Solution Processed Materials Applied in Memory Devices

Abstract

In this dissertation the perovskite oxides and biomaterial were prepared by solution process and applied to the nonvolatile memory and organic thin film transistor applications Hence the dissertation is divided into two parts one is the investigation of sol-gel perovskite oxide-based devices and the other is the investigation of solution biomaterial-based devices The multi-spin casting multilayered barium titanate (BTO) thin films on RRAMs without doping other elements were adopted to improve the memory performance Compared with single BTO layered RRAM the ON/OFF ratio of the two-layered BTO RRAM can be improved from 104 to 106 In addition the retention time of over 105 s without fluctuation at 85 °C Utilizing graphene oxide (GO) sandwiched between BTO layers the memory devices exhibit a non-volatile WORM memory behavior The HRS resistance LRS resistance and the ON/OFF ratio can be enhanced by stacking multi-BGB layer In addition to the BTO thin film the MTO thin films were also fabricated by the similar sol-gel method The ON/OFF ratios of Al/MTO/ITO structure was 104 To improve the performance of these devices adding Ni in preparation of quaternary compound by sol-gel method without high annealing temperature process and doping impurities is proposed For example the ON/OFF ratio of 108 can be achieved for the MTN memory devices Besides Ni (II) acetylacetone possessing two pairs of BL can not only provide an extremely low polymerization rate for smooth surfaces but contribute to the moisture resistivity Thus due to the strong bonding between Ti metal ion and BL enables the chelate effect to the stability the memory devices have good memory properties after many days under an atmospheric environment For instance the current CVs of the MTN memory device are less than 30% after 28 d In the second part of this dissertation the solution biomaterial gelatin was used to fabricate RRAM devices This part divided into three sections (1)Gelatin-based RRAM: The memory devices exhibited a high ON/OFF ratio of over 106 and a long retention time of over 105 s From the EDX analysis results the chelate effect and the simultaneous presence of carbon and oxygen elements in the rupture of filament paths can be observed (2)Al chelated gelatin-based RRAM: the transparent gelatin thin film (transmittance~86%) is suitable for application in the transparent electrical and optical devices However the transparent ITO/gelatin/ITO structure cannot present the memory switching behavior Due to the chelate effect can be developed to change the gelatin properties that the ITO electrodes can be applied The ITO/ACG/ITO structure shows high ON/OFF current ratio (>105) low operation voltage good uniformity and retention characteristics at room temperature and 85 °C The enhancement of the resistive switching properties can be attributed to the chelate effect of Al ions with gelatin Al ions further enhanced the redox reaction that occurred in the gelatin (3)Flexible gelatin-based RRAM: the flexible gelatin-based RRAM shows good memory properties including high ON/OFF ratio of more than 105 needless of a forming process the low set voltage (

Date of Award	2015 Aug 24
Original language	English
Supervisor	Yeong-Her Wang (Supervisor)