• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.123-123
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• 2003

탄소나노튜브는 지금까지의 많은 연구를 통해 다양한 분야에 대한 응용 가능성이 확인되었으며, 그 중에서도 특히 탄소나노튜브를 이용한 전계방출표시소자(carbon nanotube field emission display, CNT-FED)는 상용화를 눈앞에 두고 있는 상황이다. 본 연구에서는 탄소나 노튜브를 합성할 수 있는 여러 가지 방법 중에서 열화학기상증착법(thermal chemical vapor deposition, thermal CVD)을 이용하여 유리기판 위에 탄소나노튜브를 합성하였다. Electron beam evaporation으로 유리기판 위에 전극층으로 Cr을 150nm를 증착하고 연속하여 촉매층인 Invar(Fe-53%Ni-6%Co 합금)를 10nm의 두께로 형성하였다. 사진식각으로 Cr층을 line 패턴한 후 Cr line 내의 Invar층을 line 및 dot 패턴하였다. 나노튜브 합성을 위해 480-58$0^{\circ}C$까지 진공분위기 또는 질소 분위기에서 20분간 승온한 후 CO(150sccm)와 H$_2$(1200sccm)를 주입하여 20분간 성장시키고 질소 분위기에서 냉각시켰다. 성장된 탄소나노튜브는 SEM, TEM, Raman spectroscopy 등을 통하여 구조 및 형상분석을 하였다. 진공승온의 경우 탄소불순물인 a-C이 많은 양 증착 되었으며 탄소나노튜브는 온도에 따라 1-5$\mu\textrm{m}$의 두께로 성장하였으나, 질소분위기 승온의 경우는 a-C이 거의 증착되지 않았으며 나노튜브의 두께가 10-20$\mu\textrm{m}$였다. 본 연구에서는 diode구조를 갖는 탄소나노튜브 에미터의 수명예측을 위해 여러 가지 가속측정조건에서 전계방출 특성을 연구하였다. Anode와 cathode 간의 간격을 400$\mu\textrm{m}$로 유지한 diode 구조에 대해 $10^{-6}$ torr 이하의 진공에서 전계방출을 측정하였다. 100 line의 에미터를 60Hz의 주파수에서 1/100 duty로 구동하였으며, duty비 증가에 따라 pulse의 on-time을 고정하고 frequency를 변화시켰다. dc까지 duty비가 증가됨에 따라 방출전류의 양이 선형적으로 증가하였다. 전압을 일정하게 고정시키고 각 duty비에서 시간에 따라 방출전류를 측정한 결과 duty비가 높을수록 방출전류가 시간에 따라 급격히 감소하였다. 각 duty비에서 방출전류의 양이 1/2로 감소하는 시점을 에미터의 수명으로 볼 때 duty비 대 에미터 수명관계를 구해 높은 duty비에서 전계방출을 시킴으로써 실제의 구동조건인 낮은 duty비에서의 수명을 단시간에 예측할 수 있었다.

• Advances in nano research
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• v.5 no.3
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• pp.193-201
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• 2017

ZnO, ZnO: Cu, Ga, and ZnO: Cu, Ga, Ag thin films were obtained by oxidization of ZnS and ZnS: Cu, Ga films deposited onto glass substrates by electron-beam evaporation from ZnS and ZnS: Cu, Ga targets and from ZnS: Cu, Ga film additionally doped with Ag by the closed space sublimation technique at atmospheric pressure. The film thickness was about $1{\mu}m$. The oxidation was carried out at $600-650^{\circ}C$ in air or in an atmosphere containing water vapor. Structural characteristics were investigated by X-ray diffraction (XRD) and atomic force microscopy (AFM). Photoluminescence (PL) spectra of the films were measured at 30-300 K using the excitation wavelengths of 337, 405 and 457.9 nm. As-deposited ZnS and ZnS: Cu, Ga films had cubic structure. The oxidation of the doped films in air or in water vapors led to complete ZnO phase transition. XRD and AFM studies showed that the grain sizes of oxidized films at wet annealing were larger than of the films after dry annealing. As-deposited doped and undoped ZnS thin films did not emit PL. Shape and intensity of the PL emission depended on doping and oxidation conditions. Emission intensity of the films annealed in water vapors was higher than of the films annealed in the air. PL of ZnO: Cu, Ga films excited by 337 nm wavelength exhibits UV (380 nm) and green emission (500 nm). PL spectra at 300 and 30 K excited by 457.9 and 405 nm wavelengths consisted of two bands - the green band at 500 nm and the red band at 650 nm. Location and intensities ratio depended on the preparation conditions.

