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You searched for +publisher:"University of New South Wales" +contributor:("Seidel, Jan, Materials Science & Engineering, Faculty of Science, UNSW"). Showing records 1 – 3 of 3 total matches.

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University of New South Wales

1. Hu, Songbai. Phase Transitions in Strain-Tuned SrCoO3-δ (0<δ≤ 0.5) Thin Films.

Degree: Materials Science & Engineering, 2016, University of New South Wales

SrCoO3-δ (SCO) has been drawing large attention due to its intriguing topotactic phase transitions and promising applications in cutting-edge technologies. Recent theoretical calculations predict that SCO in thin film form can acquire many interesting electronic and magnetic properties under epitaxial strain and by undergoing phase transitions between perovskite (P) and brownmillerite (BM) phases. Therefore, the material’s phase transitions tuned by both oxygen content and epitaxial strain are of great interest for many potential applications.In this thesis, fully strained SCO thin films were grown on different substrates, i.e. LaAlO3, SrTiO3, DyScO3 and SmScO3 by pulsed laser deposition (PLD). The as-grown thin films were characterized by XRD and AFM. The results show that the out-of-plane lattice constants of SCO thin films decrease almost linearly as the in-plane strain increases; while in in-plane directions the films are fully strained by the substrates. From AFM measurements both BM and P SCO exhibit smooth terraces surface with roughness less than 0.3 nm.The crystallographic phase transitions of the SCO thin films between BM and P phase and the associated oxygen stability were then investigated in a large range of epitaxial strains (-1.2% ~ 3.9%) as a function of temperature, chemical oxidation with NaClO and as a function of time by XRD. It is found at room temperature the oxygen stability for P SCO on different substrates orders as DSO ≈ STO > SSO ≈ LAO, and the oxygen mobility in SCO sequences DSO ≈ SSO > STO ≈ LAO. At high temperature the oxygen stability in SCO on different substrates sequences STO, DSO, LAO and SSO. After that, the oxygen content of SCO on SrTiO3 was modulated locally by NaClO etching and electrical poling. The oxidised BM SCO is found to exhibit distinct morphological changes by forming small nanosized islands with boundaries preferentially in [100] or [010] directions. The conductivity, or oxygen content, of each single island is confined by these textures which can be locally patterned even further with electric poling. In addition, a strain-induced ferromagnetic-to-antiferromagnetic phase transition was observed in SrCoO3−δ films grown on DyScO3, which provide a large tensile epitaxial strain, as compared with ferromagnetic films under lower tensile strain on SrTiO3. Magnetometry results demonstrate the existence of antiferromagnetic spin correlations and neutron diffraction experiments provide a direct evidence for a G-type antiferromagnetic structure with Néel temperatures between TN ∼ 135 ± 10 K and ∼325 ± 10 K, depending on the oxygen content of the samples. Advisors/Committee Members: Seidel, Jan, Materials Science & Engineering, Faculty of Science, UNSW.

Subjects/Keywords: strain; SrCoO3-δ;

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APA (6th Edition):

Hu, S. (2016). Phase Transitions in Strain-Tuned SrCoO3-δ (0<δ≤ 0.5) Thin Films. (Doctoral Dissertation). University of New South Wales. Retrieved from http://handle.unsw.edu.au/1959.4/56958 ; https://unsworks.unsw.edu.au/fapi/datastream/unsworks:42153/SOURCE02?view=true

Chicago Manual of Style (16th Edition):

Hu, Songbai. “Phase Transitions in Strain-Tuned SrCoO3-δ (0<δ≤ 0.5) Thin Films.” 2016. Doctoral Dissertation, University of New South Wales. Accessed February 23, 2019. http://handle.unsw.edu.au/1959.4/56958 ; https://unsworks.unsw.edu.au/fapi/datastream/unsworks:42153/SOURCE02?view=true.

MLA Handbook (7th Edition):

Hu, Songbai. “Phase Transitions in Strain-Tuned SrCoO3-δ (0<δ≤ 0.5) Thin Films.” 2016. Web. 23 Feb 2019.

Vancouver:

Hu S. Phase Transitions in Strain-Tuned SrCoO3-δ (0<δ≤ 0.5) Thin Films. [Internet] [Doctoral dissertation]. University of New South Wales; 2016. [cited 2019 Feb 23]. Available from: http://handle.unsw.edu.au/1959.4/56958 ; https://unsworks.unsw.edu.au/fapi/datastream/unsworks:42153/SOURCE02?view=true.

