Behaviour of bilayer composites titanium dioxide-zinc oxide thin films resistive switching and their potential for tactile sensing device / Shafaq Mardhiyana Mohamat Kasim

This thesis covers the study on behaviour of bilayer composites metal oxide thin films resistive switching and their potential for tactile sensing application. In semiconductor, conduction mechanism is important to be analyzed for fundamental understanding on the device itself to further improve the device performance including the endurance and retention properties as well as identify the relation with resistive switching. Therefore in this work, the dominant conduction mechanisms for single and bilayer composites TiO2-ZnO thin films resistive switching device were investigated. Furthermore to achieve resistive switching devices which responsive to the touch and pressure, the suitable material, fabrication properties and comprehensive measurement need to be identified. Thus, tactile sensor may require a flexible element of touch and pressure sensitive area in order to have the intense effect during measuring the sensor sensitivity with low temperature of heat treatments as the flexible element itself has very low thermal resistance. Also, this thesis was written to propose parameters and procedure for tactile measurement. As an initial step, bilayer composites thin films metal oxide with two different sequential structures TiO2/ZnO and ZnO/TiO2 were fabricated on ITO/glass to finalize the optimal sequential structure to be deposited on ITO/PET for the flexural analysis. Fabrication processes involved were spin-coating, annealing and sputtering. The electrical and physical characterizations comprised I-V measurement with and without flexural effect, film thickness, surface morphology and cross-section. In the beginning, the characterizations were performed to investigate the optimal sequential structure which comes out with TiO2/ZnO as the significant structure compared to ZnO/TiO2 by referring to the ROFF/RON ratio and the consistency of resistive switching pinched hysteresis loop itself. Then the optimal sequential structure TiO2/ZnO was fabricated on ITO/PET and different size of top electrode were deposited for the flexural I-V measurement preparation. Besides different size of top electrode, flexural I-V measurement with different bending angle was examine as well in order to study on the effect towards resistive switching behaviour. A clamping device was proposed in order to accomplish the flexural I-V measurement process to ensure the samples were bending evenly for precise results and error reduction. The investigation on the effect of different bending angle to resistive switching characteristics show slightly significant results compared to the assessment on different size of top electrode. Overall, the results suggested that composition of TiO2 and ZnO with appropriate fabrication parameters has the potential to act as a tactile sensor because it is responsive to the bending effect and due to the internal potential that was generated from the mechanical stress which was applied to the sample. For the performance of individual device, sample with 0.3  0.3 cm metal contacts was considered as effective device due to the equality of resistance value at normal state yet it very responsive to the bending effect during convex and concave states.