• Journal of the Korean Ceramic Society
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• v.39 no.2
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• pp.210-215
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• 2002

Optical Band-pass Filter(BPF) for the selected wavelength of 4300 nm was designed and fabricated on Si wager by alternately depositing Ge and $SiO_2$ thin layers by an electron beam evaporation technique. The fabricated BPF showed the optical transmittance characteristics of 58.2% with FWHM(Full Width at Half Maximum) of 204 nm at 4300 nm, but showed the transmittance less than 5% due to the reflectance over all the wavelength ranges except 4300 nm band. The $CO_2$ sensitivity of BPF was investigated with the transmittance as a function of $CO_2$ gas concentration using a sensing cell attached to FT-IR instrument. The transmittance of BPF was almost linearly decreased with increasing of $CO_2$ concentration in the range of from 500 to 5000 ppm. The sensing structure using double BPFs showed higher slop of transmittance vs $CO_2$ concentration, and thus higher gas sensitivity than that using a single BPF, even though the former had relatively lower transmittance.

• Journal of Sensor Science and Technology
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• v.1 no.1
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• pp.53-57
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• 1992

We report the crystal growth and the electro-optic characteristics of $CdS_{1-x}Se_{x}$ thin films. $CdS_{1-x}Se_{x}$ thin films wire deposited on the alumina plate by electron beam evaporation technique in pressure of $1.5{\times}10^{-7}$ torr, voltage of 4kV, current of 2.5mA and substrate temperature of $300^{\circ}C$. The deposited $CdS_{1-x}Se_{x}$ thin films were proved to be a polycrystal with hexagonal structure through X-ray diffraction patterns. $CdS_{1-x}Se_{x}$ photoconductive films showed high photoconductivity after annealing at $550^{\circ}C$ for 30 minutes. And the films have been investigated the Hall effect, photocurrent spectra, sensitivity, maximum allowable power dissipation and response time.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.3
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• pp.262-268
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• 2009

We investigated the properties of inorganic diatomic films like silicon oxide ($SiO_2$) and zinc oxide (ZnO) and their composite films are packed as a passivation layer around Ca cells on glass substrates by using an electron-beam evaporation technique and rf-magnetron sputtering method. When these Ca cells are exposed to an ambient atmosphere, the water vapor penetrating through the passivation layers is adsorbed in the Ca cells, resulting in a gradual progress of transparency in the Ca cells, which can be represented by changes of the optical transmittance in the visible range. Compared with the saturation times for the Ca cells to become completely transparent in the atmosphere, the protection effects against permeation of water vapor are estimated for various passivation films. The thin composite films consist of$SiO_2$ and ZnO are found to show a superior protection effect from water vapor permeation compared with diatomic inorganic films like $SiO_2$ and ZnO. Also, this inorganic thin composite films are also found that their protection effect against permeation of water vapor can be significantly enhanced by choosing their suitable composition ratio and deposition method, in addition, the main factors affecting the permeation of water vapor through the oxide films are found to be the polarizability and the packing density.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.489.2-489.2
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• 2014

The planar type flexible piezoelectric energy harvesters (PEH) based on PbZr0.52Ti0.48O3 (PZT) thin films on the flexible substrates are demonstrated to convert mechanical energy to electrical energy. The planar type energy harvesters have been realized, which have an electrode pair on the PZT thin films. The PZT thin films were deposited on double side polished sapphire substrates using conventional RF-magnetron sputtering. The PZT thin films on the sapphire substrates were transferred by PDMS stamp with laser lift-off (LLO) process. KrF excimer laser (wavelength: 248nm) were used for the LLO process. The PDMS stamp was attached to the top of the PZT thin films and the excimer laser induced onto back side of the sapphire substrate to detach the thin films. The detached thin films on the PDMS stamp transferred to adhesive layer coated on the flexible polyimide substrate. Structural properties of the PZT thin films were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). To measure piezoelectric power generation characteristics, Au/Cr inter digital electrode (IDE) was formed on the PZT thin films using the e-beam evaporation. The ferroelectric and piezoelectric properties were measured by a ferroelectric test system (Precision Premier-II) and piezoelectric force microscopy (PFM), respectively. The output signals of the flexible PEHs were evaluated by electrometer (6517A, Keithley). In the result, the transferred PZT thin films showed the ferroelectric and piezoelectric characteristics without electrical degradation and the fabricated flexible PEHs generated an AC-type output power electrical energy during periodically bending and releasing motion. We expect that the flexible PEHs based on laser transferred PZT thin film is able to be applied on self-powered electronic devices in wireless sensor networks technologies. Also, it has a lot of potential for high performance flexible piezoelectric energy harvester.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.193-196
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• 2001

