• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.11
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• pp.956-960
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• 2009

The characteristics of organic films can be affected by the temperature of evaporation source because the temperature of evaporation source has an effect on substrate temperature during OLED fabrication process using the thermal evaporation. To investigate the characteristics of OLED devices fabricated by using thermally damaged organic films, I-V-L and half life-time in OLED devices fabricated with various substrate temperatures were measured. During emission layer(EML) evaporation, OLED devices with a structure of ITO(100 nm)/ELM200(50 nm)/NPB(30 nm)/$Alq_3$(55 nm)/LiF(0.7 nm)/Al(100 nm) were fabricated at various substrate temperatures(room temperature, $30^{\circ}C$, $40^{\circ}C$, and $50^{\circ}C$). The characteristics of current density and luminance versus applied voltage in OLED devices fabricated shows that many electrical currents flowed and high brightness appeared at low voltage, but that the lifetime of OLED devices dropped suddenly. This phenomenon explained that the crystallization of $Alq_3$ thin film appeared owing to the substrate heating during evaporation.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1256-1261
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• 2009

Seawater amounts to 70% of the earth and represents a quite unlimited resource for the production of fresh water by desalination processes and for the extraction of dissolved salts present in it. Recently, the falling film evaporation has increased in interest as an efficient method for seawater desalination system. In the desalination system, the flow characteristics of the falling film is very important issue to make highly efficient system. So, this study is taken to investigate numerically the falling film thickness on the inlet Renold Number ranges are 400 to 700. Numerical simulations are performed using FLUENT6.3.26, a commercial CFD code.

• Electrical & Electronic Materials
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• v.9 no.7
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• pp.690-695
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• 1996

We have systematically investigated the characterization of V$_{2}$O$_{5}$ thin films as a counter electrode for lithium based complementary electrochromic devices. The V$_{2}$O$_{5}$ thin films were prepared by thermal vacuum evaporation with varing the substrate temperature and film thickness. In electrochromic devices for smart windows, the WO$_{3}$ thin films with 400-800 nm thickness require to be capable of reversibly injection 10-15 mC/cm$^{2}$ of lithium, which is readily accomplished charge-balanced switching in a V$_{2}$O$_{5}$ thin films with 100-150nm thick. The V$_{2}$O$_{5}$ thin films produces considerably small changes in optical modulation properties in the visible and near infrared region(500-1100 nm) compared to the amorphous WO$_{3}$ thin films on 10-15 mC/cm$^{2}$ of lithium injection and the V$_{2}$O$_{5}$ thin films can therefore act as a counter electrode to WO$_{3}$ in a lithium based complementary clectrochromic devices. After 10$^{5}$ coloration/bleaching switching time, the degradation does not occurs and the devices exhibit a stable optical modulation in V$_{2}$O$_{5}$ thin films. It has shown that the injected lithium ion amounts in crystalline V$_{2}$O$_{5}$ thin films with the same thickness is large by 3-5 mC/cm$^{2}$ of lithium compared to the amorphous thin films in the same driving conditions. Therefore, to optimize the device performance, it is necessary to choose an appropriate film thickness and crystallinity of V$_{2}$O$_{5}$ for amorphous WO$_{3}$ film thickness as a working electrode.

• Journal of the Korean Vacuum Society
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• v.17 no.5
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• pp.466-472
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• 2008

Purple Gold is the alloy consisting of 78wt%Au-22wt%Al, and is expressed as a chemical formula, $AuAl_2$. Lately it is being used for the material of accessories or the decorative ornaments, being one of the colored golds having the peculiar purple color, like White Gold and Pink Gold. Purple Gold has the weak point in shaping through casting process due to the bad malleability and castability, being the intermetalic compound of Au and Al. Therefore, it is possible to produce the final product only by the cutting and the grinding process or to use it as a decorative coat with the thin film evaporation. This study implemented two kinds of thin film experiments. One is the case that heat treatment was made after Au and Al deposition evaporated separately with a weight ratio 78:22 on the 200nm$SiO_2$/Si substrate. The other is the case that the surface deposition was made through the vacuum evaporation, keeping the glass substrate temperature remain room temperature, using the bulk $AuAl_2$ as a source. The final film property was measured, focusing on the Purple Gold's color and thickness through the bare eye inspection, the microstructure analysis, the surface resistance analysis, the color difference analysis, and XRD analysis. Purple Gold was not formed, as the excessive surface agglomeration occurred, in case of being produced and treated thermally with 12.5nmAu/40nmAl/200nm$SiO_2$/Si structure. Our results suggest that of Purple Gold films, showing the same purple color as the bulk's, were successfully deposited with the direct thermal evaporation from the $AuAl_2$ bulk source.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.85-87
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• 2009

Despite the success of $Cu(In,Ga)Se_2$ (CIGS) based PV technology now emerging in several industrial initiatives, concerns about the cost of In and Ga are often expressed. It is believed that the cost of those elements will eventually limit the cost reduction of this technology. one candidate to replace CIGS is $Cu_2ZnSnSe_4$ (CZTSe), fabricated by co-evaporation technique. Effects of substrate temperature of $Cu_2ZnSnSe_4$ absorber layer on the performance of thin films solar cells were investigated. As substrate temperature increased, the grain size of $Cu_2ZnSnSe_4$ films increased presumably. At a optimal condition of substrate temperature is $320^{\circ}C$, the solar cell shows a conversion efficiency of 1.79% with $V_{OC}$ of 0.213V, JSC of $16.91mA/cm^2$ and FF of 49.7%.

