Defects and Interface Engineering of SnO2 Based Nanomaterials for High Performance Memory Applications

Non-volatile memories with larger capacity, faster operation speed, lower power consumption, smaller size and simpler fabrication process are strongly desired in the big data era. Recently, oxide-based random-access memories (OxRAMs) have been considered as a promising solution to meet these requirements. By achieving multiple resistance states in metal oxides, the memory capacity can be multiplied at the same cell size hence the development of metal oxide switching materials is important for achieving high-performance memory devices. In this thesis, a transparent metal oxide (SnO2) was selected for developing resistive switching-based RRAMs. Three strategies for improving the resistive switching behaviour were proposed and investigated, based on the solution-processed SnO2 thin films, which covered the following aspects: a. Defects engineering: to facilitate multi-level resistance states in metal oxides, defects engineering via cation doping has been investigated. The possibility of forming cationic and ionic defects in SnO2 by doping has been explored through density functional theory. Cationic defects Mn3+ interstitials in Mn-doped SnO2 were synthesized through a new solution-processed approach and by altering the doping level, multi-resistance states in Mn-doped SnO2 have been achieved successfully. b. Layer design: to alter the migration and redox process of defects in metal oxides, an alternative multi-layer structure was designed. By inserting pure SnO2 layer as the ionic defects diffusion barrier, the migration and redox of ionic defects in the Mn-doped SnO2 layer can be modified. Stable multi-level resistive switching, high On/Off ratio, excellent retention and low operation voltage have been achieved. c. Graphene/metal oxide nanocomposites: graphene can be used as electrodes or buffer layer in RRAMs which can increase the device flexibility or modify the switching mechanism. However, due to the high hydrophobic behaviour of graphene, the fabrication of uniform and dense graphene derived thin film through solution-process is challenging. In addition, the lack of bandgap also limits the application of graphene in various electronic devices. A facile approach (UV irradiation) was employed to modify the hydrophilicity and open the bandgap of graphene. The UV treatment can induce H2O dissociative absorption on graphene, which effectively enhanced the interface interaction between graphene and SnO2. This significantly improved the thin film quality of graphene/SnO2 for resistive switching, with more stable switching behaviour and lower SET/RESET voltages. More importantly, according to the density functional theory calculation results, bandgap of graphene can be opened to 0.75 eV. This work provides a systematic study on strategies which improve the metal oxide resistive switching behaviour for high density data storage devices. The proposed strategies of defect engineering, layer design and graphene/metal oxide composites may provide new insights to develop metal oxide-based devices microelectronic devices.

Grantor dc:publisher

UNSW, Sydney

Year dc:date

2018

Author dc:creator

• Xu, Zhemi

• Defects
• Tin Oxide
• Graphene
• Interface

Statement dc:rights

• open access
• CC BY-NC-ND 3.0
• free_to_read

Licence

• https://purl.org/coar/access_right/c_abf2
• https://creativecommons.org/licenses/by-nc-nd/3.0/au/

Language dc:language

EN

Identifier

https://doi.org/10.26190/unsworks/3578

OAI identifier oai:identifier

oai:unsworks.library.unsw.edu.au:1959.4/60747