Direct Liquid Injection Chemical Vapor Deposition

Thin film technology, based on different chemical and physical methods, enabled miniaturization, co-integration, and amelioration of the performance of the devices. Chemical vapor deposition (CVD) systems ensure high productivity and demonstrate excellent film uniformity (up to 12 inch wafers) and repeatability with high throughput for a variety of different films of oxides, nitrides, metals, chalcogenides, etc. In the last two decades, direct liquid injection (DLI)-CVD enabling the usage of solid and liquid precursors has proven to be one of the most versatile CVD process to meet industrial requirements. In this chapter, the requirements to the precursors suitable for DLI-CVD, different classes of available precursors, and models used to describe the evaporation are overviewed. Then, different liquid delivery devices used in DLI-CVD such as capillary tubes, syringes, aerosol delivery systems, and valves are reviewed in detail

Piezoelectric Response in Hybrid Micropillar Arrays of Poly(Vinylidene Fluoride) and Reduced Graphene Oxide

International audienceThis study was dedicated to the investigation of poly(vinylidene fluoride) (PVDF) micropillar arrays obtained by soft lithography followed by phase inversion at a low temperature. Reduced graphene oxide (rGO) was incorporated into the PVDF as a nucleating filler. The piezoelectric properties of the PVDF-rGO composite micropillars were explored via piezo-response force microscopy (PFM). Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) showed that α, β, and γ phases co-existed in all studied samples, with a predominance of the γ phase. The piezoresponse force microscopy (PFM) data provided the local piezoelectric response of the PVDF micropillars, which exhibited a temperature-induced downward dipole orientation in the pristine PVDF micropillars. The addition of rGO into the PVDF matrix resulted in a change in the preferred polarization direction, and the piezo-response phase angle changed from -120° to 20°-40°. The pristine PVDF and PVDF loaded with 0.1 wt % of rGO after low-temperature quenching were found to possess a piezoelectric response of 86 and 87 pm/V respectively, which are significantly higher than the |d33eff| in the case of imprinted PVDF 64 pm/V. Thus, the addition of rGO significantly affected the domain orientation (polarization) while quenching increased the piezoelectric response

Tutoriel: Ferroelectric thin films for acoustic applications

International audienceTutoriel: Ferroelectric thin films for acoustic application

Epitaxy of LiNbO3 thin films

International audience<font face="null"&gt<span style="font-size: 13px;"&gtEpitaxy of LiNbO3 thin films</span&gt</font&g

Effet des contraintes et transition de phase dans des couches minces de PbTiO3 obtenues par MOCVD

Raman spectroscopy, X-ray diffraction (XRD) and Transmission Electron Microscopywere used to investigate the origin and stress effects on phase transitions in PbTiO3(PTO) epitaxial thin films. A thickness series of epitaxial PTO films were deposited onsubstrates inducing compressive (SrTiO3 and LaAlO3) and tensile (MgO) misfit stressesto vary the stress level in the films.We showed that the VH polarization configuration is essential for Raman investigationof residual stress in PTO thin films as oblique modes are absent, and that E(3TO) hardmode is the unique reliable mode. In order to obtain information about the dominant cdomains,spectra must be collected on the film cross section. The residual stress originatesnot only from misfit stresses, but also from thermal and phase transformationstresses.Phase transitions and domain state transformations were investigated using high temperatureXRD and Raman spectroscopy. It was found that ferroelectric cluster size inhigh temperature phase is increased and Tc is higher in highly stressed films.Cette étude réalisée par Spectroscopie Raman, Diffraction de Rayons X et MicroscopieElectronique en Transmission porte sur l’origine et l’effet des contraintes sur la transitionde phase dans des couches épitaxiées de PbTiO3 (PTO). Des films minces de PTOde différentes épaisseurs ont été déposés sur plusieurs substrats de façon à faire varier ledésaccord de maille film-substrat pour générer des films sous contrainte de compression(SrTiO3 et LaAlO3) et sous tension (MgO).Les contraintes résiduelles dans les films PTO ont été déterminées à partir des spectresRaman mesurés exclusivement en configuration de polarisation VH pour éliminer lesmodes obliques; le mode dur E(3TO) est apparu le seul mode fiable pour l’estimationdes contraintes. Pour caractériser les domaines c qui sont prépondérants, les spectres ontdû être mesurés sur la tranche des films. Les contraintes résiduelles proviennent nonseulement du désaccord de maille, mais aussi de contraintes thermiques ou liées à latransition de phase.Les transitions de phase et les changements d’états de domaines dans les films ont étéanalysés par diffraction des RX et spectroscopie Raman à haute température. Il est apparuque la taille des clusters ferroélectriques à haute température est plus grande et Tcplus élevée dans les films très contraints

Temperature-dependent resonant Raman scattering of yttria doped zirconia phases in thermal barrier coatings

International audience<div id="abs0010" style=""&gt<p id="sp0045" style=""&gt<font face="arial, helvetica"&gt<span style="font-size: 13px;"&gtTo understand the strong Raman scatteringintensity of metastable t′-YSZ thermal barrier coatings, aboutthree times than other phases of yttria doped zirconia, a carefulinvestigation of high temperature phase is performed by ultravioletRaman scattering at 355 nm up to 1500 °C. The studied specimens arethermal barrier coating as well as single crystals of monocliniczirconia and cubic yttria stabilized zirconia. The ultravioletRaman scattering efficiency of cubic and metastable zirconiaindicate a crossover between the laser line and the band gap ofthese phases that are well explained by Loudon’s resonant Ramanscattering model. In the case of pure zirconia, the Ramanscattering intensity presents a tetragonal martensitic phasetransition at around 1050–1200 °C with a small anomaly of Ramanintensity. From this study, one can infer that the strong Ramanscattering intensity of t′-YSZ may originate from thephotoelasticity effect of the ferroelasticphase.</span&gt</font&gt<br /&gt</p&gt</div&g

From green piezoelectric materials to designed hybrid piezoelectric energy harvesters

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Energy Harvesting with lead free LiNbO3

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Can LiNbO3 be an alternative for PZT in vibrational energy harvesters?

International audienceObtaining high power output from piezoelectric harvesters in many applications requires a high electromechanical coupling coefficient, hence the preference and common use of bulk PZT in piezoelectric vibrational energy harvesters (PVEHs). However, in short future, PZT has to be replaced by lead-free materials. Ferroelectric LiNbO3 presents figure of merit similar to that of PZT and are potential materials for PVEHs. However, the studies of energy harvesters based on LiNbO3 were limited so far by the difficulty to obtain this material in the form of films with physical properties similar to those of single crystal and by its incompatibility with silicon technology. Recently, the LiNbO3 thin films of single crystalline quality on Si were achieved by wafer on wafer technology. Moreover, it was shown that pulsed-injection MOCVD is suitable method for deposition of high quality LiNbO3 thin films, offering a possibility to obtain the films on larger and non-conformal surfaces and to develop more complex heterostructures. Hybrid harvesters (i.e. ones which combine more than one type of harvesting transducer) have had increasing interest in the literature but the bulk of the work has simply involved adding multiple individual transducers placed into one package. Our research concerns the possibility of using an individual transducer element to scavenge multiple types of energy, i.e thermal and vibration. It was reported that combining piezoelectric and thermal effects could amplify the displacement in piezoelectric actuators, which therefore demonstrates that generated charges can be increased with a structure dedicated for hybrid harvesting

Chemical and Strain Engineering of Functional Oxides

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