A5031905765- Ferroelectric and Piezoelectric Materials
- Acoustic Wave Resonator Technologies
- Multiferroics and related materials
- Nanowire Synthesis and Applications
- Electronic and Structural Properties of Oxides
- Semiconductor materials and devices
- Advancements in Semiconductor Devices and Circuit Design
- Quantum Dots Synthesis And Properties
- Semiconductor Quantum Structures and Devices
- GaN-based semiconductor devices and materials
- Magnetic and transport properties of perovskites and related materials
- Force Microscopy Techniques and Applications
- Anodic Oxide Films and Nanostructures
- ZnO doping and properties
- Physics of Superconductivity and Magnetism
- Advanced Frequency and Time Standards
- Advanced Thermodynamics and Statistical Mechanics
- Semiconductor materials and interfaces
- Superconducting and THz Device Technology
- Advanced Sensor and Energy Harvesting Materials
- Advanced Condensed Matter Physics
- Quantum Computing Algorithms and Architecture
- Advanced Thermoelectric Materials and Devices
- Ga2O3 and related materials
- Dielectric materials and actuators
Karlsruhe Institute of Technology
2016-2022
École Polytechnique Fédérale de Lausanne
2013-2018
University of California, Santa Barbara
2012
Max Planck Institute of Microstructure Physics
2009-2010
We describe the fabrication and measurement of microwave coplanar waveguide resonators with internal quality factors above 10 million at high powers over 1 low powers, best power results approaching 2 million, corresponding to ~1 photon in resonator. These are achieved by controllably producing very smooth clean interfaces between resonators' aluminum metallization underlying single crystal sapphire substrate. Additionally, we a method for analyzing resonator response, which can directly...
Use of ferroelectric domain-walls in future electronics requires that they are stable, rewritable conducting channels. Here we demonstrate nonthermally activated metallic-like conduction nominally uncharged, bent, ferroelectric-ferroelastic the ubiquitous Pb(Zr,Ti)O3 using scanning force microscopy down to a temperature 4 K. New walls created at K by pressure exhibit similar robust and intrinsic conductivity. Atomic resolution electron energy-loss spectroscopy confirms conductivity...
Conductive domain walls (DWs) in ferroic oxides as device elements are a highly attractive research topic because of their robust and agile response to electric field. Charged DWs possessing metallic-type conductivity hold the highest promises this aspect. However, intricate creation, low stability, interference with nonconductive hinder investigation progress toward future applications. Here, we find that conversion nominally neutral ferroelastic 90° into partially charged Pb(Zr0.1Ti0.9)O3...
The velocity of individual 180° domain walls in thin ferroelectric films PbZr0.1Ti0.9O3 is strongly dependent on the thickness top Pt electrode made by electron-beam induced deposition (EBID). We show that when varied range <100 nm wall seen to change 7 orders magnitude. attribute this huge velocities similarly large resistivities for EBID as extrapolated from four-point probe measurements. motion governed supply charges wall, determined resistivity, and which described using a modified...
Using a combination of first-principles calculation and high-resolution scanning TEM, the authors report novel structural characteristics ferreoelastic 90${}^{\ensuremath{\circ}}$ domain wall in PbTiO${}_{3}$. They highlight discovery sharp discontinuity variation lattice parameters across wall. The calculations show that oxygen vacancies prefer to cluster plane adjacent asymmetric walls. Understanding interaction with walls is important because such defects are used tailor properties...
Ordered patterns of highly compliant ferroelastic domains have been created by use tensile strained epitaxial Pb(Zr,Ti)O3 thin films, very low defect density, grown on DyScO3 substrates. The effect 180° switching well-ordered a/c 90° domain is investigated a combination transmission electron microscopy, piezoelectric force and X-ray diffraction. It shown that a-domains, having an in-plane polarization, can be completely removed local level out-of-plane electric field. modifications the...
Defect engineering is one of the cornerstones modern electronics industry. Almost all electronic devices include materials that have been doped by ion bombardment. For where crystallinity essential, such as ferroelectrics, defect type and concentration can vastly influence properties are often used to optimize device performance. This study shows a method effectively control density position on nanoscale sites in thin films Pb(Zr,Ti)O 3 via focused beam microscopy. allows for exceptional...
We report on a growth study of self-catalyzed GaAs nanowires based time-resolved in situ X-ray structure characterization during molecular-beam-epitaxy combination with ex scanning-electron-microscopy. reveal the evolution nanowire radius and polytypism distinguish radial processes responsible for tapering side-wall growth. interpret our results using model diameter self-stabilization including shape liquid Ga-droplet its
The growth of regular arrays uniform III-V semiconductor nanowires is a crucial step on the route toward their application-relevant large-scale integration onto Si platform. To this end, not only does optimal vertical yield, length, and diameter uniformity have to be engineered, but also, control over nanowire crystal structure has achieved. Depending particular application, with varying area density are required for device efficiency. However, substantially influences presents an additional...
