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Articles you may be interested inEffect of double layer coating on carbon nanotubes for field emission and secondary electron emission measurement J.The authors measured the field emission ͑FE͒ and secondary-electron emission ͑SEE͒ of carbon nanotubes ͑CNTs͒ after coating with wide-band-gap materials, such as MgO and CsI. The FE was increased successively after MgO coating and subsequent CsI coating for both single-walled and multiwalled CNTs. SEE also showed the same increase after monolayer and double-layer coating. The field-enhancement factor, , was calculated from the Fowler-Nordheim equation of FE results, and SEE yield, ␦, was measured directly from the SEE measurements, for both monolayer-and double-layer-coated nanotubes. Both values showed similar trends that may be described as follows: ͑1͒ The trend for the double-layer-coated CNTs was higher than that for the monolayer-coated CNTs. ͑2͒ The trend for the single-walled CNTs was higher than that for the multiwalled CNTs.
Single-walled carbon nanotubes (SWNTs) are known to have a p-type charge transfer character in the atmosphere. The energy state of SWNTs can be modulated by doping with either an electron donor or an acceptor. In this study, iodine molecules are chosen for intercalation to SWNTs to predict the charge transfer tendency between them. Field-effect transistors (FETs) using iodine intercalated SWNTs (I-SWNTs) are fabricated and their electronic properties are investigated to better understand the charge transfer between iodine and SWNTs by changing gate voltages. Under vacuum, I-SWNT FETs exhibit weak n-type character, indicating that electrons are transferred slightly from the iodine to the SWNTs. After exposure to O2 gas, n-type characters are reduced; however, they still retain their original type.
Wide-band-gap semiconductors such as indium, tin, molybdenum, and chromium oxides have stimulated considerable attention in recent years as promising cold-cathode materials due to their remarkable physical and chemical stability during the cold electron emission process. 1-2 Especially, indium oxide (direct band gap : 3.6 eV) can be one of the most attractive conductive oxides for field emission because of its relatively low electron affinity (3.5 eV), high chemical inertness and sputter resistance. We synthesized nano-composite of singlewalled carbon nanotube and In 2 O 3 . The field-emission behavior was investigated in detail.
▪ ExperimentThe shortened-SWCNTs were prepared as reported. 3 An indium chloride of 0.025 M, ammonium chloride of 1.4 M, and thioacetamide of 0.1 M were used as precursor solutions. Indium oxide coated-single walled carbon nanotubes (In 2 O 3-coated SWNTS) by chemical-bath-deposition method. The pH of the solution was adjusted by adding a 0.1 M HCl solution. The temperature of the reaction mixture was kept constant using a water bath at 60 o C for 2 h. The original colorless solutions become lemonish yellow after mixing and finally bright yellowforming In 2 S 3 films. These films were then taken out from the bath, etched in 1% dilute HCl for 5 s, and finally dried in air. Air sintering of above films was carried out at 400 o C for 30 min. Indium oxide layer thickness was controlled as a function of reaction time. Scanning electron microscopy and x-ray diffraction investigations revealed the morphology and structure of In 2 O 3 coated SWNTs. Field-emission of the as-grown indium oxide coated-SWNTs was also measured. The same nanotube sample was used for emission measurement before and after In 2 O 3 coating for correct comparison.
▪ Result and discussionX-ray diffraction (Figure 1-a)) spectra indicate that the deposited products are cubic bixbyite In 2 O 3 . The morphology of the as-deposited In 2 O 3 was observed by a scanning electron microscope. As displayed in Figure 1-b) a sharp tip were grown on the SWNTs. The square and triangular facets of the pyramid are indexed to the (400) and (222) planes, respectively. 4
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