Segregation phenomena and conductivity limits of doped indium oxide thin films

该项目将开发一个更好的理解的多晶施主掺杂的氧化铟薄膜的导电性的限制。将评估是否可以实现具有比用现有技术获得的膜更高的电导率的膜。在较低的加工温度下抑制氧的掺入和避免缺陷偏析是实现这一目标的指导原则。我们将使用不同掺杂和预处理的In2O3靶的磁控溅射和共溅射来故意降低薄膜中的氧含量。将采用具有种子层以增强结晶的低温沉积来抑制缺陷浓度的平衡，这涉及表面氧交换和扩散以及掺杂剂扩散引起的偏析。偏析将使用原位X射线光电子能谱进行量化，这也将用于确定费米能级位置和铟和掺杂剂的化学状态。热力学和动力学缺陷的性质进行了研究，在operando的高温电导率和霍尔效应松弛和退火测量在不同的气氛和霍尔效应测量与电化学极化的样品。数值解的时间相关的扩散方程将进行描述相应的实验观察。此外，通过使用载流子迁移率的温度依赖性分析确定晶界势垒高度来验证晶界的偏析。测量还应澄清为什么Sn掺杂的膜对于某些载流子浓度不表现出与用其他掺杂剂（例如Zr、Ti、Mo、Ce）掺杂的膜一样高的载流子迁移率，以及是否可以识别可以克服这种限制的处理路线。

This project will develop an improved understanding of the limits of electrical conductivity of polycrystalline donor-doped In2O3 thin films. It will be evaluated whether films with higher conduc-tivities than those obtained with present technologies can be realized. Suppressing oxygen incor-poration and avoiding defect segregation at lower processing temperatures are the guiding principles for this goal. We will use magnetron sputtering of differently doped and pre-treated In2O3 targets and co-sputtering to deliberately reduce the oxygen content in the films. Low-temperature deposition with seed layers to enhance crystallization will be employed to suppress equilibration of defect concentrations, which involves surface oxygen exchange and diffusion and dopant diffusion induced segregation. Segregation will be quantified using in-situ X-ray photoelectron spectroscopy, which will also be used to determine the Fermi energy position and the chemical states of indium and the dopants. Thermodynamic and kinetic defect properties are investigated in-operando by high-temperature conductivity and Hall-effect relaxation and annealing measurements in different atmospheres and by Hall-effect measurements with electrochemical polarisation of the samples. Numerical solutions of the time dependent diffusion equation will be performed to describe the corresponding experimental observations. Segregation to grain boundaries will furthermore be validated by determination of grain boundary potential barrier heights using temperature-dependent analysis of the carrier mobility. The measurements shall also clarify why Sn-doped films do not exhibit as high carrier mobilities as films doped with other dopants (for example Zr, Ti, Mo, Ce) for certain carrier concentrations and whether processing routes can be identified by which this limitation can be overcome.