電泳沈積奈米碳管及其電子場發射特性研究

Abstract

本研究利用電泳沈積（electrophoretic deposition, EPD）的方式，製作奈米碳管場發射源。首先經由拉曼（Raman）光譜分析選取具有最高IG/ID比值、結晶性較佳的Xintek多壁奈米碳管。為增加懸浮液穩定性，我們在碳管表面進行官能基化處理，於H2SO4/HNO3溶液中經過不同處理條件，使碳管表面接上羧基，實驗結果得知在酸中浸泡24小時可以得到較高的懸浮液穩定性，並保持碳管結晶性。調控電泳之電壓與時間，以直流電將奈米碳管均勻沈積在鋁基板上，分別使用去離子水（添加分散劑SDS）、乙醇、與二甲基甲醯胺（DMF）作為溶劑。為了增加碳管薄膜與基材間的附著力，並移除多餘的溶劑，將電泳得到之薄膜進行後續熱處理，我們發現熱處理對於乙醇、二甲基甲醯胺的薄膜形貌影響不大，但會影響在SDS水溶液中電泳之薄膜裂縫的分佈行為。經由電子場發射特性量測，得知最佳熱處理溫度分別是：二甲基甲醯胺200 ℃、乙醇200 ℃，SDS水溶液250 ℃。其電子場發射量測所得到最佳的起始電場分別是：二甲基甲醯胺4.0 V/μm、乙醇3.7 V/μm，SDS水溶液3.7 V/μm。

In the study, multiwall carbon nanotubes (CNTs) were deposited on the Al substrate by electrophoretic deposition (EPD) as electron field emitters. In order to obtain stable and uniform CNT suspension for the EPD, we first optimized surface functionalization conditions to attach carboxyl group onto CNTs. According to Raman scattering spectroscopy and ultraviolet-visible (UV-Vis) absorption spectroscopy, stable CNT suspension could be prepared by immersing CNTs in the H2SO4/HNO3 aqueous solution for 24 hours. Electrophoretic deposition of CNTs on the Al substrate was carried out using various solvents: aqueous sodium dodecyl sulfate (SDS) solution, ethanol and dimethylformamide (DMF), followed by thermal anneal to remove solvents and improve adhesion between CNTs and the substrate. It was found that the surface morphology of the CNT films deposited in ethanol and DMF was independent on the anneal temperature. On the other hand, cracks developed over the CNT film deposited in aqueous SDS solution after high temperature anneal. The surface morphology of the EPD CNT films strongly affects electron field emission characteristics. The turn-on fields were determined to be 4.0 V/□m, 3.7 V/□m and 3.7 V/□m for the CNT films prepared in DMF, ethanol and aqueous SDS, respectively.