Thick Nb-Doped Bismuth Titanate Film with Controllable Grain Orientation

In the current work, we reported a potential approach to obtain thick ceramic films with controllable grain orientation based on magnetic alignment and polymerization techniques. The slurry containing 40 vol% Bi₄Ti_2.96Nb_0.04O₁₂ (BINT) ceramic powder, monomer, initiator, and catalyst was drop coated on a Pt substrate and then moved into a vertical 10 T magnetic field. In 1–2 min, the ceramic particles were aligned by a strong magnetic force in slurry and then in situ locked by polymerization on the substrate. After sintering at 1000°C, a BINT ceramic film (50–80 μm in thickness) with a highly a / b plane orientation was obtained. Theoretically, the grain orientation in the films can be easily controlled by adjusting the magnetic field direction. This approach is readily applicable to other materials with a non-cubic structure and is expected to facilitate the fast preparation of grain-oriented thick films.     

Fabrication and Electrical Properties of Lead Zirconate Titanate Thick Films on Si Substrate by Using Lanthanum Nickelate Buffer Layer

Lead zirconate titanate PbZr_0.53Ti_0.47O₃ (PZT) thick films have been deposited on silicon substrate by modified metallorganic decomposition process. Crack-free PZT films of 8 μm thickness can be obtained by using lanthanum nickelate LaNiO₃ (LNO) as buffer layer. The greater LNO thickness, the greater thickness of crack-free PZT can be obtained. The X-ray diffraction measurements show the films exhibit a single perovskite phase with (110) preferred orientation. SEM measurements showed the PZT thick films have a columnar structure with grain size about 60–200 nm. The thickness dependence of ferroelectric, dielectric, and piezoelectric properties of PZT thick films have been characterized over the thickness range of 1–8 μm. For PZT with thickness of 8 μm, P _r and E _c are 30 μC/cm² and 35 kV/cm, and dielectric constant and dielectric loss are 1030 and 0.031, respectively. The piezoelectric coefficient ( d ₃₃) of PZT with 8 μm thickness is obtained to be 77 pm/V. PZT thick films on LNO-coated Si substrate are potential for MEMS applications.     

Low Temperature Preparation of Ferroelectric Relaxor Composite Thick Films

In this work, the fabrication and characterization of a composite films comprising classical ferroelectric (PbTiO₃, PT) and relaxor (PbMg_1/3Nb_2/3O₃, PMN) material is reported. Thick films consisting of ferroelectric and relaxor phases in the thickness range of 2–10 μm are fabricated on Pt-coated Si substrates at a temperature of ≤550°C via a modified sol–gel route. The phase purity of the composite films was determined by X-ray powder diffraction pattern. The morphology and composition homogeneity were analyzed by scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), and by X-ray mapping method, respectively. High dielectric permittivity (ɛ≈1100) and low loss values (tan δ≈0.03) at 1 kHz and room temperature were measured on 2-μm-thick composite films for a particular composition of 83 mol% of a PT phase and 17 mol% of a PMN phase, with associated remanent polarization of P ≈31.6 μC/cm² and coercive field of E _c ≅166 kV/cm. Piezo-response force microscopy analysis of the composite film showed that the film is piezoelectric and switchable. The temperature dependence of the effective dielectric permittivity and loss of the films at different frequencies was studied in the temperature range −50° to 200°C. In the temperature range used for applications (−50° to +100°C) the composite shows quite low temperature coefficient of capacitance (TCC=100%( C _T− C _−50°)/ C _−50°C))=18%, much lower than both PMN thick film and PT film in the same temperature range. This composition is therefore promising for low TCC applications.     

Preparation of Highly Dense PZN–PZT Thick Films by the Aerosol Deposition Method Using Excess-PbO Powder

Lead zinc niobate–lead zirconate titanate thick films with a thickness of 50–100 μm were deposited on silicon and alumina substrates using the aerosol deposition method. The effects of excess lead oxide (PbO) on stress relaxation during postannealing were studied. Excess PbO content was varied from 0 to 5 mol%. The as-deposited film had a fairly dense microstructure with nanosized grains. The films deposited on silicon were annealed at temperatures of 700°C, and the films deposited on sapphire were annealed at 900°C in an electrical furnace. The annealed film was detached and cracks were generated due to the high residual compressive stress and thermal stress induced by thermal expansion coefficient mismatch. However, the film deposited using powder containing 2% of excess PbO showed no cracking or detachment from the substrate after the postannealing process. The PbO evaporation at elevated temperature during the postannealing process seemed to have reduced the residual compressive stress. The remanent polarization and relative dielectric constant of the 50 μm thick films annealed at 900°C were 43.1 μC/cm² and 1400, respectively, which were comparable with the values of a bulk specimen prepared by a powder sintering process.     

