In-situ Tracer Diffusion in Solids

固体中的原位示踪扩散

• 批准号: 327867869
• 负责人: Professor Dr. Harald Schmidt
• 金额: --
• 依托单位: Institut für Metallurgie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2016
• 资助国家: 德国
• 起止时间: 2015-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/327867869?language=en
• 关键词: situ; Tracer; Diffusion; Solids

One of the most important analytical methods for the experimental determination of diffusivities, activation energies and diffusion mechanisms in solids is based on the use of stable tracers. A rare stable isotope of an element is deposited on the surface of the material under investigation. After diffusion annealing at elevated temperature the tracer is redistributed. After cooling down and subsequent isotope depth profile analysis by e. g. Secondary Ion Mass Spectrometry tracer self-diffusivities can be determined.During the last years the method of neutron reflectometry was established in this field of research. The method allows to determine diffusion length < 1 nm and diffusivities down to 10-26 m2/s on thin films and bulk materials. The drawback of this - and all other tracer methods – is that the diffusion processes cannot be monitored in-situ, directly during annealing. There is always a cool down of the sample to room temperature necessary. For various modern metastable and nanoscale materials systems an in-situ detection of diffusivities during the actual diffusion process is of big advantage.Due to the actual advancement of the Neutron Reflectometry method in form of the “Focusing Reflectometry”, higher neutron intensities can be produced at the sample, which will allow to record a reflectivity pattern in less than 5 min. This will enable an in-situ detection of self-diffusion in solids during annealing for the first time. A quasi-continuous detection of diffusivities as a function of time becomes possible. In addition, the error of a single measurement is significantly reduced and activation energies can be determined more precisely. The aim of the present research project is the quantification of self-diffusivities in-situ during annealing with neutron reflectometry using “amorphous Germanium” as a model system. The experiments should be done to test the method on a broad base and to give the necessary conditions for future development. Experiments for a quasi-continuous detection of time-dependent diffusivities during structural relaxation and crystallization will be done. The work should also help to establish this method in the field of diffusion science.In the framework of the prolongation proposal present here, a method for the determination of activation energies in a single annealing experiment (isochronic method) developed during the first period should be tested and refined. In addition, systematic investigations on the diffusion in amorphous Si1-xGex should be carried out, while the advantages of the in-situ method (high sample throughput, time dependence of diffusivities) will be used.

固体中扩散系数、活化能和扩散机制的实验测定的最重要的分析方法之一是基于稳定示踪剂的使用。一种稀有的稳定同位素沉积在被研究物质的表面。在高温下扩散退火后，示踪剂重新分布。在冷却和随后的同位素深度剖面分析后，G.二次离子质谱示踪剂的自扩散系数可以测定，近年来在这一研究领域建立了中子反射法。该方法允许在薄膜和块体材料上确定< 1 nm的扩散长度和低至10-26 m2/s的扩散率。这种方法和所有其他示踪方法的缺点是，不能在退火过程中直接原位监测扩散过程。总是需要将样品冷却至室温。对于各种现代亚稳态和纳米级材料系统，在实际扩散过程中原位检测扩散率具有很大的优势。由于中子反射法以“聚焦反射法”的形式的实际进步，可以在样品处产生更高的中子强度，这将允许在不到5分钟的时间内记录反射率图案。这将首次实现退火期间固体中自扩散的原位检测。作为时间的函数的扩散率的准连续检测成为可能。此外，单次测量的误差显著降低，并且可以更精确地确定活化能。本研究项目的目的是在退火过程中与中子反射仪使用“非晶锗”作为模型系统的自扩散率原位量化。应进行实验，以在广泛的基础上测试该方法，并为未来的发展提供必要的条件。将进行结构弛豫和结晶过程中随时间变化的扩散率的准连续检测实验。这项工作也应该有助于建立这种方法在该领域的扩散science.In的延长建议的框架内，在这里，一个单一的退火实验（等时法）的活化能的测定方法，在第一阶段期间开发的应进行测试和完善。此外，在非晶Si 1-xGex扩散的系统调查应进行，而原位方法的优点（高样品吞吐量，时间依赖性的扩散率）将被使用。