Publications by Paul Muralt | EPFL Graph Search

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In this article an experimental method of characterization and modeling of ferroelectric materials is presented. The reversible and irreversible contributions of polarization are separated. The measurements of these effects are performed simultaneously giving a perfect separation. Investigations on switching behavior under different electric field strengths permit final representation of totally irreversible effects by a two-dimensional (2D) function. This function, a Preisach-type density, allows us to ext

Micro-solid oxide fuel cell (mu SOFC) structures with annular Pt electrodes have been fabricated by means of silicon micromachining. The annular cathodes contained a defined triple phase boundary (TPB) length, which allowed the derivation of the ionic curr ...

Electrode stability, interdiffusion, phase purity and deviation from stoichiometry at the PZT-electrode interface are key issues in PZT thin film integration. This article highlights the use of transmission electron imaging combined with energy dispersive spectroscopy (EDS) for the investigation of these phenomena. The accuracy of the EDS analysis is discussed. It will be shown that using a standard PZT sample and controlled conditions, reliable analysis can be performed. Diffusion mechanisms have been stud

Structural and dielectric properties of epitaxial SrTiO3 (STO) thin films on LaAlO3 substrates fabricated by a two-step growth technique using pulsed laser deposition were investigated by in situ and ex situ observations in terms of strain relaxation from ...

The domain nucleation and growth during polarization switching in Pb(Zr,Ti)O-3 (PZT) ferroelectric thin film capacitors with Pt top (TE) and bottom electrodes (BE) were studied by means of atomic force microscopy (AFM). The experimental configuration used in this study differs from that conventionally used (AFM tip/PZT/BE) where the AFM tip acts as a positionable TE. A small ac voltage was applied between the electrodes with a step by step increasing dc bias voltage. The induced piezoelectric vibration was

Using pulsed-laser deposition, a two-step growth technique was applied to epitaxial SrTiO3 (STO) thin films on LaAlO3 substrates providing a way to obtain an effective strain relaxation in these films otherwise strained due to lattice mismatch between film ...

The underlying physical mechanism of the so-called colossal dielectric constant phenomenon in CaCu3Ti4O12 CCTO thin films were investigated by using semiconductor theories and methods. The semiconductivity of CCTO thin films originated from the acceptor de ...

Engineering materials with highly tunable physical properties in response to external stimuli is a cornerstone strategy for advancing energy technology. Among various approaches, engineering ionic defects and understanding their roles are essential in tail ...

Accurate property determination of the piezoelectric thin film material Al(1-x)Sc(x)N is necessary for designing the next generation of radio frequency resonators in mobile communication, and for testing results of ab initio calculations. Sound velocity an ...

Strontium barium niobate thin films have been deposited by pulsed laser deposition on (111)-textured Pt films, p-doped Si(I 00) and Nb doped STO (SrTiO3) single crystals. The deposition parameters were optimized for obtaining phase pure (001)-oriented films from stochiometric targets. The samples were annealed in oxygen to improve top electrode adhesion and reduce oxygen vacancies. The SBN/substrate interfaces were investigated by means of TEM combined with EDAX chemical analysis. Growth on silicon resulted

Yttria stabilized zirconia (YSZ) with 8 mol% Y was deposited by reactive magnetron sputtering onto oxidized (100) silicon substrates. It was possible to switch film texture from (111) to (200) by applying a strong RF substrate bias. Transmission electron m ...

Piezoelectric thin films of PbZrxTi1-xO3 (PZT) on membranes are the subject of keen interest for the fabrication of micro-sensors and actuators. Piezoelectric activity of the PZT on Si-based membranes has been shown, and a micromotor has been demonstrated. Standard substrates are based on Si due to the good barrier properties of SiO2 and Si3N4 layers, which protect the Si against further oxidation. For some applications, however, such structures are not appropriate. For instance, thin metallic sheets, which

Introducing symmetry breaking in materials enables the emergence of functionalities. This can be microscopically and macroscopically driven by applying external stimuli such as mechanical stress, electric field, temperature, and chemical modification. For instance, non‐zero net dipole moments are formed in a material with the presence of local charged defects or their clusters, which can alter the crystal structure, charge states, and electrostatic potential across the material. Here, a conceptual approach

With growing public interest in portable electronics such as micro fuel cells, micro gas total analysis systems, and portable medical devices, the need for miniaturized air pumps with minimal electrical power consumption is on the rise. Thus, the development and downsizing of next-generation thermal transpiration gas pumps has been investigated intensively during the last decades. Such a system relies on a mesoporous membrane that generates a thermomolecular pressure gradient under the action of an applied

The concept of a field-effect transistor with ferroelectric gate has been implemented using the GaN/AlGaN heterostructure combined with Pb(Zr,Ti)O-3 ferroelectric layer. The processing conditions were optimized in a way to obtain textured Pb(Zr,Ti)O-3 film ...

