Uncooled pyroelectric detector arrays using ferroelectric ceramics and thin films

This paper presents a fully integrated PVDF-on-silicon pyroelectric sensor array. The pyroelectric sensor has two main features: a subpixel low noise charge amplifier and a self-absorbing layered structure. The integrated low noise charge amplifier is implemented in a standard CMOS process technology. It is located directly under the sensing structure, maximizing the pixel fill factor. The self-absorbing pyroelectric sensor is a three-layer stack, consisting of a conductive polymer as an absorber layer and front electrode, a thin PVDF film as the pyroelectric material, and a rear metal layer acting as a reflector layer and rear electrode. The manufacture of the pyroelectric sensor array requires five maskless post-CMOS processing steps and is compatible with any n-well, double metal, double polysilicon, CMOS process. The array has an average pixel voltage sensitivity of 2200 V/W at 100 Hz, an NEP of 2.4/spl times/10/sup -11/ W//spl radic/Hz at 100 Hz, and a specific detectivity of 4.4/spl times/10/sup 8/ cm /spl radic/Hz/W at 100 Hz.

Electrocaloric response modulated by misfit strain in different oriented epitaxial ferroelectric thin films

Preface. Pulsed Laser Ablation-Deposition and Characterization of Ferroelectric Metal Oxide Heterostructures R. Ramesh, O. Auciello, V.G. Keramidas, R. Dat. Low Energy Ion Bombardment Induced Effects in Multi-Component Electroceramic Thin Films S.B. Krupanidhi. Growth and Properties of Pb(Mg1/3Nb2/3)O3 - PbTiO3 and Pb(Zr,Ti)O3 Thin Films by Pulsed Laser Deposition A. Safari, C. Tantigate, J. Lee. Wavelength Dependence in Pulsed Laser Deposition of ZnO Thin Films D. Craciun, V. Craciun. Organometallic Chemical Vapor Deposition of Lead Zirconate Titanate M. de Keijser, P.J. van Veldhoven, G.J.M. Dormans. Alkoxide Precursors for Ferroelectric Thin Films M.I. Yanovskaya, N.Ya. Turva, L.I. Solov'Yova. Deposition of Undoped and Doped Pb (Mg,Nb)O3 - PbTiO3, PbZrxTi1-xO3, Alkaline Earth Titanate and Layered Perovskite Thin Films on Pt and Conductive Oxide Electrodes by Spin - On Processing: Correlation of Growth and Electrical Properties M. Klee, U. Mackens, J. Pankert, W. Brand, W. Klee. Relationships between Ferroelectric 90 Degrees Domain Formation and Electrical Properties of Chemically Prepared Pb(Zr,Ti)O3 Thin Films B.A. Tuttle, T.J. Garino, J.A. Voigt, T.J. Headley, D. Dimos, M.O. Eatough. Characterization of Sol-Gel Pb(ZrxTi1-x)O3 Thin Film Capacitors with Hybrid (Pt,RuO2) Electrodes H.N. Al-Shareef, O. Auciello, A.I. Kingon. Organically Modified Sol-Gel Precursors for Ferroelectric Deposition by Spin Coating P. Gaucher, J. Hector, J.C. Kurfiss. Preparation and Properties of Calcium Modified Lead Titanate Thin Films M.L. Calcada, F. Carmona, R. Sirera, B. Jimenez. Microstructure of Lead Titanate-Based Thin Films L. Pardo, J. Ricote, M.L. Calzada. Stoichiometry and Phase Structure of Sol-Gel Derived PZT-Based Thin Films M. Kosec, Y. Huang, E. Sato, A. Bell, N. Setter, G. Dra i , S. Bernik, T. Beltram. Liquid Phase Epitaxy of Na1-yKyTa1-xNbxO3 on KTaO3 Substrates Z. Sitar, R. Gutmann, P. Gunter. Pulse Switching Characterization of Ferroelectric Thin Films P.K. Larsen, R. Cuppens, G.J.M. Dormans. Polarization, Conduction, and Breakdown in Non-Ferroelectric Perovskite Thin Films R. Waser. Anomalous Logarithmic Dependencies in CD.C. Breakdown of Ferroelectric Thin Films J.F. Scott. The Shape of the Hysteresis Curve of Ferroelectric Single Crystals and Ceramics G. Arlt. Fast Transient Measurements on Electroceramic Thin Films G.W. Dietz, M. Schumacher, R. Waser. The Influence of Dopants on the Leakage Current in PZT Thin-Film Ferroelectric Capacitors D.J. Wouters, G. Willems, G. Groeseneken, H.E. Maes, K. Brooks, R. Klissurska. Photo-Induced Storage and Imprinting in (Pb,La)(Zr,Ti)O3 Thin Films D. Dimos, W.L. Warren, B.A. Tuttle. Depletion, Depolarizing Effects and Switching in Ferroelectric Thin Films A.K. Tagantsev, M. Landivar, E. Colla, K.G. Brooks, N. Setter. Nonstoichiometry, Defects, and Charge Transport in PZT M.V. Raymond, D.M. Smyth. X-Ray Diffraction Line Profile Analysis of ZnO Thin Films Deposited on Al-SiO2-Si Substrates P. Sutta, Q. Jackuliak, V. Tvarozec, I. Novotny. Electron Emission from Ferroelectrics H. Gundel. Integration of Ferroelectric Thin Films for Memory Applications H. Achard, H. Mace. Processing and Device Issues of High Permittivity Materials from Drams B.E. Gnade, S.R. Summerfelt, D

