Marlis Ortel

• High performance TFTs showing excellent stability even in air were developed based on investigations describing physical and chemical mechanisms related to zinc oxide film growth and its electrical properties. Therefore the growth and nucleation of zinc oxide thin films deposited by pulsed spray pyrolysis utilizing non-toxic materials were correlated to the boiling curve and Leidenfrost effect of water which was employed as solvent. The optimized deposition parameters were utilized to fabricate ZnO-TFTs. Different growth conditions and their impact on trap state formation inside the bulk material were analyzed taking chemical purity and grain boundary models into account. Moreover it was distinguished between the contribution of surface and bulk trap state on the storage and gate bias stress stability in different atmospheres. Mainly surface states which are sensitive to humid atmosphere show significant impact on the electrical stability of TFTs. Hence different fluoro-terminated compounds which bind selective on active surface sites which are either related to Zn2+-ions or hydroxyl-groups were investigated. 4,4,4-Trifluoro-1-phenylbutane-1,3-dione which chalets to Zn2+-ions was found to be a suitable candidate to reduce the number of surface trap states significantly which leads to highly stable TFT performance and a strong increase in mobility. Since this approach has not been reported elsewhere yet a patent application was filed.