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Growth of Vertically Aligned CNTs with Ultra Thin Ni Catalysts
유제황,Yi-Yin Yu,Chang-Seok Lee,Jin Jang,Kyu-Chang Park,Ki-Seo Kim 한국전기전자재료학회 2008 Transactions on Electrical and Electronic Material Vol.9 No.2
We report on the growth mechanism of vertically aligned carbon nanotubes (VACNTs) using ultra thin Ni catalysts and direct current plasma enhanced chemical vapor deposition (PECVD) system. The CNTs were grown with -600 V bias to substrate electrode and catalyst thickness variation of 0.07 nm to 3 nm. The CNT density was reduced with catalyst thickness reduction and increased growth time. Cone like CNTs were grown with ultra thin Ni thickness, and it results from an etch of carbon network by reactive etchant species and continuous carbon precipitation on CNT walls. Vertically aligned sparse CNTs can be grown with ultra thin Ni catalyst.
유제황,김기서,유이인,이이상,장진,박규창,이창석 한국정보디스플레이학회 2008 Journal of information display Vol.9 No.4
Field emitter arrays (FEAs) were developed using carbon nanotubes (CNTs) as electron emission sources. The CNTs were grown using a selective-positioning technique with a resist-protection layer. The light emission properties were studied through the electron emission of the CNTs on patterned islands, which were modulated with island diameter and spacing. The electron emission of CNT arrays with 5 m diameters and 10 m heights increased with increased spacing (from 10 m to 40 m). The electron emission current of the 40-m-island-spacing sample showed a current density of 1.33 mA/cm2 at E = 11 V/µm, and a turn-on field of 7 V/m at 1 A emission current. Uniform electron emission current and light emission were achieved with 40 m island spacing and 5 m island diameter.
열 및 불산 처리를 통한 탄소나노튜브의 전자 방출 특성의 향상 연구
김기서,유제황,이창석,임한얼,안정선,장진,박규창,Kim, K.S.,Ryu, J.H.,Lee, C.S.,Lim, H.E.,Ahn, J.S.,Jang, J.,Park, K.C. 한국진공학회 2008 Applied Science and Convergence Technology Vol.17 No.2
본 연구에서는 열 및 불산을 이용한 후처리 공정이 레지스트층을 이용하여 제작된 탄소나노튜브의 전자 방출 특성에 미치는 영향에 대하여 연구하였다. 전자 방출 전류는 초기에 $8V/{\mu}m$의 전계에서 $4.2{\mu}A/cm^2$의 전류에서 열 및 불산 처리 시 각각 $7.5mA/cm^2$ 및 $79mA/cm^2$로 향상되었다. 하지만 열 및 불산 처리를 동시에 실시한 경우 전류 밀도는 $426mA/cm^2$ 및 $656mA/cm^2$로 향상된 전자 방출 특성을 얻을 수 있었다. 전자 방출 특성은 처리 순서에 따라 증가하는 양이 다르게 나타났으며, 가장 우수한 전자 방출 특성은 열 처리를 먼저 시행 후, 불산 처리를 하는 공정에서 나타났다. 이는 열 처리에 의한 탄소나노튜브의 결정성의 증가와 이후 불산 처리에 의한 불소 결합의 증가에 기인함을 알 수 있었다. 강한 불소 결합은 탄소나노튜브 에미터의 전자 방출 특성의 향상에 크게 기여를 하였다. We studied the effect of thermal annealing and hydrofluoric (HF) acid treatment on the field emission properties of carbon nanotube field emitter arrays (CNT-FEAs) grown with the resist-assisted patterning (RAP) process. After thermal and HF treatment, it was observed that the electron emission properties were remarkably improved. The enhanced electron emission was also found to depend strongly on the sequence of the treatments; the electronemission current density is 656 $mA/cm^2$ with the process of thermal treatment prior to HF treatment while the current density is reduced by 426 $mA/cm^2$ with the reversal processes. This is due to the increased crystalline structure by thermal annealing and then strong fluorine bond was formed by HF treatment.
