• Journal of the Microelectronics and Packaging Society
• /
• v.26 no.2
• /
• pp.15-21
• /
• 2019

We investigated the structural, electrical and optical properties of zinc oxide (ZnO) ultra-thin films grown at $150^{\circ}C$ by atomic layer deposition (ALD). Diethylzinc and deionized water were used as metal precursors and reactants, respectively, for the deposition of ZnO thin films. The growth rate per ALD cycle was a constant 0.21 nm/cycle at $150^{\circ}C$, and samples below 50 cycles had amorphous properties due to the relatively thin thickness at the initial ALD growth stage. With the increase of the thickness from 100 cycles to 200 cycles, the crystallinity of ZnO thin films was increased and hexagonal wurtzite structure was observed. In addition, the particle size of the ZnO thin film increased with increasing number of ALD cycles. Electrical properties analysis showed that the resistivity value decreased with the increase of the thin film thickness, which is correlated with the decrease of the grain boundary concentration in the thicker ZnO thin film due to the increase of grain size and the improvement of the crystallinity. Optical characterization results showed that the band edge absorption in the near ultraviolet region (300 nm~400 nm) was increased and shifted. This phenomenon is due to the increase of the carrier concentration with the increase of the ZnO thin film thickness. This result agrees well with the decrease of the resistivity with the increase of the thin film thickness. Consequently, as the thickness of the thin film increases, the stress on the film surface is relaxed, the band gap decreases, and the crystallinity and conductivity are improved.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.7 no.2
• /
• pp.166-173
• /
• 2019

In this paper, the reaction properties of silica source in the accelerated curing conditions using autoclave and the fundamental properties of inorganic Micro Defect Free(MiDF) concrete using silica source are studied. Studies show that Si ions elution rate from silica source in autoclave curing is higher in amorphous source. In tap water conditions, solids which is source after autoclaved curing show a higher mass reduction in amorphous materials, which is attributed to the higher elution rate of ion. In $Ca(OH)_2$ solution conditions, amorphous materials show higher mass increase, due to increase in C-S-H minerals. From experiment for influence on the properties of MiDF concrete by using nano silica materials, the specimen with silica fume shows an increase in compressive strength and a decrease in absorption depending on replacement rate up to 5.5%, while nano silica with amorphous phase and high-fineness shows a decrease in compressive strength and decrease in the water absorption. The specimen with nano silica increases the pore below 10,000nm, but reduces pore between 10,000 and 100,000nm. The above results show that the porosity and absorption rate of MiDF concrete can be reduced by using amorphous nano-size silica. However, to reduce the pore of 50 to 10,000nm, better dispersion of nano material in the cement matrix will be necessary. We will focus on the this item in the next research.

• Journal of Biosystems Engineering
• /
• v.24 no.2
• /
• pp.115-122
• /
• 1999

Because of their small mass, volume, solid state construction and long life, light-emitting diodes(LEDs) hold promises as a lighting source for intensive plant production system. Spectral characteristics and light intensity of LEDs were tested to investigate their feasibility as artificial lighting sources for growth and morphogenesis control in transplant production system. Blue, green, and red LEDs had a peak-emission wavelength at 442nm, 522nm, and 673nm, respectively. Their half width defined as the difference between upper and lower wavelength in the intensity equivalent to 50% of the maximum intensity showed 26nm, 41nm, and 74nm, respectively. Photosynthetic photon flux(PPE) at the distance of 9cm under the LEDs array was measured as $235{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ for red, $109{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ for green, and $75{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ for blue LEDs. At the same distance, green LEDs had the illuminance of 13,0001x, nine to ten times higher than those of red and blue LEDs. Red, green, and blue LEDs at a distance of 9cm had the irradiance of $46W{\cdot}m^{-2},\;19W{\cdot}m^{-2},\;8W{\cdot}m^{-2}$, respectively. Light intensity of blue, green, and red LEDs increased linearly in proportion to the magnitude of the current applied to the operating circuit. Thus the light intensity of LEDs was controlled by the applied current in operating circuit.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.08a
• /
• pp.187-187
• /
• 2012

