• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.271-271
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• 2014

본 연구에서는 최근 다양한 전자 소자로써의 연구가 진행되고 있는 그라핀을 SiO2/Si 기판 위에 전자빔 식각(Electron-Beam Lithography)을 이용하여 후면 게이트 전극 구조의 그라핀 채널을 갖는 삼단자 소자를 형성하고 가스 유입이 가능한 진공 Probe Measurement System을 이용하여 금속 전극과 그라핀 간의 접촉저항 (Rc) 및 길이가 다른 채널저항(Rch)를 구하고, 채널 길이, 가스 유량, 온도, 게이트 전압에 따른 I-V 변화를 측정함으로써, 후면 게이트 전극 구조의 그라핀 채널을 갖는 삼단자 소자의 가스 센서로서의 가능성을 연구하였다. 후면 게이트 전극 구조의 그라핀 채널을 갖는 삼단자 소자는 전자빔 식각(Electron-Beam Lithography)에 의해 패턴을 제작하고 Evaporator를 이용하여 전극을 증착 하였다. 소자의 소스 (Source)와 드레인 (Drain)은 TLM (Transfer Length Method)패턴을 이용하여 인접한 두 개의 전극간 범위를 변화시키는 형태로 제작함으로써 소스-드레인간 채널 길이가 다르게 하였다. 이 때 전극의 크기는 가로, 세로 각각 $20{\mu}m$, $40{\mu}m$이며 전극간 간격은 $20/30/40/50/60{\mu}m$로 서로 다르게 배열 하였다. 제작된 그라핀 소자는 진공 Probe Measurement System 내에서 게이트 전압(VG)를 변화시킴으로써 VG 변화에 따른 소자의 특성을 평가하였는데, mTorr 상태의 챔버 내로 O2 가스를 주입하여 그라핀의 Dangling bond 및 Defect site에 결합 된 가스로 인한 전기적 특성의 변화를 측정하고, 이 때 가스의 유량을 50 sccm에서 500 sccm 까지 변화시킴으로써 전기적 특성 변화를 측정하여 센서 소자의 민감도를 평가하였다. 또한, 서로 다르게 배열한 소스-드레인 간의 채널 길이로 인하여 채널과의 접촉 면적에 따른 센서 소자의 민감도 또한 평가할 수 있었다. 그리고 챔버 내 온도를 77 K에서 400 K까지 변화시킴으로써 온도에 따른 소자의 작동 범위를 확인하고 소자의 온도의존성을 평가하였다.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.47.1-47.1
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• 2011

We report on a direct measurement of two-dimensional chemical and electrical distribution on the surface of photovoltaic Cu(In,Ga)$Se_2$ thin-films using a nano-scale spectroscopic and electrical characterization, respectively. The Raman measurement reveals non-uniformed surface phonon vibration which comes from different compositional distribution and defects in the nature of polycrystalline thin-films. On the other hand, potential analysis by scanning Kelvin probe force microscopy shows a higher surface potential or a small work function on grain boundaries of the thin-films than on the grain surfaces. This demonstrates the grain boundary is positively charged and local built-in potential exist on grain boundary, which improve electron-hole separation on grain boundary. Local electrical transport measurements with scanning probe microscopy on the thin-films indicates that as external bias is increases, local current is started to flow from grain boundary and saturated over 0.3 V external bias. This accounts for carrier behavior in the vicinity of grain boundary with regard to defect states. We suggest that electron-hole separation at the grain boundary as well as chemical and electrical distribution of polycrystalline Cu(In,Ga)$Se_2$ thin-films.

• Journal of the Korean Vacuum Society
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• v.8 no.1
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• pp.63-69
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• 1999

The characteristic parameters of high density plasma source (Helical Resonator) have been measured with Langmuir probe to get the plasma density electron temperature, ion current density, etc. Optical emission spectra of Si and SiCl have been analyzed in $Cl_2$$/poly-Si system to elucidate etching mechanism. In this system, the main reaction to remove silicon atoms on the surface is proceeding mostly through chemical reaction, not pure physical reaction. The emission intensity of SiCl (chemical etching product) increases much faster than Si (pure physical etching product) with increasing the concentration of impurities (P). This is due to the electron transfer from substrate to the surface via Si-Cl bond. As a result, Si-Cl bond becomes more ionic and mobile, therefore the Cl-containing etchant forms $SiCl_x$ with surface more easily. Consequently, for the removal of Si atom from poly silicon surface, the chemical etching is more favorable than physical etching with increasing P concentrations.

• Analytical Science and Technology
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• v.14 no.3
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• pp.203-211
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• 2001

In this paper it was described on the intereference effect of uranium to analyze Cs in $UO_2$ by Electron Probe Micro Analysis(EPMA) and the beam stability of Cs $L_{\alpha}$ X-ray intensity for some Cs compounds. According to the experimental results, the CsI showed the highest $L_{\alpha}$ X-ray intensity among the tested Cs compounds at the experimental condition; 15~30 kV of accelerating voltage and PET, LiF crystal. When 100 nA of beam current was applied to Cs compounds, Cs $L_{\alpha}$ X-ray intensity was continuously decreased with increasing time. The decreasing rate of Cs $L_{\alpha}$ X-ray intensity was directly proportional to the applied beam current and accelerating voltage but inversely proportional to the applied beam size. It was found that uranium interference can be prevented by using Cs $L_{\alpha}$ X-ray wavelength of Lif crytal for Cs analysis in $UO_2$ by EPMA.

