A density-driven phase transition between semiconducting and metallic polyamorphs of silicon
A density-driven phase transition between semiconducting and metallic polyamorphs of silicon
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DOI：
10.1038/nmat1458
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发表时间：
2005-09-01
期刊：
影响因子：
41.2
通讯作者：
Machon, D
中科院分区：
文献类型：
--
作者：
Mcmillan, PF;Wilson, M;Machon, D
硅的非晶和晶体形式是众所周知的四面体配位半导体。高压研究已经揭示了包含6、8和12倍配位原子的各种金属晶体结构之间广泛的多态性（1,2）。在常温或高压下熔化硅会产生导电液体，其平均配位大于4（参考文献3）。由于金刚石结构半导体的快速结晶，这种液体通常不能被淬火成玻璃(4)。固体非晶硅是通过化学或物理气相沉积等合成途径获得的，其结果是四面体键合半导体状态。长期以来，人们一直推测非晶固体和非晶液体可以代表非晶状态的两种多晶形式，它们通过密度或熵驱动的转换联系在一起（5-8）。这种多晶转变被认为发生在几种不同类型的液体和玻璃体系中（9-14）。在这里，我们提出了密度驱动的固体非晶硅半导体和金属形式之间的多晶态转变的实验证据。这些实验与分子动力学模拟相结合，将非晶固体的行为映射到液体状态。
Amorphous and crystalline forms of silicon are well-known, tetrahedrally coordinated semiconductors. High-pressure studies have revealed extensive polymorphism among various metallic crystal structures containing atoms in six-, eight- and 12-fold coordination(1,2). Melting silicon at ambient or high pressure results in a conducting liquid, in which the average coordination is greater than four (ref. 3). This liquid cannot normally be quenched to a glass, because of rapid crystallization to the diamond-structured semiconductor(4). Solid amorphous silicon is obtained by synthesis routes such as chemical or physical vapour deposition that result in a tetrahedrally bonded semiconducting state. It has long been speculated that the amorphous solid and the liquid could represent two polymorphic forms of the amorphous state that are linked by density- or entropy-driven transformations(5-8). Such polyamorphic transitions are recognized to occur among several different types of liquid and glassy systems(9-14). Here we present experimental evidence for the occurrence of a density- driven polyamorphic transition between semiconducting and metallic forms of solid amorphous silicon. The experiments are combined with molecular dynamics simulations that map the the behaviour of the amorphous solid on to that of the liquid state.