| Carbon nanotubes(CNTs) have attracted much attention because of their unique structure and properties since their discovery. One important potential application for the CNTs is as electron field emission sources in cold cathode flat panel displays and electron guns. In order to allow electron field emission to achieve a high electron current density, the number density of electron emission sites must be as large as possible, the emission current from each emission site must be as large as each carbon nanotube can tolerate, the emission current must be as uniform as possible among all emission sites, and the electric field screening effect caused by surrounding carbon nanotubes and other conductive structures must be reduced to an optimized level.In this work, Carbon nanotubes films were deposited on Ni films and stainless steel substrates by microwave plasma CVD (MPCVD) method. We improved the field emission properties of carbon nanotubes films by optimizing the deposition conditions. Meantime, we fabricated cathode-ray tube (CRT) type lighting-elements.1) Field emission properties of carbon nanotubes films grown on patterned Ni linesCarbon nanotubes (CNTs) films were grown on patterned Ni lines coated substrate by microwave plasma chemical vapour deposition (MWPCVD). Ni films deposited on ceramics substrates by d.c. magnetron sputtering are used as catalysts for growing the CNTs. The ceramics substrates were mechanically polished using various grinding and polishing powders in order to uniform Ni film. Before growing CNTs, the Ni films were patterned to be lines by laser writing technology and then the CNTs were deposited on the catalyst patterns. The source gas for growing the CNTs was a mixture of H2 and CH4. The gas flow rate of H2 is 100 sccm, and the growth pressure was 6.5x103 Pa, various deposition times were applied to control the length of the carbon nanotubes. Scanning electron microscopy (SEM) was used to determine the morphology of carbon nanotubes. Raman spectroscopy was used to analyze the structure of carbon nanotubes. The field emission characteristics of the samples were measured by using a diode structure. The transparent anode was made of coating phosphor onto an ITO coated glass plate. The CNT samples as the cathode were separated from the anode by a mica sheet with a suitable hole as the emission area. The gap between the anode and the cathode was 500 um. The measurement was conducted under pressure of 3.6x10-5 Pa.. By varying process conditions such as Ni layerthickness, gas flow rate, deposition time, reactive temperature, the optimum conditions for field electron emission were found. When gas flow rate of CH4 was 5 sccm, Ni film thickness was 150 nm, deposition time was 5 min, and reactive temperature was 700-800C, the field emission properties are best. At this condition, all nanotubes are well aligned as characterized by SEM. Turn-on field of 1.3 V/u m, emission current density of 6.8 mA/cm2 and field enhancement factor of 8477 were achieved.2) Field emission properties of carbon nanotubes films on stainless steel substrates Carbon nanotubes (CNTs) were synthesized from methane and hydrogen gas mixture directlyon stainless steel plates by microwave plasma chemical vapor deposition (MWPCVD). The SEM images show that the CNTs are of uniform with high density and lest amorphous carbon quantity, and their diameters are ranged from 30 to 60 nm, they are multi-wall nanotubes. The Raman spectrum shows more defect density in nanotube . In the field emission test, when anode was made of an ITO coated glass plate, the current density of sample attains 31 mA/cm2, at the electric field of 6.67 V/ u m, but when anode was made of coating phosphor onto an ITO coated glass plate, the current density attains 3.75 mA/cm2, at the electric field of 6 V/u m. The CNTs film could be a good cold cathode for flat panel display applications.Pretreatment conditions of stainless steel substrates influence on field emission properties of carbon nanotubes. By varying pretreatment conditions of the subs...
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