• Analytical Science and Technology
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• v.13 no.5
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• pp.565-572
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• 2000

In this paper it was described on the standards for Xe analysis by Wavelength Dispersive X-ray Spectrometer (WDS) of Electron Probe Micro Analyser. According to the experimental results, CsI and $BaCO_3$ are appropriate compounds as standard specimen for Cs, I and Ba which has not suitable pure metal standards. In the beam current of 10-30 nA range, the Cs x-ray intensity measured from CsBr and CsI was proportional to the beam current. It was found that the linear regression factor R, showing the linearity between the atomic number and x-ray intensity between In and Nd elements, was higher than 0.99 at 25 kV and PET crystal. The caJlculated x-ray intensity of Xe standard from this linear regression equation was 1.095 times higher than that ofTe at 25 kV.

• Applied Microscopy
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• v.46 no.1
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• pp.27-31
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• 2016

It has been investigated what kind of characteristic X-ray in electron probe micro-analyzer (EPMA) is effective for the determination of compounds of Si series materials. After comparing the characteristic X-rays among the primary and secondary lines in $K_{\alpha}$ and $K_{\beta}$ obtained from the Si series standard samples, it was found that the secondary line of $K_{\alpha}$ exhibited the most informative spectrum although the intensity was considerably weak. As a result of analyzing the spectrum shapes of the Si series standard samples, the spectrum shape of the secondary line of $K_{\alpha}$ for SiC was different from those for other Si compounds. To grasp the characteristics of the shape, a line was perpendicularly drawn from the peak top to base line in order to divide a spectrum into two areas. The area ratio of right to left was defined to call as the asymmetry index here. As a result, the asymmetry index value of the SiC was greater than one, while those of other Si compounds were less than one. It was found from the EPMA analysis that identification of SiC became successful to distinguish from other Si compounds and this method was applicable for micro-sized compounds in a practical composite material.

• Journal of the Korean Ceramic Society
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• v.41 no.1
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• pp.92-95
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• 2004

Using the Micro-Pulling Down (${\mu}$-PD), $MnO_2$ and $Tb_4O_7$ co-doped crack-free stoichiometric $LiNbO_3$ single crystals were grown in 1.0 mm diameter and 25-30 mm length for c-axis. The homogeneous distributions of $MnO_2$ and $Tb_4O_7$ concentration were confirmed by the Electron Probe Microanalysis (EPMA). Also, the infrared OH absorption band of the single crystals observed by using a Fourier Transform-Infrared Spectrophotometer (FT-IR) at room temperature and the photoluminescence spectra was measured with respect to the $MnO_2$ and $Tb_4O_7$ doping.

• Journal of the Mineralogical Society of Korea
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• v.11 no.2
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• pp.117-125
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• 1998

Crystallization behavior of platinum minerals within Pt-Sb-Bi bearing ore magmas and mineralogical properties of the existing minerals were investigated at 1,00$0^{\circ}C$ by synthetic experiment. High purity reagents were used as starting materials and silica tubings as containers. Reaction products were analysed by reflecting microscopy, X-ray diffraction, electron probe microanalysis, and micro-hardness test. Stable minerals at 1,00$0^{\circ}C$ are platinum, electron probe microanalysis, and micro-hardness test. Stable minerals at $1,000^{\circ}C$ are platinum, stump-flite (PtSb) and geversite (PtSb2). They are in equilibrium with liquid (ore magma). Platinum contains considerable amount of Sb of 7.5 at.%, whereas Bi only up to 0.9 at.%. Pure stumpflite is hexagonal with space group P63/mmc, and unit cell parameters are a=4.1318(6), c=5.483(1)$\AA$. VHN50=417(2)$\AA$. Geversite has cubic structure with space group Pa3. Cell parameters are a=6.4373(2)$\AA$ and Vicker hardness values VHN50=663.5 (566~766). Both stumpflite and geversite show solid solution and their end-members are Pt48.8Sb40.7-Bi10.5, and Pt33.7-Sb59.8Bi6.5, respectively. Although stumpflite (m.p. $1,043^{\circ}C$) and unnamed PtBi (m.p. 7$65^{\circ}C$) do not form a complete solid solution at $1,000^{\circ}C$, they are known, at $600^{\circ}C$, to form a continuous solid solution. Geversit (m.p. $1,226^{\circ}C$) also forms complete solid solution with insizwaite (m.p. $660^{\circ}C$). Unit cell dimensions of the minerals above increases with the amount of Bi substituting for Sb.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.3
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• pp.120-123
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• 2005

The 5 mol% ZnO doped $LiNbO_3$ film and the 2 mol% MgO doped $LiNbO_3$ film were grown on the $LiNbO_3$ (001) substrate by liquid phase epitaxy (LPE) method with $Li_2CO_3-V_2O_5$ flux system. The crytsallinity and the lattice mismatch between $Zn:LiNbO_3$, film and $Mg:LiNbO_3$, film were analyzed by x-ray rocking curve (XRC). In addition, the ZnO and MgO distribution in the cross-section of the multilayer thin films was observed using electron probe micro analyzer (EPMA).

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.16 no.6
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• pp.235-239
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• 2006

ZnO-doped near-stoichiometric $LiNbO_3$ single crystals of $0.8{\sim}1.0mm$ diameter and $30{\sim}35mm$ length were grown by the micro-pulling down (U-PD) method. The structure of the grown crystals was confirmed by powder x-ray diffraction (XRD) patterns. Electron probe micro analysis (EPMA) showed that Zn ions were homogeneously incorporated In grown crystals. The threshold in ZnO doping level was confirmed that an abrupt change in the features of $OH^-$ absorption band as doping level reaching about 2 mol%.