Origin of the metallic properties of heavily boron-doped superconducting diamond
Origin of the metallic properties of heavily boron-doped superconducting diamond
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DOI：
10.1038/nature04278
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发表时间：
2005-12-01
期刊：
影响因子：
64.8
通讯作者：
Oguchi, T
中科院分区：
文献类型：
--
作者：
Yokoya, T;Nakamura, T;Oguchi, T
通过电子能带结构计算和杂质能级可以很好地描述轻掺杂半导体的物理性质(1)。这些特性构成了当今半导体技术的基础。如果掺杂浓度n超过临界值n(c)，则体系通过绝缘体到金属的转变并表现出金属行为；这被广泛接受为杂质能级合并形成能带的结果(2)。然而，对非nc掺杂半导体的电子结构尚未进行详细的研究。因此，最近在重硼掺杂金刚石（4,5）中，在绝缘体到金属跃迁(3)附近出现的超导性的观察激发了对超导性的金属态的基本起源的讨论。有两种方法被用来描述这种金属态：在杂质带(6)或本征金刚石带（7-9）中引入载流子。在这里，我们通过实验证明了掺杂依赖的占据电子结构与金刚石带一致，表明金刚石带中的空穴在决定重硼掺杂金刚石超导体的金属性质方面起着重要作用。这支持了金刚石带方法和相关预测，包括在硅和锗中实现掺杂诱导超导的可能性(7)。这也为金刚石基器件的可能发展提供了基础（10）。
The physical properties of lightly doped semiconductors are well described by electronic band- structure calculations and impurity energy levels(1). Such properties form the basis of present- day semiconductor technology. If the doping concentration n exceeds a critical value n(c), the system passes through an insulator- to- metal transition and exhibits metallic behaviour; this is widely accepted to occur as a consequence of the impurity levels merging to form energy bands(2). However, the electronic structure of semiconductors doped beyond nc have not been explored in detail. Therefore, the recent observation of superconductivity emerging near the insulator- to- metal transition(3) in heavily boron- doped diamond(4,5) has stimulated a discussion on the fundamental origin of the metallic states responsible for the superconductivity. Two approaches have been adopted for describing this metallic state: the introduction of charge carriers into either the impurity bands(6) or the intrinsic diamond bands(7-9). Here we show experimentally that the doping- dependent occupied electronic structures are consistent with the diamond bands, indicating that holes in the diamond bands play an essential part in determining the metallic nature of the heavily boron- doped diamond superconductor. This supports the diamond band approach and related predictions, including the possibility of achieving dopant- induced superconductivity in silicon and germanium(7). It should also provide a foundation for the possible development of diamond- based devices(10).