Publications by Paul Muralt | EPFL Graph Search

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Capacitors in metal-insulator-metal structure have been fabricated with different bottom electrodes. It has been found that the observed losses are enormous at gigahertz frequencies unless due care is taken not only for the conductivity of the bottom electrode but also its thickness. Very thin bottom electrodes (thickness similar to 100 nm) modify the dielectric response substantially and major loss contributions arise from the substrate, the electrode resistance, and the contacts. A simple approach is sugg

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) imaging is employed to characterize the surface of patterned noble metal (Pt) and titania (TiO2) thin films deposited on oxidized silicon wafers. ToF-SIMS is used to follow the different process steps during the thin films patterning as well as the post-processing cleaning. Both positive and negative ToF-SIMS modes reveal the presence of contaminants, due to the etching processes (Cl- Al-,(+)), but only on the etched surfaces. Elements due to the pos

Pb(Zr,Ti)O-3 (PZT) and Pb(Zr,Ti,Nb)O-3 (PNZT) thin films were grown on platinized silicon substrates by r.f. magnetron sputtering followed by a post-annealing treatment. The Niobium, Nb, concentration varied from 1 to 7 at.% by increment of 1 at.%. The effects of the Nb introduction on the PZT electrical properties, i.e, dielectric, ferroelectric and piezoelectric ones were investigated. The relative dielectric constant (epsilon (T)) was very sensitive to the Nb introduction; epsilon (T) reaches 1100 for a

The piezoelectric response of silicon diaphragms covered with sputter-deposited PbZr0.45Ti0.55O3 (PZT) films has been investigated in view of their application in ultrasonic micro-actuators. The behaviour of resonance frequencies and quasistatic deflections has been studied as a function of membrane thickness and d.c. bias. The total stress in the films and the piezoelectric constant, d(31), have been derived by means of two different methods. The results are consistent with direct strain measurements by op

Pb(Zr, Ti)O-3 (PZT) and Pb(Zr, Ti, Nb)O-3 (PNZT) thin films have been deposited on platinized silicon substrates by sputtering followed by a postannealing treatment. The Nb concentration in the films varied between 1 and 7 at. % with increments of 1 at. %. The effects of Nb modification on the piezoelectric response, and particularly on the longitudinal piezoelectric coefficient d(33), have been investigated. The introduction of Nb enhances the dielectric and piezoelectric properties of the PZT films. The b

Pb(Zr1–xTix)O3 thin films (x = 0.55 and 0.85) were prepared on fine grained, polished ZrO2 ceramic substrates by a sol-gel method. The high thermal expansion of ZrO2 relative to Si allows the preparation of thicker PZT films with reduced thermal stress. For the x = 0.85 films, this reduction of thermal stress gives a preference of (001) over (100) oriented domains. For x = 0.55 films, square P–E hysteresis loops were obtained with: Pr = 36 µC/Cm2, and Ec = 45 kV/cm, at a field of 160 kV/cm. Pyroelectric fig

An epitaxial 200 nm thick film of Pb(Zr0.40Ti0.60)O-3 (PZT) has been deposited by reactive rf magnetron sputtering on conductive Nb-doped SrTiO3 (100) (STO). The patterning process involved electron-beam lithography of polymethylmethacrylate, fabrication of a 75 nm thick Cr hard mask layer by means of a lift-off process, and dry etching of PZT. The smallest PZT features obtained were 100 nm in lateral dimensions. Piezoelectric sensitive scanning force microscopy in the contact mode revealed a strong increas

A piezoelectric thin film sandwiched between two conductors is the basic structure for high frequency bulk acoustic wave devices. For that purpose, AlN thin films deposited by DC reactive sputtering on various electrode materials were investigated, Highly c-axis oriented thin films as thick as 2.5 mu m were grown on various substrates and analyzed. Intrinsic stress values ranging from strong compression to high tension were observed and piezoelectric d(33,f) coefficients up to 3.9 pm/V were measured. The fi

The transverse piezoelectric coefficient e31,f of Al1-xScxN thin films was investigated as a function of composition. It increased nearly 50% from x = 0 to x = 0.17. As the increase of the dielectric constant was only moderate, these films are very suitable for energy harvesting, giving a 60% higher transformation yield (x = 0.17) as compared to pure AlN. A higher doping might even lead to a 100% augmentation. The thickness strain response (d33,f) was found to increase proportionally to the ionic part of th

The pyroelectric properties of Pb1-xCaxTiO3 (x = 0-0.3) thin films have been greatly improved by including porosity in the microstructure. Control of nucleation and growth by variation of the heating rate was used to process porous, low dielectric constant films on platinized silicon wafers. Electrical characterization of poled films showed pyroelectric coefficients of up to similar to 200 mu C/m(2) K and permitivities as low as epsilon(r) approximate to 55. The resulting high figure-of-merit p/epsilon(r) i

Growth and properties of sputter in situ sputter deposited Pb(Z,Ti)O-3 (PZT) thin films have been studied on (111)-textured Pt electrodes as a function of seed layers of the type (TiO2)(x)(PbO)(y). The PZT process was run with a limited lead excess resulting in pyrochlore nucleation on bare Pt electrodes. When the electrode was covered with a dense seed layer, perovskite was obtained everywhere. Ti rich seed layers yielded (111)-textured PZT even for very thin seed layers. Pb rich seed layers nucleated as P

