• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.171-174
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• 2004

The stochiometric $AgGaSe_2$ polycrystalline mixture of evaporating materials for the $AgGaSe_2$ single crystal thin film was prepared from horizontal furnace. To obtain the single crystal thin films, $AgGaSe_2$ mixed crystal and semi-insulating GaAs(100) wafer were used as source material and substrate for the Hot Wall Epitaxy (HWE) system, respectively. The source and substrate temperature were fixed at $630^{\circ}C$ and $420^{\circ}C$, respectively. The thickness of grown single crystal thin films is $2.1{\mu}m$. The single crystal thin films were investigated by photoluminescence and double crystal X-ray diffraction(DCXD) measurement. The carrier density and mobility of $AgGaSe_2$ single crystal thin films measured from Hall effect by van der Pauw method are $4.89{\times}10^{17}\;cm^{-3},\;129cm^2/V{\cdot}s$ at 293K, respectively. From the photocurrent spectrum by illumination of perpendicular light on the c - axis of the $AgGaSe_2$ single crystal thin film, we have found that the values of spin orbit splitting ${\Delta}S_o$ and the crystal field splitting ${\Delta}C_r$ were 0.1762 eV and 0.2494 eV at 10 K, respectively. From the photoluminescence measurement of $AgGaSe_2$ single crystal thin film, we observed free excition $(E_X)$ observable only in high quality crystal and neutral bound exciton $(D^o,X)$ having very strong peak intensity And, the full width at half maximum and binding energy of neutral donor bound excition were 8 meV and 14.1 meV, respectively. By Haynes rule, an activation energy of impurity was 141 meV.

• Bulletin of the Korean Chemical Society
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• v.35 no.8
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• pp.2505-2511
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• 2014

Indium oxide nanocrystals ($In_2O_3$ NCs) with sizes of 5.5 nm-10 nm were synthesized by hot injection of the mixture precursors, indium acetate and oleic acid, into alcohol solution (1-octadecanol and 1-octadecence mixture). Field emission transmission electron microscopy (FE-TEM), High resolution X-Ray diffraction (X-ray), Nuclear magnetic resonance (NMR), and Fourier transform infrared spectroscopy (FT-IR) were employed to investigate the size, surface molecular structure, and crystallinity of the synthesized $In_2O_3$ NCs. When covered by oleic acid as a capping group, the $In_2O_3$ NCs had a high crystallinity with a cubic structure, demonstrating a narrow size distribution. A high mobility of $2.51cm^2/V{\cdot}s$ and an on/off current ratio of about $1.0{\times}10^3$ were observed with an $In_2O_3$ NCs thin film transistor (TFT) device, where the channel layer of $In_2O_3$ NCs thin films were formed by a solution process of spin coating, cured at a relatively low temperature, $350^{\circ}C$. A size-dependent, non-monotonic trend on electron mobility was distinctly observed: the electron mobility increased from $0.43cm^2/V{\cdot}s$ for NCs with a 5.5 nm diameter to $2.51cm^2/V{\cdot}s$ for NCs with a diameter of 7.1 nm, and then decreased for NCs larger than 7.1 nm. This phenomenon is clearly explained by the combination of a smaller number of hops, a decrease in charging energy, and a decrease in electronic coupling with the increasing NC size, where the crossover diameter is estimated to be 7.1 nm. The decrease in electronic coupling proved to be the decisive factor giving rise to the decrease in the mobility associated with increasing size in the larger NCs above the crossover diameter.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.37-37
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• 2010

Silicate-silsesquioxane or siloxane-silsesquioxane hybrid thin films are strong candidates as matrix materials for ultra low dielectric constant (low-k) thin films. We synthesized the silicate-silsesquioxane hybrid resins from tetraethoxyorthosilicate (TEOS) and methyltrimethoxysilane (MTMS) through hydrolysis and condensation polymerization by changing their molar ratios ([TEOS]:[MTMS] = 7:3, 5:5, and 3:7), spin-coating on Si(100) wafers. In the case of [TEOS]:[MTMS] 7:3, the dielectric permittivity value of the resultant thin film was measured at 4.30, exceeding that of the thermal oxide (3.9). This high value was thought to be due to Si-OH groups inside the film and more extensive studies were performed in terms of electronic, ionic, and orientational polarizations using Debye equation. The relationship between the mechanical properties and the synthetic conditions of the silicate-silsesquioxane precursors was also investigated. The synthetic conditions of the low-k films have to be chosen to meet both the low orientational polarization and high mechanical properties requirements. In addition, we have investigated a new solution-based approach to the synthesis of semiconducting chalcogenide films for use in thin-film transistor (TFT) devices, in an attempt to develop a simple and robust solution process for the synthesis of inorganic semiconductors. Our material design strategy is to use a sol-gel reaction to carry out the deposition of a spin-coated CdS film, which can then be converted to a xerogel material. These devices were found to exhibit n-channel TFT characteristics with an excellent field-effect mobility (a saturation mobility of ${\sim}\;48\;cm^2V^{-1}s^{-1}$) and low voltage operation (< 5 V). These results show that these semiconducting thin film materials can be used in low-cost and high-performance printable electronics.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.10
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• pp.802-807
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• 2001

The (S $r_{0.85}$C $a_{0.15}$)Ti $O_{3}$(SCT) thin films are deposited on Pt-coated electrode (Pt/TiN/ $SiO_2$/Si) using RF sputtering method. The composition of SCT thin films deposited on Si substrate at woom temperature is close to stoichiometry(1.102 in A/B ratio). The maximum dielectric constant of SCT thin films is obtained by annealing at 600[$^{\circ}C$]. The capacitance characteristics had a stable value within $\pm$4[%]. The drastic decrease of dielectric constant and increase of dielectric loss in SCT thin films is observed above 200[kHz]. SCT thin films used in this study show the phenomena of dielectric relaxation with the increase of frequencey.cey.