Council of Science Editors:

Hu S. Phase Transitions in Strain-Tuned SrCoO3-δ (0<δ≤ 0.5) Thin Films. [Doctoral Dissertation]. University of New South Wales; 2016. Available from: http://handle.unsw.edu.au/1959.4/56958 ; https://unsworks.unsw.edu.au/fapi/datastream/unsworks:42153/SOURCE02?view=true


University of New South Wales

2. Heo, Yooun. Exploration of Novel Functional Properties in Ferroelectrics via Scanning Probe Microscopy.

Degree: Materials Science & Engineering, 2016, University of New South Wales

Scanning Probe Microscopy (SPM) has emerged as an essential instrument to probe and characterise materials, correlate local responses spatially, and manipulate and write features directly. With the development of SPM techniques, ferroelectrics at the nanoscale have attracted great interests in the past decade to exploit their novel properties and functionality for a wide range of applications based on photovoltaic, nanoelectronics and micromechanical systems. Of various characterisation tools, SPM techniques are effectively used to probe mechanical and electrical properties in a variety of ferroelectrics. Initially, the mechanical force of AFM tips is used to study and control phase transition behaviour of a multiferroic material, BiFeO3 (BFO). Force-Distance (F-D) spectroscopy is also employed to measure mechanical properties and softening behaviour during phase transformation between T- and R- phase in highly strained BFO thin films grown on LaAlO3 (LAO) substrate. Extraordinary softening behaviour, compared to bulk BFO, is observed in this BFO film. This work is followed in the latter chapter by extending the force based techniques to investigate elastic properties of doped BFO samples. Force-volume mapping technique is used along with single-point F-D curve measurements to reveal statistics of elasticity between undoped, Ca-doped and La-doped BFO thin films. These results reveal tuneable elasticity of BFO thin films as a result of chemical doping. Structural and electronic properties of a ferroelectric BaTiO3-δ are also studied by several techniques of SPM. By an after-growth oxygen cooling process, oxygen deficient barium titanate are characterised by PFM and c-AFM, showing strong correlation between oxygen vacancy and electronic conduction and resistive switching properties. Pulsed-mode current-voltage (I-V) spectroscopy measurements are shown to evaluate fatigue behaviour of resistive switching. These results highlight the use of robust PFM and c-AFM techniques with pulse mode I-V measurements to fully characterise electronic properties and the functionality of oxygen deficient ferroelectric thin films for promising storage memory applications.Extensive studies of electronic properties and conduction at domain walls in tensile strained BFO grown on GdScO3 (GSO) are carried by SPM along with X-ray diffraction (XRD) and Scanning Transmission Electron Microscopy (STEM) analysis. Enhanced domain wall conduction is observed from c-AFM images in comparison to PFM images. Moreover, temperature dependent c-AFM images conclude that the electric transport in the material is thermally activated for phase boundaries between R- and O- phase. STEM observations reveal structurally wide boundaries as a pivotal point for the enhanced conduction at the boundaries. These results open new pathways of using phase boundaries in this system for nanoelectronic applications.Overall, these studies suggest that SPM can provide highly detailed information and a deep insight into novel properties in ferroelectrics, experimentally… Advisors/Committee Members: Seidel, Jan, Materials Science & Engineering, Faculty of Science, UNSW.

Subjects/Keywords: BiFeO3; Ferroelectrics; Scanning Probe Microscopy; BaTiO3

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Heo, Y. (2016). Exploration of Novel Functional Properties in Ferroelectrics via Scanning Probe Microscopy. (Doctoral Dissertation). University of New South Wales. Retrieved from http://handle.unsw.edu.au/1959.4/57108 ; https://unsworks.unsw.edu.au/fapi/datastream/unsworks:42495/SOURCE02?view=true

Chicago Manual of Style (16th Edition):

Heo, Yooun. “Exploration of Novel Functional Properties in Ferroelectrics via Scanning Probe Microscopy.” 2016. Doctoral Dissertation, University of New South Wales. Accessed February 23, 2019. http://handle.unsw.edu.au/1959.4/57108 ; https://unsworks.unsw.edu.au/fapi/datastream/unsworks:42495/SOURCE02?view=true.

MLA Handbook (7th Edition):

Heo, Yooun. “Exploration of Novel Functional Properties in Ferroelectrics via Scanning Probe Microscopy.” 2016. Web. 23 Feb 2019.

Vancouver:

Heo Y. Exploration of Novel Functional Properties in Ferroelectrics via Scanning Probe Microscopy. [Internet] [Doctoral dissertation]. University of New South Wales; 2016. [cited 2019 Feb 23]. Available from: http://handle.unsw.edu.au/1959.4/57108 ; https://unsworks.unsw.edu.au/fapi/datastream/unsworks:42495/SOURCE02?view=true.

