Selective Passivation of Electrical Defects in Metal Oxides

1962年，报道了第一个固态金属氧化物气敏元件。从那时起，金属氧化物因其优异的耐化学性而在传感器领域获得了高度的重视。2004年以来，细野研制出了第一个基于金属氧化物的薄膜晶体管(TFT)，推动了金属氧化物另一个快速发展的应用领域。即使在非晶态和纳米晶体薄膜中也具有很高的迁移率、可见光区的透明性以及廉价沉积技术的溶液可加工性，这使得这种材料对于创新的电子应用非常有兴趣，例如用于透明和智能显示器。金属氧化物的动态表面结构在传感器和催化应用中具有很大的优势，但作为晶体管的有源层却是其主要缺点。即使在长期运行的情况下，逻辑电路也需要很高的稳定性和可靠性。这些标准在金属氧化物晶体管的应用中被证明是非常具有挑战性的。特别是，电子设备对湿度的高灵敏度与设备特性的显著不稳定性相关。超薄膜及其纳米颗粒和无定形特性使这种效应变得更加增强。特别是在廉价和低温工艺中，这是广泛应用的先决条件，在材料中加入了更高密度的杂质，产生了大量的缺陷态，这些缺陷态充当阻碍晶体管正常运行的电活性位置。低温(&lt；200°C)喷射沉积氧化锌作为一种大面积涂层工艺是可能的，但随着温度的降低，性能会有显著的损失。因此，对这些活性中心进行钝化不仅可以显着提高器件的稳定性，而且可以在保持性能不变的情况下显著降低工艺温度。在该项目中，采用各种方法在沉积期间和/或沉积后选择性地钝化这些缺陷。在这方面，含氟分子以其独特的性质而闻名，例如特氟龙对水。AG Wagner和AG Röschenthaler已经在金属氧化物晶体管操作方面展示了特殊的含氟分子提供的特殊钝化性能。本项目的重点是系统地修饰含氟分子中的功能化学基团，以了解其钝化机理，并确定更好的金属氧化物晶体管的钝化程序和策略。

In 1962 the first solid state metal oxide gas-sensor was reported. Since then metal oxides gained high importance in the fields of sensors due to their excellent chemo-resistive properties. Since 2004 another fast developing field of application for metal oxides was promoted by Hosono who fabricated the first metal oxide based thin-film transistor (TFT). High mobility even in amorphous and nano-crystalline films, transparency in the visible range and solution processability by cheap deposition technology make the class of material highly interesting for innovative electronic applications, e.g. for transparent and smart displays. The dynamic surface structure of metal oxides serves as big advantage for sensor and catalysis applications but represents the major drawback of the material as active layer in transistors. Logic circuits require high stability and reliability even under long term operation. These criteria turned out to be very challenging in metal oxide transistor application. Especially, a high sensitivity of the electrical devices towards humidity was correlated to the significant instability of device characteristics. The effect becomes even more enhanced by the ultra-thin films and their nanoparticular and amorphous character.Especially in cheap and low temperature processes, which are a prerequisite for wide spread applications, an increased density of impurities is incorporated in the material creating a high number of defect states which act as electrically active sites hampering proper transistor operations. Low temperature (< 200 °C) spray deposited ZnO is possible as a large-area coating process, but exhibits a dramatic performance loss with decreasing temperature. Hence passivation of these active sites is not only necessary to improve device stability significantly but also to reduce the process temperature dramatically while keeping the performance constant. In this project various approaches are followed to selective passivate those defects during and/or after deposition. In this respect, Fluor containing molecules are known for their unique properties, e.g. Teflon towards water. AG Wagner and AG Röschenthaler have already demonstrated exceptional passivation properties offered by specific Fluor containing molecules with respect to metal oxide transistor operations. Focus in this project is to systematically modify functional chemical groups in Fluor containing molecules, which allow to understand their passivation mechanism and to identify superior passivation procedures and strategies for metal oxide transistors.