Semiconductor-metal Transition in Epitaxial VO_2 Thin Films on TiO_2 (100) Considering a Phase Equilibrium PDF Download
Are you looking for read ebook online? Search for your book and save it on your Kindle device, PC, phones or tablets. Download Semiconductor-metal Transition in Epitaxial VO_2 Thin Films on TiO_2 (100) Considering a Phase Equilibrium PDF full book. Access full book title Semiconductor-metal Transition in Epitaxial VO_2 Thin Films on TiO_2 (100) Considering a Phase Equilibrium by Xing Zhong. Download full books in PDF and EPUB format.
Author: Xing Zhong Publisher: ISBN: Category : Electronic dissertations Languages : en Pages : 133
Book Description
Vanadium dioxide (VO_2), standing out from the thermochromic vanadium oxide family (VO, V_2 O_3,V_2 O_5,VO_2), is intensively studied for its abrupt and reversible semiconductormetal transition (SMT) that happens slightly above room temperature (T_c 340 K). Interestingly, the transition can be triggered not only by temperature change, but also by many other forms of excitations, e.g. infrared irradiation, external strain, and applied voltage. The underlying mechanism of the transition is still in debate, and a model to describe the transport properties near T_c is needed for utilizing this material. Recent studies have revealed that near the transition, there is a phase coexistence between the semiconducting monoclinic phase and the metallic rutile phase in this material. In this presentation, the growth of epitaxial VO_2 thin films on TiO_2 substrates by chemical vapor deposition and the characterizations of their structural and electrical properties will be discussed. Detailed studies on DC resistivity, current-voltage characteristics and impedance spectroscopy of deposited films at various ambient temperatures have been performed. By considering the ensemble average of the transport properties of VO_2 films near T_c as a superposition of the transport properties of the two phases, and assuming a distribution of transition temperatures across the whole film, we have derived parameterized models to fit the temperature dependence of both resistivity and impedance of VO_2 thin films in the vicinity of SMT. Voltage triggered breakdown in micron-scale two-terminal planar VO_2 devices has been tested and modeled. An avalanching-like breakdown mechanism is elicited by considering a competition between Joule heating and heat dissipation, that could explain the faster-than-expected transition observed in this kind of devices. To further study the physics of SMT, the design and implementation of a cross-spectrum analyzer for measuring VO_2 transport noise near T_c will be demonstrated. Our preliminary results reveal a significant increase in the noise power spectral density near the transition, possibly induced by the metastability of current percolation.
Author: Xing Zhong Publisher: ISBN: Category : Electronic dissertations Languages : en Pages : 133
Book Description
Vanadium dioxide (VO_2), standing out from the thermochromic vanadium oxide family (VO, V_2 O_3,V_2 O_5,VO_2), is intensively studied for its abrupt and reversible semiconductormetal transition (SMT) that happens slightly above room temperature (T_c 340 K). Interestingly, the transition can be triggered not only by temperature change, but also by many other forms of excitations, e.g. infrared irradiation, external strain, and applied voltage. The underlying mechanism of the transition is still in debate, and a model to describe the transport properties near T_c is needed for utilizing this material. Recent studies have revealed that near the transition, there is a phase coexistence between the semiconducting monoclinic phase and the metallic rutile phase in this material. In this presentation, the growth of epitaxial VO_2 thin films on TiO_2 substrates by chemical vapor deposition and the characterizations of their structural and electrical properties will be discussed. Detailed studies on DC resistivity, current-voltage characteristics and impedance spectroscopy of deposited films at various ambient temperatures have been performed. By considering the ensemble average of the transport properties of VO_2 films near T_c as a superposition of the transport properties of the two phases, and assuming a distribution of transition temperatures across the whole film, we have derived parameterized models to fit the temperature dependence of both resistivity and impedance of VO_2 thin films in the vicinity of SMT. Voltage triggered breakdown in micron-scale two-terminal planar VO_2 devices has been tested and modeled. An avalanching-like breakdown mechanism is elicited by considering a competition between Joule heating and heat dissipation, that could explain the faster-than-expected transition observed in this kind of devices. To further study the physics of SMT, the design and implementation of a cross-spectrum analyzer for measuring VO_2 transport noise near T_c will be demonstrated. Our preliminary results reveal a significant increase in the noise power spectral density near the transition, possibly induced by the metastability of current percolation.
