• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1313-1314
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• 2007

This paper presents organic thin-film transistors (OTFTs) with poly(3-hexylthiophene)(P3HT) semiconductor and several polymeric dielectric materials of poly(vinyl phenol)(PVP), poly(vinyl alcohol)(PVA), and polyimide(PI) by using soluble process. The fabricated OTFT's have inverted staggered structure using transmission line method(TLM) pattern. In order to evaluate the electrical characteristics of the OTFT, capacitance-voltage(C-V) and current-voltage(I-V) were measured. C-V graphs were measured at several frequencies of 100 Hz, 1 kHz, and 1 MHz and ID-VDS graphs according to $V_{GS}$. The current on/off ratio and threshold voltage with each of PVP, PVA, and PI based OTFTs were measured to $10^3$, and -0.36, -0.41, and -0.62 V. Also, the calculated mobility with each of PVP, PVA, and PI was 0.097, 0.095, and 0.028 $cm^{2}V^{-1}s^{-1}$, respectively. In the cases of PVP and PVA, the hole mobility of P3HT was in excellent agreement with the published value of 0.1 $cm^{2}V^{-1}s^{-1}$.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 제4회 영호남학술대회 논문집
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• pp.92-96
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• 2002

Hot wall epitaxy 방법을 이용하여 chalcopyrite 구조를 가진 고품질의 $AgInS_{2}$ 박막을 성장 하였다. 광전류 스펙트럼을 측정한 결과， 30K에서 300K까지는 단지 A 와 B 두개의 봉우리가 관측되었고 반면에 10K에서는 A,B,C 세 개의 봉우리가 관측되었다. 이때 이들 봉우리들은 band-to-band 전이에 기인하는 것으로 관측되었다. 광전류 측정으로부터 $AgInS_{2}$의 가전자대 갈라짐이 측정되었고 이로부터 10k에서 결정장에 의한 갈라짐 $D_{cr}$과 스핀궤도에 의한 갈라짐 $D_{so}$은 각각 0.150eV와 0.009eV로 관측되었다. 또한 에너지 밴드갭의 온도 의존성 $E_{g}(T)$에 대하여 연구하였고 성장된 $AgInS_{2}$ 박막의 에너지 밴드갭은 1.868eV 임을 알았다.

• 한국재료학회지
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• 제12권7호
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• pp.587-590
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• 2002

A silver indium sulfide ($AgInS_2$) epilayer was grown by the hot wall epitaxy method, which has not been reported in the literature. The grown $AgInS_2$ epilayer has found to be a chalcopyrite structure and evaluated to be high quality crystal. From the photocurrent measurement in the temperature range from 30 K to 300 K, the two peaks of A and B were only observed, whereas the three peaks of A, B, and C were seen in the PC spectrum of 10 K. These peaks are ascribed to the band-to-band transition. The valence band splitting of $AgInS_2$ was investigated by means of the photocurrent measurement. The crystal field splitting, $\Delta_{cr}$ , and the spin orbit splitting, $\Delta_{so}$ , have been obtained to be 0.150 eV and 0.009 eV at 10 K, respectively. And, the energy band gap at room temperature has been determined to be 1.868 eV. Also, the temperature dependence of the energy band gap, $E_{g}$(T), was determined.d.

• Bulletin of the Korean Chemical Society
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• 제10권1호
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• pp.8-12
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• 1989

The polycrystalline powder of (BaLa)(MgMo)$O_6$ has been prepared at $1350^{\circ}C$ in a nitrogen flowing atmosphere. The powder X-ray diffraction pattern indicates that (BaLa)(MgMo)$O_6$ has a cubic perovskite structure ($a_0$ = 8.019(3) $\AA)$ with 1:1 ordering or $Mg^{2+}$ and $Mo^{5+}$ in the oxide lattice. The infrared spectrum shows two strong absorption bands with their maxima at 600(${\nu}3$) and 365(${\nu}4$) cm-1, which are attributed to $2T_{1U}$, modes of molybdenum octahedra MoO6 in the crystal lattice. According to the magnetic susceptibility measurement, the compound shows a paramagnetic behavior which follows the Curie-Weiss law below room temperature with the effective magnetic moment 1.60(1){$\mu}B$, which is consistent with that of spin only value ($1.73{\mu}B$) for $Mo^{5+}$ ($4d^1$ electronic configuration). From the thermogravimetric and X-ray diffraction analyses, it has been found that (BaLa)(MgMo)$O_6$ decomposes gradually into $BaMoO_4$, $MoO_3$ and unidentified phases above $900^{\circ}C$ in an ambient atmosphere, absorbing about 0.25 mole $O_2$ per mole of Mo ion, which also supports that oxidation state of $Mo^{5+}$ in the (BaLa)(MgMo)$O_6$.

