New ways to tune the multi-functionality of oxide thin films for memory applications
type: CreativeWork
description: This thesis presents studies on engineering the electrical and magnetic properties in oxide thin films using vertically-aligned nanocomposites (VAN). The works aim to enhance their multi-functionality for various memory applications. First, electroforming-free resistive switching (RS) with high ON/OFF ratio is realized in a novel model VAN system based on self-assembled Sm-doped CeO2 and SrTiO3 films that allow separate tailoring of nano-scale ionic and electronic channels at a high density (1012 inch-2). These devices allow precise engineering of the resistance states, thus enabling large and tunable ON/OFF ratios and high stability for acting as resistive random access memory (RRAM) devices. Second, the ferromagnetic insulating (FMI) and metallic (FMM) properties of La0.9Ba0.1MnO3 (LBMO) are tuned using VAN. La0.9Ba0.1MnO3 is FMI in bulk but usually shows metallicity in plain films. By using VAN consisting of CeO2 nanocolumns embedded in a La0.9Ba0.1MnO3 matrix, the FMI property is maintained in thin film form. The CeO2 phase acts as strain-controlling nanocolumns and at the same time, produces light Ce doping of the LBMO and thus filling of intrinsic cation vacancies. Together these reduce the unwanted double exchange (DE) coupling. This is hard to realize in plain LBMO films which contain cation vacancies, and have several strain-relaxing LBMO phases which result in an enhanced Mn4+/Mn3+ ratio, and hence to DE coupling and metallicity. Besides, by varying the growth temperature of the LBMO–CeO2 VAN, the system is engineered from a FMI to a FMM and the magnetoresistance is highly tunable, which are correlated to the tuning of the lateral size of both phases. These effects are attributed to a dimension change-induced change in the electronic band structure. The tunable properties of LBMO–CeO2 VAN make it a good candidate as low-power-consumption, high-Tc FMI and FMM components in magnetic random access memory (MRAM) and spintronic devices. Last, in-situ electric f…
abstract: This thesis presents studies on engineering the electrical and magnetic properties in oxide thin films using vertically-aligned nanocomposites (VAN). The works aim to enhance their multi-functionality for various memory applications. First, electroforming-free resistive switching (RS) with high ON/OFF ratio is realized in a novel model VAN system based on self-assembled Sm-doped CeO2 and SrTiO3 films that allow separate tailoring of nano-scale ionic and electronic channels at a high density (1012 inch-2). These devices allow precise engineering of the resistance states, thus enabling large and tunable ON/OFF ratios and high stability for acting as resistive random access memory (RRAM) devices. Second, the ferromagnetic insulating (FMI) and metallic (FMM) properties of La0.9Ba0.1MnO3 (LBMO) are tuned using VAN. La0.9Ba0.1MnO3 is FMI in bulk but usually shows metallicity in plain films. By using VAN consisting of CeO2 nanocolumns embedded in a La0.9Ba0.1MnO3 matrix, the FMI property is maintained in thin film form. The CeO2 phase acts as strain-controlling nanocolumns and at the same time, produces light Ce doping of the LBMO and thus filling of intrinsic cation vacancies. Together these reduce the unwanted double exchange (DE) coupling. This is hard to realize in plain LBMO films which contain cation vacancies, and have several strain-relaxing LBMO phases which result in an enhanced Mn4+/Mn3+ ratio, and hence to DE coupling and metallicity. Besides, by varying the growth temperature of the LBMO–CeO2 VAN, the system is engineered from a FMI to a FMM and the magnetoresistance is highly tunable, which are correlated to the tuning of the lateral size of both phases. These effects are attributed to a dimension change-induced change in the electronic band structure. The tunable properties of LBMO–CeO2 VAN make it a good candidate as low-power-consumption, high-Tc FMI and FMM components in magnetic random access memory (MRAM) and spintronic devices. Last, in-situ electric f…
author: Yun, Chao
language: en
keywords: Vertically aligned nanocomposite, Functional oxide thin films, Resistive random access memory, Ionic and electronic conductivity, Ferromagnetic insulator and ferromagnetic metal, Magnetoelectrics and multiferroics
license: https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/43367d5d-94ce-4a0d-b4f4-9ab0ab3c0f3f/download
license: https://www.rioxx.net/licenses/all-rights-reserved/
date published: 2019-10-20
date modified: 2026-07-22T22:24:31Z
provider: Cambridge University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Cambridge

PropertyValue
property ID: DOI
value: 10.17863/CAM.44906