MFM-8 Itamambuca, Brazil November 10-14, 2013

Transcription

1 The Eighth Multifunctional Materials Workshop (MFM-8) MFM-8 Itamambuca, Brazil November 10-14, 2013 Meeting Program & Abstract Book

2 Thank you to our MFM-8 Sponsors: 2

3 MFM-8 is the eighth in a series of pioneering materials and device research forums. It follows the previous seven meetings held in Pucon Chile, Bariloche Argentina, Huatulco Mexico, Copper Canyon Mexico, Kodiak Island, and Gamboa Panama. The format of the meeting promotes interaction among leading groups around the world in the emerging field of multifunctional electronic materials. Through targeted invitations and a time-tested format that promotes discussion, the workshop will explore cutting-edge ideas, and enable international collaboration for the advancement of multifunctional materials and devices. MFM-8 will enable interaction between researchers from industry, government, and academia in more than 10 countries, to address the current issues, research, and future approaches to multifunctional materials technology. Multifunctional materials have an enormous potential impact to enable new device functionalities through coupling of material properties, as well as increasing current technology performance, reliability and flexibility, while decreasing cost, size, and power. Foreseeable applications include tunable passive elements, tunable sensors, multifunctional photonic/electronic elements, spin electronics, quantum devices, etc. Multifunctional oxide materials promise novel and flexible device designs that incorporate ferroelectric, piezo-electric, magneto-electric, superconducting, semi-magnetic and non-linear optical functions. Major challenges in realizing the potential of multifunctional oxide systems include understanding property coupling, the controlled growth of materials and design of hetero-structures to enable effective and tunable coupling, and device design and manufacturability to realize the potential of these materials in both military and civilian applications. This workshop will challenge participants to generate innovative ideas for the synthesis of oxide materials and engineered oxide hetero-structures, the coupling of functional oxide properties, next-generation applications for the engineered materials, and manufacturability and device design to utilize coupled oxide properties in next-generation multifunctional systems. Through the unifying theme of functional oxides, the workshop will bring together communities that do not ordinary interact in national and international conferences. 3

4 While multi-ferroic oxides will be represented, the emphasis will be placed on engineered synergies through hetero-structures or composites. Invited participants will present both experimental and theoretical backgrounds and will include experts in complex oxide and oxide hetero-structure growth and characterization, functional oxide properties and property coupling (including techniques for characterization of coupling, with emphasis on figures of merit. Special target areas will include tunable device and circuit applications, properties of defects and defect enabled functionality, hetero-ferroic materials and applications, and interactive coupling of both bulk and thin film materials and hetero-structures. Workshop Co-Chairmen Dr. Leszek Malkinski, University of New Orleans, USA Dr. Antonio Ferreira, University of Sao Paulo, Brazil Workshop Organizer: Dr. Colin Wood 4

5 Sunday, Nov. 10th 6:00pm - 10:00 pm Registration 6:30 pm - 10:00 pm Informal reception with refreshments 5

6 Monday, Nov. 11th Breakfast: 7:30 9:00 9:00-9:20 Welcome & Orientation - Leszek Malkinski, Antonio Ferriera and Colin Wood SESSION 1: CHAIR: GAIL BROWN 9:20-9:50 Jeremy Levy :Room-Temperature Electronically-Controlled Ferromagnetism at the LaAlO 3 /SrTiO 3 Interface 9:50-10:15 Zebignew Celinsky: On-wafer Microwave Devices Based on Magnetic Oxides 10:15-10:40 Denis David: Applications of Fluorine-doped Tin Oxide to photovoltaic cells and magnetic devices Break: 10:40-11:00 SESSION 2 : CHAIR: JOSE FERNANDO CHUBACI 11:00-11:30 Mark Rzchowski: New Multifunctionalities at Complex Oxide Heterointerfaces 11:30-11:55 Knut Peters: Fabulite Gemstone or Oxide electronics substrate? 11:55-12:20 Ravi Droopad: Structure and Properties of Crystalline oxide on Compound Semiconductors Lunch: 12:20-2:00 SESSION 3: CHAIR: HAROLD HWANG 2:00-2:30 Charles Ahn: Interfacial multifunctional oxide structures 2:30 2:55 Leszek Malkinski: New sacrificial layers for fabrications of free-standing multifunctional structures 2:55 3:20 Franz Justa: TBA Break: 3:20 Informal Networking Dinner: 7:00 6

7 Tuesday, Nov. 12th Breakfast: 7:30 9:00 Schooner boat event/networking and Discussions Dinner: 7: 00 7

8 Wednesday, Nov. 13th Breakfast: 7:30 9:00 SESSION 4: CHAIR: BYOUNGHAK LEE 9:00-9:30 Juan Salafranca: Insulating ferromagnetic LaCoO 3-δ films: a new functionality induced by ordered oxygen vacancies 9:30-9:55 Antonio Ferreira da Silva: Properties of Oxide and Nitride Films Deposited by Ion Beam Assisted Method Break: 10:20 10:50 SESSION 5 : CHAIR: ROBERT STAMPS 10:50-11:20 Robert Stamps: Dynamic Probes of Low Symmetry Interactions and Spin Textures 11:20-11:45 Gail Brown: Transmission Electron Microscopy Studies on Oxide Interfaces 11:45-12:10 Jose Fernando Chubaci: Ionizing radiation sensitive oxides thin films Lunch: 12:10-2:00 SESSION 6: CHAIR: Herman Kohlstedt 2:00-2:30 Byounghak Lee: Theory of Rashba interactions in perovskite oxides 2:30-2:55 Claus Schneider: TBA 3:00 Excursion 2 Dinner: 7:00 8