In this report, the plasmonic nanopores of less than 5 nm diameter were fabricated on the apex of the pyramidal cavity array. The metallic pyramidal pit cavity can also utilized as the plasmonic bioreactor, and the fabricated Au or Al metallic nanopore can provide the controllable translocation speed down using the plasmonic optical force. Initially, the SiO2 nanopore on the pyramidal pit cavity were fabricated using conventional microfabrication techniques. Then, the metallic thin film was sputter-deposited, followed by surface modification of the nanometer thick membrane using FESEM, TEM and EPMA. The huge electron intensity of FESEM with ~microsecond scan speed can provide the rapid solid phase surface transformation. However, the moderate electron beam intensity from the normal TEM without high speed scanning can only provide the liquid phase surface modification. After metal deposition, the 100 nm diameter aperture using FIB beam drilling was obtained in order to obtain the uniform nano-aperture. Then, the nanometer size aperture was reduced down to ~50 nm using electron beam surface modification using high speed scanning FESEM. The followed EPMA electron beam exposure without high speed scanning presents the reduction of the nanosize aperture down to 10 nm. During these processes, the widening or the shrinking of the nanometer pore was observed depending upon the electron beam intensity. Finally, using 200 keV TEM, the diameter of the nanopore was successively down from 10 nm down to 1.5 nm.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.27 no.7
• /
• pp.472-476
• /
• 2014

We report the characteristics of thin-film transistor (TFT) to make the bi-channel structure with stacked $Mg_{0.1}Zn_{0.9}O$ (Mg= 10 at.%) and ZnO. The ZnO and $Mg_{0.1}ZnO_{0.9}O$ thin films were deposited by radio frequency (RF) co-sputter system onto the thermally oxidized silicon substrate. A total thickness of active layer was 50 nm. Firstly, the ZnO thin films were deposited to control the thickness from 5 nm to 30 nm. Sequentially, the $Mg_{0.1}ZnO_{0.9}O$ thin films were deposited to change from 45 nm to 20 nm. The bi-layer TFT shows more improved properties than the single layer TFT. The field effect mobility and subthreshold slope for $Mg_{0.1}ZnO_{0.9}O$/ZnO-TFT are $7.40cm^2V^{-1}s^{-1}$ and 0.24 V/decade at the ZnO thickness of 10 nm, respectively.

• Journal of the Korean Society of Tobacco Science
• /
• v.16 no.2
• /
• pp.163-171
• /
• 1994

This experiment was conducted to investigate the discrimination of cigarette brands and the similarity between Korea and America cigarette brands by near infrared spectra. Statistical tools such as principal component analysis (PCA) and mahalanobis distance(M.D) were used. The discrimination rate of the Korea and the America cigarette brands, determined by position number which was calculated with PCA and M.D, was 94% and 87%, respectively. The spectra of the 10 America cigarette brands were selected by averaging 5 sample spectra for each brand and another 5 spectra for each brand were investigated to use as the sample spectra. Comparing the sample spectra with the selected spectra by M.D using 410-1090 nm, 1110-1850 nm and 1970-2490 nm wavelength, the discrimination rate which was determined by the closest M.D between the sample and the selected spectra was 100% when each spectra was investigated on the same time. But the discrimination rate decreased 50% when the sample and the selected spectra were investigated on the different time. Excluding 1970-2490 nm wavelength, the discrimination rate increased up to 90% when the sample and the selected spectra were investigated on the different time. Comparing the spectra of Korea cigarette brands with those of America cigarette brands by M.D using only 410-1090 nm and 1110-1850 nm wavelength, the spectra of Expo(G) was similar to Winston, Vantage(U.L) and Benson & hedges(M.), the spectra of Hanaro(D) was similar to Carrel, Winston(L), Vantage(U.L), \Vantage and Carrel(L), the spectra of Hanaro(L) was similar to Winston(L) , Carton, Vantage and Carmel(L) and the spectra of Pinetree was similar to Kent, Kool, Kent(G.L), Merit and Benson & hedges(L), respectively. Key Words : NIRS, cigarette brands discrimination

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.21 no.10
• /
• pp.881-884
• /
• 2008

In this study, polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) in the composition from 51/49, was deposited on platinum for a metal-ferroelectric-metal structure. From XRD patterns, the 70 nm- and 140 nm-thick PVDF-TrFE films showed the intensity peak of near $20^{\circ}$ connected to a ferroelectric phase. Moreover, the thicker film indicated the higher intensity than thinner one. The difference of the remanent polarization (2Pr) at 0 V is decreased gradually from 10.19 to $5.7{\mu}C/cm^2$ as the thickness decrease from 140 to 70 nm. However, when the thickness decreased to 50 nm, the 2Pr rapidly drop to $1.6{\mu}C/cm^2$ so the minimum critical thickness might be at least 70 nm for device. Both different thickness films, 70 and 140 nm, indicated that the characteristic of current density-voltage was measured for $10^{-6}{\sim}10^{-7}A/cm^2$ below 15 V and the thicker film maintained relatively lower current density than thinner one. From these results, we can expect that the electrical properties for the devices particularly ferroelectric thin film transistor using PVDF-TrFE copolymer were able to be on the trade-off relationship between the remanent polarization with the bias voltage and the leakage current.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.08a
• /
• pp.297-297
• /
• 2011