• Journal of Magnetics
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• v.5 no.1
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• pp.19-22
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• 2000

The effects of a hard-biased Held on the magnetic and magnetoresistive properties of a crossed spin-valve head are investigated by computer simulation with particular emphasis on the asymmetry of the output signal. The spin-valve considered in this work is NiMn (25 nm)/NiFe (2.5 m)/Cu (3 nm)/NiFe (5.5 m), with a length of 1500 m and a width of 600 nm. A simple model is used where each magnetic layer consists of a single domain, and the magnetoresistance is a function of the angle between the magnetization directions of the two magnetic layers. The ideal crossed spin-valve structure is not realized with the present model and magnetic parameters, but the deviation from ideality is decreased by the hard-biased field. This results in the improvement of the linearity of the output signal with the use of the bias field. The magnetoresistance ratio and magnetoresistive sensitivity, however are reduced. The magnetic properties including the magnetoresistance are found to be strongly affected by magnetostatic interactions, particularly the inter-layer magnetostatic field.

• Korean Journal of Materials Research
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• v.30 no.3
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• pp.131-135
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• 2020

Silver nanowire (AgNW) networks have been adopted as a front electrode in Cu(In,Ga)Se2 (CIGS) thin film solar cells due to their low cost and compatibility with the solution process. When an AgNW network is applied to a CIGS thin film solar cell, reflection loss can increase because the CdS layer, with a relatively high refractive index (n ~ 2.5 at 550 nm), is exposed to air. To resolve the issue, we apply solution-processed ZnO nanorods to the AgNW network as an anti-reflective coating. To obtain high performance of the optical and electrical properties of the ZnO nanorod and AgNW network composite, we optimize the process parameters - the spin coating of AgNWs and the concentration of zinc nitrate and hexamethylene tetramine (HMT - to fabricate ZnO nanorods. We verify that 10 mM of zinc nitrate and HMT show the lowest reflectance and 10% cell efficiency increase when applied to CIGS thin film solar cells.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.10
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• pp.620-624
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• 2015

We have studied structural, optical and electrical properties of In-Ga-doped ZnO (IGZO) thin films. The IGZO thin films were deposited on the corning 1737 glass by RF magnetron sputtering method. The RF power in sputtering process was varied as 30, 50, 70, and 90 W respectively. All of the IGZO thin films transmittance in the visible range (400 nm ~ 800 nm) was above 83%. XRD analysis showed the IGZO thin films amorphous structure of the thin films without any peak. And also IGZO thin film have low resistivity ($1.99{\times}10^{-3}{\Omega}cm$), high carrier concentration ($6.4{\times}10^{20}cm^{-3}$), and mobility ($10.3cm^2V^{-1}s^{-1}$). By the studies we found that IGZO transparent thin film can be used as optoelectronic material and introduced application possibility for future electronic devices.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1331-1332
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• 2007

In the present works, we investigate the thermal characteristics on Ag/$As_{2}S_{3}$ and Ag/$As_{40}Ge_{10}Se_{15}S_{35}$ amorphous chalcogenide thin film structure for PMC (Programmable Metallization Cell).As the results of resistance change with the temperature on Ag/$As_{40}Ge_{10}Se_{15}S_{35}$ amorphous chalcogenide thin film, the resistance was abruptly dropped from the initial resistance of 1.32 M ${\Omega}$ to the saturated value of 800 ${\Omega}$ at $203^{\circ}C$. On the other hand, the resistance increased to 1.3 $M{\Omega}$ at $219^{\circ}C$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.3
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• pp.177-181
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• 2018

We prepared ZnS thin films via chemical bath deposition (CBD) in an aqueous solution of ammonia ($NH_3$) and hydrazine ($N_2H_4$). The composition ratio of hydrazine used was 0%, 17%, 22%, 29%, or 50%. We investigated the effects of hydrazine and ammonia on the growth, and the structural and optical properties of ZnS in terms of surface uniformity, voids, and grain size. We found that during the growth of ZnS films, hydrazine was very effective for improving the surface morphology and layer uniformity with fast layer formation, while it had no effect on the bandgap energy, $E_g$.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.528-532
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• 1995

Ferromagnetic resonance experiments have been used to investigate the magnetic properties of amorphous $Co_{89.5}Zr_{10.5}$ thin films deposited by DC magnetron sputtering method. In the thickness range from $350\;{\AA}$ to $3,200\;{\AA}$, measurements were carried out in a static magnetic field perpendicular and parallel to the film plane and in a conventional 9.44 GHz spectrometer at room temperature. The ferromagnetic resonance spectra by the field perpendicular to the film plane showed standing spin wave. The spacing and the relative intensities between the various spin wave resonance peaks are analysed considering surface magnetic anisotropy. The surface magnetic anisotropy constant ($K_{so},\;K_{sd}$) of amorphous $Co_{89.5}Zr_{10.5}$ thin films are $0.02\;erg/\textrm{cm}^2$ and $0.55\;erg/\textrm{cm}^2$ respectively regardless of the film thickness except for $3,200\;{\AA}$ film. In case of $3,200\;{\AA}$ these values are $0.46\;erg/\textrm{cm}^2$ and $0.55\;erg/\textrm{cm}^2$ respectively.