http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Low Turn-on Voltage Field Emission Triodes with Selectively Grown Carbon Nanotube Emitters
Hyung Soo Uh 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.45 No.2
Field emitter arrays with a low turn-on voltage have been fabricated by using the selective growth of carbon nanotubes (CNTs) in a microwave plasma-enhanced chemical vapor deposition (MPCVD) system. CNTs with multi-walled structure were grown on a patterned Ni catalyst layer by a gas mixture of methane and hydrogen at a low temperature of 500 C. In order to avoid gate-emitter short, the gate electrodes were placed underneath the cathode electrodes, this being called an under-gate-type triode structure. Electron emission from CNT emitters was easily modulated by changing the gate voltage. The turn-on voltage was as low as 38 V, and the anode current of 14 A was extracted at a gate voltage of 55 V, which corresponds to an emission current density of 275 mA/cm2. The excellent emission properties suggest that the arrays have potential for application in eld-emission displays and vacuum microelectronics.
Enhancement of Electron Field Emission from Density-Controlled Carbon Nanotubes
Hyung Soo Uh,Sang Sik Park,Byung Whan Kim,Euo Sik Cho,Naesung Lee,Sang Jik Kwon 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.III
In this study, we investigated the effect of catalyst pretreatment by NH$_3$ plasma on the growth of CNTs by plasma-enhanced chemical vapor deposition and their field emission properties. Thickness of catalytic Ni was varied from 5 to 100 {\AA}. It was found that the catalyst nanoparticles which were essential for the CVD synthesis of CNTs were formed well after plasma pretreatment and the size of the nanoparticles was strongly dependent on the Ni thickness and plasma pretreatment. In field emission measurement using diode-type configuration, the low-density and smaller-diameter CNTs synthesized from Ni catalyst layer after NH$_3$ plasma pretreatment showed a smaller electric-field-screening effect, which, in turn, increased the field enhancement factor by a factor of 4 compared with as-grown CNTs from Ni without plasma pretreatment. CNT emitters obtained from plasma-pretreated 25-{\AA}-thick Ni catalysts showed excellent field emission characteristics with a very low turn-on field of 1.1 V/$\mu$m at 10 $\mu$A/cm$^2$ and a high emission current density of 1.9 mA/cm$^2$ at 4.0 V/$\mu$m, respectively. In addition, experimental results revealed that the catalyst thickness might be optimized for electron emission efficiency.
Hyung Soo Uh 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.47 No.3
In this paper, we demonstrate that eld emission eciency can be greatly increased by improving the vertical alignment and/or by reducing the density of carbon nanotubes (CNTs). Ni catalyst was deposited by e-gun evaporation before optional rapid-thermal-annealing (RTA) treatment. CNTs were then grown with a gas mixture of acetylene and ammonia on silicon substrate by using DC plasma-enhanced chemical vapor deposition (PECVD). The eect of RTA treatment on the growth characteristics of CNTs was investigated. We observed that Ni catalyst lm was agglomerated by RTA treatment, resulting in the formation of Ni nano-particles to act as catalyst for growth of CNTs. In addition, by changing the RTA temperature and Ni thickness, the size and distribution of Ni nano-particles were changed, which subsequently changed the geometry and density of CNTs. Compared with as-grown CNTs without RTA treatment, the CNTs grown through RTA treatment had further improved eld emission characteristics. In particular, CNTs sparsely distributed by pertinent Ni thickness and RTA conditions reduced the turn-on voltage more signicantly.
Effect of Plasma Pretreatment on the Structure and Emission Characteristics of Carbon Nanotubes
Hyung-Soo Uh,Euo Sik Cho,Jong Duk Lee,Sang Jik Kwon,Sang Sik Park,Seok-Rim Choi,Soo Myun Lee 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.43 No.51
Carbon nanotubes (CNTs) were grown on Ni-coated TiN/Si substrates by using microwave plasma chemical vapor deposition with a gas mixture of H2/CH4 at a low temperature of 500 C. The eect of H2-plasma pretreatment on the diameter of grown CNTs was investigated. We found that the average diameter of CNTs could be easily controlled by using the H2-plasma pretreatment time before CNTs growth and varied from 36 nm to 26 nm as the pretreatment time changed from 5 min to 15 min. However, any further increase in the pretreatment time gave rise to a rapid decrease in CNTs growth. After 25 min of the plasma pretreatment, scanning electron microscopy observation exhibited the destruction of the CNTs. The impact of the plasma pretreatment time on the emission behavior of CNTs was also investigated in a diode-type electron-emission conguration. The variation of the CNT diameter due to the plasma pretreatment caused a drastic change in emission properties. The turn-on voltages of CNT emitters varied from 3.5 V/m to 9 V/m, depending on the hydrogen-plasma pretreatment conditions. The close relationship between the electron-emission characteristics and the pretreatment time indicates that the pretreatment condition may be a key process parameter in CNTs growth for eld-emission displays and should be optimized.
High-Sensitivity CCD Image Sensor using Capacitive-Inverted-Feedback Source-Follower Circuit
SangsikPark,HyungsooUh,SeokrimChoi,JunghyunNam 한국물리학회 2002 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.41 No.4
A high-sensitivity CCD image sensor that utilizes a new output structure has been developed. The structure utilizes an enhancement inverter, a coupling capacitor, and resistors, in addition to the conventional source follower. The output of the source follower is inverted, and the AC component of that signal is fed back to the gate of the load transistor of the source follower to modulate the impedance. The overall gain improvement can be estimated from a simple small-signal analysis, and the results match well to the circuit simulation. A 1/4-inch 250,000-pixel color CCD image sensor was fabricated employing the new output circuit. The fabrication process is the same as that for conventional CCD image sensors since the inverter in this circuit consists of enhancement mode transistors. It is observed that 14 % of the sensitivity improvement in the CCD image sensor is achieved by the new structure and the linearity shows no distortion compared to conventional image sensors over the full range of imaging illumination.
Sang-HyeonLee,JaekyuLee,YongseokAhn,DaewonHa,GwanhyeobKoh,TaeyoungChung,KinamKim,HyungSooUh 한국물리학회 2002 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.40 No.4
If the tight electrical performance requirements of the cell transistors used in giga-bit density DRAM are to be met, the leakage currents through the junction and the transistor should be controlled very carefully. In this paper, we propose a novel cell transistor using LOcalized Channel and Field Implantation (LOCFI) for low-power, reliable operation in a giga-bit density DRAM and beyond. When a LOCFI cell transistor is used, the data retention time is greatly improved by virtue of the reduced cell leakage currents resulting from the suppressed ion implantation damage at the storage node.