uv Studies of Tetrahedral Bonding in Diamondlike Amorphous Carbon
uv Studies of Tetrahedral Bonding in Diamondlike Amorphous Carbon
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DOI：
10.1103/physrevlett.78.4869
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发表时间：
1997-06
影响因子：
8.6
通讯作者：
V. Merkulov;J. Lannin;C. Munro;S. Asher;V. Veerasamy;W. Milne
中科院分区：
文献类型：
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作者：
V. Merkulov;J. Lannin;C. Munro;S. Asher;V. Veerasamy;W. Milne
我们报道了具有广泛四面体键合的无氢类金刚石非晶碳薄膜的紫外拉曼散射研究。紫外拉曼光谱为这些材料中存在sp - 3键合的C原子提供了直接证据。实验结果与理论预测非常一致，有助于提高对非晶碳网络中类金刚石部分形成机制的理解。[S0031-9007(97)03420-0]十多年来，类金刚石非晶碳（DLC）引起了科学和工业领域的极大兴趣。无氢DLC具有高硬度、化学惰性、热稳定性、2ev宽光隙和负电子亲和等有趣而有用的特性。因此，这种材料在涂层技术和电子器件应用中具有重要意义。通常，它是由真空电弧[2,3]或脉冲激光沉积[4]方法产生的。通过蒸发或溅射制备的常规非晶碳（a-C）主要由三重或sp - 2键合原子组成，与之相反，DLC含有显著的组分（高达80 at）。%)的四重键或sp键C原子。尽管对DLC进行了大量的实验工作，但sp - 3c原子存在的证据多少是间接的，sp - 3c含量的测量在本质上往往是经验的。虽然已经对DLC进行了中子衍射和电子衍射研究，但是sp - 3c成键的信息不能轻易地从测量中提取出来。DLC中sp - 3c分数的估计通常是通过透射电子能量损失谱（EELS）进行的，它依赖于与sp - 2c原子存在相关的从1s能级到空p - p态的跃迁损失[2,6]。虽然原则上振动光谱可以更直接地探测成键的变化，但大多数可用的实验技术在DLC的研究中都没有成功。核磁共振（NMR）可以检测sp - 3c原子[7,8]，但需要较厚的样品，而在DLC的情况下，由于高应力和随之而来的分层，这是相当困难的。非弹性中子散射也需要非常厚的样品。通常，拉曼散射是一种方便的非晶固体振动表征工具，在这种情况下，它代表声子态密度（PDOS），由耦合参数加权
We report ultraviolet (uv) Raman scattering studies of hydrogen-free, diamondlike amorphous carbon thin films with a wide range of tetrahedral bonding. The uv Raman spectra are shown to provide direct evidence for the presence of sp 3 -bonded C atoms in these materials. The experimental results are found to be in excellent agreement with theoretical predictions and contribute to an improved understanding of the mechanism by which the diamondlike fraction develops within the amorphous carbon network. [S0031-9007(97)03420-0] For over a decade, diamondlike amorphous carbon (DLC) has stimulated great interest from both scientific and industrial perspectives. Hydrogen-free DLC has interesting and useful properties [1], such as high hardness, chemical inertness, thermal stability, wide optical gap of ,2 eV, and negative electron affinity. Therefore, this material is important for coating technology and electronic device applications. Typically, it is produced by vacuum arc [2,3] or pulsed laser deposition [4] methods. In contrast to conventional amorphous carbon (a-C) prepared by evaporation or sputtering which consists mostly of threefold or sp 2 -bonded atoms, DLC contains significant fractions (up to 80 at. %) of fourfold or sp 3 -bonded C atoms. In spite of extensive experimental work on DLC, evidence for the presence of sp 3 C atoms is somewhat indirect and measurements of the sp 3 C content tend to be empirical in nature. Although neutron [5] and electron diffractions studies [3] of DLC have been performed, information about the sp 3 C bonding cannot be readily extracted from the measurements. Estimates of the sp 3 C fraction in DLC are usually made by transmission electron energy loss spectroscopy (EELS) which relies on the loss of transitions from the 1s level to the empty p p states [2,6] associated with the presence of sp 2 C atoms. While vibrational spectroscopies in principle can probe changes in bonding more directly, most of the available experimental techniques have not been successful in studies of DLC. Nuclear magnetic resonance (NMR) can detect sp 3 C atoms [7,8] but requires thick samples which are rather difficult to make in the case of DLC due to the high stress and consequent delamination. Inelastic neutron scattering also requires very thick samples. Typically, Raman scattering is a convenient tool for vibrational characterization of amorphous solids, in which case it represents the phonon density of states (PDOS), weighted by a coupling parame