9 Thursday, Nov. 14th Breakfast: 7:30 9:00 SESSION 7: CHAIR: JUAN SALAFRANCA 9:00-9:30 Herman Kohlstedt : Digging Deep: A modified Total Electron Yield to Study Buried Material Properties in Oxide Devices by Soft X -Ray Absorption Spectroscopy 9:30-9:55 Federico Rosei: Multifunctional materials for electronics and photonics 9:55-10:20 Ruud Steenwelle: All-oxide piezo electric MEMS by pulsed laser deposition 10:20-10:50 Break SESSION 8 : CHAIR: JEREMY LEVY 10:50-11:20 Clas Persson: Nanostructured ZnO-X alloys with tailored properties for optoelectronics 11:20-11:45 Harold Hwang: Terahertz Responses in Oxides: Nonlinear effects and engineered structures 11:45-12:00 Best Speaker Award and Farewell 12:15 Lunch Coach to Hotel near GRU and GRU airport will leave early afternoon to allow participants to catch late evening flights, or stay overnight in local hotel for flights leaving on the 15th 9

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11 Room-Temperature Electronically-Controlled Ferromagnetism at the LaAlO 3 /SrTiO 3 Interface Feng Bi, 1 Mengchen Huang, 1 Chung-Wung Bark, 2 Sangwoo Ryu, 2 Chang-Beom Eom, 2 Patrick Irvin 1 and Jeremy Levy 1,* 1 Dept. of Physics & Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania, 15260, USA. 2 Dept. of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin, 53706, USA. *Correspondence to: jlevy@pitt.edu Reports of emergent conductivity, superconductivity, and magnetism at oxide interfaces have helped to fuel intense interest in their rich physics and technological potential. Here we employ magnetic force microscopy to search for room-temperature magnetism in the wellstudied LaAlO 3 /SrTiO 3 system. Using electrical top gating to deplete electrons from the oxide interface, we directly observe an in-plane ferromagnetic phase with sharply defined domain walls. Itinerant electrons, introduced by a top gate, align antiferromagnetically with the magnetization, at first screening and then destabilizing it as the conductive state is reached. Subsequent depletion of electrons results in a new, uncorrelated magnetic pattern. This newfound control over emergent magnetism at the interface between two non-magnetic oxides portends a number of important technological applications. 11

12 On-wafer Microwave Devices Based on Magnetic Oxides Z. Celinski Center for Magnetism and Magnetic Nanostructures, University of Colorado Colorado Springs, 1420 Austin Bluffs Parkway, Colorado Springs, CO We present a series of microwave devices that utilize magnetic oxides. In the first part of the talk, we will describe the properties of Ba hexagonal ferrites grown on a Pt/Si wafer using a metal-organic decomposition technique. We will show how Al doped hexagonal ferrites can be combined with ferroelectric materials such as strontium bismuth tantalite or PZT and briefly describe the properties of such heterostructures. Finally, we will demonstrate the properties of an on-wafer notch filter utilizing the Ba hexagonal ferrite. In the second part, I will present the properties of some liquid crystal based on-wafer microwave devices such as true time delay lines or band pass filters. We have demonstrated the operation of these devices up to 110 GHz. I will discuss how device performance can be improved by the use of liquid crystal/magnetic oxide nanorod colloids; specifically, how these colloids enable higher speed switching and control. 12

13 Applications of Fluorine-doped Tin Oxide to photovoltaic cells and magnetic devices D. G. F. David, M. V. Santos da Silva, J. da Cruz Cerqueira, T. Souza da Silva, T. Neres dos Santos, J. de Souza Sampaio, J. S. de Almeida, R. A. Bittencourt, A. Ferreira da Silva. Instituto de Física, Universidade Federal da Bahia, Salvador, BA, , Brazil Thin films of Fluorine-doped Tin Oxide (FTO) have been considered for various applications as transparent conductive windows and sensors, and have been both experimentally and theoretically studied. Various methods of fabrication have been developed such as sputtering, laser ablation, IBAD, thermal evaporation, CVD, sol-gel and spray pyrolysis. This work is aimed at the fabrication and the characterization of FTO films obtained by spray pyrolysis (0.5 to 0.8 m thick), with applications to photovoltaic cells and magnetic devices. Experimental results are compared with first principles calculations. For the first application, we developed the deposition of copper indium diselenide (CIS) films by electro-deposition (1.5 m thick) on FTO films as a solar radiation absorber. The hetero-junction formed by these two films does not work well, perhaps due to band alignment mismatch, and an attempt is made now to form another junction by inserting an InSe film between them. Experimental results will be discussed. The possibility of creating magnetization in tin oxide films produced by the sol-gel technique and co-doped by Fe + Ni was recently demonstrated (G. Korotcentkov and Sang Do Han, Mat. Chem. Phys ). First principles calculations made in our laboratory showed that it would be possible to obtain a spin polarization when the doping Ni atoms are coupled with oxygen vacancies. For this application, we are checking the possibility to manufacture Nickel-doped SnO 2 films in order to verify if it possible to get some spin polarization. In this project, we will modify the solution of precursors in our spray pyrolysis system. 13