It is more difficult to nucleate AlN-ScN alloy thin films (AlScN) in pure (0001)-texture than it is with pure AlN thin films. AlN thus can serve as seed layer for AlScN. Equipment limitations may lead to the problem of a vacuum break between AlN and AlScN ...

Vibration mode and resonance frequency of piezoelectric MEMS ultrasonic sensors was investigated on buckled diaphragm structures. The buckling of the diaphragms was introduced intrinsically through residual stress control of the piezoelectric film, and ext ...

Micro‐solid oxide fuel cell (micro‐SOFC) systems are predicted to have a high energy density and specific energy and are potential power sources for portable electronic devices. A micro‐SOFC system is under development in the frame of the ONEBAT project [1‐3]. In this presentation, we report on the fabrication and characterization of a sub‐system assembly consisting of a startup heater and a micro‐reformer bonded to a Si chip with electrochemically‐active micro‐SOFC membranes. A functional carrier including

Ultrathin aluminum nitride (AlN) films are of great interest for integration into nanoelectromechanical systems for actuation and sensing. Given the direct relationship between crystallographic texture and piezoelectric (PZE) response, x-ray diffraction ha ...

Aluminum nitride thin films have been grown by reactive magnetron sputter technique using a pulsed power supply. The highly (002)-textured columnar films deposited on platinized silicon substrates exhibited quasi-single-crystal piezoelectric properties. The effective d(33) was measured as 3.4 pm/V, the effective e(31) as 1.0 C/m(2). The pyroelectric coefficient turned out to be positive (4.8 mu C m(-2) K-1) due to a dominating piezoelectric contribution. Thin-film bulk acoustic resonators (TFBAR) with funda

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Characterization and model of ferroelectrics based on experimental Preisach density

Experimental study of single triple-phase-boundary and platinum-yttria stabilized zirconia composite as cathodes for micro-solid oxide fuel cells

Stoichiometry and interdiffusion in PZT thin films studied by transmission electron microscopy

Structural and dielectric properties of strain-controlled epitaxial SrTiO3 thin films by two-step growth technique

High resolution study of domain nucleation and growth during polarization switching in Pb(Zr,Ti)O-3 ferroelectric thin film capacitors

Strain relaxation of epitaxial SrTiO3 thin films on LaAlO3 by two-step growth technique

Physical aspects of colossal dielectric constant material CaCu3Ti4O12 thin films

Tailoring dielectric permittivity of epitaxial Gd-doped CeO2-x films by ionic defects

Material Parameter Extraction for Complex AlScN Thin Film Using Dual Mode Resonators in Combination with Advanced Microstructural Analysis and Finite Element Modeling

Microstructural and electrical properties of (Sr,Ba)Nb2O6 thin films grown by pulsed laser deposition

Nanoporous YSZ film in electrolyte membrane of Micro-Solid Oxide Fuel Cell

Buffer electrodes for deposition of lead zirconium titanate films on metallic substrates

Tunable and Persistent Macroscopic Polarization in Nominally Centrosymmetric Defective Oxides

Dimensional and structural control of silica aerogel membranes for miniaturized motionless gas pumps

Ferroelectric gate for control of transport properties of two-dimensional electron gas at AlGaN/GaN heterostructures

Ex-situ AlN seed layer for (0001)-textured Al0.84Sc0.16N thin films grown on SiO2 substrates

Vibration Mode of MEMS Ultrasonic Sensors on Buckled Diaphragms with Piezoelectric Resonance Frequency Modification

Micro-solid oxide fuel cells running on reformed hydrocarbon fuels

Effect of AlN seed layer on crystallographic characterization of piezoelectric AlN

Properties of aluminum nitride thin films for piezoelectric transducers and microwave filter applications