Publisher Correction: Large anisotropy of ferroelectric and pyroelectric properties in heteroepitaxial oxide layers.

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Large anisotropy of ferroelectric and pyroelectric properties in heteroepitaxial oxide layers.

Epitaxial PbZr0.52Ti0.48O3 (PZT) layers were integrated on Si(001) with single PZT {001} orientation, mosaïcity below 1° and a majority of a-oriented ferroelectric domains (∼65%). Ferroelectric and pyroelectric properties are determined along both the out-of-plane and in-plane directions through parallel-plate capacitor and coplanar interdigital capacitor along the <100>PZT direction. A large anisotropy in these properties is observed. The in-plane remnant polarization (21.5 µC.cm-2) is almost twice larger than that measured along the out-of-plane direction (13.5 µC.cm-2), in agreement with the domain orientation. Oppositely, the in-plane pyroelectric coefficient (-285 µC.m-2.K-1) is much lower than that measured out-of-plane (-480 µC.m-2.K-1). The pyroelectric anisotropy is explicated in term of degree of structural freedom with temperature. In particular, the low in-plane pyroelectric coefficient is explained by a two-dimensional clamping of the layers on the substrate which induces tensile stress (from thermal expansion), competing with the decreasing tetragonality of a-domains (shortening of the polar c-axis lattice parameter). Temperature-dependent XRD measurements have revealed an increased fraction of a-domains with temperature, attesting the occurrence of a partial two-dimensional clamping. These observed properties are of critical importance for integrated pyroelectric devices.

[Telemedicine and lung transplanted patients: A feasibility study]. / Télé-suivi des patients transplantés pulmonaires : étude de faisabilité

BACKGROUND: Lung transplant patients are characterized by a high use of healthcare resources and an elevated rate of hospitalization. In lung transplant recipients, spirometry home monitoring has been advocated for the early detection of acute infection and rejection of the allograft. We will test a new system that allows regular monitoring of the patient's pulmonary status at home after discharge from hospital. METHODS: This study will be prospective and in addition to usual healthcare. The main aim of this feasibility study will be to evaluate the compliance of patients in performing three spirometric measurements per week. Patients will have received a lung transplant more than three months prior to entering the study. The home equipment will comprise a data transmitting box (Twitoo(®)) and a spirometer. A decrease of 10% from baseline in one or more parameters will generate an alarm, which will lead to the transplant physician calling the patient and possibly inviting him to the hospital. EXPECTED RESULTS: The feasibility will be considered as acceptable for an average compliance of 70%. The coefficient of variation and the number of spiro-measurements will be adjusted according to the results obtained.

Insulator-metal transition of VO2 ultrathin films on silicon: evidence for an electronic origin by infrared spectroscopy.

We report on the first simultaneous observations of both electronic and structural temperature-induced insulator-to-metal transition (IMT) in VO2 ultrathin films, made possible by the use of broad range transmission infrared spectroscopy. Thanks to these techniques, the infrared phonon structures, as well as the appearance of the free carrier signature, were resolved for the first time. The temperature-resolved spectra allowed the determination of the temperature hysteresis for both the structural (monoclinic-to-rutile) and electronic (insulator-to-metallic) transitions. The combination of these new observations and DFT simulations for the monoclinic structure allows us to verify the direct transition from monoclinic (M1) to rutile and exclude an intermediate structural monoclinic form (M2). The delay in structural modification compared to the primer electronic transition (325 K compared to 304 K) supports the role of free charges as the transition driving force. The shape of the free charge hysteresis suggests that the primer electronic transition occurs first at 304 K, followed by both its propagation to the heart of the layer and the structural transition when T increases. This study outlines further the potential of VO2 ultrathin films integrated on silicon for optoelectronics and microelectronics.