14 The 2D Electron Gas at Complex Oxide Heterointerfaces* M.S. Rzchowski, Physics Department, University of Wisconsin-Madison Since the discovery of conductivity at the (001) interface between the band insulators SrTiO 3 and LaAlO 3, extensive research has explored the structural and electronic characteristics of this and similar complex oxide heterointerfaces. One of the most intriguing aspects involves how this conducting medium interacts with the underlying complexities of the oxide materials, and also with the new electronic and structural configurations provided by the interface itself. The (111) interface of LaAlO 3 / SrTiO 3, provides an additional array of electronic and structural landscapes, where for instance details of the electronic band structure lead to predictions of topologically protected states. We discuss transport measurements, structural characterizations, and theoretical calculations of the 2DEG at (111) interfaces, and speculate on future applications. *Work done in collaboration with T. Hernandez, D.J. Felker, J. Irwin, M. Sayanagi, S. Ryu, E.Y. Tsymbal, D.D. Fong, H. Zhou, C.B. Eom. Work supported by National Science Foundation DMREF , NEB , FRG

15 Fabulite Gemstone or Oxide electronics substrate? Knut Peters CrysTec GmbH SrTiO3 is one of the most popular substrate materials for epitaxial thin film growth in many research area of oxide electronics. Based on long term experience with it s origin as main substrate for high temperature superconductor development and with respect to the superior property of the TiO2 surface termination it will often be the desired substrate material. This presentation gives an overview about light and shadow of that material starting from growth technique, limitations in size, crystalline perfection, homogeneity and purity. Alternative substrates will be demonstrated. Furthermore the process of TiO2 termination will be explained in detail. Defect pattern of incomplete TiO2 termination will be discussed 15

16 Structure and Properties of Crystalline oxide on Compound Semiconductors R. Droopad 1, R. Contreras-Guerrero 1, B. L. Lee 1, Q. Qiao 2, R. F. Klie 2, J. Veazey 3, J. Levy 3 1 Ingram School of Engineering, Texas State University, San Marcos, TX Dept. of Physics, University of Illinois Chicago, Chicago, IL Dept. Of Physics, University of Pittsburgh, PA Compound semiconductors are fast becoming important in CMOS devices as the semiconductor industry is investigating their use as high mobility channels to enable low power operations. To reduce operating power, it has also been proposed that a ferroelectric layer as part of a gate dielectric stack can provide a means of reducing the gate voltage for turning on a transistor and reducing the sub-threshold swing below the classical limit of 60mV/decade. A ferroelectric layers on a compound semiconductor can also be used as a single transistor memory element and as a means of designing reconfigurable logic devices. These applications would only be possible if a single crystal oxide layer can be deposited on semiconductors with a low density of defect states that does not affect transistor operations. In this presentation we will discuss the interface between a ferroelectric BaTiO 3 and GaAs in terms of the bonding chemistry and oxide properties. This work is supported by the AFOSR under Grant # FA

17 Interfacial coupling in oxide materials Charles Ahn Yale University, Princeton, NJ USA Complex oxide materials exhibit a strong interplay between spin, charge, and lattice effects. This coupling leads to a variety of novel properties, including colossal magnetoresistance and a range of electron transport behavior. The possibility of integrating these different kinds behavior with other types of functionalities has motivated the development of new, artificially structured complex oxide-based materials systems. In some cases, the atomicscale interface of these structures can dominate the observed behavior, with new physical properties emerging. 17

18 New sacrificial layers for fabrications of free-standing multifunctional structures Leszek M. Malkinski University of New Orleans, Advanced Materials Research Institute Built-in stresses between layers in multilayered films can be used to design complex 3- dimensional microstructures and nanostructures using origami techniques. Film patterns deposited on a sacrificial layer tend to bend, twist or fold when the sacrificial layer is selectively etched or dissolved. Deformation of the patterns released from the sacrificial layer alters their magnetic, electronic and optical properties. Sacrificial layer must have distinctly different properties from the structure built on top it and from the substrate, so that the highly selective etching of the sacrificial layer will leave the structure and the substrate almost unaffected. In addition to the selective etching the sacrificial layer determines the growth of the structure. Sacrificial layers of organic materials can be deposited from the liquid phase by spin-coating, whereas various physical deposition techniques can be used to deposit single crystal or polycrystalline inorganic sacrificial layers. We have successfully fabricated microtubes of multifunctional magnetic-piezoelectric multilayes on sacrificial layers of photoresist and on polycrystalline Cu films. We have recently studied new sacrificial layers. NaCl films were frown by e-beam evaporation on MgO substrates at 350 o C. Subsequently, various transition metal heteroepiaxial multilayers (Cr, Fe, Au) were deposited at the same temperature. Spin coating and sputtering were used to deposit sacrificial layers of glucose. The advantage of both types of layers is that they are soluble in water and they are both ecofriendly and bio-compatible. Therefore, structures grown on salt or sugar have great potential for applications in biotechnology and medicine. The process of release of structures form the substrate frequently requires removal of the structures form the chamber using acetone or Cuetchant to fabricate structure. Recently, we have proposed to use Zn films as a sacrificial layer. Interesting feature of Zn is that is sublimates in vacuum chamber at the temperature of about 250 o C. Both NaCl and Zn layers enable growth of either polycrystalline films or heteroepiaxial multifunctional structures on top of them. 18

