• 한국표면공학회지
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• 제29권6호
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• pp.660-665
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• 1996

Thin films of indium oxide and indium tin oxide have been prepared by d.c. magnetron sputtering onto the fused silica substrates kept at 90, 200 and $300^{\circ}C$. In order to elucidate the optical absorption process in low energy region below 3 eV, we have analyzed the absorption coefficients obtained from reflectance and transmittance measurements for these films based on the Lucovsky model. It has been found for the first time that a defect center in the band gap is located at 0.8~1.4 eV below the Fermi level in all films and arises from oxygen vacancies in their films. The optical absorption in low energy region is explained to be dominated by the transition of electrons trapped at the positively charged (+2e) oxygen vacancies with s-like nature to the conduction band formed from the 5s-orbit in indium atoms.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권1호
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• pp.12-17
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• 1999

$MgIn_2Se_4 and MgIn_2Se_4 : Ni^{2+}$ single crystals were grown in the rhombohedral structure by the chemical transport reaction (C.T.R.) method using iodine as a transport agent. The optical absorption measured near the fundamental band edge showed that the optical energy band structure of these compounds had a direct band gap. The fundamental absorption band edge of these single crystals shift to a shorter wavelength region by decreasing temperature and the temperature dependence of the optical energy gaps in these compounds satisfy Varshni equation. The impurity optical absorption peaks due to nickel are observed in $MgIn_2Se_4 and MgIn_2Se_4 : Ni^{2+}$ single crystal. These impurity optical absorption peaks can be attributed to the electronic transitions between the split energy levels of $Ni_{2+}$ ions located at $T_d$ symmetry site of $MgIn_2Se_4$ host lattice. In the hotoluminescence spectrum of the single crystal at 10 K, a blue emission with a peak at 687nm and a green emission with a peak at 815nm for the $MgIn_2Se_4$ single crystal were observed.

• 한국전기전자재료학회논문지
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• 제24권9호
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• pp.760-765
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• 2011

Znic sulfide (ZnS) thin films were deposited on glass substrates by radio frequency magnetron sputtering. The substrate temperature varied from room temperature (RT) to $500^{\circ}C$. The structural and optical properties of ZnS films were studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive analysis of X-ray (EDAX) and UV-visible transmission spectra. The XRD analyses reveal that ZnS films have cubic structures with (111) preferential orientation, whereas the diffraction patterns sharpen with the increase in substrate temperatures. The FESEM images indicate that ZnS films deposited at $400^{\circ}C$ have nano-sized grains with a grain size of ~ 67 nm. Then films exhibit relatively high transmittance of 80% in the visible region, with an energy band gap of 3.71 eV. One obvious result is that the energy band gap of the film increases with increasing the substrate temperatures.

• 한국재료학회지
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• 제19권3호
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• pp.125-131
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• 2009

In this report, the structural and optical properties of sol-gel derived $Mg_xZn_{1-x}O$ thin films upon changes in the composition and annealing temperature were investigated. The $Mg^{2+}$ content and the annealing temperature were varied in the range of $0{\leq}x{\leq}0.35$ and $400^{\circ}C{\leq}T{\leq}600^{\circ}C$, respectively. The films exhibited a hexagonal wurtzite structure of a polycrystalline nature. The optical transmittance exceeded 85% and the optical band gap of the film was tuned as high as 3.84 eV at a value of x = 0.35 (annealed at $400^{\circ}C$), which was evidently the maximum $Mg^{2+}$ content for the single-phase polycrystalline $Mg_xZn_{1-x}O$ thin films prepared in this experiment. The optical band gap and photoluminescence emission were tailored to the higher energy side while maintaining crystallinity without a significant change of the lattice constant.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 춘계학술대회
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• pp.170-173
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• 2006

[ $CuInS_2$ ] filims were appeared from 0.84 to 1.27 of Cu/In composition ratio and sulfur composition ratios of $CuInS_2$ thin films fabricated, Also when Cu/In composition ratio was 1.03, $CuInS_2$ thin film with chalcopyrite structure had the highest XRD peak (112). And lattice constant (a) of and grain size of the film tin s ambient were appeared a little larger than those in only Vacuum The films in S ambient were p-type with resistive of around $10^{-1}{\Omega}cm$ and optical energy band gaps of the films in S ambient were appeared a little larger than those in only Vacuum. Analysis of the optical energy band gap of $CuInS_2$ thin films a value of 1.53eV.

