| Transparent and flexible electronic devices are widely used due to their bendability and good visual perception.Bendable,transparent and non-toxic thin film transistor?TFT?is the key to achieve green,flexible and transparent display.The preparation process of the transparent and flexible TFT with aluminum-doped zinc oxide?AZO?electrodes is studied in this thesis.High performance,environmentally friendly and flexible TFT devices can be fabricated by designing new electrodes structure,optimizing preparation methods and process parameters.Firstly,a transparent stacked AZO/Al/AZO/Al/AZO source/drain?S/D?electrodes which can be prepared by physical vapour deposition?PVD?method was designed in this paper.The conductivity of the multi-layer film can be improved by the nano-Al interlayer due to Al layer can provide more carriers;and the efficient plasma coupling between the Al and AZO layer can improve the transmittance.The experimental results show that the stacked film has an excellent performance with a transparency of 82.64%,a resistivity of 6.64×10-3??cm and a work function of 3.95 eV,when two layers of 4 nm Al layers are inserted into AZO.The IGZO-TFT device with these transparent stacked S/D electrodes exhibits a saturation mobility(?sat)of 3.2 cm2 V-1s-1,an Ion/Ioff of 1.59×106,and a transmittance of 72.5%.Then,the research on the preparation of AZO S/D electrodes by pulse laser deposition?PLD?method at room temperature was carried out.The quality of films is improved with the increase of laser energy.When the energy exceeds 450 mJ,the quality of films will decrease,owing to the deposition rate is too fast.The optimized transparent AZO S/D electrodes exhibit a resistivity as low as 1.4×10-3??cm,a high transmittance of 93.7%;and the work function is3.68 eV,the barrier height between the AZO S/D electrodes and the IGZO semiconductor is low,which is beneficial to transport electron.The corresponding IGZO-TFT with this transparent AZO S/D electrodes has a low contact resistance?0.3 M??,which contribute to good ohmic contact between the S/D electrodes and the semiconductor layer;The IGZO-TFT device exhibit a saturation mobility of 7.7 cm2 V-1s-11 and an Ion/Ioff of 3.59×106.Based on the high performance and transparent AZO S/D electrodes,the research on transparent AZO gate electrode was further carried out.The experimental results show PVD method is beneficial to the crystallization of AZO film and can improve the electrical properties of the gate electrode.In a low-oxygen environment,the electrode has a exhibit excellent performance with a resistivity of 4.8×10-3??cm,a transmittance of 88%,and a roughness of0.888 nm.The optimized IGZO-TFT device with this transparent AZO gate electrode exhibits a saturation mobility of 9 cm2 V-1s-1,an Ion/Ioff of 6.05×106 and a SS of 0.326 V/dec.Based on the above research,an IGZO-TFT device with all transparent AZO electrodes was realized,and its mobility is as high as 9.17 cm2 V-1s-1,the Ion/Ioff is 5.14×106,and the SS is 0.235 V/dec.The paper also explores a flexible IGZO-TFT based with all transparent AZO electrodes on polyethylene naphthalate?PEN?substrate.The IGZO-TFT exhibit excellent performance with a saturation mobility of 7.9 cm2 V-1s-1 and an Ion/Ioff of 4.58×106,a SS of 0.235 V/dec and a transmittance of 58.1%.The device exhibit good optical and electrical stability after bending,which demonstrate the device has enormous potential in the field of flexible and transparent electronics. |
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