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This paper reports on the piezoelectric-microelectromechanical system micro-fabrication process and the behavior of piezoelectric stacks actuated silicon cantilevers. All oxide layers in the piezoelectric stacks, such as buffer-layer/bottom-electrode/film/top-electrode: YSZ/SrRuO 3 /Pb(Zr,Ti) 3 /SrRuO 3 , were grown epitaxially on the Si template of silicon-on-insulator substrates by pulsed laser deposition. By using an analytical model and finite element simulation, the initial bending of the cantilevers was calculated. These theoretical analyses are in good agreement with the experimental results which were determined using a white light interferometer. The dependences of the cantilever displacement, resonance frequency and quality factor on the cantilever geometry have been investigated using a laser-Doppler vibrometer. The tip displacement ranged from 0.03 to 0.42 μm V −1 , whereas the resonance frequency and quality factor values changed from 1010 to 18.6 kHz and 614 to 174, respectively, for the cantilevers with lengths in the range of 100-800 μm. Furthermore, the effect of the conductive oxide electrodes on the stability of the piezoelectric displacement of the cantilevers has been studied.

In this paper we investigated the effects of built-in stress on the dielectric and piezoelectric properties of sputtered AlN layers, meant to be implemented in micromachined piezoelectric vibration energy harvesters. Test structures including cantilevers, 4-point bending beams and metal-insulator-metal capacitors were manufactured with reactive sputtered AlN layers in a thickness range of 400-1200 nm. Various bias conditions during the deposition process allowed controlling the built-in stress level in the layers, from tensile to compressive. The clamped dielectric permittivity ε 33 S , the voltage response and the piezoelectric coefficient e 31 of the deposited AlN layers were measured by performing capacitance, voltage-deflection and 4-point bending measurements, respectively. In addition, we obtained from electrical impedance analyses the generalized electromechanical coupling (GEMC) and the quality factors of the fabricated test cantilevers, which are the critical parameters directly connected to the performance of the device in terms of energy harvesting. It is found that the permittivity ε 33 S and the piezoelectric constant e 31 were not significantly affected by the different stress levels for a given layer thickness. However, the GEMC and the quality factor were found to be decreasing for structures that have a larger residual stress. We concluded that large residual stress has to be avoided in order to optimize the output power of AlN-based vibration harvesters.

The electrical and physical properties of CeO 2 -HfO 2 nanolaminates on Si͑100͒, by pulsed laser deposition, are investigated. Layers were deposited using pure CeO 2 and HfO 2 targets at various substrate temperatures ranging from 220 to 620°C at Ar + H 2 and O 2 and in situ postdeposition anneal of nanolaminates performed by controlled cooling from deposition temperature to room temperature under high oxygen pressure. After layer growth and anneal, top and bottom Au electrodes were deposited by sputtering. Electrical characterization was done by C-V and I-V measurements. The highest k value of 30 was found for the laminates deposited at 520°C in Ar + H 2 ambient. It is found that the properties of CeO 2 -HfO 2 nanolaminates deposited at reducing atmosphere are dependent on the layer thickness. Thicker layers showed a higher dielectric constant and higher leakage current densities than thinner layers.As a result of aggressive scaling of the dimensions of complementary metal-oxide silicon ͑CMOS͒ devices, research on new high dielectric constant ͑high-k͒ materials for replacing SiO 2 has become a major issue in materials science of dielectrics in recent years. HfO 2 is the most promising candidate, and has been investigated intensively by the semiconductor industry and research institutions. CeO 2 is also one of the promising candidates because it is thermodynamically stable on silicon, which is advantageous for reducing interfacial SiO 2 regrowth. 1 CeO 2 with its fluorite structure has a very small lattice mismatch of 0.35% on silicon that allows epitaxial or highly oriented crystalline layers. CeO 2 also has a k value of 20-26 and a bandgap of approximately 6 eV. 2 Laminated structures are used for tailoring the electrical and physical properties of oxides. 3 Conduction and valence band offsets the dielectric constant and in particular the leakage current properties of the resulting composite dielectric can be engineered by lamination. Pulsed laser deposition ͑PLD͒ is known for its flexibility and precision for growing atomically smooth alternating layers on various substrates. 4 In this work, first results of laminated CeO 2 -HfO 2 dielectric layers deposited by PLD are presented. ExperimentalCeO 2 -HfO 2 nanolaminates were grown on HF-dipped silicon ͑100͒ substrates at temperatures varying from 220 to 620°C by PLD from high-density, pure ͑above 99.99% purity͒ CeO 2 and HfO 2 targets in an ultrahigh vacuum ͑UHV͒-PLD system ͑with a base pressure below 5 ϫ 10 −9 mbar͒. A 248 nm KrF laser is used for PLD at 1 and 3 J/cm 2 for CeO 2 and HfO 2 targets, respectively. Target-tosubstrate distance was 45 mm and laser repetition rate was 5 Hz for all deposited layers. These settings resulted in a deposition rate of 0.125 nm/s. A 0.1 mbar Ar + H 2 ͑5%͒ gas mixture was used as deposition ambient to create a reducing atmosphere to prevent excessive silicon oxide formation during deposition, as well as to reduce the CeO 2 first layer to Ce 2 O 3 . The latter is thermodynamically more stable on silicon than CeO 2 toward SiO 2...

Films of BaTiO3 ranging from 20 nm to 300 nm in thickness were grown with pulsed laser deposition on Nb:SrTiO3. The quality of the layers was investigated using atomic force microscopy, X‐ray reflectivity and X‐ray diffraction. Both the micrographs and the X‐ray reflectivity spectra indicate a smooth surface of the layers. The X‐ray diffraction profiles measured using synchrotron radiation show features characteristic for highly crystalline thin films. The application of an external electric field parallel to the c axis changes an hkl reflection of BaTiO3 to an hk reflection. Due to the anomalous dispersion, the intensities of these two reflections are not equal and the atomic displacements can be determined from the intensity differences. The electric field‐induced intensity changes can be as large as a few percent, which makes data collection from a 100 nm film using Cu Kα radiation from an X‐ray tube feasible. The ΔI/I values of a number of reflections from the 20 and 50 nm films were measured using synchrotron radiation. The observed ΔI/I values were in good agreement with the intensity changes expected for polarization switching in the bulk.