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20 Insulating ferromagnetic LaCoO 3-δ films: a new functionality induced by order oxygen vacancies Juan Salafranca 1,2,*, Neven Biškup 1,2, Virat Mehta 3,4, Yuri Suzuki 3,4,5, Stephen J. Pennycook 2,6, Sokrates T. Pantelides 6,7,2 and Maria Varela 2,1 1 Departamento de Física Aplicada III, Universidad Complutense de Madrid, Spain. 2 Materials Science and Technology Division, Oak Ridge Nationally Laboratory, USA. 3 Department of Material Science and Engineering, University of California, USA. 4 Materials Sciences Division, Lawrence Berkeley National Laboratory, USA. 5 Deptartment of Applied Phys. & Geballe Lab. for Advanced Materials, Stanford University, USA. 6 Department of Physics and Astronomy, Vanderbilt University, USA. 7 Department of Electrical Engineering and Computer Science, Vanderbilt University, USA. *Correspondence to: jsalafra@ucm.es Exploring phase transitions generated through defect ordering constitutes a new avenue towards finding novel physical phenomena and new functionalities in transition metal oxides. Ordered defects may not only enhance or suppress existing properties, but also lead to collective states absent in the perfect crystallographic phase, or in samples with randomly distributed defects. Along these lines, the origin of ferromagnetism in strained epitaxial LaCoO 3 films has been a long-standing mystery. By combining atomically-resolved Z- contrast imaging, electron-energy-loss spectroscopy and density-functional calculations, we demonstrate that, in epitaxial LaCoO 3 films, oxygen vacancy superstructures release strain, control the film s electronic properties, and give rise to ferromagnetism via the excess electrons in the Co d-states.. Although oxygen vacancies typically electron dope a material, ordered vacancies induce Peierls-like minigaps which, after strain-accommodating lattice and magnetic relaxation, lead to a band structure radically different from the bulk material, which is indeed insulating. Figure: High resolution Z-contrast image of a LaCoO 3-δ film on SrTiO 3 showing the O vacancy superlattice. Inset (light green): 3D model according to DFT calculations. Co ions are represented by dark blue spheres, O ions by red spheres. Distorted tetrahedra (blue polyhedra), and bulk-like octahedra (red) indicate different Co environments. Large green arrows denote the spin direction for the high spin Co. Acknowledgments: U.S. Department of Energy (DOE), Basic Energy Sciences (BES), Materials Sciences and Engineering Division, ORNL s Shared Research Equipment (ShaRE) User Program (DOE-BES); ERC starting Investigator Award, grant # STEMOX and Fundación Caja de Madrid; Juan de la Cierva Program, JCI ; Director, Office of Science, Office of BES, Materials Sciences and Engineering Division (Contract Numbers DE-AC02-05CH11231 and DE- SC ); U.S DOE grant DE-FG02-09ER46554 and the McMinn Endowment; NERSC (DOE, contract no. DE-AC02-05CH11231). 20

21 Properties of Oxide and Nitride Films Deposited by Ion Beam Assisted Method A.Ferreira da Silva 1, H. Jonas da Costa 1, M.V.S. da Silva 1, D.G.F. David 1, J.F.D. Chubaci 2, M. Matsuoka 2, J.A. Freitas, Jr. 3, J.G. Tischler 3, G. Baldissera 4 and C. Persson 4,5 1 Institute of Physics, Universidade Federal da Bahia, Salvador, BA, , Brazil 2 Institute of Physics, Universidade de São Paulo, SP, , Brazil 3 Naval Research Laboratory, Washington, DC, USA 4 Department of Materials Science and Engineering, Royal Institute of Technology, SE Stockholm, Sweden 5 Department of Physics, University of Oslo, NO-0316 Oslo, Norway The optical and electronic properties of oxides HfO 2, CeO 2 and TiO 2 have drawn intensive research, mostly because of their potential applications for optoelectronic and electronic devices. To date, there is an increasing interest in developing deposition techniques to yield high quality films for the fabrication of oxides and III-Nitride based high-efficiency multijunction solar cells, and high frequency and high power devices. However, there are major roadblocks preventing the full realization of these envisioned devices. Therefore, using unconventional deposition techniques to reduce these technical difficulties are highly desirable. In this work we have investigated the properties of these oxides and a nitride namely InN deposited by a modified Ion Beam Assisted Deposition (IBAD) technique, as an approach to overcome some of the technical challenges. It is presented a calculation of the optical response properties for such materials by the firstprinciples means, employing the GW method to describe single-particle excitations and the Bethe Salpeter equation to model the two-particle exciton interactions. The absorption coefficient is analyzed. The results are compared to some measurements. Complete analyses of the optical properties extracted from both XPS and theoretical calculations are in progress. 21

