應用於場發射顯示器之低溫成長奈米碳管研究

Abstract

由於要將奈米碳管應用於玻璃基板之場發射顯示器以降低成本，且達到大面積面板之製作，因此便需要在低於玻璃熔點(~570℃)的溫度環境下，以化學氣相沉積法(chemical vapor deposition)的方式來成長奈米碳管。而要在低溫(500℃)成長奈米碳管，催化金屬的熔點是決定性的因素之一。本論文中，我們發現兩種新穎的催化金屬鎳鈀(NiPd)及鐵碳(FeC)合金適合在低溫下成長奈米碳管。從相圖可以得知它們分別在重量百分比鎳:鈀=40:60及鐵:碳=95.7:4.3的比例下有最低熔點1237及1147℃。相對於單金屬而言，合金較低的熔點讓它們可以在低溫的環境下具有較高的活性成長奈米碳管。我們的研究顯示，使用鎳鈀及鐵碳作為催化金屬在低溫下所成長出的奈米碳管，將有較優越的場發射特性，尤其使用鎳鈀所成長的奈米碳管將有低起始電場(turn-on field)3.7 V/um及高場發射電流(current density)152.3 mA/cm2。此外，所成長出的碳管密度大約為1010/cm3。 在加入閘極的三極結構方面，我們利用控制閘極介電層的厚度，改變奈米碳管尖端與閘極間的相對位置以製造平行閘極(planar-gate)和底閘極(under-gate)的結構，並期待以底閘極來增加陽極電流的控制能力並減少閘極的漏電流。 最後，我們利用上述新穎的催化金屬在低溫的環境(500℃)下於玻璃基板(PD200)上成長奈米碳管，經由在塗覆螢光粉的陽極加上高電壓後，而得到經由場發射之後在陽極板上的螢光情形。 經過我們的研究，目前已經可以利用熱化學氣相沉積法的系統，並配合新穎的催化金屬，在低溫的環境下成長密度均勻的奈米碳管。同時我們也將其應用在玻璃基板上製造場發射顯示器，如能配合適當的三極結構，加強閘極控制能力，相信將對於場發射顯示器有所改善，並期待在未來大尺寸且高解析度奈米碳管場發射顯示器的誕生。

In order to decrease the price and improve the uniformity of CNT-FEDs, the thermal CVD process is necessary for the synthesis of CNTs on glass substrate at a low temperature below the melting point of glass (~570℃). For the growth of CNTs on glass substrate at low temperature, the melting point of catalyst is one of the critical factors. In our study, two novel catalysts NiPd and FeC were discovered for CNT growth at low temperature. The lowest melting points 1237 ℃and 1147 ℃ occur as the weight percentages of NiPd and FeC are Ni:Pd = 40:60 and Fe:C=95.7:4.3, respectively. As compared with the mono-metal, the alloys were more suitable for CNTs growth at low temperature because of the lower melting points. In our research, the CNTs grown at low temperature with NiPd and FeC as the catalysts revealed superior field emission characteristics. The CNTs grown by NiPd especially showed a low turn-on field (3.7 V/um) and a high current density (152.3 mA/cm2). Moreover, the density of CNTs is about 1010/cm3. For the gated triode structures, the under-gate and planar-gate structures were fabricated with various thicknesses of dielectric layers and the relative positions between CNT tips and gate electrode. And we expected that the under-gate structure would contribute to the anode current control and the reduction of gate leakage current. Finally, CNTs were grown on glass substrate at low temperature by utilizing novel catalysts as described above. The luminescent image that corresponded to the electron emission from the CNTs was obtained on the anode phosphor substrate which is applied a high voltage. The uniform CNT films were grown successfully at low temperature with the novel catalysts by thermal CVD. Simultaneously, CNTs were grown on glass substrate for the application of field emission display. We think that the field emission display will be developed if a proper gate structure is combined with the glass substrate. Then, we expect that a large size field emission display with higher resolution will be fabricated in the future.