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HL: Fachverband Halbleiterphysik

HL 44: ZnO and its relatives: Devices

HL 44.6: Talk

Tuesday, April 1, 2014, 12:00–12:15, POT 151

XPS investigations of selective surface passivation for highly stable metal oxide TFTs — •Yulia Trostyanskaya, Marlis Ortel, Torsten Balster, and Veit Wagner — Campus Ring 1, 28759 Bremen, Germany

Zinc oxide thin film transistors (TFTs) showing high electron mobilities (7 cm2/Vs in air) were prepared by spray pyrolysis. In air the transistors showed considerable hysteresis and shift in threshold voltage during operation. After selective surface passivation with benzoyl-1,1,1-trifluoroacetone (BTA) the hysteresis and operational stability improved significantly. Analysis of chemical composition and binding properties of the passivation material is crucial to develop a microscopic model of the semiconductor-passivation interaction. By means of X-ray photoelectron spectroscopy (XPS) was found that a monolayer of BTA bond to Zn can be achieved by desorption of weakly bonded multilayers at 30°C only. The BTA-Zn bond withstands high temperatures but decomposition of the compound was observed at 170°C. This is far above the operation temperature of TFTs. The decomposition was monitored by XPS, the F-peak was split from the original one at 688.5 eV to a second one at 685.3eV. This indicates the formation of Zn-F bonds by decomposing the CF3-group. The analysis shows the excellent suitability of BTA as passivation layer due to strong bonding properties of BTA to Zn and high chemical stability under standard operation conditions of TFTs.