Platinum (Pt) is a noble metal with low resistivity and resilience to oxidation, which is largely used in micro-electronic devices. In order to facilitate the integration of Pt thin films on silicon substrate, we are showing the ability to control their orientation by using [Ca2Nb3O10](-) nanosheets (CNOns) as seed layer. Pt thin films were sputtered on silicon coated by CNOns (CNOns/SiO2/Si), and on TiO2/SiO2/Si substrates for comparison, at temperatures ranging from room temperature up to 625 degrees C. Under pure argon, highly (111) textured Pt thin films were obtained on both substrates, regardless of the deposition temperature. However, by using an oxygen/argon mixture, highly (200) textured films could be obtained, only on CNOns/SiO2/Si substrate, when the substrate temperature is above 550 degrees C. X-ray diffraction, scanning electron microscopy, and atomic force microscopy were used to characterize the crystalline quality, thickness, surface morphology and roughness of the Pt thin films. Their resistivity was measured at room temperature by the four-point probes method.

a. Normandie Université, UNICAEN, ENSICAEN, CNRS, GREYC, Caen, France b. Normandie Université, UNICAEN, ENSICAEN, CNRS, CRISMAT, Caen, France c. Université de Lyon, Ecole centrale de Lyon, INL UMR CNRS5270, Ecully, France d. Department of Materials Science and Engineering, Cornell University, Ithaca, New York, USA e. Kavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, New York, USA

Lead zirconate titanate Pb(Zr,Ti)O 3 (PZT) is a well know ferroelectric material with excellent piezoelectric properties, namely large piezoelectric coefficients, low leakage current and reliable performance, which makes it very suitable as an actuator material in Micro-ElectroMechanical Systems (MEMS). The performance of piezoelectric MEMS is, however, strongly dependent on the film quality. In the present work, the epitaxial growth of PZT is desired as it can help to reduce high-frequency losses, to allow for larger electromechanical coupling and to increase the final device sensitivity. We used an epitaxially grown conductive oxide bottom electrode, namely 45 nm thick La 2/3 Sr 1/3 MnO 3 (LSMO) films, deposited on SrTiO 3 buffered (001) silicon substrates using a combination of pulsed laser deposition and reactive molecular beam epitaxy techniques. The 500 nm thick c-axis oriented PZT layers were deposited at 600°C by magnetron sputtering on the LSMO films on STO/Si (001). The piezoelectric and ferroelectric properties of the PZT layers were studied by PiezoForce Microscopy on as-grown PZT films and Polarization versus Electric field measurements on samples covered with Pt top electrodes. The PZT films exhibited good piezoelectric and ferroelectric properties with a remanent polarization higher than 20 µC·cm −2 , which makes them suitable for the fabrication of piezoelectric MEMS based on doubly-clamped LSMO suspended structures.

The decrease of the growth temperature of platinum (Pt) thin film on silicon substrate was studied using Ca2Nb3O10 nanosheets (CNOns) as seed layer. These nanosheets were obtained by the delamination of the layered perovskite KCa2Nb3O10 and they were deposited on silicon substrates by the Langmuir–Blodgett method. Pt thin films were sputtered on silicon coated by CNOns (CNOns/SiO2/Si), and on TiO2/SiO2/Si substrates for comparison, at temperatures ranging from room temperature up to 625 °C. X-ray diffraction, scanning electron microscopy, and atomic force microscopy were used to characterize the crystalline quality, thickness, surface morphology and roughness of the Pt thin films. Highly (111) textured Pt thin films were obtained on CNOns/SiO2/Si at substrate temperature as low as 200 °C. The full width at half maximum of the rocking curve of the (111) X-ray peak was about one degree, indicating a high crystalline orientation. The resistivity was measured at room temperature by the four point probes method to confirm the quality of Pt thin films elaborated at low temperatures. These results pave the way for easier integration of highly textured platinum thin film in low temperature microelectronic processes.

