Study on the Lateral Field Emission Devices Using the Metal Thin Films and Carbon Nanotubes as the Emitter Materials
|關鍵字:||奈米碳管;側向式場發射元件;金屬薄膜;carbon nanotubes;lateral field emission devices;metal thin films|
For the sake of improving field emission characteristics of field emission devices to apply on high performance devices, lower operation voltage, and higher field emission current are required in field emission devices. In this thesis, two kinds of lateral field emitters are proposed to accomplish such aims. Thin film edge field emitters with small emitter-to-collector gap as small as 150 nm are proposed to reduce the operation voltage. The distance between emitter and collector is defined by the thickness of amorphous silicon and hence could be controlled precisely. After the devices are fabricated, the samples are treated by C2H4 and H2 individually to improve the field emission characteristics further. The cobalt thin film edge field emitters treated with C2H4 gas could enhance field emission current by increasing the roughness of Co surface due to the graphite layers and carbide formation, thus a higher field enhancement factor. For the Co emitter, the turn-on voltage at an emission current of 100 nA could be reduced to 8 V after being treated with C2H4 gas. As compared with treated with C2H4, the improvement of field emission characteristics of Co emitters treated with H2 was not so obvious due to less increase of roughness and the turn-on voltage was 12 V. On the other hand, the change of roughness of the palladium field emitters treated with C2H4 and H2 gas was not apparent due to the large difference of surface energy between Pd and under-layer, W. The turn-on voltage of Pd emitters treated with C2H4 was 25.5V. However, it could be reduced to 6.5 V after the Pd ones being treated with H2 to form the PdHX which owns lower work function than pure Pd. Additionally, two types of emission devices, co-planar and step-type ones, based on carbon nanotubes are proposed. The turn-on voltage of co-planar type lateral field emission devices with emitter-to-collector gap fixed at 2 μm is 9 V. On the other hand, step-type lateral field devices are also proposed to improve the field emission characteristics. In contrast to the co-planar ones, the distance between the tips of CNTs and collector could be shrunk by increasing the thickness of oxide under collector and hence could lower the operation voltage and enhance the field emission current. The turn-on voltage of step-type lateral field emission devices could be further reduced to 1.8 V. According to the experimental results, the field emission characteristic of CNTs is better than the metal thin films even with a shorter emitter-to-collector distance.
|Appears in Collections:||Thesis|
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