Selective Passivation of Electrical Defects in Metal Oxides

1962年，第一个固态金属氧化物气体传感器被报道。从那时起，金属氧化物由于其优异的化学电阻性能在传感器领域得到了高度重视。自2004年以来，细野细野推动了金属氧化物另一个快速发展的应用领域，他制造了第一个金属氧化物薄膜晶体管（TFT）。即使在非晶和纳米晶体薄膜中也具有高迁移率，可见范围内的透明度以及廉价沉积技术的溶液可加工性使这类材料对创新电子应用非常感兴趣，例如透明和智能显示器。金属氧化物的动态表面结构为传感器和催化应用提供了巨大的优势，但也代表了该材料作为晶体管有源层的主要缺点。逻辑电路需要高稳定性和可靠性，即使在长期运行的情况下。这些标准在金属氧化物晶体管的应用中是非常具有挑战性的。特别是，电气器件对湿度的高灵敏度与器件特性的显著不稳定性相关。超薄膜及其纳米颗粒和非晶态特性进一步增强了这种效果。特别是在廉价和低温工艺中，这是广泛应用的先决条件，增加的杂质密度被掺入材料中，产生大量的缺陷状态，这些缺陷状态作为电活性位点阻碍了晶体管的正常工作。低温（< 200°C）喷雾沉积ZnO可以作为大面积的涂层工艺，但随着温度的降低，ZnO的性能损失很大。因此，钝化这些活性位点不仅可以显著提高器件稳定性，而且可以在保持性能不变的情况下显著降低工艺温度。在这个项目中，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已经展示了特定含氟分子在金属氧化物晶体管操作方面提供的卓越钝化性能。本项目的重点是系统地修饰含氟分子中的功能化学基团，从而了解其钝化机制，并确定金属氧化物晶体管的最佳钝化程序和策略。

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.