Focusing Performance and Thermal Property of Carbon-nanotube Emitter-based X-ray Sources
이승호,김완선,유제황,김경숙,박헌국 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.11
Carbon-nanotube (CNT) emitter-based X-ray sources have been extensively investigated as newimaging devices. The electron-beam trajectory in the CNT emitter-based X-ray sources were simulatedto determine the optimized conditions for high focusing performance and limited thermaldamage to the anode. The beam trajectory from the cathode to the anode was simulated, and thefocal spot size (FSS) of the beam was determined by varying the structure of the electrode in theX-ray system. The temperature change of the anode caused by the electron-beam was calculated. The effects of electrode voltage and of the distance between the electrode and the anode on theFSS were significant while the effect of electrode thickness was small in all structures. When theelectron-beam was emitted with an FSS of 170 μm and a power of 130 W, the thermal damage tothe anode was reduced by using a 2-ms pulsed-voltage operation for a duration of 8 ms.
박규창,윤현식,유제황,장진,문종현,임성훈 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.48 No.6
We report on the electron emission properties of carbon nanotubes grown in holes with a triodetype direct-current (DC) plasma-enhanced chemical vapor deposition (PECVD) system. In this study, the growth of CNTs in gate holes for field-emission displays was performed by using a silicon-nitride (SiNx) capping layer on a Ni catalyst. The CNTs grown with a 3 μm hole pattern show the highest electron emission and the lowest turn-on field properties. The highest emission current of CNTs grown with a 3 μm hole pattern appears to be due to non-field screening by neighboring CNTS. Also, we can grow CNTs with a gate-hole pattern and measure the electron emission properties by using a triode structure. Two CNTs can be grown in gate holes with a 3 μm hole diameter. The electron emission anode current density is 0.9 μA/cm2 at a 35 V gate bias and a 2.0 kV anode bias.p
임성훈,윤현식,유제황,문종현,박규창,장진,문병연,Lim Sung Hoon,Yun Hyun Sik,Ryu Je Hwang,Moon Jong Hyun,Park Kyu Chang,Jang Jin,Moon Byeong Yeon 한국진공학회 2005 Applied Science and Convergence Technology Vol.14 No.4
본 연구는 실리콘 질화막 박막을 덮개층으로 사용하여 탄소나노튜브를 성장하고, 성장된 나노튜브의 전자방출특성을 조사하였다. 탄소 나노튜브는 triode PE-CVD 장치에 의해 성장되었으며, 탄소나노튜브의 밀도는 실리콘 질화막의 두께에 따라 크게 변하였다. 탄소 나노튜브의 밀도가 $10^{4}$/$cm^{2}$에서 전자방출 특성이 가장 우수하였으며, 이때 전자방출특성은 문턱전계 1.2 V/$\mu$m, 전류밀도는 3.6 V/$\mu$n의 전기장에서 0.17 mA/$cm^{2}$으로 측정 되었다. 또한, 진공 챔버에서 질소($N_{2}$) 분위기 하에서 전자방출 안정성을 조사하였으며, 탄소나노튜브의 밀도가 감소함에 따라 전자방출 안정성이 향상되었고, 탄소나노튜브의 밀도가 $10^{4}$/$cm^{2}$ 인 경우 $1\times10^{-4}$ A/$cm^{2}$ 이상의 전류가 흐르는 특성을 보였으며, 이 경우 $1\times$$10^{-5}$ Torr의 압력하에서 방출 전류의 안정도는 최소인 $2\%$를 유지하였다. We report on the field emission properties from vertically aligned carbon nanotubes (CNTs) produced by a triode PECVD with a SiNx capping layer on metal catalyst. It is found that the CNTs density can be controlled by the capping layer thickness and decreases with increasing SiNx thickness. The CNT density of $\~$ 104/$cm^{2}$ exhibited highest electron emission characteristics, the threshold field of 1.2 V/$\mu$m and the current density of 0.17 mA/$cm^{2}$ at 3.6 V/$\mu$m. We have carried out investigation of electron emission stability under ambient gas of N2. The electron emission stability was improved with decreasing CNT density. Under $1\times$$10^{-5}$ Torr ambient pressure, the CNTs in 5 $\mu$m hole show electron emission current higher than $1\times$$10^{-4}$ A/cm2 and it's electron emission uniformity has $2\%$.