碳與金屬碳化物材料之製備與鑑定

Abstract

本研究提供多樣性之合成法，以分子化合物為前驅物，成功地製備薄膜與奈米尺寸之粉末材料。 在第二章節中, 分別以Me3CCH=Ta(CH2CMe3)3 與Me3CN=Ta(CH2CMe3)3 為單源前驅物，利用低壓化學氣相沉積法成長TaC與TaCN薄膜材料。同時，藉由所收集之揮發性副產物，合理地推論與比較前驅物在沉積過程中的反應途徑。 在第三章中，適當的選擇早期過渡金屬氯化物，包含四氯化鈦、四氯化鋯、四氯化鉿、三氯化釩、五氯化鈮與五氯化鉭，分別與正丁基鋰在溶液相中反應，生成含 [金屬-碳] 鍵結之膠態物質，視為金屬碳化物的前驅物。此前驅物經由熱處理，行β-hydrogen elimination 以及reductive elimination反應，即可合成出奈米尺寸之金屬碳化物。 第四章以相同的概念，利用1-chlorobutane 與鈦箔或是微米尺寸的鈦金屬粉末反應，製備奈米尺寸的碳化鈦粉末。1-chlorobutane不僅扮演提來源之角色，碳化金屬。同時也提供氯蝕刻鈦金屬，縮小鈦金屬尺寸。反應中生成TiClx揮發性分子，其中二氯化鈦、三氯化鈦行自身氧化還原反應，再度生成奈米尺寸之鈦金屬粒子與四氯化鈦揮發性分子，參與反應。 在第五章中，依據相同的化學還原方式，也可成功地運用在碳材的合成。六氯苯提供含六碳苯環(C6) 為石墨之基本架構單元，加以鋰金屬還原，進行偶合反應，使得六碳苯環得以偶合堆積成石墨之層狀結構。此石墨材料呈現棒狀外型，與利用鈉金屬還原反應比較，有著極大不同的現象。此碳棒材料平均尺寸為0.3 ´ 5.0微米，同時利用碳十三固態核磁共振儀，偵測類石墨排列與不規則排列之碳比例為1 : 1。 在第六章中，利用低壓化學氣相沉積法，以SiCl3CCl3為前驅物、石英為基材，製備平坦之非晶相碳薄膜。以X光光電子能譜儀鑑定，於773 K沉積的薄膜組成為90 %碳與10 %氯；於1273 K沉積的薄膜組成為100 %碳。在沉積過程當中，以線上紅外線光譜儀偵測出揮發性副產物為四氯化矽、四氯化碳，以及四氯乙烯。當以矽晶片為基材時，薄膜沉積與基材蝕刻同時發生，進而成長出捲曲狀之薄膜。

In this thesis I present several methods to synthesize the nanoparticles and thin films by employing bottom-up concept relied on the chemical reduction of the reagents. In Chapter 2, we synthesize Me3CCH=Ta(CH2CMe3)3 and Me3CN=Ta(CH2CMe3)3 precursors to deposit thin films by chemical vapor deposition and analyze the thermolysis of the precursors in the reaction. The difference between the nature of these two precursors and the characteristic of the films is discussed in the content. Syntheses of nano-sized cubic phase early transition metal carbides from metal chlorides and n-butyllithium is represented in Chapter 3. This study has shown that by proper selection of reaction precursors, nBuLi and MClx (M = Ti, Zr, Hf, V, Nb and Ta), transition metal carbides can be prepared at temperatures significantly lower than those employed in the traditional methods. The formation of metal-alkyl bonds takes place in solution and undergoes the β-hydrogen elimination and the reductive elimination after heat treatment. Furthermore, titanium carbide can be produced by 1-chlorobutane and nanosized titanium powders or foil by employing the similar concept as described in Chapter 4. 1-Chlorobutane not only acts as the carbon source to carbourize the Ti metal but also provides the chlorine atoms to etch the Ti metal into smaller size and generating volatile TiClx molecules. The disproportionation of TiCl2 and TiCl3 provides another growth route of the nano-sized metal powders, with the evolution of TiCl4 vapor. The apparently simple procedure is a complex heterogeneous process combining etching, deposition and carbourization reactions. In Chapter 5, we take C6Cl6 as the building blocks and Li as the coupling reagent to generate carbon rods with the graphene sheets perpendicular to the longitude direction. The morphology of the rods is very different from that of the nano graphite previous reported employing Na as the reducing agent. The average size was 0.3 * 5 μm. Ratio of the graphite-like and the disordered carbon atoms, determined by solid-state 13C-NMR, was 1 : 1. In Chapter 6, smooth amorphous carbon films were deposited from SiCl3CCl3 on quartz substrates at 773 – 1273 K by low-pressure chemical vapor deposition using a hot-wall reactor. XPS studies showed that the films grown at 773 K contained 90% C and 10% Cl, while the films grown at 1273 K contained 100% C. SiCl4, CCl4, and Cl2C=CCl2 were detected by on-line FT-IR studies. The extrusion of dichlorocarbene, :CCl2, from SiCl3CCl3 provided the source of carbon in the reaction. On Si substrates, an etching process at the film-substrate interface assisted the lift-off of the films from the substrates. The C films curled and formed rolls.