Segregation phenomena and conductivity limits of doped indium oxide thin films

该项目将提高对多晶供体掺杂In2O3薄膜电导率极限的理解。将评估是否可以实现比现有技术获得的电导率更高的薄膜。在较低的加工温度下抑制氧的掺入和避免缺陷分离是实现这一目标的指导原则。我们将使用磁控溅射不同掺杂和预处理的In2O3靶材和共溅射来故意降低薄膜中的氧含量。采用种子层低温沉积来增强晶化，抑制缺陷浓度的平衡，包括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，这也将用于确定铟和掺杂剂的费米能量位置和化学状态。通过高温电导率、霍尔效应弛豫和不同气氛下的退火测量以及电化学极化的霍尔效应测量，研究了样品的热力学和动力学缺陷性质。时间相关扩散方程的数值解将被执行来描述相应的实验观察。通过利用载流子迁移率的温度依赖分析来确定晶界势垒高度，进一步验证晶界的偏析。测量还应澄清为什么在某些载流子浓度下，掺杂sn的薄膜不如掺杂其他掺杂剂（如Zr、Ti、Mo、Ce）的薄膜表现出高载流子迁移率，以及是否可以确定加工路线，从而克服这一限制。

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.