Poling of lead zirconate titanate pyroelectric thin films has been studied. Poling temperature and electrical field were optimized to achieve high figures of merit. We have found a direct correlation between the onset of degradation current and the final pyroelectric coefficient showing that thermal activation for defect motion is imperative for poling. We have proposed that defects and defect dipole complexes play a major role to obtain stable and metastable domain configurations after dc poling at high te

In this work, bar- and disk-shaped resonators were fabricated using Al(0.8)4Sc(0.16)N thin film Sensitivity analysis of the resonators' resonance frequencies with respect to the piezoelectric material parameters revealed that resonance analysis can be used ...

Piezoelectrics are materials that linearly deform in response to an applied electric field. As a fundamental prerequisite, piezoelectric materials must have a noncentrosymmetric crystal structure. For more than a century, this has remained a major obstacle ...

An efficient, electrically conductive, chemical barrier for the integration of piezoelectric Pb(Zr,Ti)O3 (PZT) films on reactive metal substrates has been developed, opening new possibilities for PZT integration on micromechanical and semiconductor devices, Very reactive zir conium films have been taken in order to test the quality of the specially designed RuO2/Cr buffer under the condition of in situ sputter deposition of PZT at 600 degrees C. The PZT/RuO2 interface was found to be free of intermediate ph

The effective piezoelectric coefficient e(31) has been measured on sol-gel processed Pb(ZrxTi1-x)O-3 thin films with Zr concentrations ranging from 45 to 60%. The largest value was observed at 45% Zr, although dielectric constant and effective d(33) peak at 53% Zr. The findings suggest that the optimal composition for microactuators and sensors is less than or equal to 45% Zr, i.e., in the tetragonal part of the phase diagram.

Pb(Zr-x, Ti1-x)O-3 (PZT) piezoelectric thin films are of major interest in MEMS technology for their ability to provide electro-mechanical coupling. In this work, the effective transverse piezoelectric coefficient e(31,f) of sol-gel processed films was investigated as a function of composition, film texture and film thickness. Dense, textured and crack-free PZT films have been obtained on silicon substrates up to a thickness of 4 mum. Crystallization anneals have been performed for every 0.25 mum. Nucleatio

The effective piezoelectric coefficient e(31) has been measured on sol-gel processed Pb(ZrxTi1-x)O-3 thin films with Zr concentrations ranging from 45 to 60%. The largest value was observed at 45% Zr, although dielectric constant and effective d(33) peak at 53% Zr. The findings suggest that the optimal composition for microactuators and sensors is less than 45% Zr, i.e., in the tetragonal part of the phase diagram.

It is shown that a strong but diffuse dielectric anomaly, commonly expected only in disordered ferroelectrics, may be inherent in strained and defect-free perovskite ferroelectric thin films. The origin of this unusual anomaly, which was never predicted for a defect-free system, is the overcritical trace of a critical point in the film phase diagram, This possibility is illustrated by the mean-field thermodynamic calculations performed for (111)-oriented PbTiO3 films epitaxially grown on dissimilar cubic su

Combinatorial high vacuum chemical vapor deposition (HV-CVD) of mixed HfO2-Nb2O5 thin films has been demonstrated to yield amorphous layers at substrate temperatures where individually deposited pure HfO2 and Nb2O5 films are polycrystalline. Spectroscopic ...

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The effect of bottom electrode on the performance of thin film based capacitors in the gigahertz region

Imaging by time-of-flight secondary ion mass spectrometry of plasma patterned metal and oxide thin films

Ferroelectric and piezoelectric properties of Nb doped PZT films

Piezoelectric actuation of PZT thin-film diaphragms at static and resonant conditions

Evaluation of niobium effects on the longitudinal piezoelectric coefficients of Pb(Zr, Ti)O-3 thin films

Sol-gel deposition of PZT thin films on ceramic ZrO2 substrates

Size effect in mesoscopic epitaxial ferroelectric structures: Increase of piezoelectric response with decreasing feature size

Aluminum nitride thin films for high frequency applications

Piezoelectric AlScN thin films: A semiconductor compatible solution for mechanical energy harvesting and sensors

High figure-of-merit porous Pb1-xCaxTiO3 thin films for pyroelectric applications

Mixed titania-lead oxide seed layers for PZT growth on Pt(111): a study on nucleation, texture and properties

Poling of ferroelectric thin films

Determination of elastic and piezoelectric properties of Al0.84Sc0.16N thin films

Induced giant piezoelectricity in centrosymmetric oxides

Pb(Zr,Ti)O3 thin films on zirconium membranes for micromechanical applications

In-plane piezoelectric coefficient of PZT thin films as a function of composition

{100}-textured, piezoelectric Pb(Zr-x Ti1-x)O-3 thin films for MEMS: integration, deposition and properties

Which PZT thin films for piezoelectric microactuator applications?

Strain-induced diffuse dielectric anomaly and critical point in perovskite ferroelectric thin films

Combinatorial Discovery and Optimization of Amorphous HfO2-Nb2O5 Mixture with Improved Transparency