• 한국전자통신학회논문지
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• 제14권5호
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• pp.877-886
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• 2019

본 연구에서는 band anticrossing 모델을 사용하여 온도와 조성비 변화에 따른 4원계 질화물계 화합물 반도체 $In_yGa_{1-y}As_{1-x}N_x$의 에너지 밴드갭과 광학상수를 계산하였다. 300K의 조성비 구간($0{\leq}x{\leq}0.05$, $0{\leq}y{\leq}1.0$)에서 에너지 밴드갭들이 연속적으로 감소하며, 계산된 휨 매개변수는 0.522eV가 사용되었다. 에너지 밴드갭 계산 결과는 다른 연구 결과와 대체로 잘 일치하였다. 또한 에너지 밴드갭 결과를 새롭게 제안한 모델식에 적용하여 굴절률 n과 고주파 유전상수 ${\varepsilon}$를 계산하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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• pp.99-100
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• 2007

ZnO films on $Al_2O_3$ substrates were grown using a pulsed laser deposition method. Through photoluminescence (PL) and X-ray diffraction (XRD) measurements, the optimum growth conditions for the ZnO growth were established. The results of the XRD measurements indicate that ZnO films were strongly oriented to the c-axis of the hexagonal structure and epitaxially crystallized under constraints created by the substrate. The full width half maximum for a theta curve of the (0002) peak was $0.201^{\circ}$. Also, from the PL measurements, the grown ZnO films were observed to give free exciton behaviour, which indicates a high quality of the epilayer. The Hall mobility and carrier density of the ZnO films at 293 K were estimated to be $299\;cm^2/V\;s$ and $8.27\;{\times}\;10^{16}\;cm^{-3}$, respectively. The absorption spectra revealed that the temperature dependance of the optical band gap on the ZnO films was $E_g(T)\;=\;3.439\;eV\;-\;(5.30\;{\times}\;10^{-4}\;ev/K)T^2(367\;+\;T)$.

• Advances in nano research
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• 제3권1호
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• pp.13-27
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• 2015

Size dependent emission properties and the interband optical transition energies in group-III nitride based quantum dots are investigated taking into account the geometrical confinement. Exciton binding energy and the optical transition energy in $Ga_{0.9}In_{0.1}N$/GaN and $Al_{0.395}In_{0.605}N$/AlN quantum dots are studied. The largest intersubband transition energies of electron and heavy hole with the consideration of geometrical confinement are brought out. The interband optical transition energies in the quantum dots are studied. The exciton oscillator strength as a function of dot radius in the quantum dots is computed. The interband optical absorption coefficients in GaInN/GaN and AlInN/AlN quantum dots, for the constant radius, are investigated. The result shows that the largest intersubband energy of 41% (10%) enhancement has been observed when the size of the dot radius is reduced from $50{\AA}$ to $25{\AA}$ of $Ga_{0.9}In_{0.1}N$/GaN ($Al_{0.395}In_{0.605}N$/AlN) quantum dot.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.225-225
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• 2011

The dielectric and optical properties of GaInZnO (GIZO), HfInZnO (HIZO) and InZnO (IZO) thin films on glass by RF magnetron sputtering method were investiged using reflection electron energy loss spectroscopy (REELS). The band gap was estimated from the onset values of REELS spectra. The band gaps of GIZO, HIZO and IZO thin films are 3.1 eV, 3.5 eV and 3.0 eV, respectively, Hf and Ga incorporated into IZO results in an increase in the energy band gap of IZO by 0.5 eV and 0.1 eV. The dielectric functions were determined by comparing the effective cross section determined from experimental REELS with a rigorous model calculation based on the dielectric response theory, using available software package, good agreement between the experimental and fitting results gives confidence in the accuracy of the determined dielectric function. The main peak of Energy Loss Function (ELF) obtained from IZO shows at 18.42 eV, which shifted to 19.43 eV and 18.15 eV for GIZO and HIZO respectively, because indicates the corporation of cation Ga and Hf in the composition. The optical properties represented by the dielectric function e, the refractive index n, the extinction coefficient k, and the transmission coefficient, T of HIZO and IZO thin films were determined from a quantitative analysis of REELS. The transmission coefficient was increased to 93% and decreased to 87% in the visible region with the incorporation of Hf and Ga in the IZO compound.

• 한국표면공학회지
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• 제37권4호
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• pp.191-195
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• 2004

Gallium or sulphur additions in $CuInSe_2$ were prepared using RF magnetron sputtering and pulsed laser deposition respectively. All of the observed thin films shows a chalcopyrite structure with the S and Ga addition increases the favourable (112) peak. The optical absorption coefficients were slightly decreased. The energy band gap of films could be shifted from 1.04 to 1.68 eV by adjusting the mole ratio of S/(S+Se) and Ga/(In+Ga). It is possible to obtain the optimum energy band gap by adding S or Ga solute at a certain ratio in favour of Se and In respectively. It is also necessary to control the ratio of Ga and S additions and to retain a certain portion of In and Se to provide better properties of thin films.