Structure and Field Electron Emission of Carbon Nanotubes Dependent on Growth Temperature
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Structure and Field Electron Emission of Carbon Nanotubes Dependent on Growth Temperature Yoon Huh, Jeong Yong Lee, Tae Jae Lee1, Seung Chul Lyu1, and Cheol Jin Lee1 Dept. of Materials Science and Engineering, Korea Advanced Institute of Science and Technology, Daejeon, 305-701, Korea Rep. 1 Dept. of Nano-Technology, Hanyang University, Seoul, 133-791, Korea Rep. ABSTRACT This present work deals with the temperature dependence on the growth and structure of CNTs grown by thermal CVD. The vertically aligned CNTs are synthesized on iron (Fe)deposited silicon oxide (SiO2) substrate by thermal CVD using acetylene gas at temperatures in the range 750-950 ºC. Configuration and structural characteristics of CNTs have been investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). As the growth temperature increases from 750 to 950 ºC, the growth rate and the average diameter increase while the density decreases by a factor of about 2. TEM images show that the relative amount of crystalline graphitic sheets increases with increasing the growth temperature and a higher degree of crystalline perfection can be achieved at 950 ºC. The HRTEM images reveal consistently that the degree of crystalline perfection increases progressively as the growth temperature increases. This result demonstrates that the growth rate, diameter, density, and crystallinity of carbon nanotubes can be controlled with the growth temperature. INTRODUCTION The carbon nanotube (CNT), which was discovered by Iijima at NEC in 1991, is a novel material having a variety of physical properties [1,2]. Especially, because it has a excellent electron emission characteristic, it has been considered attractive as a field electron emitter in field emission display (FED), advantages of which are high screen quality, high efficiency, and low consume power [3]. The growth of carbon nanotubes (CNTs) using chemical vapor deposition (CVD) methods has attracted much attention because of many advantages such as high purity, high yield, selective growth, and vertical alignment [4-7]. It has been found that the structure of carbon materials is dependent on the growth parameters such as reaction temperature, catalyst, reaction gas, etc. A strict control of growth condition allows design of the structure of carbon materials in the nanometer regime. Especially the growth temperature is crucial for selective and controlled growth of CNTs, which is necessary for many applications. A number of research groups reported that the growth of CNTs could be controlled by varying the growth parameters of CVD process. However, there are not many systematic studies on the temperature-controlled growth of CNTs using thermal CVD [8-10]. EXPERIMENT The oxide layer was grown to 30 nm onto the p-type (100) Si substrate, the resistivity and size of which are 15 Ω-cm and 20 mm×30 mm each. The substrate was soaked in ethanol, cleaned in an ultra-sonicator for 5 min, and blown with N2 gas in order to remove dust from the S8.31.1
wafer surface. We mounted the cl
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