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Smart-City Development Management: Goals and Instruments
KALENYUK, Iryna,TSYMBAL, Liudmyla,UNINETS, Iryna International Journal of Computer ScienceNetwork S 2022 International journal of computer science and netw Vol.22 No.1
At the present stage of the world economic development, a new economic system is being formed, in which non-economic values, in particular environmental and social parameters, have become widespread. A new vision of economic activity is being formed, which acquires the qualities of Smart-economy. The purpose of this paper is reveal the features of managing the development of smart cities as specific entities of the Smart-economy. New functions of economic entities are formed within the framework of the Smart-economy concept, while their role and weight in the localities' activity or formation have changed. Determining that the key trends in the Smart-economy development are such as digitalization, greening, socialization, institutionalization, and urbanization, this is necessary to note that all these trends are most active in the formation of urban ecosystems. These trends are determined by the general population growth and the urban population growth, which requires considerable attention to planning each city's development itself. Such planning could ensure the comfort of living for all its inhabitants, quality, safe, and modern life. The Smart-city's key elements and the intellectualized approach implementation planes to the decision of these or those tasks are definedIt is determined that a new ecosystem of governance is being formed.
Yin, Y. W.,Burton, J. D.,Kim, Y-M.,Borisevich, A. Y.,Pennycook, S. J.,Yang, S. M.,Noh, T. W.,Gruverman, A.,Li, X. G.,Tsymbal, E. Y.,Li, Qi Nature Publishing Group 2013 NATURE MATERIALS Vol.12 No.5
The range of recently discovered phenomena in complex oxide heterostructures, made possible owing to advances in fabrication techniques, promise new functionalities and device concepts. One issue that has received attention is the bistable electrical modulation of conductivity in ferroelectric tunnel junctions (FTJs) in response to a ferroelectric polarization of the tunnelling barrier, a phenomenon known as the tunnelling electroresistance (TER) effect. Ferroelectric tunnel junctions with ferromagnetic electrodes allow ferroelectric control of the tunnelling spin polarization through the magnetoelectric coupling at the ferromagnet/ferroelectric interface. Here we demonstrate a significant enhancement of TER due to a ferroelectrically induced phase transition at a magnetic complex oxide interface. Ferroelectric tunnel junctions consisting of BaTiO<SUB>3</SUB> tunnelling barriers and La<SUB>0.7</SUB>Sr<SUB>0.3</SUB>MnO<SUB>3</SUB> electrodes exhibit a TER enhanced by up to ~ 10,000% by a nanometre-thick La<SUB>0.5</SUB>Ca<SUB>0.5</SUB>MnO<SUB>3</SUB> interlayer inserted at one of the interfaces. The observed phenomenon originates from the metal-to-insulator phase transition in La<SUB>0.5</SUB>Ca<SUB>0.5</SUB>MnO<SUB>3</SUB>, driven by the modulation of carrier density through ferroelectric polarization switching. Electrical, ferroelectric and magnetoresistive measurements combined with first-principles calculations provide evidence for a magnetoelectric origin of the enhanced TER, and indicate the presence of defect-mediated conduction in the FTJs. The effect is robust and may serve as a viable route for electronic and spintronic applications.
