标题: | 利用微波电浆化学气相沉积法于金矽液态基材上合成钻石之研究 Diamond synthesis on Au-Si liquid substrate by using microwave plasma chemical vapor deposition |
作者: | 高志光 Chih-Kuang Kao 张立 Li Chang 材料科学与工程学系 |
关键字: | 钻石;微波电浆化学气相沉积法;液态基材;Diamond;MPECVD;liquid subctrate;Au-Si |
公开日期: | 2001 |
摘要: | 摘 要 使用化学气相沈积法在固态基材上合成钻石已经有二十余年的光景,然而在高品质的钻石成长方面仍未有重大突破,钻石在合成时直接影响钻石品质的因素很多,包括电源功率、甲烷浓度、气体流量、系统压力、温度及基材的表面型态等。就基材而言传统上的选择不外乎考虑晶格匹配性、基材缺陷、表面能及是否能与碳形成碳化物等因素,材料遍及了周期表内所能想像到的元素及化合物,然而效果并不显着。因此,本论文研究重点着眼于基材,异于传统上使用固态基材的方式,我们利用低温化合物来形成液态基材在化学气相系统下合成钻石。 实验选用金矽合金为基材,并控制其重量百分比约1比2,熔点约为700℃,于压力20TORR真空腔体内,使用甲烷作碳源,氢电浆为解离甲烷的工具来合成钻石,藉由改变偏压大小、甲烷浓度、孕核方式、成长时间、图案控制等参数,并使用XRD、RAMAN、TEM、SEM、EDS、ELLS等工具来分析钻石品质及观察钻石在液态基材上成核及成长的机制。 实验结果发现: 1.利用金矽液态基材来合成钻石,可以得到品质不错的钻石。 2.在金矽液态基材上合成钻石,钻石的成核机制与在固态基材上合成钻石有所不同,基材会形成类似须晶的单晶的矽,且朝311方向成长,然后钻石会沉积在上面。 3.拢起的单晶矽与钻石具有非常平整的界面,界面结构为氧化矽或碳化矽。 4.钻石的尺寸与基材拢起物具有密切关系,拢起物直径越粗则钻石尺寸越大。 5.利用图案的方式,同时在固态与液态的基材合成钻石,钻石会先在具有液态的地方成核并成长,显示钻石对液态基材与固态基材具有蛮高选择比。 6.改变偏压大小会对钻石的成核密度造成影响,正偏压越高成核密度用高。 7.改变成长浓度对成核密度没有太大变化,对晶形的影响性较大,浓度越低晶形越好。 Abstract Chemical vapor deposition of diamond films on solid state substrates has been investigated for the past two decades, but the growth of high quality or highly oriented diamond film accepted by applications has not been achieved yet. Many parameters of growth process would affect directly the quality of diamond, such as methane concentration, gas flow rate, working pressure, substrate temperature, and surface conditions of substrate. The selection of substrate materials for diamond film deposition has to consider lattice structure, surface energy, carbon solubility of the substrates, or the affinity with carbon to form carbide phase. Furthermore, elements or compounds attempted to use as substrates for diamond deposition have covered all over the periodic table, but the effect on improvement quality of diamond is not notable. Thus, in this thesis, we used a low melting point alloy as substrate for chemical vapor deposition of diamond, which was very different to the conventional solid-state substrate. The liquid-state would exist at the temperature of chemical vapor deposition and to promote the synthesis of diamond. We used Au-Si alloy as substrate, which has the melting point about 700oC by using Au-Si weight ratio in 1:2. Diamond was synthesized by microwave assisted plasma chemical vapor deposition system, and hydrogen and methane was used as gas source. Then, we investigated the mechanism of the nucleation and growth of diamond synthesis on liquid state substrate under various bias voltage, methane concentration, and nucleation, growth duration, and patterned substrate by X-Ray Diffraction, Raman, Transmission Electron Microscopy, Scanning Electron Microcopy, Energy Dispersive Spectrometry, and Electron Energy Loss Spectrum analysis technology. In this study, we found: 1. The high quality diamond was obtained by using Au-Si liquid substrate. 2. The mechanism of diamond nucleation on liquid substrate was different on convention solid substrate. Substrate would form protrudent single crystal silicon, in cone shapel, and each protrudent single crystal silicon oriented along [311] crystallographic direction. Then, diamond was deposited on t top of the protrudent single crystal silicon. 3. The planar interface between diamond and silicon was observed, and silicon oxide and silicon carbide was existed at the interface. 4. The size of diamond depended on the size of the protrudent Si, and the thicker protrudent would form larger-size diamond. 5. When diamond deposited on the patterned substrates, diamond shows selective nucleation on the pattern where the liquid alloy had been formed, indicating that diamond nucleation have highly selective between liquid state and solid state substrate. 6. Varying bias voltages affects the diamond nucleation density. The higher nucleation density could be formed, by increasing bias positive voltage. 7. The variation on methane concentration was not found to affect the nucleation densities; however, the shape of diamond depends on the methane concentration. The methane concentration lower than 0.3%would result in well-faceted diamond. |
URI: | http://140.113.39.130/cdrfb3/record/nctu/#NT900159021 http://hdl.handle.net/11536/68271 |
显示于类别: | Thesis |