A black aluminum (B-Al) film was deposited onto the surface of a stack structure of platinum/Pb(ZrxTi1-x)O-3/platinum (Pt/PZT/Pt) to convert light into a heat variation and the heat variation into a polarization change. A comparison was performed between B-Al/Pt/PZT/Pt and conventional Pt/PZT/Pt structures. An absorbance higher than 95% was measured for the B-Al layer over a large range of wavelengths varying from 350 nm to 1000 nm. The theoretical model shows that heat diffusion was extremely fast through the layers, and the sample holder played a key role in the variation and stabilization of the system temperature. A doubled variation of the polarization was observed when the light was applied onto the surface of the stack structure with stable B-Al on the top. This behavior was interpreted by the larger temperature variations induced under the highly absorptive B-Al layers, in good correlation with the theoretical model prediction based on the heat fluxes in the structures. This result is very promising for possible pyroelectric energy harvesting applications. Published under license by AIP Publishing.

TbxDy1 − xFe2 (Terfenol-D) thin films were grown in situ at 500 °C on Pt/TiO2/SiO2/Si substrate by multi-target sputtering. The thickness effect of the Terfenol-D layer on the microstructure and on the magnetic properties was investigated. Magnetic force microscopy was used to observe local domain patterns. Strong changes in the shape of magnetic domains were observed when the thickness of the Terfenol-D film was increased. Transmission Electron Microscopy observations showed that in situ elaboration at 500 °C gives rise to large diffusion of the platinum of the bottom electrode into the Terfenol-D film leading to different sub-layers. Saturation magnetization values increased from 500 to 840 kA/m, and coercive fields from 15 to 140 kA/m, respectively, when the thickness of the Terfenol-D film was varied from 100 to 1000 nm. Co-sputtering of Pt and Terfenol-D through the entire film thickness led to a similar saturation magnetization as well as an interesting strong decrease of the coercive field of these mixed films.

TbxDy1−xFe2/Pt/Pb(Zrx, Ti1−x)O3 thin films were grown on Pt/TiO2/SiO2/Si substrate by multi-target sputtering. The magnetoelectric voltage coefficient αΗΜΕ was determined at room temperature using a lock-in amplifier. By adding, in series in the circuit, a capacitor of the same value as that of the device under test, we were able to demonstrate that the magnetoelectric device behaves as a voltage source. Furthermore, a simple way to subtract the stray voltage arising from the flow of eddy currents in the measurement set-up, is proposed. This allows the easy and accurate determination of the true magnetoelectric voltage coefficient. A large αΗΜΕ of 8.3V/cm. Oe was thus obtained for a Terfenol-D/Pt/PZT thin film device, without DC magnetic field nor mechanical resonance.

Heterostructures of piezoelectric Pb(Zr,Ti)O3 and magnetostrictive Galfenol were fabricated by sputtering and pulsed laser deposition on platinized Si substrates with the aim to induce a magnetoelectric coupling between the layers of the two materials. In this study, no intermediate layer was introduced between Pb(Zr0.56Ti0.44)O3 and Galfenol in contrast to most of the previous thin films studies. The obtained magnetoelectric coupling constant is in the range of 6–7 V/(cm Oe), indicating that an undisturbed piezoelectric-magnetostrictive interface can outbalance small deteriorations of the ferroic properties of the active materials.

Tb0.3Dy0.7Fe2/Pt/PbZr0.56Ti0.44O3 (Terfenol-D/Pt/PZT) magnetoelectric (ME) thin films were deposited on Pt/TiO2/SiO2/Si substrate. The ME voltage coefficient αHME was determined at room temperature using a lock-in amplifier and by applying to the sample an alternating magnetic field of a few mT. Surprisingly, very similar responses were obtained from a simple commercial capacitor set in series with a small loop of wire. This allowed us first to accurately model and reproduce the frequency response of the ferroelectric PZT layer alone. We also observed that, at low frequency, the voltage across the ferroelectric capacitor and the current in the circuit did not decrease significantly when diminishing then removing, the area of the conductive loop. One major conclusion is that eddy currents in the lead wires, rather than the classical electromotive force across conductive loops, contribute significantly to the total voltage response, at least for thin film ME devices. A model taking into account eddy currents was then developed for the extraction of the true αHME. A large αHME of 4.6 V/cm.Oe was thus obtained for the Terfenol-D/Pt/PZT thin film device, without DC magnetic field.

