Self-diffusion of the constituent elements in LaAlO3

镧铝氧化物（LaAlO3）在与半导体工业直接相关的基础研究中占有突出地位：半导体工业领域最具挑战性的任务之一是CMOS结构的持续小型化。为了实现这一目标，需要使用具有高介电常数的新材料。LaAlO3具有高介电常数和低晶格失配特性，是一种非常有前途的栅极介电材料。此外，从基础的角度来看，LaAlO3也是一种非常有趣的材料：在与SrTiO3的界面处，形成了二维电子气体，这是目前基础研究的课题。这种界面效应形成了新型电子元件（如氧化物场效应晶体管）的物理基础。考虑到LaAlO3的这种突出作用，单晶和薄膜中缺乏实验自扩散数据尤其不利。如今，计算机模拟材料成分的迁移率是非常强大的，但仍然需要实验参考数据来验证/评估结果。在本项目中，这些参考数据将在尽可能具有特征的实验条件下获得（材料的确定结构和杂质的化学分析）。因此，本项目的主要目标是通过对单晶LaAlO3和LaAlO3薄膜中所有组成元素进行示踪扩散测量，为LaAlO3提供缺失的扩散参考数据。SrTiO3/LaAlO3异质结构中相互扩散的测量将提供实验信息（扩散曲线），这将是在这种特殊情况下模拟阳离子迁移率耦合的基础。此外，阳离子的迁移率与异质结构的微观结构之间的关系将被显示出来。这也为LaAlO3组分的原子传输提供了相关信息，这对于理解SrTiO3在更高工艺温度下的异质系统行为至关重要。这种认识不仅对制造很重要，而且对预测异质结构的长期稳定性也很重要。

Lanthanum aluminum oxide (LaAlO3) occupies a prominent role in fundamental research directly related to the semiconductor industry: one of the most challenging tasks in the field of semiconductor industry is the continuous downsizing of CMOS structures. To achieve this goal, the use of new materials with high permittivity is required. With a high dielectric constant, and low lattice mismatch with silicon, LaAlO3 is a very promising gate dielectric. In addition, LaAlO3 is also a very interesting material from a fundamental point of view: at the interface with SrTiO3, a two-dimensional electron gas is formed, which is currently the subject of fundamental research. This interface effect forms the physical basis for novel electronic components (e.g. oxide field-effect transistors).Considering this prominent role of LaAlO3, the lack of experimental self-diffusion data in single crystals and thin films is particularly disadvantageous. Computer simulations of the mobility of the constituents of a material are very powerful nowadays - but experimental reference data are still necessary to verify/evaluate the results. Such reference data are to be obtained in this project under experimental conditions that are as well characterized as possible (defined structure of the material and chemical analysis of the impurities).The main goal of this project is therefore to provide the missing diffusion reference data for LaAlO3 by performing tracer diffusion measurements of all constituent elements in single crystalline LaAlO3 and thin LaAlO3 films. The measurement of interdiffusion in the SrTiO3/LaAlO3 heterostructure will supply experimental information (diffusion profiles) which will be the basis for modelling the coupling of the cation mobilities in this special case. Furthermore, a correlation between the mobility of the cations and the microstructure of the heterostructure will be shown. This also provides the relevant information on the atomic transport of the constituents for LaAlO3, which already exists for SrTiO3 and which is crucial for understanding the behaviour of the heterosystem at higher process temperatures. This understanding is not only important in manufacturing but also for predictions on the long-term stability of the heterostructures.