22 Dynamic Probes of Low Symmetry Interactions and Spin Textures R. L. Stamps SUPA-School of Physics and Astronomy, University of Glasgow, Glasgow, UK G12 8QQ A variety of interesting phenomena emerge in systems where inversion symmetries do not exist. We discuss here consequences for excitations and dynamics in different contexts. In the first case we describe some unusual resonance features that are expected for magnetic nanoelements arranged in low symmetry configurations.[1] We also discuss some features of electromagnetic wave propagation associated with magnetoelectric couplings arising from Dzyaloshinsky-Moriya interactions, including nonreciprocal waves.[2] The possibility is discussed of using spinwaves as a probe of chiral interactions in a spin texture. Lastly, we describe new types of chiral electron probes of magnetism.[3] Figure 1: Nonreciprocity of a surface polariton on a single phase canted multiferroic. The nonreciprocity of the surface modes can be affected by an electric field. [1] L. Heyderman, R. L. Stamps, unpublished. [2] V. Gunawan, R. L. Stamps, Journal of Physics-Condensed Matter, 24, (2012). [3] C. Greenshields, R. L. Stamps, S. Frank-Arnold, New Journal of Physics, 14, (2012). 22

23 Transmission Electron Microscopy Studies on Oxide Interfaces G. J. Brown 1, K. Mahalingam 1, A. Aronow 1, M. Liu1, Z. Zhou 2, O. Obi 2, T. Nan 2, S. Beguhn 2, S. Stoute 2, J. Lou 2, X. Yang 2, Y. Gao 2, M. Li 2, S. Rand 2 and N. X. Sun 2 1 Materials & Manufacturing Directorate, Air Force Research laboratory, Wright-Patterson AFB, Ohio, USA 2 Electrical and Computer Engineering Department, Northeastern University, Boston, MA, USA Layered multiferroic heterostructures with two or more ferromagnetic and piezo/ferroelectric layers with strong strain mediated magnetoelectric coupling between the layers are of high interest for voltage control of magnetic properties. The quality of the interface between the layers plays an important role in the magnetoelectric coupling strength. While there has been much work on higher temperature deposition processes for various multiferroic heterostructures, such as molecular beam epitaxy or pulsed laser deposition, there has been less work on low temperature, wet chemistry processes such as spin spray deposition. Recently we performed transmission electron microscopy (TEM) studies on Fe 3 O 4 /ZnO heterostructures fabricated by the spin-spray process developed by Dr. Nian Sun s team at Northeastern University. This deposition process results in a very uneven interface at the nanometer scale so identifying the exact boundary between the Fe 3 O 4 and ZnO layers was enhanced by using an Energy filtered TEM image to create colored maps of Fe and Zn in the layers. High resolution TEM images show how the crystal structure transitions across the interface and also identified some issues with porosity at the interface. 23

24 Ionizing radiation sensitive oxides thin films. José Fernando D. Chubaci, M. Matsuoka, P. O. de Souza, R. de Rosa, R. F. Gennari, S. Watanabe LACIFID IFUSP Ionic Crystals, Thin Films and Dating Laboratory Institute of Physics, University of São Paulo, São Paulo, Brazil of corresponding author: Nowadays various techniques to produce high quality thin films are available. It is possible to produce thin films over almost any substrate and to reproduce the properties of any material in the form of a thin film. The ion beam assisted deposition (IBAD) technique, to produce thin films, where a film is produced by the evaporation by electron beam of a metal or a compound into a substrate with the simultaneous bombardment by an ion beam introduced the possibility to produce films at room temperature, over almost any substrate with high adhesion and hardness. In this work the electron beam evaporator of the IBAD system was used to evaporate chunks of silicate glasses produced in the Lab to form silicate glass thin films. To keep the stoichiometry of the films similar to the bulk silicate glasses the substrate was bombarded by oxygen ion beams. The melted glass was evaporated at a rate of 0.2 nm/s and was simultaneous bombarded by an oxygen ion beam with energy varying from 200 to 800 ev to produce films of 50 nm thicknesses in a vacuum chamber with base pressure of 10-5 Pa. The films were produced on Si(100) and alumina substrates. Photoluminescence (PL), UV-VIS-NIR optical absorption and optically stimulated luminescence were studied for these samples. Rutherford backscattering (RBS) was used to evaluate the films stoichiometry. These glass thin films have reproduced the main optical properties of their glass precursors showing optical bands in the UV region. The RBS spectra of the thin films showed the presence of all the components of the glass that was doped with silver. Photoluminescence (PL) emission measurements from the emission spectra peak at 350 nm showed increased response with radiation dose in the range mgy to kgy. The PL emission from these thin films showed the presence of PL peaks similar to those from bulk glasses exposed to ionizing radiation. The thin films can reproduce some of the physical characteristics of the precursors. Photoluminescence response showed sensitivity to ionizing radiation. We are working to find best production condition of the silicate glasses thin films to develop applications as ionizing radiation sensor passive or active. 24