Abstract Charged domain walls in ferroelectric materials are of high interest due to their potential use nanoelectronic devices. While previous approaches have utilized complex scanning probe techniques or frustrative poling here we show the creation charged thin films during simple polarization switching using either a conductive tip patterned top electrodes. We demonstrate that is accompanied - without exception by appearance and these can be displaced erased reliably. ascertain from...
Heterostructures consisting of PbZr0.2Ti0.8O3 and PbZr0.4Ti0.6O3 epitaxial films on a SrTiO3 (100) substrate with SrRuO3 bottom electrode were prepared by pulsed laser deposition. By using the additional interface provided ferroelectric bilayer structure changing sequence layers, content dislocations elastic domain types was varied in controlled manner. The resulting microstructure investigated transmission electron microscopy. Macroscopic measurements have shown large impact formation 90°...
The dependence of the formation ferroelastic stripe domain patterns on thermal history is investigated by detailed piezoresponse force microscopy and X-ray diffraction experiments after during annealing tensile strained tetragonal Pb(Ti,Zr)O3 epitaxial thin films DyScO3 substrates. In particular, pattern reversibly interchanged between a cross-hatched if are cooled at different rates above temperature a-domains. Different types 180° non-180° can be created, depending treatment. changes in...
The absence of a realistic polarization screening scenario at the pivotal ferroelectric-metal interface impedes widespread application low-dimensional ferroelectric heterostructures. Employing quantitative atom-resolved (scanning) transmission electron microscopy and first-principles calculations, we report that structural chemical reconstruction universally lowers symmetry interface. Irrespective strain mismatch, termination diffusion, polar catastrophe, electrode type, is executed by...
The a/c domain pattern of tetragonal PbZr0.10Ti0.90O3 thin films under tensile misfit strain is investigated by piezoresponse force microscopy and X-ray diffraction. results show a hierarchical ordering the dense structure into larger superstructures. latter exhibit preferred orientation occasionally form distinct patterns such as flux closure loops net polarization. Additionally, residual measured with reciprocal space maps a-domain fraction determined theoretical calculations correlated...
Properties of ferroelectric domain walls are attractive for future nano- and optoelectronics. An important element is the potential to electrically erase/rewrite inside working devices. Dense wall patterns, formed upon cooling through phase transition, were demonstrated. However, room temperature writing done with a cantilever tip, one stripe at time, reduction inter-wall distance limited by tip diameter. Here, we show, temperature, controlled formation arrays sub-tip-diameter spacing (i.e.,...
Multilayers consisting of two tetragonal compositions PbZr0.2Ti0.8O3 and PbZr0.4Ti0.6O3 were deposited onto a SrRuO3 electrode grown on vicinal (1 0 0) SrTiO3 substrate. It has been shown by extensive structural investigations comprising transmission electron microscopy in conventional high resolution mode, reciprocal space mapping piezoresponse force that with decreasing layer thickness transition from a-domains confined to individual layers propagating through the whole film takes place....
Semiconductor nanowires are a class of materials that recently have gained increasing interest in solar-cell applications and light-emitting devices. Finding reproducible processing conditions is fundamental for their future mass production. In this work, the stability individual epitaxial GaAs (NWs) under molecular beam epitaxy (MBE) studied by means time-resolved situ micro X-ray diffraction (μXRD) method scanning electron microscopy. Our proposed μXRD nondestructive characterization...
Epitaxial ferroelectric PbZr0.2Ti0.8O3 thin films were grown by pulsed laser deposition. was doped with Cr acting as acceptor ion. Microstructural characterization performed (high resolution) transmission electron microscopy. The voltage dependence of polarization, dielectric constant, and leakage current measured respect to the content. To derive electronic properties, PZT considered a wide-gap semiconductor which allows treating metal-PZT interface Schottky contact. found facilitate...
Ferroelectric switching in circular and ring capacitors has been performed using a stroboscopic mode of piezoresponse force microscopy. A simple geometric model incorporating the characteristic domain wall motion is sufficient to describe but which however breaks down when attempting switching. Analysis dynamics implies that moves faster along perimeter both circle electrode structures.
The microstructure of ferroelectric [PbZr x Ti1− O3/PbZr y O3] n epitaxial multilayers (x/y = 0.2/0.4, 0.4/0.6) deposited on SrRuO3-coated SrTiO3 substrates by pulsed-laser deposition with different layer periodicity and thickness was characterized means transmission electron microscopy. Electron diffraction contrast analysis revealed a very clear well-separated sequence. microstructures PbZr0.2Ti0.8O3/PbZr0.4Ti0.6O3 PbZr0.4Ti0.6O3/PbZr0.6Ti0.4O3 show similar tendency in the dependence...
<italic>In situ</italic> RHEED enables a height-resolved determination of the crystal structure vertical nanowires <italic>via</italic> self-shadowing and ensemble shadowing.