Single phase $CuInS_2$ thin film with the highest diffraction peak (112) at diffraction angle $(2\theta)$ of $27.7^{\circ}$ and the second highest diffraction peak (220) at diffraction angle $(2\theta)$ of $46.25^{\circ}$ was well made with chalcopyrite structure at substrate temperature of $70^{\circ}C$, annealing temperature of $250^{\circ}C$, annealing time of 60 min. The $CuInS_2$ thin film had the greatest grain size of $1.2{\mu}m$ and Cu/In composition ratio of 1.03. Lattice constant of a and c of that $CuInS_2$ thin film was 5.60 A and 11.12 A respectively. Single phase $CuInS_2$ thin films were accepted from Cu/In composition ratio of 0.84 to 1.3. P-type $CuInS_2$ thin films were appeared at over Cu/In composition ratio of 0.99. Under Cu/In composition ratio of 0.96, conduction types of $CuInS_2$ thin films were n-type. Also, fundamental absorption wavelength, the absorption coefficient and optical energy band gap of p-type $CuInS_2$ thin film with Cu/In composition ratio of 1.3 was 837 nm, $3.0{\times}104cm^{-1}$ and 1.48 eV respectively. When Cu/In composition ratio was 0.84, fundamental absorption wavelength, the absorption coefficient and optical energy band gap of n-type $CuInS_2$ thin film was 821 nm, $6.0{\times}10^4cm^{-1}$ and 1.51 eV respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.05a
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• pp.59-62
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• 1996

Plasma displays (PDP) as a large area wall-hanging display device are rabidly developed with flat CRT, TPT LCD and etc. Especially, AC Plasma Display Panels(AC PDPs) have the inherent memory function which is effective for large area displays. The memory function in AC PDPs is caused by the accumulation of the electrical charge on the protecting layer formed on the dielectric layer. This MgO protective layer prevents the dielectric layer from sputtering by ion in discharge plasma and also has the additional important roll in lowering the firing voltage due to the large secondary electron emission coefficient). Until now, the MgO Protective layer is mainly formed by E-Beam evaporation. With increasing the panel size, this process is difficult to attain cost reduction, and are not suitable for large quantity of production. To the contrary, the methode of shuttering are easy to apply on mass production and to enlarge the size of the panel and shows the superior adhesion and uniformity of thin film. In this study, we have prepared MgO protective layer on AC PDP Cell by reactive magnetron sputtering and studied the effect of MgO layer on the surface discharge characteristics of ac PDP.

• Transactions on Electrical and Electronic Materials
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• v.4 no.1
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• pp.7-10
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• 2003

Single phase CuInS$_2$ thin film with the strongest diffraction peak (112) at diffraction angle (2$\theta$) of 27.7$^{\circ}$ and the second strongest diffraction peak (220) at diffraction angle (2$\theta$) of 46.25$^{\circ}$was well made with chalcopyrite structure at substrate temperature of 70$^{\circ}C$. annealing temperature of 250$^{\circ}C$, annealing time of 60 min. The CuInS$_2$ thin film had the greatest grain size of 1.2 Um when the Cu/In composition ratio of 1.03, where the lattice constant of a and c were 5.60${\AA}$ and 11.12${\AA}$, respectively. The Cu/In stoichiometry of the single-phase CuInS$_2$thin films was from 0.84 to 1.3. The film was p-type when tile Cu/In ratio was above 0.99 and was n-type when the Cu/In was below 0.95. The fundamental absorption wavelength, absorption coefficient and optical band gap of p-type CuInS$_2$ thin film with Cu/In=1.3 were 837nm, 3.OH 104 cm-1 and 1.48 eV, respectively. The fundamental absorption wavelength absorption coefficient and optical energy band gap of n-type CuInS$_2$ thin film with Cu/In=0.84 were 821 nm, 6.0${\times}$10$^4$cm$\^$-1/ and 1.51 eV, respectively.

• Journal of Korean Ophthalmic Optics Society
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• v.7 no.1
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• pp.75-78
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• 2002

Thirty three layer $TiO_2/SiO_2$ coating mirrors with high reflectance through a 620~820nm wavelength range have been designed and fabricated by electron beam evaporation method. Multilayer films were deposited on glass(BK7) and sequentially. The high reflector design is based on alternating high and low refractive index layers. $n_H$ and $n_L$ such that a "stopband"(or area of high reflectivity) is created that is centered around the design wavelength. ${\lambda}_0$. The measured transmittance spectrum with an incident wavelength at an incident angle of $40^{\circ}{\pm}7^{\circ}$ exhibited a reflectance of 99.9% at the wavelength of 620~820nm but high peak transmittance in the wavelength region from 700 to 740nm.