A study of dielectric thin film materials for display applications.

Nam, T., 2006. A study of dielectric thin film materials for display applications. PhD, Nottingham Trent University.

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By advances in information and telecommunication technology (ICT), a display device is one of the most important information technologies. In particular, flat panel displays and technologies have been considered as the centre of a next generation engine in society, academia, business, and other communities.

This thesis is based on an inorganic alternative current thin film electroluminescent (ACTFEL) device which is one of the flat panel display technologies. Investigation of electrical and dielectric properties of Ba0.5Sr0.5TiO3 (BST) thin film to enhance device stability and reduce a driving voltage of the TFEL device was carried out. In addition, yttrium oxide dielectric thin film, yellow emitting ZnS:Mn and blue emitting SrS:Cu,Ag phosphors are also discussed. These thin films and TFEL devices were fabricated by rf-magnetron sputtering method except for the aluminium(Al) electrode, which was deposited by thermal evaporation.

Various characterisations techniques were applied to the candidate dielectric thin films and the EL devices. These were performed by fabricating Metal-Insulator-Semiconductor (MIS) capacitors and lateral- and surface emitting- TFEL devices, respectively. Meanwhile, materials and device engineering included laser annealing and barrier layers were utilised.

In this study the optimum growth conditions for rf-sputtered barium strontium titanate (BST) thin films were established. The substrate temperature, sputtering pressure, oxygen ratio, and rf power were 300 to 350 °C, 10 mTorr, 10% O2 mixture, and 100 watts, respectively. Also, it is found that an additional post-annealing process was necessary to improve BST thin films. Thus, BST thin films prepared in the optimum conditions showed a high dielectric constant of 32.4 and a high breakdown field of 8 MV/cm. Thus, the charge storage capacity of 100 nm-thick BST thin films is as high as 22.95 °C/cm2, which is 8 times larger than the minimum requirement of charge storage capacity in selecting candidate dielectric material. Leakage current was as low as 1.58 μA/cm2 at 80 V. In device structures, BaxSr1-xTiO3 (BST)/ZnS:Mn/Y2O3 EL devices exhibited far better performance in turn-on characteristics, luminance and device stability compared to other BaxSr1-xTiO3(BST)/ZnS:Mn/ BaxSr1-xTiO3 (BST) and Y2O3/ZnS:Mn/Y2O3 EL devices.

For blue emitting SrS:Cu,Ag EL devices, the device performance had a high correlation with barrier layer thickness. A 10 nm-thick barrier layer and 5-laser pulse at 1.8 J/cm2 laser annealing process were the optimum conditions for the barrier layers. Meanwhile, high laser fluence (> 2.0 J/cm2) may cause a "laser ablation" effect on the surface of the samples and as a result, a lower performance was observed. Therefore, overall improvement of EL emission could be achieved by combination of the device and materials engineering.

Item Type: Thesis
Creators: Nam, T.
Date: 2006
ISBN: 9781369314090
Rights: © Copyright 2006.
Divisions: Schools > School of Science and Technology
Record created by: Jeremy Silvester
Date Added: 18 Sep 2020 09:58
Last Modified: 20 Jul 2023 10:14
URI: https://irep.ntu.ac.uk/id/eprint/40801

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