Council of Science Editors:

Heo Y. Exploration of Novel Functional Properties in Ferroelectrics via Scanning Probe Microscopy. [Doctoral Dissertation]. University of New South Wales; 2016. Available from: http://handle.unsw.edu.au/1959.4/57108 ; https://unsworks.unsw.edu.au/fapi/datastream/unsworks:42495/SOURCE02?view=true


University of New South Wales

3. Faraji Ouch Hesar, Nastaran. Nanoscale characterization of ZnO, PbTiO3, CH3NH3PbI3 and thin film growth of Cu2OSeO3.

Degree: Materials Science & Engineering, 2018, University of New South Wales

Scanning probe microscopy (SPM) is a method to image and measure on the nanometre and atomic scale which has enabled significant progress in science and engineering. In this thesis this technique was used to study the electrical and piezoelectric properties of different materials. Materials were chosen based on their potential applications in science and technology. Each chapter in this dissertation is allocated to a specific material.ZnO with different structures has seen widespread research interest because of piezoelectricity properties that are used in a wide range of applications. In this dissertation the response of ZnO nano and microstructure platelets in dark and under laser illumination was studied using c-AFM. The results show that the grain boundaries in ZnO platelets are sensitive to light with energy below the band gap. This is due to the defect levels at grain boundaries and photoexcited carriers. The piezoelectric response of ZnO nano and microstructure platelets was studied by the PFM technique. Application of electrical field alters the piezoresponse in individual grains. These observations suggest new pathways for using conducting ZnO in optoelectronics devices which rely on grain and grain boundary engineering.Electrical conduction at domain walls of PbTiO3 (PTO) single crystals was also studied in this dissertation. PTO is a well-known ferroelectric material that has considerable ferroelectric and piezoelectric properties. It has applications in electrical devices like piezoelectric transducers and up to now studies are only focussed on piezoelectric domains for this material. Here, the study is focus on domain wall conductivity conducted by conductive atomic force microscopy (c-AFM). Naturally occurring 180° domains exhibit current flow along the delineating domain wall. The domain wall current flow shows Schottky-like rectifying behaviour.The nanoscale effects of photochemically-active additives on grain boundaries in CH3NH3PbI3 solar cells was studied. Scanning probe microscopy under light illumination, in particular Kelvin probe force microscopy, was applied to study the surface potential changes under laser light illumination. The recently found improvement in efficiency of BQ added solar cells can be clearly seen in vanishing contact potential differences at grain boundaries under illumination, rendering the material more uniform in solar cell operating conditions. Our findings shed light onto halide perovskite materials and functional additive design for improved solar cell performance.IIn addition to SPM measurements on ZnO and PTO, the growth of Cu2OSeO3 thin films is also discussed in this dissertation. The focus was to study the magnetic skyrmion systems in this material. The insulator Cu2OSeO3 has gained interest because of the possibility of electrical control of magnetism in insulator materials, which is energetically more efficient in comparison to metallic systems. Thin films were grown by the pulsed laser deposition (PLD) technique on MgO and NdGaO3 substrates. The grown thin… Advisors/Committee Members: Seidel, Jan, Materials Science & Engineering, Faculty of Science, UNSW.

Subjects/Keywords: Nanoscale; Thin film

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Faraji Ouch Hesar, N. (2018). Nanoscale characterization of ZnO, PbTiO3, CH3NH3PbI3 and thin film growth of Cu2OSeO3. (Doctoral Dissertation). University of New South Wales. Retrieved from http://handle.unsw.edu.au/1959.4/60085

Chicago Manual of Style (16th Edition):

Faraji Ouch Hesar, Nastaran. “Nanoscale characterization of ZnO, PbTiO3, CH3NH3PbI3 and thin film growth of Cu2OSeO3.” 2018. Doctoral Dissertation, University of New South Wales. Accessed February 23, 2019. http://handle.unsw.edu.au/1959.4/60085.

MLA Handbook (7th Edition):

Faraji Ouch Hesar, Nastaran. “Nanoscale characterization of ZnO, PbTiO3, CH3NH3PbI3 and thin film growth of Cu2OSeO3.” 2018. Web. 23 Feb 2019.

Vancouver:

Faraji Ouch Hesar N. Nanoscale characterization of ZnO, PbTiO3, CH3NH3PbI3 and thin film growth of Cu2OSeO3. [Internet] [Doctoral dissertation]. University of New South Wales; 2018. [cited 2019 Feb 23]. Available from: http://handle.unsw.edu.au/1959.4/60085.

Council of Science Editors:

Faraji Ouch Hesar N. Nanoscale characterization of ZnO, PbTiO3, CH3NH3PbI3 and thin film growth of Cu2OSeO3. [Doctoral Dissertation]. University of New South Wales; 2018. Available from: http://handle.unsw.edu.au/1959.4/60085

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