• 한국재료학회:학술대회논문집
• /
• 한국재료학회 2011년도 추계학술발표대회
• /
• pp.18.1-18.1
• /
• 2011

Some applications of carbon nanotubes (CNTs) as field emitters, such as x-ray tubes and microwave amplifiers, require high current emission from a small emitter area. To emit the high current density, CNT emitters should be optimally fabricated in terms of material properties and morphological aspects including high crystallinity, aspect ratio, distribution density, height uniformity, adhesion on a substrate, low outgassing rate during electron emission in vacuum, etc. In particular, adhesion of emitters on the substrate is one of the most important parameters to be secured for high current field emission from CNTs. So, we attempted a novel approach to improve the adhesion of CNT emitters by incorporating metal oxide layers between CNT emitters. In our previous study, CNT emitters were fabricated on a metal mesh by filtrating the aqueous suspensions containing both highly crystalline thin multiwalled CNTs and thick entangled multiwalled CNTs. However, the adhesion of CNT film was not enough to produce a high emission current for an extended period of time even after adopting the metal mesh as a fixing substrate of the CNT film. While a high current was emitted, some part of the film was shown to delaminate. In order to strengthen the CNT networks, cobalt-nickel oxides were incorporated into the film. After coating the oxide layer, the CNT tips seemed to be more strongly adhered on the CNT bush. Without the oxide layer, the field emission voltage-current curve moved fast to a high voltage side as increasing the number of voltage sweeps. With the cobalt-nickel oxide incorporated, however, the curve does not move after the second voltage sweep. Such improvement of emission properties seemed to be attributed to stronger adhesion of the CNT film which was imparted by the cobalt-nickel oxide layer between CNT networks. Observed after field emission for an extended period of time, the CNT film with the oxide layer showed less damage on the surface caused by high current emission.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
• /
• pp.154-154
• /
• 2008

Although the screen printing technology using photosensitive carbon nanotube (CNT) paste has many advantages such as low cost, simple process, uniform emission, and capability of mass production, the CNT paste needs to be improved further in CNT dispersion, printability, adhesion, electrical conductivity, population of CNT emitters, etc. Ball milling has been frequently employed to prepare the CNT paste as ball milling can mix its ingredients very well and easily cut the long, entangled CNTs. This study carried out a parametric approach to fabricating the CNT paste in terms of low-energy ball milling and a paste composition. Field emission properties of the CNT paste was characterized with CNT dispersion and electrical conductivity which were measured by a UV-Vis spectrophotometer and a 4-point probe method, respectively. Main variables in formulating the CNT paste include a length of milling time, and amounts of CNTs and conductive inorganic fillers. In particular, we varied not only the contents of conductive fillers but also used two different sizes of filler particles of ${\mu}m$ and nm ranges. Among many variations of conductive fillers, the best field emission characteristics occurred at the 5 wt% fillers with the mixing ratio of 3:1 for ${\mu}m$-and nm-sizes. The amount and size of fillers has a great effect on the morphology, processing stability, and field emission characteristics of CNT emitter dots. The addition a small amount of nm-size fillers considerably improved the field emission characteristics of the photosensitive CNT paste.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
• /
• pp.353-353
• /
• 2008

Carbon nanotubes (CNTs) are attractive for field emitter because of their outstanding electrical, mechanical, and chemical properties. Several applications using CNTs as field emitters have been demonstrated such as field emission display (FED), backlight unit (BLU), and X-ray source. In this study, we fabricated a CNT cathode using transparent ultra-thin CNT film. First, CNT aqueous solution was prepared by ultrasonically dispersing purified single-walled carbon nanotubes (SWCNTs) in deionized water with sodium dodecyl sulfate (SDS). To obtain the CNT film, the CNT solution in a milliliter or even several tens of micro-litters was deposited onto a porous alumina membrane through vacuum filtration process. Thereafter, the alumina membrane was solvated by the 3 M NaOH solution and the floating CNT film was easily transferred to an indium-tin-oxide (ITO) glass substrate of $0.5\times0.5cm^2$ with a film mask. The transmittance of as-prepared ultra-thin CNT films measured by UV-Vis spectrophotometer was 68~97%, depending on the amount of CNTs dispersed in an aqueous solution. Roller activation, which is a essential process to improve the field emission characteristics of CNT films, increased the UV-Vis transmittance up to 93~98%. This study presents SEM morphology of CNT emitters and their field emission properties according to the concentration of CNTs in an aqueous solutions. Since the ultra-thin CNT emitters prepared from the solutions show a high peak current density of field emission comparable to that of the paste-base CNT emitters and do not contain outgassing sources such as organic binders, they are considered to be very promising for small-size-but-high-end applications including X-ray sources and microwave power amplifiers.

• 한국재료학회:학술대회논문집
• /
• 한국재료학회 2006년도 추계학술발표대회 및 제11회 신소재 심포지엄
• /
• pp.26.1-26.1
• /
• 2006

