Download or read book Epitaxial Thin Films and Heterojunctions of Electron Doped Manganite La1 Xhfxmno3 written by Libin Jin and published by . This book was released on 2017-01-26 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Epitaxial Thin Films and Heterojunctions of Electron Doped Manganite La1-xHfxMnO3" by Libin, Jin, 靳立彬, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled EPITAXIAL THIN FILMS AND HETEROJUNCTIONS OF ELECTRON DOPED MANGANITE La Hf MnO 1-x x 3 Submitted by Jin Libin For the Degree of Master of Philosophy at The University of Hong Kong in October 2015 The strong electron correlated system like perovskite oxides in transition metal oxides have been studied for many years. Most efforts have been focused mainly 3+ 4+ on the hole-doped manganites with Mn /Mn double exchange interaction. Recently, the tetravalent ions doping has attracted considerable attention to make electron doping LaMnO compounds. Such electron-doped manganites may be applied for fabrication of all-manganites devices potentially. The sensitivities to magnetic fields, currents, electric fields, photo illumination and mechanical strain make the electron-doped manganites of great interests for relevant applications. In this thesis, thin films and heterojunctions of tetravalent hafnium doped perovskite manganite La Hf MnO were fabricated. The hafnium shows a 1-x x 3 unique tetravalent state as well as an ion radius closed to trivalent lanthanum ion. These properties make the investigation on La Hf MnO system relatively 1-x x 3 simple and reliable. The structural and physical properties of La Hf MnO (x=0.1, 0.2, 0.3) thin 1-x x 3 films were studied systematically. The crystal structure and epitaxy of La 1- Hf MnO thin films were examined by X-ray diffraction. The temperature x x 3 dependent resistance and magnetization of different samples were investigated in detail. Both temperature dependent resistance and field dependent magnetization indicated the evident transition between paramagnetic and ferromagnetic states. The electronic structures of epitaxial La Hf MnO were measured by X-ray 0.9 0.1 3 Photoelectron Spectroscopy. Both spectrum of Mn 3s and Mn 2p demonstrated 2+ 3+ the composition of Mn /Mn ions. Such evidence strongly suggested the electron-conductive mechanism in La Hf MnO systems. 0.9 0.1 3 The heterojunctions composed of oxygen-deficient SrTiO and 3-δ La Hf MnO thin films have been studied. These heterojunctions demonstrate 0.9 0.1 3 good rectifying characteristics with very low leakage current and high breakdown voltage in a wide temperature range. X-ray diffraction and electron backscattering diffraction measurements reveal that both SrTiO and La Hf MnO layers 3-δ 0.9 0.1 3 have single crystal nature and [001]-orientation. Transmission electron microscope images show an excellent epitaxial growth of SrTiO and 3-δ La Hf MnO layers. Such all-oxides junctions utilizing the bi-layer 0.9 0.1 3 heterostructure may be applied in microelectronic devices. The n-i-p heterojunctions have been fabricated by depositing an n-type La Hf MnO layer on p-type Si with a thin SrTiO intermediate layer. These 0.9 0.1 3 3 junctions exhibit excellent rectifying properties for temperature from 20 K to 300 K. Under illumination of 630 nm light a remarkable photocurrent has been observed. The photosensitivity is over 1200% under -3 V bias and illumination of the light at room temperature, demonstrating very a pronounced photocurrent effect. The injection of photo-carriers could be responsible for the observed phenomenon. The obtained results in this thesis demonstrate the electron-conductive mechanism in La Hf MnO system. The La Hf MnO based heterojunctions 1-x x 3 0.9 0.1 3 show remarkable characteristics and may

Download or read book Epitaxial Thin Films and Heterojunctions of Electron Doped Manganite La1 xHfxMnO3 written by 靳立彬 and published by . This book was released on 2015 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Preparation and Properties of Epitaxial Thin Films of La1 Xbaxmn03 on Various Substrated written by Ngai-Shek Soong and published by Open Dissertation Press. This book was released on 2017-01-26 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Preparation and Properties of Epitaxial Thin Films of La1-xBaxMn03 on Various Substrated" by Ngai-shek, Soong, 宋毅碩, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled PREPARATION AND PROPERTIES OF EPITAXIAL THIN FILMS OF La Ba MnO ON VARIOUS SUBSTRATES 1-x x 3 submitted by Ngai-Shek SOONG for the degree of Master of Philosophy at The University of Hong Kong in December 2002 Epitaxial thin films of La Ba MnO (LBMO) were on deposited SrTiO 0.8 0.2 3 3 (100) (STO), LaAlO (100) (LAO), MgO (100) and Y O - ZrO (100) (YSZ) 3 2 3 2 substrates by using an off-axis magnetron sputtering. The properties of fabricated LBMO thin films were studied by using X-ray diffraction, dc four-probe measurements, surface profiler and atomic force microscopy. For LBMO thin films grown on STO, X-ray diffraction patterns showed that the films were highly c-axis oriented and fully epitaxial. The obtained values of full width at half maximum (FWHM) of the (002) rocking curves were small, indicating good crystallinity of the films. The temperature of insulator-metal transition, T, decreased as the thickness of the thin film increased. This was different from other systems with similar perovskite structure such as La Ca MnO and La Sr MnO . The electrical 1-x x 3 1-x x 3 resistivity of LBMO/STO thin film for temperature T2 4.5 expression of ρ(T) =ρ +ρ T +ρ T (Eq.1). The values of ρ ρ ρ all increased 0 2 4.5 0, 2, 4.5 with increasing thickness d, except d=350A, implying a phase transition may have occured. The anomalous electrical behavior of LBMO/STO system could not be explained by considering only the decreasing of transfer integral on in-plane e electrons. The orbital degree of freedom played a crucial role in determining the electrical properties of tensile-stressed LBMO thin films due to the relatively large ratio of c/a. For LBMO/LAO thin films, X-ray diffraction patterns and small FWHM values implied good crystallinity of the thin films. The decreasing value of out-of- plane lattice parameters with increasing thickness suggested the existence of compressive strain within the LBMO/LAO system. The temperature dependence of resistivity measurement showed that T decreases as the thickness of thin film increased. This is consistent with the double-exchange theory, which states that compressive strain enhances T . The temperature dependence of resistivity of LBMO/LAO thin films were also fitted well to expression (Eq.1), The values of ρ 0, ρ ρ all increased with increased thickness. 2, 4.5 La Ba MnO was also deposited on YSZ or MgO substrates respectively, 0.8 0.2 3 which having larger lattice mismatch. Peaks other than (00l) orientation were observed in X-ray measurements indicating the thin films were c-axis oriented but not highly epitaxial. A fairly large value of the FWHM of the (002) diffraction peak suggested that the films were highly crystalline. Insulator-metal (I-M) transition were not observed in LBMO/MgO films and only appear in LBMO/YSZ films with d>1200A. These were mainly due to that large lattice mismatches between LBMO and YSZ or MgO substrates which generate a large number of grains and grain boundaries in the thin films, which in turn decrease the electron transfer integral. DOI: 10.5353/th_b2663683 Subjects: Thin films Epitaxy