Rapid Formation of Zinc Oxide Films by an Atmospheric-Pressure Chemical Vapor Deposition Method

Zinc oxide films were prepared by an atmospheric-pressure chemical vapor deposition method using (acetylacetonato)-zinc as a source material. Transparent and uniform ZnO films of considerable area (20 × 70 mm, ∼0.3 μm thick) could be obtained easily on a crown glass (CGW #200) with a high deposition rate. The deposition rate first remained constant with increasing substrate temperature ( T _s), then increased abruptly from 120 nm/min at T _s= 550°C to 220 nm/min at T _s= 600°C, and finally stopped increasing above T _s= 600°C. The maximum preferred orientation and best crystallinity of the films were obtained at T _s= 550°C.     

Sol–Gel Preparation of Thick PZN–PZT Film Using a Diol-Based Solution Containing Polyvinylpyrrolidone for Piezoelectric Applications

Dense and crack-free lead zinc niobate–lead zirconate titanate (PZN–PZT) films were deposited on silicon and glass substrates by spin coating using a sol containing propanediol and polyvinylpyrrolidone. Single-layer PZN–PZT films as thick as 0.80 μm were deposited by a single spin coating with successive heat treatments at 250° and 700°C. After heat treatment, the films were dense, crack free, and optically transparent. In addition, the crystallographic orientation of the thick film was controllable by adjusting the heat-treatment conditions. The ferroelectric properties of the (111)-oriented film were superior to those of the (100)-oriented film. On the other hand, the piezoelectric and dielectric properties of the (100)-oriented film were better than those of the (111)-oriented film. The piezoelectric coefficients ( d ₃₃) of the PZN–PZT films of 4.0-μm-thickness were 192 and 110 pC/N for the (100)-and (111)-oriented films, respectively.     

Electrophoretic Deposition of Lead Zirconate Titanate Films on Metal Foils for Embedded Components

Lead zirconate titanate (PZT) thick films in the thickness range of 5–200 μm on 20 μm copper and 25 μm platinum foils were prepared by electrophoretic deposition (EPD) for application as embedded passive components. The EPD process was conducted in glacial acetic acid medium, and the effects of deposition parameters, such as dc voltage values, processing times, and suspension aging on the film thickness and composition stoichiometry were evaluated. The dependence of the film thickness on the current and aging of the suspension was established and correlated to the chemical modifications occurring in the suspension. Films sintered at 1150°C for 30 min exhibited uniform and dense microstructures with an average grain size of 1.5 μm. A dielectric permittivity of around ∼1330 and loss tangent of 0.05 were measured for films with 8 μm of thickness. The films showed remanent polarization and a maximum polarization value of 24 and 38 μC/cm², respectively. These properties, comparable with those of bulk PZT ceramics, suggested potential applications of the EPD process for the deposition of ferroelectric thick films on metal foils for embedded component applications.     

Microstructure and Dielectric Properties of Barium Strontium Titanate Thick Films and Ceramics With a Concrete-Like Structure

Barium strontium titanate (Ba_0.6Sr_0.4TiO₃, BST) thick films and ceramics with a concrete-like structure were fabricated by a novel sol–gel-based route. In this process, well-crystallized nano-sized or micrometer-sized BST powders or their combinations are dispersed into a sol–gel matrix. Crack-free thick films and dense BST ceramics have been fabricated at a low sintering temperature with a very inhomogeneous concrete-like structure. The dielectric properties of such thick films and ceramics have been investigated. The results show that the dielectric constant and loss tangent of the thick films are 1209 and 0.016, respectively, at 0°C, 10 kHz, and those of the bulk BST ceramics are 5510 and 0.02, respectively, at 0°C, 10 kHz.     

Orientation Control Growth of Lanthanum Nickelate Thin Films Using Chemical Solution Deposition

Highly (100)- and (110)-oriented LaNiO₃ (LNO) thin films were successfully prepared on a Si (100) substrate using the chemical solution deposition method. It was somewhat surprising to find that the orientation of LNO films depended on the heating rates of the temperature range of 200°–400°C. The samples with heating rates beyond 10°C/s showed the preferential (100) orientation, while those with heating rates below 6.67°C/s showed the preferential (110) orientation. The orientation mechanism is controlled by the thermodynamics of nucleation and crystal growth. LNO films with controlled orientation having low resistivities of 2 mΩ·cm are a good basis for integrating ferroelectric applications.     

