Investigation of Titanium Oxide–Based Materials Applied to Nonvolatile Memory Devices

Abstract

Due to the floating gate structure gradually approach its physical limitation in Flash memories Emerging non–volatile memories such as phase change random access memory (PCRAM) magnetic random access memory (MRAM) and resistive random access memory (RRAM) are widely investigated There are some advantages such as CMOS fully compatibility high speed operation good reliability and high capacity in RRAM devices In this case RRAM exhibits high potential for the next generation In this dissertation some kinds of resistive random access memory (RRAM) devices with various kinds of TiO2–based materials served as the resistive switching layers are fabricated researched and investigated First the fabrication and characterization of a RRAM with a ITO/TiO2/Pt structure at room temperature are reported According to the transmission electron microscope (TEM) and energy dispersive spectroscopy (EDS) analysis the characteristic of fabricated TiO2 thin film layer was measured and investigated The fabricated device exhibits bipolar resistance switching behavior over one hundred DC switching cycles and shows stable retention characteristics for over 104 seconds under a 100 mV stress It is also found that the electrical conduction mechanism is Ohmic conduction during whole resistive switching steps The other part is described the fabrication and analysis of the Zn2TiO4 RRAM cell at room temperature From the I–V measurements four different resistive states are obtained by applying different current compliance value in set process These four resistance states show good retention characteristics without any degradation and can be clearly distinguished from one another by more than 104 seconds under 100 mV bias voltage Furthermore it is found that the fabricated ITO/Z2TiO4/Pt RRAM cell is durable and reliable It is found that the current conduction in high resistive state is first dominated by Ohmic conduction caused by the intrinsic carriers in the Zn2TiO4 thin film and then turned to SCLC mechanism In low resistance state the current conduction mechanism is dominated by Ohmic conduction mechanism

Date of Award	2018 Jul 30
Original language	English
Supervisor	Shoou-Jinn Chang (Supervisor)