Author: Publisher: ISBN: Category : Aeronautics Languages : en Pages : 1040
Book Description
Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
Author: Shriram Ramanathan Publisher: Springer Science & Business Media ISBN: 1441906649 Category : Technology & Engineering Languages : en Pages : 344
Book Description
Thin Film Metal-Oxides provides a representative account of the fundamental structure-property relations in oxide thin films. Functional properties of thin film oxides are discussed in the context of applications in emerging electronics and renewable energy technologies. Readers will find a detailed description of deposition and characterization of metal oxide thin films, theoretical treatment of select properties and their functional performance in solid state devices, from leading researchers. Scientists and engineers involved with oxide semiconductors, electronic materials and alternative energy will find Thin Film Metal-Oxides a useful reference.
Author: Ngai-Shek Soong Publisher: Open Dissertation Press ISBN: 9781361192412 Category : Languages : en Pages :
Book Description
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
Author: Scott Eric Madaras Publisher: ISBN: Category : Thin films Languages : en Pages : 146
Book Description
Vanadium Dioxide (VO2) is a strongly correlated material which has been studied for many decades. VO2 has been proposed for uses in technologies such as optical modulators, IR modulators, optical switches and Mott memory devices. These technologies are taking advantage of VO2’s insulator to metal transition (IMT) and the corresponding changes to the optical and material properties. The insulator to metal transition in VO2 can be accessed by thermal heating, applied electric field, or ultra-fast photo induced processes. Recently, thin films of VO2 grown on Titanium Dioxide doped with Niobium (TiO2:Nb), have shown promise as a possible UV photo detector with high quantum efficiency which utilizes a heterostructure between these two materials. In this work, the dynamics of the IMT on thin films of VO2 is explored. We show that surface plasmons generated in an Au thin film can induce the insulator to metal transition in a thin film of VO2 due to the enhanced electric field as well as help detect the IMT via changes in its resonance condition. Time resolved pump probe studies were also done on thin films of VO2 grown on TiO2 and TiO2:Nb, using UV photon energy of 3.1 eV (400nm wavelength). The fluence threshold of the IMT at 3.1 eV was significantly lower than published values for the 1.55 eV pump fluence. The time response of the IMT shows uncommon reflectivity dynamics in these samples. The response was partially attributed to internal interference of the reflected probe beam from the inhomogeneous layers formed inside the film by different phases of VO2, and can be elucidated by a diffusion model with respect to its optical properties. Finally, the photocurrent generation time constants for the sample with highest quantum efficiency are given and compared to its ultrafast photo induced IMT time constants.
Author: James S. Speck Publisher: ISBN: Category : Science Languages : en Pages : 588
Book Description
Our understanding and control of epitaxial oxide heterostructures has progressed along multiple frontiers including magnetic, dielectric, ferroelectric, and superconducting oxide materials. This has resulted in both independent rediscovery and the successful borrowing of ideas from ceramic science, solid-state physics, and semiconductor epitaxy. A new field of materials science has emerged which aims at the use of the intrinsic properties of various oxide materials in single-crystal thin-film form. Exploiting the potential of these materials, however, will only be possible if many fundamental and engineering questions can be answered. This book represents continued progress toward fulfilling that promise. Technical information on epitaxial oxide thin films from industry, academia and government laboratories is presented. Topics include: dielectrics; ferroelectrics; optics; superconductors; magnetics; magnetoresistance.
Author: Xing Zhong
Author: Xing Zhong
Author: 
Author: Roya Molaei
Author: 
Author: Shriram Ramanathan
Author: Ngai-Shek Soong
Author: Lin Yang
Author: Scott Eric Madaras
Author: James S. Speck
Author: Joyeeta Nag