25 Theory of Rashba interactions in perovskite oxides Byounghak Lee Texas State University. San Marcos, TX The perovskites exhibit variety of interesting material characteristics, including magnetism, ferroelectricity, and superconductivity. High quality perovskite oxides can be grown epitaxially, using molecular beam epitaxy or pulsed laser deposition to achieve artificially tailored heterostructures. Moreover, it has also been shown that epitaxial growth of the perovskite crystal can be achieved on silicon and gallium arsenide a necessary condition for integration with current technologies. Unlike conventional semiconductors in which the effective mass is a fraction of the bare electron mass, perovskite semiconductors can have band masses up to ten times the bare electron mass. This distinction is expected to lead to strong correlation effects in perovskite two-dimensional electron systems (2DESs). Perovskite oxide 2DESs with strong spin-orbit interaction (SOI) can be valuable for spintronics. Interplay between strong correlation and SOI can play a key role for a robust control of magnetic or superconducting properties. In this study we present a theory that applies directly to strong SOI induced spin splitting in 2DESs formed at t2g perovskite surfaces and heterojunctions and establishes some essential differences from SOI in conventional semiconductors. In particular we find that interaction spin-splitting magnitudes are controlled by changes in metal-oxygen-metal bond angles and by atomic spin-orbit interaction strengths. Using qualitative considerations based on a two-center approximation for tight-binding-model matrix elements, we demonstrate that Rashba spin-orbit interactions in complex-oxide two-dimensional electron gases are due primarily to changes in metal-oxygen-metal bond angles at surfaces and interfaces. We verify this conclusion by comparing our picture with illustrative ab initio electronic structure calculations. 25

26 Digging Deep: A modified Total Electron Yield to Study Buried Material Properties in Oxide Devices by Soft X -Ray Absorption Spectroscopy E. Kröger, A. Petraru*, Q. Quer, M. Kalläne, R. Soni*, S. Thiess, L. Kipp, K. Rossnagel, and H. Kohlstedt* Institute of Experimental and Applied Physics, University of Kiel, Kiel, Germany *Nanoelektronik, Technische Fakultät der Christian-Albrechts-Universität zu Kiel, Kiel, Germany Interface characteristics are of crucial importance in modern electronic devices. Electronic devices realize their full potential when an external electric field is applied. In general the application of an electric field to devices, being simultaneously subject to photon irradiation, is an interesting approach to study a rather broad spectrum of fundamental issues and practically oriented questions. We applied soft X-ray absorption spectroscopy to study dielectric and ferroelectric capacitors under a simultaneously applied electric field. Capacitors with the layer sequences (top to bottom) Pt/PZT/PT, Au/PZT/CFO/SRO, Pt/STO/Pt, Au/NiCu/SiO 2 /Ti/Pt were investigated by soft X-ray spectroscopy using a modified total electron yield mode. Here, two ammeters (instead of one) were applied to measure the photocurrents towards the top and bottom electrode of the devices while being subject to soft X-rays. The photocurrents were studied in dependency of the polarization state of the ferroelectric capacitors and with and without an applied external dc-voltage. The geometry of the capacitors as well as the thickness of the top electrode was optimized for these experiments. The obtained photocurrents are a result of three mayor contributions: first, electrons due to the outer photoelectric effect leaving the top electrode, second, electron-hole pair generation and third, core-level excitations in case the photon energy was near to an absorption edge (L 2, L 2 edge of Ti, Fe, Ni) of a material. In accordance to the large penetration depth of soft X-rays of about 100 nm, buried interface can be analyzed. For experimental verification asymmetric capacitor structures were used in which the lower interfacial material acted as chemical tracer (i.e. Ti, CFO or Fe). In case of ferroelectric capacitors, the method allowed to determine the internal electric field. The interplay of photo current distributions in dependency of the applied bias as well as inner potential barriers will be discussed. Limits of the method are related to photo catalytic reactions due to inner electric fields paired with high a soft X-ray photon flux and long exposure times. STO: SrTiO 3 SRO: SrRuO 3 PZT: PbZr x Ti 1-x O 3 CFO: CoFe 2 O 4 NiCu: Ni 48 Cu 52 26

