Wannier-Mott Excitons in Nanoscale Molecular Ices.
Wannier-Mott Excitons in Nanoscale Molecular Ices.
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纳米级分子冰中的万尼尔-莫特激子。
DOI：
10.1103/physrevlett.119.157703
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发表时间：
2017
影响因子：
8.6
通讯作者：
Chen YJ
中科院分区：
文献类型：
--
作者：
Chen YJ
光的吸收产生Wannier-Mott激子是决定低带隙、高介电常数半导体的光学和光伏性质的基本特征。这样的激子，与电子空穴分离的数量级大于晶格尺寸，在很大程度上限于这些半导体，但在这里，我们发现的证据Wannier-Mott激子形成固体一氧化碳（CO）的带隙和低的介电常数。这是建立通过观察，在沉积温度的几度K的变化可以移动固体CO的电子吸收光谱的几百个波数，再加上最近的发现，CO的沉积导致自发形成的薄膜内的电场。这些所谓的自发电场，在这里接近，强烈依赖于温度。我们发现，一个简单的静电模型再现所观察到的温度依赖性的光谱位移的基础上的斯塔克效应的空穴和电子居住几个nm的距离，确定Wannier-Mott激子的存在。CO的自发电效应同时解释了真空紫外光谱对沉积温度敏感性的长期谜团。
The absorption of light to create Wannier-Mott excitons is a fundamental feature dictating the optical and photovoltaic properties of low band gap, high permittivity semiconductors. Such excitons, with an electron-hole separation an order of magnitude greater than lattice dimensions, are largely limited to these semiconductors but here we find evidence of Wannier-Mott exciton formation in solid carbon monoxide (CO) with a band gap ofand a low electrical permittivity. This is established through the observation that a change of a few degrees K in deposition temperature can shift the electronic absorption spectra of solid CO by several hundred wave numbers, coupled with the recent discovery that deposition of CO leads to the spontaneous formation of electric fields within the film. These so-called spontelectric fields, here approaching, are strongly temperature dependent. We find that a simple electrostatic model reproduces the observed temperature dependent spectral shifts based on the Stark effect on a hole and electron residing several nm apart, identifying the presence of Wannier-Mott excitons. The spontelectric effect in CO simultaneously explains the long-standing enigma of the sensitivity of vacuum ultraviolet spectra to the deposition temperature.