Tb0.3Dy0.7Fe2/Pt/PbZr0.56Ti0.44O3 (Terfenol-D/Pt/PZT) magnetoelectric (ME) thin films were deposited on Pt/TiO2/SiO2/Si substrate. Ferroelectric and magnetic properties were characterized at room temperature. At zero dc magnetic field and out of mechanical resonance, a variation of the voltage across the ferroelectric film was obtained when a small external ac magnetic field was applied to the device. The corresponding ME voltage coefficient was 1.27 V/cm Oe. On the same sample, local magnetic domain patterns were imaged by magnetic force microscopy. Reversible changes in magnetic domain patterns were observed when a dc electric field of 120 to 360 kV/cm was applied to the ferroelectric layer. These results confirm that both magnetic control of ferroelectric polarization and electric control of magnetization are achievable on ME thin films devices deposited on silicon substrates.

TbxDy1-xFe2 thin films are grown on Pt/TiO2/SiO2/Si substrate by multi-target sputtering. In order to achieve the best magnetic properties, samples grown while heating the sample holder (in situ films) are compared to those prepared at room temperature followed by thermal annealing. The effect of Tb, Dy and Fe content is also examined. It is found that the magnetic properties are very sensitive to the deposition parameters. Magnetization value as high as 680 emu/cm(3) with very low coercivity is achieved in a 140 nm thick film whose composition (Tb0.3Dy0.7)Fe-2 corresponds to the TERFENOL-D formulation. Observation of soft ferromagnetism and high magnetization are related to crystallization of nano-grains (size 7-10 nm) as deduced from microstructure investigation by X ray diffraction and transmission electron microscopy. It is shown the possibility of growing TERFENOL-D thin films with properties suitable for observation of extrinsic magneto-electric coupling in future thin film devices combining piezoelectric and magnetostrictive materials on metallized silicon substrate. (C) 2013 Elsevier B.V. All rights reserved.

Ways to sense electric field using PZT capacitors are investigated. Duality rules a priori apply to material physics, linking polarization to magnetization properties, i.e. D(E) to B(H) curves, but no real electrical flux gate or charge gate does exist which would be the dual of the common flux gate magnetometer. The Landau - Khalatnikov equations are applied to ferroelectric materials subjected to both a DC and an AC pumping signal. They are solved to get the model of the PZT capacitors dynamics. They are experimentally investigated using the Sawyer Tower method. A second harmonic detection is a way to extract the DC excitation.

Tb0.3Dy0.7Fe2/Pt/PbZr0.56Ti0.44O3 (Terfenol-D/Pt/PZT) thin films were sputtered on Pt/TiO2/SiO2/Si substrate. PZT and Terfenol-D layers were chosen for their large piezoelectric and magnetostrictive coefficients, respectively. 4%–5% magnetocapacitance has been measured on a Terfenol-D/Pt/PZT stack at room temperature. A magnetoelectric (ME) voltage coefficient of 150 mV/cm Oe was obtained at low dc magnetic field out of mechanical resonance. This work demonstrates the possibility to achieve ME effect in integrated devices involving Terfenol-D and PZT thin films providing that the diffusion, which may occur between both active layers is reduced using an intermediate layer.

Aluminum nitride (AlN) thin films were deposited at room temperature by pulsed laser deposition, and their nanostructure and piezoelectric properties were investigated as a function of fluence. For all fluences, the films were found to consist of an amorphous AlN matrix containing crystalline AlN nanoparticles with size of 6–7 nm. These nanoparticles spark off the good piezoelectric response, with d33 piezoelectric coefficients between 2.3 and 3.8 pm V−1, similar to those obtained for (002)-oriented AlN films deposited at higher temperatures. These results indicate that nanocrystalline AlN films deposited at room temperature are good candidates for integration in acoustic wave applications.

Laser induced forward transfer (LIFT) is a laser direct write technique based on laser ablation. A UV-absorbing triazene polymer (TP) has been used as a sacrificial dynamic release layer (DRL) to propel other materials forward without damage. The effect of different laser pulse lengths (nanosecond and picosecond) on standard frontside TP ablation and backside TP ablation of aluminium thin films has been studied. Whilst the picosecond ablation causes the shock wave and the flyer to be faster, the ablation rate is considerably lower, suggesting an increase in ablation product energies and a decrease in loss mechanisms. The effect of beam energy homogeneity was seen to be an important factor for good flyer generation.