Investigation of ZITO Thin Film by co-sputter and its application

Abstract

In this dissertation amorphous zinc indium tin oxide (ZITO) thin film transistors (TFTs) were fabricated at different deposition condition We applied these thin films in thin film transistor photodetector and phototransistor First we apply ZITO thin film as channel layer to the fabrication of TFT with SiO2 gate dielectric By varying the flow rate of oxygen we found the optimal oxygen rate was 6% And to further improve our devices we varied the SnO2 RF power to change the Sn content We found the performance was decreasing with increasing the Sn content To confirm this situation we sustained SnO2 RF power and decreased the IZO RF power that made Sn content also increased The result showed the same way too Additionally we report the effect of cation composition on the device performance Then base on our optimal deposition condition It was found that the field-effect mobility were 13 183 cm2/Vs threshold voltage of 0 39V subthreshold swing of 0 28 V/decade and Ion/Ioff of 4 25×105 for ZITO TFT with SiO2 gate dielectric Furthermore we used transparent conducting oxide (TCO) as our electrodes Through fast and easy process we fabricated ZITO-based thin film transistor with TCO electrodes In the second part of our experiment the fabrication of ZITO thin film transistor with a SiN dielectric on a glass substrate was demonstrated The room temperature deposited ZITO channel with SiN exhibits threshold voltage of 0 57 V drain-source current on/off ratio of 105 subthreshold swing of 0 381 V/decade and field-effect mobility of 9 73 cm2/Vs Compared with SiO2 dielectric the performance of ZITO-based TFT deposited in same condition have improved a lot These results could be contributed to the higher k material for the increased higher gate capacitance and hydrogen passivation In the third part a deep-UV and near-UV ZITO photodetector and phototransistor were fabricated It was also found that the phototransistor rejection ratio for Ion-off ratio and responsivity of drain current with various gate bias (IDS-VGS) under dark and under illumination for ZITO channel layer can even reach 3 orders and 4 orders of magnitude respectively which is better than ZITO photodetector Therefore we believe that these results represent a significant step toward achieving high photosensitivity A ZITO TFT is used in deep UV photodetection exhibits low power consumption and high photosensivity potentially

Date of Award	2014 Jul 11
Original language	English
Supervisor	Shoou-Jinn Chang (Supervisor)