• 방사선산업학회지
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• 제10권1호
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• pp.1-5
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• 2016

In this study, the effect of high-energy proton irradiation on the optical properties of polyacrylonitrile (PAN) films was investigated. PAN thin films spin-coated on a substrate were irradiated 150 keV proton ions at various fluences. The changes in the chemical structure and optical properties were investigated by FT-IR and UV-vis spectroscopy. The results of the FT-IR analysis revealed that the cyclization reaction took place by proton irradiation and the degree of cyclization increased with an increasing fluence. Based on the UV-vis analysis, the optical band gap of PAN decreased from 2.84 to 2.52 eV with an increasing fluence due to the formation of carbon clusters by proton irradiation. In addition, the number of carbon atoms per carbon cluster and the number of carbon atoms per conjugation length were found to be increased with an increasing fluence.

• Bulletin of the Korean Chemical Society
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• 제19권6호
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• pp.654-660
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• 1998

$[Fe^{II}Fe^{III}BPLMP(OAc)_2](BPh_4)_2$ (1), a new model for the reduced form of the purple acid phosphatases, has been synthesized by using a dinucleating ligand, 2,6-bis[((2-pyridylmethyl)(6-methyl-2-pyridylmethyl)amino) methyl]-4-methylphenol (HBPLMP). Complex I has been characterized by X-ray diffraction method as having (μ-phenoxo)bis(acetato)diiron core. Complex 1 was crystallized in the monoclinic space group C2/c with the following cell parameters: a=41.620(6) Å, b=14.020(3) Å, c=27.007(4) Å, β=90.60(2)°, and Z=8. The iron centers in the complex 1 are ordered as indicated by the difference in the Fe-O bond lengths which match well with typical $Fe^{III}-O\; and\; Fe^{II}-O$ bond lengths. Complex 1 has been studied by electronic spectral, NMR, EPR, SQUID, and electochemical methods. Complex 1 exhibits strong bands at 592 nm, 1380 nm in $CH_3CN$ (ε = 1.0 × 103 , 3.0 × 102). These are assigned to $phenolate-to-Fe^{III}$ and intervalence charge-transfer transitions, respectively. Its NMR spectrum exhibits sharp isotropically shifted resonances, which number half of those expected for a valence-trapped species, indicating that electron transfer between $Fe^{II}\;and\;Fe^{III}$ centers is faster than NMR time scale. This complex undergoes quasireversible one-electron redox processes. The $Fe^{III}_2/Fe^{II}Fe^{III}\;and\;Fe^{II}Fe^{III}/Fe^{II}_2$ redox couples are at 0.655 and -0.085 V vs SCE, respectively. It has $K_{comp}=3.3{\times}10^{12}$ representing that BPLMP/bis(acetate) ligand combination stabilizes a mixed-valence $Fe^{II}Fe^{III}$ complex in the air. Complex 1 exhibits a broad EPR signal centered near g=1.55 which is a characteristic feature of the antiferromagnetically coupled high-spin $Fe^{II}Fe^{III}$ system $(S_{total}=1/2)$. This is consistent with the magnetic susceptibility study showing the weak antiferromagnetic coupling $(J= - 4.6\;cm^{-1},\; H= - 2JS_1{\cdot}S2)$ between $Fe^{II}\; and \;Fe^{III}$center.

• 한국자기학회지
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• 제5권5호
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• pp.778-781
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• 1995