Low-noise charge sensitive readout for pyroelectric sensor arrays using PVDF thin film

A planar multi target sputtering approach was used to deposit PbTiO3 (PT) and Pb(Zr, Ti)O3 (PZT) films on TiO2/Pt bottom electrodes for the use in thin film pyroelectric IR detector arrays. PZT films with a Zr content of 28 at% (PZ28T) exhibited the best pyroelectric coefficient of typically 2×10−4 Cm−2K−1. The PZ28T films have been used for fabricating a two dimensional 11×6 pixel pyroelectric detector array on Si wafers. The array pixels with a sensitive area of 280 ×280 μm2 have a noise lequivalent power NEP of less than 0.7 nW at 1 Hz. It is planned to use the detector array in systems for motion detection.

Preparation and properties of lead-based ferroelectric thin films

The creation of multilayer resistive memory devices based on nanolayer memristive compositions with thin ferroelectric (FE) films, in which resistance switching is caused by a combination of effects related to the influence of interface regions, polarization states, charge transport mechanisms, and microscopic features of nanostructures, requires the development of new experimental approaches to the study of local electrophysical properties. One of the most common ways to investigate local electrophysical properties is the use of various atomic force microscopy (AFM) techniques, including the Kelvin probe microscopy, tunneling AFM, and piezoresponse AFM. The main reason for switching from AFM to scanning tunneling microscopy techniques when studying the local resistive properties of memristive compositions with FE films is the need to stabilize the probe-sample contact. The main obstacle to the effective use of AFM techniques to study the local ferroelectric properties in nanolayer memristive compositions with thin FE films is the occurrence of a strain gradient during scanning, which leads to the contribution of the flexoelectric effect and direct piezoelectric effect in the measurement results. In this work, we have developed a method of investigating the local FEproperties using scanning tunneling microscopy (STM) and spectroscopy (STS) techniques under ultra-high vacuum conditions. The essence of the proposed approach is to identify the contribution of polarization charges, as well as the features of their screening on the free surface of the FE film, to the results of STS measurements at different polarization orientations in the FE film. In combination with STM measurements of local morphological features, the analysis of experimental results makes it possible to identify the state of FE polarization, determine the contribution of the surface screening of polarization charges to the manifestation of memristive effects, and investigate the correlation between the local resistive and FE properties in nanolayer memristive compositions with thin FE films.

