磷属化物和硫属化物半导体合金的电子结构和玻璃化转变。第一部分：$ppσ$网络的形成
Electronic structure and the glass transition in pnictide and chalcogenide semiconductor alloys. Part I: The formation of the $ppσ$-network
摘要：
半导体玻璃表现出许多独特的光学和电子异常。我们已经提出了一个半现象学的方案（J. Chem. Phys. 132，044508（2010）），其中这些异常中的几个产生于深中间带隙电子态，所述深中间带隙电子态驻留在玻璃化转变以上的活化输运所固有的高应变区域上。在这里，我们演示了在分子水平上如何实现这种情况下，在一个重要的类半导体玻璃，即硫族元素和磷族元素的合金。玻璃本身和本征电子中间能隙态都是由于形成由$σ$键合的原子$p$ -轨道组成的网络而出现的，所述轨道仅弱杂化。尽管有大量的弱键，这些$ppσ$ -网络是稳定的竞争类型的键合，同时表现出高度的结构简并性。的稳定性合理化的帮助下，在此提出的结构模型，其中$ppσ$网络的高对称性结构的破坏和扭曲的版本。后一种结构表现出精确的八面体配位并且是完全共价键合的。本方法提供了一个微观路线，在玻璃半导体的电子和结构激发的完全一致的描述。
英文摘要：
Semiconductor glasses exhibit many unique optical and electronic anomalies. We have put forth a semi-phenomenological scenario (J. Chem. Phys. 132, 044508 (2010)) in which several of these anomalies arise from deep midgap electronic states residing on high-strain regions intrinsic to the activated transport above the glass transition. Here we demonstrate at the molecular level how this scenario is realized in an important class of semiconductor glasses, namely chalcogen and pnictogen containing alloys. Both the glass itself and the intrinsic electronic midgap states emerge as a result of the formation of a network composed of $σ$-bonded atomic $p$-orbitals that are only weakly hybridized. Despite a large number of weak bonds, these $ppσ$-networks are stable with respect to competing types of bonding, while exhibiting a high degree of structural degeneracy. The stability is rationalized with the help of a hereby proposed structural model, by which $ppσ$-networks are symmetry-broken and distorted versions of a high symmetry structure. The latter structure exhibits exact octahedral coordination and is fully covalently-bonded. The present approach provides a microscopic route to a fully consistent description of the electronic and structural excitations in vitreous semiconductors.
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