• Current Applied Physics
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• v.18 no.12
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• pp.1496-1506
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• 2018

Organic/inorganic ultraviolet photodetector was fabricated using thermal evaporation technique. Organic/inorganic heterojunction based on thermally evaporated copper (II) acetylacetonate thin film of thickness 200 nm deposited on an n-type silicon substrate is introduced. I-V characteristics of the fabricated heterojunction were investigated under UV illumination of intensity $65mW/cm^2$. The diode parameters such as ideality factor, n, barrier height, ${\Phi}_B$, and reverse saturation current, $I_s$, were determined using thermionic emission theory. The series resistance of the fabricated diode was determined using modified Nord's method. The estimated values of series resistance and barrier height of the diode were about $0.33K{\Omega}$ and 0.72 eV, respectively. The fabricated photodetector exhibited a responsivity and specific detectivity about 9 mA/W and $4.6{\times}10^9$ Jones, respectively. The response behavior of the fabricated photodetector was analyzed through ON-OFF switching behavior. The estimated values of rise and fall time of the present architecture under UV illumination were about 199 ms and 154 ms, respectively. Finally, enhancing the photoresponsivity of the fabricated photodetector, post-deposition plasma treatment process was employed. A remarkable modification of the device performance was noticed as a result of plasma treatment. These modifications are representative in a decrease of series resistance and an increase of photoresponsivity and specific detectivity. The process of plasma treatment achieved an increment of external quantum efficiency from 5.53% to 8.34% at -3.5 V under UV illumination.

• Progress in Superconductivity and Cryogenics
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• v.9 no.1
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• pp.5-8
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• 2007

We have investigated the superconducting properties and surface morphology of $Sm_xBa_yCu_3O_{6+z}$ thin films deposited on LMO/IBAD-MgO/Hastelloy which prepared with different composition ratio by co-evaporation method(EDDC, Evaporation using Drum in Dual Chambers). We observed the composition ratio of SmBCO thin films by EDS analysis. We fabricated SmBCO thin film with critical current density of $1.5{\times}10^6A/cm^2$ at composition ratio of SM:Ba:Cu=1.10:2.01:3(at 77 K self-field). And, we confirmed that substitution of Sm-Ba did not occur at Cu rich phase by EDS analysis.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.10a
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• pp.35.1-35.1
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• 2011

New photovoltaic (PV) materials and manufacturing approaches are needed for meeting the demand for lower-cost solar cells. The prototypal thin-film photovoltaic absorbers (CdTe and $Cu(In,Ga)Se_2$) can achieve solar conversion efficiencies of up to 20% and are now commercially available, but the presence of toxic (Cd,Se) and expensive elemental components (In, Te) is a real issue as the demand for photovoltaics rapidly increases. To overcome these limitations, there has been substantial interest in developing viable alternative materials, such as $Cu_2ZnSnS_4$ (CZTS) is an emerging solar absorber that is structurally similar to CIGS, but contains only earth abundant, non-toxic elements and has a near optimal direct band gap energy of 1.4~1.6 ev and a large absorption coefficient of ${\sim}10^4\;cm^{-1}$. The CZTS absorber layers are grown and investigated by various fabrication methods, such as thermal evaporation, e-beam evaporation with a post sulfurization, sputtering, non-vacuum sol-gel, pulsed laser, spray-pyrolysis method and electrodeposition technique. In the present work, we report an alternative method for large area deposition of CZTS thin films that is potentially high throughput and inexpensive when used to produce monolithically integrated solar panel modules. Specifically, we have developed an aqueous chemical approach based on chemical bath deposition (CBD) with a subsequent sulfurization heat treatment. Samples produced by our method were analyzed by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, absorbance and photoluminescence. The results show that this inexpensive and relatively benign process produces thin films of CZTS exhibiting uniform composition, kesterite crystal structure, and good optical properties. A preliminary solar cell device was fabricated to demonstrate rectifying and photovoltaic behavior.

• Korean Journal of Materials Research
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• v.14 no.10
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• pp.683-687
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• 2004

The BON thin films were grown on the Si substrate by the RF-PECVD method. When stored at the room temperature, the phase separation or transition of BON thin films occurred on the surface, due to the hydrophilic property of BON. The oxidation of BON thin films occurred mainly by the evaporation of B, O and N. The oxidized BON thin films consisted of an amorphous phase and a bit of the polycrystalline phase.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.8
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• pp.864-869
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• 2013

As the size of mechanical components decreases, capillary forces and surface tension become increasingly significant. A major problem in maintaining high reliability of these small components is that of large frictional forces due to capillary action and surface tension. Unlike the situation with macro-scale systems, liquid lubrication cannot be used to reduce friction of micro-scale components because of the excessive capillary and drag forces. In this work, the feasibility of using evaporation to coat a thin film of organic lubricant on a solid surface was investigated with the aim of reducing friction. Petroleum and silicone oils were used as lubricants to coat a silicon substrate. It was found that friction could be significantly reduced and, furthermore, that the effectiveness of this method was strongly dependent on the coating conditions.