奈米碳管於場發射元件之應用

Abstract

本論文主要針對場發射材料與元件結構為主題作深入探討。在場發射材料的合成部分，我們利用微波電漿輔助化學氣相沉積系統，藉由控制催化層厚度來成長不同形態的奈米碳管。此外，由場發射測試中可以發現，奈米碳管具有非常優異的場發射特性，而密度較高的奈米碳管因為電場之遮蔽效應(screening effect)使得其場發射特性並不因其具有較高密度之場發射源而變好。為了進一步改善奈米碳管之場發射特性，我們亦提出了利用高密度電漿處理來改變奈米碳管之密度以降低電場之遮蔽效應，實驗結果證實在適當的條件之下，奈米碳管之場發射起始電場(由 0.9 V/um 下降至 0.19 V/um)可以大幅降低，而場發射電流亦可大幅增加(上升至 15 mA/cm2 操作於0.8 V/um時)。 除了利用電漿後處理的方式，我們藉著遮蔽效應，在過密碳管中只有邊緣的部分易於發射電子的觀念，設計不同大小的方形矩陣來增加總邊長的方式，有效增加發射源面積，以達到降低起使電壓的目的。同時，利用此法，更可以節省碳管後處理的製程步驟，節省時間以及節省成本。 為了符合場發射顯示器低電壓操作的目的，我們利用一控制閘極來製造奈米碳管之場發射三極元件，我們以半導體製程技術縮小了元件的尺寸，並利用選擇性成長奈米碳管的技術，以控制奈米碳管成長長度的方式來製作場發射三極元件，為了有效降低閘極電流，使射出電子能有效到達陽極，以增加亮度顯示，及避免碳管過長，其與閘極接觸而產生短路現象。我們提出閘極上絕緣層三極結構來克服上述問題。同時順利地將閘極操作電壓降低到18 伏特；達到低壓操作及低漏流的目的。

Field emission materials and devices are synthesized and fabricated in this thesis. For the synthesis of field emission materials, carbon nanotubes (CNTs) with various morphologies have been synthesized using microwave plasma-enhanced chemical vapor deposition (MPECVD) by controlling the thickness of the catalyst film. The fabricated CNTs emission arrays showed excellent field emission properties, however, the field emission properties of the high density CNTs degraded for the screening effect of the electric field. To improve the field emission properties of the CNTs, a post treatment process via plasma was proposed. The results depicted the field emission properties can be upgraded with proper plasma post treatment conditions. Besides the plasma post treatment, we make use of the concept of screening effect that only the CNTs on the edge of the densely grown area could be easily emitted the electrons. The different pattern dimension arrays were applied to increase the total length. The increase of length means the raise of emitting area. The great improvement of turn-on field were achieved. At the same time, we could improve the electrical characteristics without extra process like plasma post treatment and cost down. The CNTs triode structures with an extraction gate were proposed to achieve the low voltage modulation. CNTs triodes with reduced gate diameter were fabricated by the semiconductor fabrication process and the selective growth of CNTs with controlled length. To lower the gate current effectively and avoid the short circuit problem between gate and emitters, we proposed an insulated gate structure field emission triode. The turn-on gate voltage was 18 V. It has successfully reduced the gate leakage current and the short circuit problem between gate and emitters to improve the field emission characteristics.