Three methods for fabricating thin film capacitors are investigated using sputtering, sol-gel, and atomic layer deposition (ALD) techniques for advanced packaging applications for embedded capacitors. In particular, the microstructures and the electrical properties of ceramic oxide films Au/Ti/Al2O3 for ALD are being studied while ferroelectric thin films Au/Ti/BaTiO3 for sol-gel and Cu/Ba1-XSrXTiO3 for sputtering are being discussed in detail. The upper Au/Ti electrode layer is deposited by dc magnetron sputtering on top of Al2O 3 (ALD process) and on BT layer to complete the Au/Ti/BaTiO 3/Ni/Cu/FR4/Cu (sol-gel process) structure respectively whereas Cu is deposited by sputtering on top of the BST layer to complete the Cu/Ba1-XSrXTiO3/Cu/SiO2/Si (sputtering process). After a careful comparison is done, ALD for the Al 2O3 thin film seems to show the most promising process for its low temperature at 150degC and for its electrical properties like a capacitance of 0.88nF/mm2 with less then plusmn2% tolerances, a dissipation factor of less than 0.018, and a low leakage current less than 0.1muA/cm2 at 4 V

The use of ferroelectric polarization to promote electron–hole separation has emerged as a promising strategy to improve photocatalytic activity. Although ferroelectric thin films with planar geometry have been largely studied, nanostructured and porous ferroelectric thin films have not been commonly used in photo-electrocatalysis. The inclusion of porosity in ferroelectric thin films would enhance the surface area and reactivity, leading to a potential improvement of the photoelectrochemical (PEC) performance. Herein, the preparation of porous barium titanate (pBTO) thin films by a soft template-assisted sol–gel method is reported, and the control of porosity using different organic/inorganic ratios is verified by the combination of scanning electron microscopy and ellipsometry techniques. Using piezoresponse force microscopy, the switching of ferroelectric domains in pBTO thin films is observed, confirming that the ferroelectric polarization is still retained in the porous structures. In addition, the presence of porosity in pBTO thin films leads to a clear improvement of the PEC response. By electrochemical poling, we also demonstrated the tuning of the PEC performance of pBTO thin films via ferroelectric polarization. Our work offers a simple and low-cost approach to control the morphology optimization of ferroelectric thin films, which could open up the development of materials with great potential for PEC applications.

The metalorganic decomposition-derived SrBi2Ta2O9 (SBT) ferroelectric thin films were annealed in forming gas (5%H2+95%N2), and their fatigue characteristics were investigated. Although the hysteresis loops of these films had an unacceptable degradation under such a H2-containing reducing atmosphere, no obvious polarization fatigue with electric field cycling could be observed. However, an increase of P*r was observed over the initial period of the fatigue test. It could be viewed as a competition between the increase of P*r due to the leakage current and the decrease of P*r due to switching polarization. H2 played an important role in the increasing in the leakage current of SBT thin films, forming more weak pinning centers of domain walls, and degradation in the fatigue characteristics.

Ferroelectric thin films have attracted great attention for its rich applications in energy-efficient electronic devices because of their relevant physical properties such as high dielectric constants, electrically switchable polarization, and high piezoelectric coefficients [1].In fact, the growing demand for miniaturized microelectronics has inspired diverse research efforts towards the engineering of ferroelectric properties and domain architectures in the ultrathin regime [2].Thus, comprehending the structural and electrical properties of ferroelectric thin films on the nanoscale became crucial.Recently, a lot of effort has been put into studying ferroelectric oxide superlattices with complex topologies such as longrange vortex-antivortex arrays of polarization [3].These works have called for an in-depth structural investigation of the superlattice structures, since the orientation and arrangement of ferroelectric domains define the macroscopic ferroelectric properties in ferroelectric thin films.Here, we report on a newly discovered local order state in superlattices consisting of ferroelectric lead titanate and dielectric strontium titanate using a complete three-dimensional diffuse X-ray scattering data analyzed with 3D-deltaPDF method [4].The data was collected with single crystal diffuse X-ray scattering technique, which, to the best of our knowledge, was used for the first time to study local order in single crystalline thin films.This work will not only contribute to gaining useful insights on structure-property correlations of ferroelectric oxide superlattices, but also lay groundwork for developing a novel non-disruptive solid-state characterization technique for analyzing local structures of thin films.