The mixed ferrite $Ni_{x}Co_{1-x}Fe_{2}O_{4}$ have been investigated by X-ray and $M\"{o}ssbauer$ spectoscpy. From the results of X-ray diffraction measurement the structure for this system is spinel, and the lattice constant is in accord with Vegard's law. $M\"{o}ssbauer$ spectra of $Ni_{x}Co_{1-x}Fe_{2}O_{4}$ have been taken at various temperature ranging from 13 to 800 K. The isomer shifts indicate that the valence states of the irons at both A(tetrahedral) and B(octahedral) sithe are found to be in ferric high-spin states. The variation of magnetic hyperfine fields at the A and B sites are explained on the basis on A-B and B-B supertransferred hyperfine interactions. It is found that Debye temperatures for the A and B sites of $CoFe_{2}O_{4}$ and $NiFe_{2}O_{4}$ are found to be ${\theta}_{A}=734{\pm}5K,\;{\theta}_{B}=248{\pm}5K,\;and\;{\theta}_{A}=378{\pm}5K,\;{\theta}_{B}=357{\pm}5K$, respectively. Atomic migration of $Ni_{0.3}Co_{0.7}Fe_{2}O_{4}$ starts near 450 K and increases rapidly with increasing temperature to such a degree that 61 % of the ferric ions at the A site have moved over to the B site by 700 K.

• 한국자기학회지
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• 제5권5호
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• pp.846-853
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• 1995

국소섭동을 포함하는 비대칭성 계의 전자구조 물성을 연구하기 위해서 밀접 결합 (tight-binding ; TB) linear-muffin-tin-orbital(LMTO) 방법과 회귀(recursion ; R) 방법을 결합한 실공간 전자구조 방법인 제일원리-자체충족적-스핀분극 TB-LMTO-R 방법을 개발하였다. 이 방법을 강자성 물질인 bcc Fe, hcp Co, fcc Ni등에 적용하여 송이의 크기, 회귀 계수, TB-LMTO Hamiltonian의 차수등을 변화시키며 국소 상태밀도와 자기 모멘트등의 수치적 수렴도를 고찰하였다. 송이 크기는 5,000개 원자 이상, 연속 분수 계수 n은 40이상, TB-LMTO Hamiltonian의 차수는 2차 이상이며 TB-LMTO-R 방법이 기존의 LMTO 방법의 결과와 거의 일치하는 결과를 준다는 사실을 얻었고 실공간 전자 구조 방법으로 TB-LMTO-R 방법의 충분한 신뢰도를 확인 하였다.

• 한국자기학회지
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• 제16권5호
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• pp.229-233
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• 2006

나노 구조 철띠의 자기적 성질을 일반기울기 근사(GGA)를 채택한 전전자 full-potenial linearized augmented plane-wave(FLAPW)에너지 띠 방법을 이용하여 이론적으로 연구하였다. 세 줄, 다섯 줄, 일곱 줄의 철선으로 이루어진 띠에서 가장자리 줄의 자기모멘트는 2.97 또는 2.98 ${\mu}_B$로 Fe 단일 직선의 값과 비슷하게 포화된 값을 가졌으며, 가운데 선의 자기모멘트는 2.82 ${\mu}_B$로 2차원 격자의 값과 같았다. 일곱 줄로 이루어진 철 띠의 전하밀도나 스핀밀도는 가장자리 영역에서 거의 평평한 분포를 보였는데, 이는 가장자리 원자로부터 배출된 p-전자로 인한 가리기에 의한 것이다. 일곱 줄로 이루어진 철 띠에서 가장자리 원자의 상태밀도는 가운데 원자에 비해 띠폭이 줄어들었는데 이는 가장자리 효과에 의한 띠좁힘 때문이다.

• 한국결정성장학회지
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• 제31권5호
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• pp.212-217
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• 2021

Silica sol에 YAG 형광체를 첨가량별로 spin 코팅 후, 코팅막의 blue LED에서 백색광이 발현되는 정도와 표면 및 곡면 코팅용 binder로써, 적용가능성을 확인하였다. SEM, PSA를 통해YAG의 입자 크기는 D₅₀: 9~10 ㎛ 내외이며, XRD를 통해 YAG의 결정구조가 garnet(Y₃Al₅O₁₂), cubic인 것을 확인하였다. 코팅막은 crack이 없고 동시에 silica sol이YAG 형광체를 균질하게 도포된 형상을 보였으며, 첨가량 증가와 비례하게 코팅막 내에서 YAG 첨가량과 두께는 최대 40 ㎛까지 증가하는 추세를 보였다. 그리고 YAG 첨가량이 증가할수록 PL emission intensity 증가와 chromatic locus 곡선 끝 방향으로 색좌표 이동을 확인하였다. Soda-lime 유리기판 표면에 코팅 후, crack이 없으며 YAG 형광체가 균질하게 도포된 코팅성과 코팅막의 백색광 발현특성을 확인할 수 있었고 이는 직접적으로 LED에 다양한 형태의 형광 형상의 구현이 가능하다는 것을 의미한다.