent throughout the world which cause human epidemics resulting millions of human infections and enormous industrial and economic damages. Thus, early diagnosis of such pathogen is of paramount importance for biomedical examination and public healthcare screening. To approach this issue, here we propose a fully integrated Rotary genetic analysis system, called Rotary Genetic Analyzer, for on-site detection of influenza A viruses with high speed. The Rotary Genetic Analyzer is made up of four parts including a disposable microchip, a servo motor for precise and high rate spinning of the chip, thermal blocks for temperature control, and a miniaturized optical fluorescence detector as shown Fig. 1. A thermal block made from duralumin is integrated with a film heater at the bottom and a resistance temperature detector (RTD) in the middle. For the efficient performance of RT-PCR, three thermal blocks are placed on the Rotary stage and the temperature of each block is corresponded to the thermal cycling, namely $95^{\circ}C$ (denature), $58^{\circ}C$ (annealing), and $72^{\circ}C$ (extension). Rotary RT-PCR was performed to amplify the target gene which was monitored by an optical fluorescent detector above the extension block. A disposable microdevice (10 cm diameter) consists of a solid-phase extraction based sample pretreatment unit, bead chamber, and 4 ${\mu}L$ of the PCR chamber as shown Fig. 2. The microchip is fabricated using a patterned polycarbonate (PC) sheet with 1 mm thickness and a PC film with 130 ${\mu}m$ thickness, which layers are thermally bonded at $138^{\circ}C$ using acetone vapour. Silicatreated microglass beads with 150~212 ${\mu}L$ diameter are introduced into the sample pretreatment chambers and held in place by weir structure for construction of solid-phase extraction system. Fig. 3 shows strobed images of sequential loading of three samples. Three samples were loaded into the reservoir simultaneously (Fig. 3A), then the influenza A H3N2 viral RNA sample was loaded at 5000 RPM for 10 sec (Fig. 3B). Washing buffer was followed at 5000 RPM for 5 min (Fig. 3C), and angular frequency was decreased to 100 RPM for siphon priming of PCR cocktail to the channel as shown in Figure 3D. Finally the PCR cocktail was loaded to the bead chamber at 2000 RPM for 10 sec, and then RPM was increased up to 5000 RPM for 1 min to obtain the as much as PCR cocktail containing the RNA template (Fig. 3E). In this system, the wastes from RNA samples and washing buffer were transported to the waste chamber, which is fully filled to the chamber with precise optimization. Then, the PCR cocktail was able to transport to the PCR chamber. Fig. 3F shows the final image of the sample pretreatment. PCR cocktail containing RNA template is successfully isolated from waste. To detect the influenza A H3N2 virus, the purified RNA with PCR cocktail in the PCR chamber was amplified by using performed the RNA capture on the proposed microdevice. The fluorescence images were described in Figure 4A at the 0, 40 cycles. The fluorescence signal (40 cycle) was drastically increased confirming the influenza A H3N2 virus. The real-time profiles were successfully obtained using the optical fluorescence detector as shown in Figure 4B. The Rotary PCR and off-chip PCR were compared with same amount of influenza A H3N2 virus. The Ct value of Rotary PCR was smaller than the off-chip PCR without contamination. The whole process of the sample pretreatment and RT-PCR could be accomplished in 30 min on the fully integrated Rotary Genetic Analyzer system. We have demonstrated a fully integrated and portable Rotary Genetic Analyzer for detection of the gene expression of influenza A virus, which has 'Sample-in-answer-out' capability including sample pretreatment, rotary amplification, and optical detection. Target gene amplification was real-time monitored using the integrated Rotary Genetic Analyzer system.

• 한국결정성장학회지
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• 제24권4호
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• pp.169-175
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• 2014

최근 각광받고 있는 디지털 프린팅을 이용한 디자인 기법은 세밀한 표현과 다양한 이미지 구현이 가능하고, 원료의 낭비가 적어 효율성이 높은 장점을 가지고 있다. 디지털 프린팅 공정에서는 cyan, magenta, yellow, black이 기본적인 디지털 4원색으로 사용되며, 도자제품에 적용되는 세라믹 안료의 경우 $1000^{\circ}C$ 이상의 고온 소성이 가능하도록 우수한 열적, 유약 안정성과 발색 특성이 요구된다. 본 연구에서는 고상합성법을 이용하여 $CaO-SnO_2-Cr_2O_3-SiO_2$ 조성의 pink-red 고온발색 무기안료를 합성하였다. $Ca(Sn,Cr)SiO_5$ 세라믹 안료의 합성 조건에 따른 물성을 XRD, SEM, PSA, FT-IR를 이용하여 분석하였고, Cr 치환량 변화가 $Ca(Sn,Cr)SiO_5$ 무기 안료의 발색 거동에 미치는 영향을 Uv-vis.와 CIE 표색계 값($L^*a^*b^*$)을 기준으로 한 색도측정을 통해 관찰하였다.

• Bulletin of the Korean Chemical Society
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• 제33권9호
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• pp.3061-3070
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• 2012

Novel 2-hexylthieno[3,2-b]thiophene-containing conjugated molecules have been synthesized via a reduction reaction using tin chloride in an acidic medium. They exhibited good solubility in common organic solvents and good self-film and crystal-forming properties. The single-crystalline objects were fabricated by a solvent slow diffusion process and then were employed for fabricating field-effect transistors (FETs) along with thinfilm transistors (TFTs). TFTs made of 5 and 6 exhibited carrier mobility as high as 0.10-0.15 $cm^2V^{-1}s^{-1}$. The single-crystal-based FET made of 6 showed 0.70 $cm^2V^{-1}s^{-1}$ which was relatively higher than that of the 5-based FET (${\mu}=0.23cm^2V^{-1}s^{-1}$). In addition, we fabricated organic photovoltaic (OPV) cells with new 2-hexylthieno [3,2-b]thiophene-containing conjugated molecules and methanofullerene [6,6]-phenyl C61-butyric acid methyl ester ($PC_{61}BM$) without thermal annealing. The ternary system for a bulk heterojunction (BHJ) OPV cell was elaborated using $PC_{61}BM$ and two p-type conjugated molecules such as 5 and 7 for modulating the molecular energy levels. As a result, the OPV cell containing 5, 7, and $PC_{61}BM$ had improved results with an open-circuit voltage of 0.90 V, a short-circuit current density of 2.83 $mA/cm^2$, and a fill factor of 0.31, offering an overall power conversion efficiency (PCE) of 0.78%, which was larger than those of the devices made of only molecule 5 (${\eta}$~0.67%) or 7 (${\eta}$~0.46%) with $PC_{61}BM$ under identical weight compositions.