일반적으로 고출력 반도체 레이저 다이오드는 발진 파장 및 광출력에 따라 다양한 분야에 응용되고 있으며, 특히 발진파장이 808 nm 대역인 고출력 레이저 다이오드의 경우 재료가공, 펌핌용 광원, 의료 분야 등 다양한 응용분야를 가진 광원 중의 하나라고 할 수 있다. 808 nm 대역의 레이저 다이오드 제작에는 현재 InGaAsP/InGaP/GaAs 및 InGaAlAs/GaAs 양자우물을 이용하여 제작되고 있으나 양자우물과 이를 둘러싸는 장벽물질간의 band-offset이 적어 효율적인 고출력 레이저 다이오드의 제작에 다소 어려움이 있기 때문에 강한 캐리어 구속 효과를 지니는 양자점 혹은 양자대쉬 구조를 사용하는 것이 고출력 레이저 다이오드를 제작할 수 있는 한 방법이다. 실험에 사용된 InP/InGaP 양자구조는 Riber사의 compact21 MBE 장치를 사용하여 성장하였으며 GaAs기판을 620-630도에서 가열하여 표면의 산화층을 제거하고 580도에서 약 100 nm 두께의 GaAs 버퍼층 및 50 nm 두께의 InGaP층을 성장하였다. 양자 구조는 MEE (migration enhanced epitaxy) 방식으로 성장되었는데, 이는 InP/InGaP 의 lattice mismatch율이 작아 양자 구조 형성이 어렵기 때문에 InP/InGaP 양자 구조 성장에 적합하다고 생각하였으며, Indium 2초, growth interuption time 10초, phosphorous 2초 그리고 growth interuption time 10초를 하나의 시퀀스로 보고, 그 시퀀스를 반복하여 양자 구조를 성장하였다. 본 실험에 사용된 P 소스는 Riber사의 KPC-250 P-valved cracker모델을 사용하였으며 InP의 성장률은 0.985${\AA}/s$이다. InP/InGaP 양자구조 성장 중에, 성장 온도, 시퀀스 수의 변화 등 다양한 조건을 변화 시켜 샘플을 성장시켰고, 양자 구조 성장을 확인하기 위하여 AFM 및 SEM을 통해 구조적 분석을 하였으며 PL 측정을 통해 광학적 분석을 진행하였다.

• The Korean Journal of Mycology
• /
• v.15 no.4
• /
• pp.217-223
• /
• 1987

Mitochondria in the L. edodes was purified by linear sucrose density gradient centrifugation. The mitochondrial ATPase activity was investigated by various wavelength illumination for 30 min at dark state. The mitochondrial ATPase activity was stimulated 1.6 fold by 680 nm illumination compared with dark control group. The mitochondrial ATPase activity of different light illumination time at 680 nm was stimulated 2.3 fold at 5 minutes compared with dark control group. Its optimum pH and temperature were found to be 7.5 and $59^{\circ}C$ after illumination for 5 minutes at 680 nm. The mitochondrial ATPase activity was activated by 5 mmol $Fe^{3+}$, 0.1 mmol $Fe^{2+}$, 0.1 mmol $Mg^{2+}$, 0.5 mmol $K^{+}$, and 0.1 mmol $Ca^{2+}$ ion. But, the enzyme was inhibited by 5 mmol $Na^{+}$ ion.

• Journal of the Korean institute of surface engineering
• /
• v.41 no.3
• /
• pp.83-87
• /
• 2008

This study described the effects of RF power, DC bias voltage, chamber pressure and gas mixing ratio on the etch rates of TiN thin film and selectivity of TiN thin film to $SiO_2$ with $BCl_3$/Ar gas mixture. When the gas mixing ratio was $BCl_3$(20%)/Ar(80%) with other conditions were fixed, the maximum etch rate of TiN thin film was 170.6 nm/min. When the DC bias voltage increased from -50 V to -200 V, the etch rate of TiN thin film increased from 15 nm/min to 452 nm/min. As the RF power increased and chamber pressure decreased, the etch rate of TiN thin film showed an increasing tendency. When the gas mixing ratio was $BCl_3$(20%)/Ar(80%) under others conditions were fixed, the intensity of optical emission spectra from radical or ion such as Ar(750.4 nm), $Cl^+$(481.9 nm) and $Cl^{2+}$(460.8 nm) was highest. The TiN thin film was effectively removed by the chemically assisted physical etching in $BCl_3$/Ar ICP plasma.