Direct observation of a two-dimensional hole gas at oxide interfaces
Lee, H.,Campbell, N.,Lee, J.,Asel, T. J.,Paudel, T. R.,Zhou, H.,Lee, J. W.,Noesges, B.,Seo, J.,Park, B.,Brillson, L. J.,Oh, S. H.,Tsymbal, E. Y.,Rzchowski, M. S.,Eom, C. B. Nature Publishing Group UK 2018 Nature materials Vol.17 No.3
<P>The discovery of a two-dimensional electron gas (2DEG) at the LaAlO3/SrTiO3 interface(1) has resulted in the observation of many properties(2-5) not present in conventional semiconductor heterostructures, and so become a focal point for device applications(6-8). Its counterpart, the two-dimensional hole gas (2DHG), is expected to complement the 2DEG. However, although the 2DEG has been widely observed(9), the 2DHG has proved elusive. Herein we demonstrate a highly mobile 2DHG in epitaxially grown SrTiO3/LaAlO3/SrTiO3 heterostructures. Using electrical transport measurements and in-line electron holography, we provide direct evidence of a 2DHG that coexists with a 2DEG at complementary heterointerfaces in the same structure. First-principles calculations, coherent Bragg rod analysis and depth-resolved cathodoluminescence spectroscopy consistently support our finding that to eliminate ionic point defects is key to realizing a 2DHG. The coexistence of a 2DEG and a 2DHG in a single oxide heterostructure provides a platform for the exciting physics of confined electron-hole systems and for developing applications.</P>
Emergence of room-temperature ferroelectricity at reduced dimensions
Lee, D.,Lu, H.,Gu, Y.,Choi, S.-Y.,Li, S.-D.,Ryu, S.,Paudel, T. R.,Song, K.,Mikheev, E.,Lee, S.,Stemmer, S.,Tenne, D. A.,Oh, S. H.,Tsymbal, E. Y.,Wu, X.,Chen, L.-Q.,Gruverman, A.,Eom, C. B. American Association for the Advancement of Scienc 2015 Science Vol.349 No.6254
<P><B>Thinning films induces ferroelectricity</B></P><P>Thin ferroelectric films are needed in computers and medical devices. However, traditional ferroelectric films typically become less and less polarized the thinner the films become. Instead of using a good ferroelectric and making it thinner, Lee <I>et al.</I> started with SrTiO<SUP>3</SUP>, which in its bulk form is not ferroelectric. This material does have naturally occurring nanosized polarized regions. and when the thickness of the SrTiO<SUB>3</SUB> films reaches the typical size of these regions, the whole film aligns and becomes ferroelectric.</P><P><I>Science</I>, this issue p. 1314</P><P>The enhancement of the functional properties of materials at reduced dimensions is crucial for continuous advancements in nanoelectronic applications. Here, we report that the scale reduction leads to the emergence of an important functional property, ferroelectricity, challenging the long-standing notion that ferroelectricity is inevitably suppressed at the scale of a few nanometers. A combination of theoretical calculations, electrical measurements, and structural analyses provides evidence of room-temperature ferroelectricity in strain-free epitaxial nanometer-thick films of otherwise nonferroelectric strontium titanate (SrTiO<SUB>3</SUB>). We show that electrically induced alignment of naturally existing polar nanoregions is responsible for the appearance of a stable net ferroelectric polarization in these films. This finding can be useful for the development of low-dimensional material systems with enhanced functional properties relevant to emerging nanoelectronic devices.</P>
Multiferroic tunnel junctions and ferroelectric control of magnetic state at interface (invited)
Yin, Y. W.,Raju, M.,Hu, W. J.,Burton, J. D.,Kim, Y.-M.,Borisevich, A. Y.,Pennycook, S. J.,Yang, S. M.,Noh, T. W.,Gruverman, A.,Li, X. G.,Zhang, Z. D.,Tsymbal, E. Y.,Li, Qi American Institute of Physics 2015 Journal of Applied Physics Vol.117 No.17
Direct imaging of the electron liquid at oxide interfaces
Song, Kyung,Ryu, Sangwoo,Lee, Hyungwoo,Paudel, Tula R.,Koch, Christoph T.,Park, Bumsu,Lee, Ja Kyung,Choi, Si-Young,Kim, Young-Min,Kim, Jong Chan,Jeong, Hu Young,Rzchowski, Mark S.,Tsymbal, Evgeny Y.,E Nature Publishing Group UK 2018 Nature nanotechnology Vol.13 No.3