Slater’s formula for perovskite ferroelectrics was modified by Barrett to include the quantum effect. Dielectric constant vs temperature (e¢ vs. T) data for Strontium titanate (ST) and Potassium tantalate (KT) in single crystals and ceramics fitted well, while the data (e¢ vs. T) for Barium titanate (BT) in single crystals and ceramics did not fit at all to Barrett’s equation. That is, ferroelectrics like ST, which show only Curie-Weiss temperature but does not show a ferroelectric transition, obey Barrett’s equation. The Curie-Weiss law fitted the data of BT well. That KT a cubic and consequently a paraelectric down to 13 K obeys Barrett’s equation is intriguing. e¢ vs T values of Barium strontium titanate (BaxSr1-xTiO3), thin films could be fitted to the Curie-Weiss law, thus eliminating the existence of quantum effect in thin films.

In the past years lead free K x Na 1‐x NbO 3 ceramics with huge d 33 ‐values, comparable to that of PbZr 1‐x Ti x O 3 , have been demonstrated [1]. The high piezoelectric coefficients are generally attributed to the presence of a monoclinic phase at the morphotropic phase boundary and the associated symmetry reduction. A recent work by Schwarzkopf et al. [2] reports that monoclinic phases can also be stabilized in ferroelectric perovskite thin films by utilizing anisotropic epitaxial strain. Another advantage of using epitaxial strain is to engineer by an appropriate choice of the substrate and film composition the arrangement and size of domains, which in turn influences on the piezo‐ and ferroelectric material properties. Ferroelectric thin films and their domain structure are commonly characterized by combining X‐ray diffraction (XRD) and piezoresponse force microscopy (PFM). While XRD gives useful crystallographic information, its local resolution is limited and a detailed study of the domains is impossible. On the other hand PFM has sufficient spatial resolution but does not provide structural information. Plan‐view transmission electron microscopy (TEM) with its ability to study structural data with high accuracy at atomic resolution is in principle ideally suited to gain detailed information on the domain structure of the film. There is, however, one major challenge. In order to preserve the as‐grown strain state of the film and thus its domain structure plan‐view TEM samples with a thick substrate layer are necessary. Since TEM is a projective method it images typically the projected potential averaged along the beam direction including both film and substrate for a plan‐view observation geometry. In this paper we will show that this challenge can be overcome by appropriate imaging conditions using high resolution scanning TEM (STEM) annular dark field (ADF) imaging. Due to the channeling effect and the reduced depth of focus in STEM mode we are able to obtain information mainly from the monoclinic distorted film, while the substrate gives rise to a uniform background intensity. As an example we study a 26 nm thin film of K 0.95 Na 0.05 NbO 3 , which was epitaxially grown on top of a (110) NdScO 3 substrate and shows giant piezoelectricity. PFM reveals a complex periodic domain structure with the coexistence of two different monoclinic domains (yellow and purple stripes in Fig. 2 a). According to XRD these domains differ from each other by the orientation of the in‐plane monoclinic distortion. Based on the structural data provided by XRD and PFM we created a supercell consisting of a K 0.95 Na 0.05 NbO 3 film, which contains two domains with a difference of the in‐plane monoclinic distortion of 2β=8 mrad, on top of a 150 nm thick rigid NdScO 3 substrate without any lattice distortion (Fig. 1 a). The chosen thickness of the substrate is a minimum value necessary to preserve the as‐grown strain state of the film. Frozen phonon simulations reveal that if the incident electron probe is transmitted first through the film, then the final high resolution STEM ADF image pattern directly reflects the domain structure of the K 0.95 Na 0.05 NbO 3 film with the evaluated shear angle 2β as in the supercell (Fig. 1 b). However, if the electron beam direction is inverted, i.e. the beam is transmitted first through the substrate, then no lattice distortion corresponding to the domain structure of the film is found in the obtained high resolution STEM ADF image. An analysis of the evolution of the electron probe inside the supercell (Fig. 1 c) shows that this 3‐dimensional sensitivity is caused by the electron channeling effect. In the present case the high resolution pattern in the final image is produced basically in the first 20‐30 nm of transmitted material. After this thickness the wave function of the electron beam is widely dispersed, irrespectively of the initial position of the electron probe. Thus the subsequent part of the specimen mainly contributes to a uniform background intensity in the final image. Consequently, the frozen phonon simulations demonstrate the feasibility of our approach to study domains in epitaxially strained ferrolectic films by plan‐view high resolution STEM ADF imaging. An experimental example for the STEM analysis of the domain structure for the above mentioned K 0.95 Na 0.05 NbO 3 film is shown in Fig 2 c. A model of the complex domain pattern including the sub‐domain structure will be discussed in the paper.

