유기물 기반의 비휘발성 메모리 소자

Abstract

The subject of this dissertation is regarding the organic non-volatile memories with the reversible bistability which is one of the emerging devices for the next generation. This work has been motivated by theoretical studies on the chemical bistability of organic materials. The research organic materials and their systems were applied to investigate the reversible bistability on the solid-state device. It was demonstrated that the organic memory devices were typically operated by the electric field-induced filament formation, the space-charge-limited current, and the electric field-induced charge transfer. In addition to operating mechanisms, the results provides the important evidences about key issues of organic non-volatile memory devices; a origin of the bistability in the nano-scaled organic layer, the behavior of charge carriers in the hybrid multilayer, and the change of conductance in a charge transfer complex. In the devices with a 30 nm PVK layer, the change of conductance basically arose from the electric field-induced filament formation which was originated from the deposited top electrode. The metallic filament as a current path could be easily oxidized by the heat of the conducting current, which shifted its electric properties from a poor metal into the reversible bistability due to a non-stoichiometric aluminum oxide or the open circuit with a low leakage. The properties of reversible bistability would be relied on the nature of the metal oxide such as the resistive random access memory without a phase transition. Accordingly, the reversible non-volatile memory with a nano-scaled organic layer could be worked by a unique material but many of them would be operated by the nature and property of the field induced filament. The active layer consisted of organic/metal/organic layers between electrodes in the devide with the hydride multilayer. The embedded metal layer was verified the aggregated nanoparticles as results of an AFM inspection. Even though the devices was sensitive to the preparing condition of embedded metal, they revealed a reversible bistability. As results of electric tests, the nanoparticles provided the embedded trap sites and the charge transporting path. However, the organic materials merely contributed to the charge transport. This non-volatile memory device was operated by space-charge-limited current in the embedded nanoparticles. In addition, the electric performance of the ON/OFF ratio and the cycle ability was improved when the embedded metal layer was changed into Al-O/Al/Al-O (5 nm) layers instead of a 5 nm Al layer. Therefore, the control of embedded trap sites might be a important parameter to achieve a device with high performance. In the spin coated TNF:PVK charge transfer complex, the charge carriers were generated and vanished by the application of an external electric field. It shows that the state of charge transfer is controllable by the application of an electric field. Indeed, each condition was also stable without a sustaining electric power. This device might be a model of all organic non-volatile memories with a reversible bistability and provided an evidence to be control the state of charge-transfer by the application of an external electric field.