• 한국재료학회:학술대회논문집
• /
• 한국재료학회 2009년도 춘계학술발표대회
• /
• pp.32.2-32.2
• /
• 2009

높은 효율성을 가지는 전계방출 디스플레이(field emission displays)를 개발하기 위해 탄소나노튜브 음극소자 (CNT cathodes)의 표면처리에 대한 연구가 활발히 진행되고 있다. 열처리가 끝난 탄소나노튜브 음극소자(CNT cathodes)의 표면에는 유기성 바인더들이 타면서 잔여물들이 생성되게 되는데 이러한 잔여물들은 전계방출을 하는데 있어서 방해요소가 된다. 전계방출이 용이하게 하기 위해서는 이러한 잔여물들을 효과적으로 제거해 주어야한다. 표면처리의 방법으로는 여러 가지가 존재하는데 그중에서 테이핑 방법을 이용한 표면처리는 열처리 후에 남은 잔여물들을 제거하면서 CNTs를 돌출시키는 효율적인 방법이다. 하지만 이러한 테이핑 방법으로도 완벽하게 잔여물을 제거하기란 쉽지 않다. 본 연구는 첫 번째 열처리가 끝난 시편을 테이핑 방법을 이용하여 표면 처리를 실시하고 그것으로 끝나는 것이 아니라 표면처리가 끝난 시편에 두 번째 열처리를 실시하여 탄소나노튜브 음극소자(CNT cathodes)에 남아있는 잔여물들을 좀 더 효과적으로 제거해 주는데 그 목적이 있다. 재열처리시 온도는 $330^{\circ}C$ ~ $420^{\circ}C$까지 $30^{\circ}C$의 차이를 주어 4단계에 걸쳐 실험을 실시하였고 재열저리를 하기전과 재열처리를 실행한 후의 전류밀도의 차이를 관찰하여 효과적으로 잔여물들이 제거되었는지에 대해서 알아보았다. 재열처리를 실행하였을 때 재열처리를 하기 전에 비하여 전류밀도에서 우월하였으며 $360^{\circ}C$ 부근에서 가장 많은 차이를 보였다.

• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.II
• /
• pp.1536-1537
• /
• 2005

We have made point electron sources using carbon nanotubes (CNTs). For the fabrication of point electron sources, CNTs were dispersed in a solution and attached on electrochemically etched W tips using electrophoresis. In our study, we have utilized various CNTs such as single-walled CNT (SWCNT), multiwalled CNT (MWCNT), and thin-MWCNT and threshold current, turn-on voltage, filed enhancement factor of each emitter have been studied upon a tube/bundle diameter and length. In addition, fieldemitted electron energy distribution of various CNT emitters is characterized.

• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.II
• /
• pp.1470-1473
• /
• 2005

We proposed new triode-type Field Emitter Arays using Carbon NanoTubes(CNT-FEAs) as electron emission sources at low electric fields. The CNTs were selectively grown on the patterned catalyst layer by Plasma-Enhanced Chemical Vapor Deposition (PECVD). In this structure, gate electrodes are located underneath the cathode electrodes and extracted gate is surrounded by CNT emitters. Furthermore, in order to control density of CNTs, we investigated effect of using rapid thermal annealing (RTA).

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2009년도 하계학술대회 논문집
• /
• pp.311-311
• /
• 2009

Carbon nanotubes (CNTs) belong to an ideal material for field emitters because of their superior electrical, mechanical, and chemical properties together with unique geometric features. Several applications of CNTs to field emitters have been demonstrated in electron emission devices such as field emission display (FED), backlight unit (BLU), X-ray source, etc. In this study, we fabricated a CNT cathode by using filtration processes. First, an aqueous CNT solution was prepared by ultrasonically dispersing purified single-walled CNTs (SWCNTs) in deionized water with sodium dodecyl sulfate (SDS). The aqueous CNT solution in a milliliter or even several tens of micro-litters was filtered by an alumina membrane through the vacuum filtration, and an ultra-thin CNT film was formed onto the alumina membrane. Thereafter, the alumina membrane was solvated by acetone, and the floating CNT film was easily transferred to indium-tin-oxide (ITO) glass substrate in an area defined as 1 cm with a film mask. The CNT film was subjected to an activation process with an adhesive roller, erecting the CNTs up to serve as electron emitters. In order to measure their luminance characteristics, an ITO-coated glass substrate having phosphor was employed as an anode plate. Our field emitter array (FEA) was fairly transparent unlike conventional FEAs, which enabled light to emit not only through the anode frontside but also through the cathode backside, where luminace on the cathode backside was higher than that on the anode frontside. Futhermore, we added a reflecting metal layer to cathode or anode side to enhance the luminance of light passing through the other side. In one case, the metal layer was formed onto the bottom face of the cathode substrate and reflected the light back so that light passed only through the anode substrate. In the other case, the reflecting layer coated on the anode substrate made all light go only through the cathode substrate. Among the two cases, the latter showed higher luminance than the former. This study will discuss the morphologies and field emission characteristics of CNT emitters according to the experimental parameters in fabricating the lamps emitting light on the both sides or only on the either side.

• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2007년도 7th International Meeting on Information Display 제7권2호
• /
• pp.1253-1256
• /
• 2007

A display device combining plasma display panel (PDP) and field emission display (FED) is proposed to achieve high luminous efficiency. The device can avoid the main energy loss channels of both PDP (ion loss) and FED (low CL efficiency). $2{\sim}6$”-diagonal test panels with carbon nano-tube (CNT) electron emitter and Xenon ambient gas showed the luminous efficiency of 4.14lm/W and brightness of $263cd/m^2$ at 35V (1kHz, 1% duty), indicating that it is a good candidate for the low voltage driven, highly efficient next generation display.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2002년도 추계학술대회 논문집 Vol.15
• /
• pp.510-513
• /
• 2002

띠모양의 에미터와 에미터와 정렬된 띠모양의 케이트 구멍을 가진 탄소나노튜브(CNT) 삼극 구조에 대하여 전계방출 시뮬레이션을 수행하였다. 전자방출은 주로 가장자리에서 발생하였으며 에미터와 게이트사이의 간격이 가까워지면 급격히 증가하였다. 전자방출 특성도 상당히 우수하였다. 한쪽 가장자리만을 사용한 삼극구조의 경우에는 방출된 전자의 궤적이 좁은 띠모양으로 형성되어 방향성이 매우 우수하게 나타났다. 띠모양의 에미터 및 게이트로 이어진 삼극구조는 제작이 용이하고 조립할 때 정렬이 쉬운 장점이 있다.