We investigated mechanical stress in thin freestanding BaTiO3 films prepared on bare silicon and on silicon, covered by a 120 nm thick, randomly oriented Al2O3 buffer. Films prepared on bare silicon by RF sputtering are essentially stress-free. However, they disintegrate after substrate removal. In contrast, the films prepared on the Al2O3 buffer have high tensile stress, but retain their structural integrity after separation from the substrate. Substrate removal is accompanied by film corrugation; at the same time, the freestanding films resonate mechanically. This seeming contradiction can be understood on the basis of a recently developed theory of 2D clamping in thin ferroelectric films.

The renormalized phonon spectrum beyond the random phase approximation in ferroelectric thin films is obtained using a Green's function technique and the transverse Ising model including anharmonic spin-phonon and phonon-phonon interactions. The temperature and film thickness dependence of the soft phonon mode energy $\ensuremath{\omega}$ is calculated for the case of positive and negative anharmonic spin-phonon interaction constants $R$ and for different surface constants ${R}_{s}$. For $Rg0$ the phonon mode energy increases with increasing temperature, $T\ensuremath{\rightarrow}{T}_{C}$, whereas for $Rl0$ the phonon mode decreases with increasing temperature. For the case of smaller surface constant compared to the bulk, ${R}_{s}l{R}_{b}$, we obtain that $\ensuremath{\omega}$ of the thin film is larger in comparison to that of the bulk, i.e., we obtain hardening of the soft mode. In the other case, ${R}_{s}g{R}_{b}$, the soft phonon mode energy of the thin films is smaller compared to the bulk, i.e., we obtain softening of the phonon mode. The first case could explain the behavior of the phonon mode, soft mode hardening in ${\mathrm{SrTiO}}_{3}$ and $(\mathrm{Ba},\mathrm{Sr}){\mathrm{TiO}}_{3}$ thin films obtained experimentally, whereas the second case is responsible for ${\mathrm{PbTiO}}_{3}$ thin films. The dependence of the phase transition temperature on film thickness and different surface spin-spin ${J}_{s}$ and spin-phonon interaction constants ${R}_{s}$ is discussed, too. The spin-phonon interaction enhances the phonon damping of the thin film. The damping increases near ${T}_{c}$ for the two cases $Rg0$ and $Rl0$. It is larger for thin films in comparison to the bulk. Taking into account the influence of an external electric field we obtain hardening of the soft phonon modes for $Rg0$ and $Rl0$.