<P>The breaking of symmetry across an oxide heterostructure causes the electronic orbitals to be reconstructed at the interface into energy states that are different from their bulk counterparts(1). The detailed nature of the orbital reconstruction critically affects the spatial confinement and the physical properties of the electrons occupying the interfacial orbitals(2-4). Using an example of two-dimensional electron liquids forming at LaAlO3/SrTiO3 interfaces(5,6) with different crystal symmetry, we show that the selective orbital occupation and spatial quantum confinement of electrons can be resolved with subnanometre resolution using inline electron holography. For the standard (001) interface, the charge density map obtained by inline electron holography shows that the two-dimensional electron liquid is confined to the interface with narrow spatial extension (similar to 1.0 +/- 0.3 nm in the half width). On the other hand, the two-dimensional electron liquid formed at the (111) interface shows a much broader spatial extension (similar to 3.3 +/- 0.3 nm) with the maximum density located similar to 2.4 nm away from the interface, in excellent agreement with density functional theory calculations.</P>
Publisher Correction: Direct imaging of the electron liquid at oxide interfaces
Song, Kyung,Ryu, Sangwoo,Lee, Hyungwoo,Paudel, Tula R.,Koch, Christoph T.,Park, Bumsu,Lee, Ja Kyung,Choi, Si-Young,Kim, Young-Min,Kim, Jong Chan,Jeong, Hu Young,Rzchowski, Mark S.,Tsymbal, Evgeny Y.,E Nature Publishing Group UK 2018 Nature nanotechnology Vol.13 No.7
In the version of this Letter originally published, in two instances in Fig. 1 the layers in the cross-sectional view of the (001) interface were incorrectly labelled: in Fig. 1b SrO<SUP>+</SUP> should have read SrO<SUP>0</SUP>; in Fig. 1c LaO<SUP>+</SUP>, AlO<SUB>2</SUB><SUP>–</SUP>, LaO<SUP>+</SUP>, TiO<SUB>2</SUB><SUP>0</SUP>, SrO<SUP>+</SUP>, TiO<SUB>2</SUB><SUP>0</SUP> should have read LaO<SUB>3</SUB><SUP>3–</SUP>, Al<SUP>3+</SUP>, LaO<SUB>3</SUB><SUP>3–</SUP>, Ti<SUP>4+</SUP>, SrO<SUB>3</SUB><SUP>4–</SUP>, Ti<SUP>4+</SUP>. In Fig. 3c the upper-right equation read –σ<SUB>s</SUB> = –e/2a<SUP>2</SUP> but should have read –σ<SUB>s</SUB> = e/2a<SUP>2</SUP> and in Fig. 3f the lower-right equation read –σ<SUB>s</SUB> = –e/2√3a<SUP>2</SUP> but should have read σ<SUB>s</SUB> = –e/2√3a<SUP>2</SUP>. These errors have now been corrected in the online version of the Letter.
Isostructural metal-insulator transition in VO<sub>2</sub>
Lee, D.,Chung, B.,Shi, Y.,Kim, G.-Y.,Campbell, N.,Xue, F.,Song, K.,Choi, S.-Y.,Podkaminer, J. P.,Kim, T. H.,Ryan, P. J.,Kim, J.-W.,Paudel, T. R.,Kang, J.-H.,Spinuzzi, J. W.,Tenne, D. A.,Tsymbal, E. Y. American Association for the Advancement of Scienc 2018 Science Vol.362 No.6418
<P><B>Separating structure and electrons in VO<SUB>2</SUB></B></P><P>Above 341 kelvin—not far from room temperature—bulk vanadium dioxide (VO<SUB>2</SUB>) is a metal. But as soon as the material is cooled below 341 kelvin, VO<SUB>2</SUB> turns into an insulator and, at the same time, changes its crystal structure from rutile to monoclinic. Lee <I>et al.</I> studied the peculiar behavior of a heterostructure consisting of a layer of VO<SUB>2</SUB> placed underneath a layer of the same material that has a bit less oxygen. In the VO<SUB>2</SUB> layer, the structural transition occurred at a higher temperature than the metal-insulator transition. In between those two temperatures, VO<SUB>2</SUB> was a metal with a monoclinic structure—a combination that does not occur in the absence of the adjoining oxygen-poor layer.</P><P><I>Science</I>, this issue p. 1037</P><P>The metal-insulator transition in correlated materials is usually coupled to a symmetry-lowering structural phase transition. This coupling not only complicates the understanding of the basic mechanism of this phenomenon but also limits the speed and endurance of prospective electronic devices. We demonstrate an isostructural, purely electronically driven metal-insulator transition in epitaxial heterostructures of an archetypal correlated material, vanadium dioxide. A combination of thin-film synthesis, structural and electrical characterizations, and theoretical modeling reveals that an interface interaction suppresses the electronic correlations without changing the crystal structure in this otherwise correlated insulator. This interaction stabilizes a nonequilibrium metallic phase and leads to an isostructural metal-insulator transition. This discovery will provide insights into phase transitions of correlated materials and may aid the design of device functionalities.</P>