27 Multifunctional materials for electronics and photonics Federico Rosei Centre for Energy, Materials and Telecommunications, INRS, 1650 Boul. Lionel Boulet, J3X 1S2 Varennes (QC), Canada The bottom up approach is considered a potential alternative for low cost manufacturing of nanostructured materials [1]. It is based on the concept of self assembly of nanostructures on a substrate, and is emerging as an alternative paradigm for traditional top down fabrication used in the semiconductor industry. We demonstrate various strategies to control nanostructure assembly (both organic and inorganic) at the nanoscale. Depending on the specific material system under investigation, we developed various approaches, which include, in particular: (i) control of size and luminescence properties of semiconductor nanostructures, synthesized by reactive laser ablation [2]; (ii) we developed new experimental tools and comparison with simulations are presented to gain atomic scale insight into the surface processes that govern nucleation, growth and assembly [3-7]; (iii) we devised new strategies for synthesizing multifunctional nanoscale materials to be used for electronics and photovoltaics [8-24]. References [1] F. Rosei, J. Phys. Cond. Matt. 16, S1373 (2004); [2] D. Riabinina, C. Durand, J. Margot, M. Chaker, G.A. Botton, F. Rosei, Phys. Rev. B 74, (2006); [3] K. Dunn, J. Derr, T. Johnston, M. Chaker, F. Rosei, Phys. Rev. B 80, (2009); [4] F. Ratto et al., Small 2, 401 (2006); [5] F. Ratto et al., Phys. Rev. Lett. 96, (2006); [6] F. Ratto, S. Heun, O. Moutanabbir, F. Rosei, Nanotechnology 19, (2008); [7] F. Ratto, T.W. Johnston, S. Heun, F. Rosei, Surf. Sci., 602, 249 (2008); [8] F. Ratto, F. Rosei, Mater. Sci. Eng. R 70, 243 (2010); [9] O. Moutanabbir, F. Ratto, S. Heun, K. Scheerschmidt, A. Locatelli, F. Rosei, Phys. Rev. B 85, (2012); [10] C. Yan et al., Adv. Mater. 22, 1741 (2010); [11] C. Yan et al., J. Am. Chem. Soc. 132, 8868 (2010); [12] R. Nechache et al., Adv. Mater. 23, (2011); [13] R. Nechache, C. Harnagea, S. Licoccia, E. Traversa, A. Ruediger, A. Pignolet, F. Rosei, Appl. Phys. Lett. 98, (2011); [14] B. Aïssa, R. Nechache, D. Therriault, F. Rosei, M. Nedil, Appl. Phys. Lett. 99, (2011); [15] G. Chen et al., D. Ma, Chem. Commun. 47, 6308 (2011); [16] G. Chen, S. Desinan, R. Rosei, F. Rosei, D. Ma, Chem. Comm. 48, (2012); [17] G. Chen, F. Rosei, D. Ma, Adv. Func. Mater. 22, (2012); [18] R. Nechache, C. Harnagea, F. Rosei, Nanoscale 4, (2012); [19] S. Li et al., Appl. Phys. Lett. 101, (2012); [20] J. Toster et al., Nanoscale 5, (2013); [21] T. Dembele et al., J. Power Sources 233, (2013); [22] S. Li et al., Chem. Comm. 49, (2013); [23] T. Dembele et al., J. Phys. Chem. C 117, (2013); [24] S. Li et al., J. Am. Cer. Soc., in press (2013). 27

28 All-oxide PiezoMEMS, device fabrication and properties R. Steenwelle and G. Rijnders 1 1 University of Twente, MESA+ Institute for Nanotechnology, POBox 217, 7500AE, Enschede, The Netherlands a.j.h.m.rijnders@utwente.nl Keywords :MEMS, Piezo, PZT, thin films, Ferroelectric oxides, such as Pb(Zr,Ti)O 3 (PZT), are very useful for electronic and photonic devices, as well as piezomechanical actuators and sensors. The ferro- and piezoelectric properties are strongly related to the crystal orientation as well as the strain state of the PZT layer, since it will influence the domain configuration within the film. Successful integration of these devices into silicon technology is therefore not only dependent on the ability of epitaxial growth on silicon substrates, but also the control of the crystallographic orientation and the residual strain state of the deposited PZT thin film. A study will be presented on the effects of the residual strain in PZT thin films on the ferroelectric and piezoelectric properties. Epitaxial (001)-oriented PZT thin film capacitors are sandwiched between SrRuO 3 electrodes. The thin film stacks are grown on different substrate-buffer-layer combinations by pulsed laser deposition. Compressive or tensile stress caused by the difference in thermal expansion of the clamped PZT film and substrate is found to influence the domain structure, and therefore the ferroelectric and piezoelectric properties. In this contribution, I will highlight recent studies on the effect of composition and misfit strain on epitaxial polydomain PZT films with Zr content ranging from 0.2 to 0.6. In this contribution, I will furthermore highlight the recent progress on the fabrication of all-oxide piezo-mems devices by large area pulsed laser deposition, up to 200mm wafer scale, as well as lift off techniques for sub-micron patterning of PZT. 28

