Diamond nanowires and the insulator-metal transition in ultrananocrystalline diamond films
Diamond nanowires and the insulator-metal transition in ultrananocrystalline diamond films
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DOI：
10.1103/physrevb.75.195431
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发表时间：
2007-05-01
影响因子：
3.7
通讯作者：
Gruen, D. M.
中科院分区：
文献类型：
--
作者：
Arenal, R.;Bruno, P.;Gruen, D. M.
n 型超纳米晶金刚石薄膜卓越的电化学、电子场发射、高温二极管和光学特性的进一步发展需要更好地了解这种材料中的电子传输。特别令人感兴趣的是当向合成气中添加约 10%体积的氮气时观察到的向金属态转变的起源。在这里，我们提供的数据表明，向金属态的转变是由于形成了被sp(2)键合的碳鞘包围的部分取向的金刚石纳米线。这些已通过扫描电子显微镜、透射电子显微镜技术（高分辨率模式、选区电子衍射和电子能量损失光谱）、拉曼光谱和小角度中子散射进行了表征。纳米线长度为 80 - 100 nm，由类似 5 nm 宽和 6 - 10 nm 长的金刚石微晶片段组成，表现出原子级尖锐的界面。每根纳米线都被包裹在 sp(2) 键合碳鞘中，为电子提供导电路径。薄膜上的拉曼光谱结合等离子体化学和物理过程的考虑表明，鞘可能由纳米碳材料组成，在某些方面类似于聚乙炔和聚腈的聚合物状混合物。讨论了控制金刚石核和负责导电性的 sp(2) 鞘同时生长的复杂相互作用，并试图更好地从理论上理解传输机制。
Further progress in the development of the remarkable electrochemical, electron field emission, high-temperature diode, and optical properties of n- type ultrananocrystalline diamond films requires a better understanding of electron transport in this material. Of particular interest is the origin of the transition to the metallic regime observed when about 10% by volume of nitrogen has been added to the synthesis gas. Here, we present data showing that the transition to the metallic state is due to the formation of partially oriented diamond nanowires surrounded by an sp(2)-bonded carbon sheath. These have been characterized by scanning electron microscopy, transmission electron microscopy techniques (high- resolution mode, selected area electron diffraction, and electron- energy- loss spectroscopy), Raman spectroscopy, and small- angle neutron scattering. The nanowires are 80 - 100 nm in length and consist of similar to 5 nm wide and 6 - 10 nm long segments of diamond crystallites exhibiting atomically sharp interfaces. Each nanowire is enveloped in a sheath of sp(2)- bonded carbon that provides the conductive path for electrons. Raman spectroscopy on the films coupled with a consideration of plasma chemical and physical processes reveals that the sheath is likely composed of a nanocarbon material resembling in some respects a polymer- like mixture of polyacetylene and polynitrile. The complex interactions governing the simultaneous growth of the diamond core and the sp(2) sheath responsible for electrical conductivity are discussed as are attempts at a better theoretical understanding of the transport mechanism.