Sensitivity enhancement of EPR spectroscopy on single crystalline surfaces under UHV conditions by employing an electrical detection scheme

采用电检测方案提高特高压条件下单晶表面 EPR 光谱的灵敏度

• 批准号: 276451810
• 负责人: Professor Dr. Thomas Risse
• 金额: --
• 依托单位: Abteilung Physikalische und Theoretische Chemie
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2015
• 资助国家: 德国
• 起止时间: 2014-12-31 至 2017-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/276451810?language=en
• 关键词: Sensitivity; enhancement; EPR; spectroscopy; single

The sensitivity of conventional electron paramagnetic resonance (EPR) spectroscopy on single crystal surfaces under ultrahigh vacuum (UHV) conditions is often insufficient to detect the limited number of defect sites available on high quality surfaces. Electrical detection of the signal known as EDMR spectroscopy offers the possibility to enhance the sensitivity of conventional cw-EPR spectroscopy by several orders of magnitude and was shown to be able to detect less than a thousand spins. In the current project this detection scheme will be implemented into an UHV apparatus to characterize paramagnetic defects at semiconductor surfaces. Paramagnetic defects play a crucial role for the functional properties many silicon-based devices such as solar cells, due to the fact that these defects create states in the band gap of the material, which act as recombination sites for charge carriers. The properties of the defect and hence the performance of the device can be significantly improved by chemical and thermal modifications of the system. Due to a lack of in-situ EPR analytics with sufficient sensitivity the impact of these modifications on the surface defects become very difficult to assess. On the one hand, this project focuses on the investigation of defects on the low index silicon surfaces (001) and (111) under ultrahigh vacuum conditions. The paramagnetic defects of the pristine surfaces will be characterized and subsequently modified under UHV conditions, which offers the possibility to correlate the observed changes in the defect structure to modification by subsequent thermal or chemical treatments such as hydrogenation or oxidation.On the other hand this strategy will be applied to characterize paramagnetic defects on single crystalline cubic SiC(001) surfaces. Apart from the characterization of defects on the pristine surface as a function of the termination and the adsorption of simple gases such as oxygen and hydrogen it will be of particular interest to explore the modification of the defect structure upon adsorption of molecules such as oligo(3-hexylthiophene) (P3HT), which are used in hybrid organic/inorganic solar cells.

传统的电子顺磁共振（EPR）光谱的灵敏度在单晶表面上的超高真空（UHV）条件下，往往是不够的，以检测有限数量的缺陷位点上的高品质的表面。被称为EDMR光谱的信号的电检测提供了将常规cw-EPR光谱的灵敏度提高几个数量级的可能性，并且被证明能够检测不到一千个自旋。在目前的项目中，这一检测方案将实施到一个特高压装置，以表征在半导体表面的顺磁缺陷。顺磁缺陷对许多硅基器件（如太阳能电池）的功能特性起着至关重要的作用，这是因为这些缺陷在材料的带隙中产生状态，这些状态充当电荷载流子的复合位点。缺陷的性质以及因此装置的性能可通过系统的化学和热改性而显著改善。由于缺乏足够灵敏度的原位EPR分析，这些改性对表面缺陷的影响变得非常难以评估。一方面，本计画着重于研究低折射率矽表面（001）与（111）在超高真空条件下的缺陷。原始表面的顺磁缺陷将被表征并随后在超高真空条件下被修饰，这提供了将所观察到的缺陷结构的变化与随后的热处理或化学处理（如氢化或氧化）的修饰相关联的可能性。另一方面，这种策略将被应用于表征单晶立方SiC（001）表面上的顺磁缺陷。除了表征原始表面上的缺陷作为终止的函数和简单气体如氧气和氢气的吸附之外，特别感兴趣的是探索在吸附分子如低聚（3-己基噻吩）（P3 HT）时缺陷结构的改性，该分子用于混合有机/无机太阳能电池。