29 ZnO-X alloys with tailored optoelectronic properties Clas Persson, a,b a Department of Materials Science and Engineering, Royal Institute of Technology, SE Stockholm, Sweden b Department of Physics, University of Oslo, P.O. Box 1048 Blindern, NO 0316 Oslo, Norway With the progress in nano-scale semiconductor technology, ZnO is a good example of a functional material suitable for numerous and different types of nano-technical applications. Bulk ZnO and cation alloying of ZnO are today extensively investigated. Surprisingly, however, only little attention has been paid to understand more advanced alloy structures. In this talk, we will discuss a somewhat unconventional type of ZnO-based materials, namely (ZnO) 1 y X y where X is an isovalent alloy compound which, depending on growth condition, can form nanocluster structures. We expect that ZnO-X alloys can be suitable materials for a variety of novel integrated nano-systems ranging from photonics, optoelectronics, biosensing, to nano-piezoelectricity applications, and even more. For instance, achieving p-type bulk ZnO is a major goal for further development of ZnO-based devices. We have also demonstrated that ZnO-ZnS exhibits strong band-gap bowing that can be utilized to enhance dopability and activate p-type acceptors [1]. This is a conceptual new type of doping method. Moreover, our theoretical studies of the optical properties of ZnO-GaN and ZnO-InN alloys, reveal intriguing material properties [2,3]. These two alloys exhibit strong band-gap bowing and, as a consequence, the energy gap is reduced by more than 1 ev to a value of about 2.3 ev in ZnO-GaN with 50% alloying content. Additional phase stability modeling of these alloy content is needed, however, already 10-15% alloy composition affect strongly the band gap. Furthermore, although alloying implies broken crystalline symmetry and semi-local density-of-states structures of the valence- and conduction-band edges, the strong exciton peak of ZnO is not diminished by the incorporation of GaN. That is, the strong exciton absorption remains in the alloy. This result indicates that the exciton coupling in the ZnO- GaN alloy is correlated both to the band-gap energy and chemical GaN content. References [1] C. Persson, C. Platzer-Björkman, J. Malmström, T. Törndahl, and M. Edoff. Strong valence-band offset bowing of ZnO 1 x S x enhances p-type nitrogen doping of ZnO-like alloys. Phys. Rev. Lett. 2006: 97, [2] M. Dou and C. Persson. Band gap reduction and dielectric function of Ga 1 x Zn x N 1 x O x and In 1 x Zn x N 1 x O x alloys. Phys. Status Solidi A 2012: 209, 75 29

30 Terahertz Responses in Oxides: Nonlinear effects and engineered structures Harold Y. Hwang 1, Nathaniel Brandt 1, Jian Lu 1, Bradford G. Perkins 1, Benjamin K. Ofori- Okai 1, Stephanie Teo 1, Prasahnt Sivarajah 1, Nathaniel Grady 3, Houtong Chen 3, Antoinette Taylor 3, Xin Zhang 3, Richard D. Averitt 2, Keith A. Nelson 1 1 Massachusetts Institute of Technology, Department of Chemistry 2 Boston University, Department of Physics 3 Boston University, Department of Mechanical Engineering 4 Los Alamos National Laboratory The terahertz (THz) region of the electromagnetic spectrum offers direct access to many physical phenomena in the solid-state. THz radiation can probe lattice and electronic motions resonantly as well as offer a unique way to observe quasiparticle motions that arise from coupling of various elementary degrees of freedom. Nonresonant effects also provide a noncontact method to study conductivity dynamics. Furthermore, the long wavelength of THz light (1 THz = 300 µm) enables the engineering of hybridized structures well within the capabilities for standard microfabrication techniques, making this region of the electromagnetic spectrum an ideal testbed for observing dynamics in metamaterials, which can also be used to further develop THz technologies. Recent developments in the generation of high-field ultrafast terahertz pulses have led to the extension of nonlinear spectroscopies to the THz range. The field enhancement in metamaterial structures has been used to achieve THz field strengths on the order of several MV/cm. THz field strengths at these magnitudes can drive highly nonlinear material responses that have been inaccessible previously. In this talk, I will present recent demonstrations of THz-frequency radiation driving nonlinear responses in a variety of oxides including correlated electron materials, ferroelectrics, and dielectric metamaterials, using both free-space and metamaterial-enhanced THz fields. THz-induced responses have been monitored with ultrashort pulses ranging from THz to optical to hard x-ray spectral ranges, measuring the conductivity, birefringence and harmonic generation, and phase-transitionmediated lattice diffraction respectively. Furthermore, I will discuss engineered photonic materials on a lithium niobate THz polaritonics platform. Time-resolved imaging of THz waves propagating in various orientations within different photonic crystal slab lattices let us directly map the band diagrams, displaying a rich set of effects including multiple eigenmodes, leaky modes, and backward propagating waves. In other periodic structures, the density necessary for dielectric homogenization was explored. 30

31 List of Attendees First Last Affiliation Charles Ahn Yale U charles.ahn@yale.edu Gail Brown AFRL Gail.Brown@wpafb.af.mil Zbigniew Celinski U CO at Colorado Springs zcelinsk@uccs.edu Jose Fernando Chubaci Universidade de Sao Paulo chubaci@if.usp.br Denis David U. Federal da Bahia denis.david@uol.com.br Ravi Droopad TX State U. rdroopad@txstate.edu Antonio Ferreira Da Silva U. Federal da Bahia ferreira.fis@gmail.com Harold Hwang MIT hhwang82@mit.edu Franz Justa franz.h.justa@gmx.at Herman Kohlstedt U Kiel hko@tf.uni-kiel.de Byounghak Lee TX State U. byounghak@txstate.edu Jeremy Levy U Pittsburg jlevy@pitt.edu Leszek Malkinski U of New Orleans lmalkins@uno.edu Clas Persson Oslo University clas.persson.research@gmail.com Knut Peters Crystech k.peters@crystec.de Federico Rosei INRS - Quebec rosei@emt.inrs.ca Mark Rzchowski U Wisconsin rzchowski@physics.wisc.edu Juan Salafranca Universidad Complutense de Madrid juanelsala@gmail.com Robert Stamps U. Glasgow Robert.Stamps@Glasgow.ac.uk Ruud Steenwelle U Twente R.J.A.Steenwelle@utwente.nl 31