Date of Graduation

5-2022

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Engineering (PhD)

Degree Level

Graduate

Department

Electrical Engineering

Advisor/Mentor

Omar Manasreh

Committee Member

Morgan E. Ware

Second Committee Member

Jeff Dix

Third Committee Member

Bothina Manasreh

Keywords

Memory resistors, Memristors, Quantum dots, Thin films

Abstract

Memristors or memory resistors are promising two-terminal devices, which have the potential to revolutionize current electronic memory technologies. Memristors have been extensively investigated and reported to be practical devices, although they still suffer from poor stability, low retention time, and laborious fabrication processes.

The primary aim of this project was to achieve a device structure of quantum dots or thin films to address a fundamental challenge of unstable resistive switching behavior in memristors. Moreover, we aimed to investigate the effects of light illumination in terms of intensity and wavelength on the performance of the fabricated memristor. The parameters such as power consumption, retention time, endurance, and stability were investigated to determine the overall performance of the device. The experiment was designed and divided into three steps. First, a memristor was designed, fabricated, and characterized to explore the resistive switching mechanism in the device. Second, the same material used in the first step was incorporated into a photodetector, which was characterized to investigate the device photosensitivity, detectivity, responsivity, and photocurrent to dark current ratio. Finally, a new device was designed, fabricated, and characterized, which showed both memristivity and photodetectivity properties. The device is called a photomemristor since it has both functions of a memristor and a photodetector.

The “bottom-up” approach was used for fabricating the proposed memristor. In bottom-up methodology, nanostructures are synthesized and then assembled onto the substrate by stacking crystal planes onto each other. The fabricated memristors demonstrated bipolar resistive switching behavior with a low working voltage, efficient power consumption, and high endurance. We suggested the resistive switching mechanism of the device is related to the formation and rupture of conducting filaments inside the switching layer of the memristor. Moreover, the conduction mechanism and electron transport in the switching layer of the device during the resistive switching process were analyzed. In addition, the effect of light illumination on the performance of the device was investigated and the SET voltage of the memristor was reduced as the light intensity increased. A gold-coated probe tip was used as the top electrode to confine the conductive filaments growth. The obtained results demonstrate significant improvement in the resistive switching behavior in terms of stability and uniformity compared to similar devices with larger electrode surface area.

This work provides new insights and suggests a measurement setup to further understand the resistive switching behavior in metal oxide and perovskite thin films for future applications of optoelectronic memristors in logic circuits, digital data storage, the internet of things, and neuromorphic computing.

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