Low-Temperature Sintering (Ba0.6Sr0.4)TiO3 Thick Film Prepared by Screen Printing

(Ba_0.6Sr_0.4) TiO₃ thick films doped with glass slurry were fabricated by the screen-printing technique. The dielectric properties and the sintering mechanism were investigated. The films can be sintered at 600°C. The dielectric constant is 88 and the dielectric loss is 0.002 with a tunability of 23.86% under 100 kV/cm. Higher dielectric constant and tunability were obtained in the samples sintered at higher temperatures. The highest tunability is 61.12% under 150 kV/cm in the sample sintered at 800°C. The low sintering temperature and dielectric loss of the glass-doped thick films make them potential candidates for LTCC and microwave tunable devices.     

Preparation of PbZrO3–PbTiO3 Ferroelectric Thin Films by the Sol–Gel Process

Ferroelectric films, PbZr _x Ti_{1− x} O₃ ( x = 0 to 0.6), have been prepared from corresponding metal alkoxides partially stabilized with acetylacetone through the sol-gel process. The films dip-coated in an ambient atmosphere were heat-treated at 400°C for decomposition of residual organics and then at temperatures between 500° and 700°C for crystallization of the films. The perovskite phase precipitated at temperatures above 560°C, accompanied by an increase in dielectric constant. The dielectric constant of the films, which was comparable with that of sintered bodies, showed a maximum (∼620) at around x = 0.52 in PbZr _x Ti_{1− x} O₃. These films showed D – E hysteresis, with slightly higher values of coercive field, compared with those of sintered bodies.     

Microstructure Evolution of Pulsed Laser-Deposited (Ba, Sr)TiO3 Films on MgO for Microwave Applications

To develop low-loss tunable microwave circuits, based on the field dependence of dielectric permittivity, phase pure (Ba_0.5, Sr_0.5)TiO₃ doped with 1% W (BST) thin films 0.3-μm thick were deposited on single crystal MgO wafers by pulsed laser deposition. The BST films were characterized by X-ray θ–2θ scans and pole figure analysis, field emission scanning electron microscopy (FESEM), and cross-sectional transmission electron microscopy (TEM), coupled with selected-area electron diffraction (SAED). Although, the X-ray θ–2θ scan indicated an epitaxial nature of BST with an out-of-plane orientation of (100), the pole figure analysis confirmed the presence (4–6%) of (111)-oriented grains in a matrix of (100) textured grains. The columnar grains exhibited an in-plane (i.e., along the plane perpendicular to the growth direction) grain size that was thickness-dependent. The cross-sectional TEM, coupled with SAED in the thickness direction, corroborated the pole figure analysis. Additionally, from X-ray analysis, it was observed that the textured films were under in-plane tension. The deposited film was characterized at microwave frequencies (1–20 GHz) using interdigitated electrodes deposited on top of the film. The film was characterized by a relatively low dielectric Q of 5–7. A 17% change in the capacitance was observed when applying a 40 V bias. From the observed microstructure, a preliminary understanding of its evolution and its relationship with the microwave dielectric properties is discussed, and some ideas to obtain truly epitaxial BST films are presented.     

Processing Effects for Integrated PZT: Residual Stress, Thickness, and Dielectric Properties

Processing effects on the dielectric properties of sol–gel-derived PbZrO₃–PbTiO₃ (PZT) films integrated onto Pt/Ti/SiO₂//Si substrates are reported. Sol–gel synthesis and deposition conditions were designed to produce films of varying thickness (95–500 nm) with consistent chemical composition (Pb (Zr_0.53Ti_0.47)O₃), phase content (perovskite), grain size (∼110 nm), crystallographic orientation (nominally (111) fiber textured), and measured residual stress. The Stoney method, using laser reflectance to determine wafer curvature, derived biaxial tensile stress values of 150 and 180 MPa for PZT films after a baseline correction for electrode interactions during thermal processing was employed. The PZT films were of high dielectric quality, with low losses and negligible dispersion. Calculated values of dielectric constant ( ̄ ') were found to decrease from 960 to 600 with decreasing film thickness. A series-capacitor model successfully recovered a room-temperature K ₁' for the PZT (1,170) in good agreement with bulk reports but was unable to reproduce the expected dielectric anomaly near 380°C. This discrepancy and the resulting diffuse phase transformation were attributed to the biaxial tensile stress present in the PZT films.     

Preparation of 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 Thin Films Via a Polyvinylpyrrolidone-Assisted Aqueous Sol–Gel Process and Dielectric Properties

Pb(Mg_1/3Nb_2/3)O₃–PbTiO₃ (PMN–PT) thin films were prepared by spin coating using aqueous solutions of metal salts containing polyvinylpyrrolidone, where niobium oxide layers and lead—magnesium–titanium oxide layers were laminated on Pt(111)/TiO _x /SiO₂/Si(100) substrates and fired at 750° or 800°C. 250 ± 20 nm thick 0.7PMN–0.3PT thin films of a single-phase perovskite could be prepared, and the film fired at 750°C had dielectric constants and dielectric loss of 1900 ± 350 and 0.13 ± 0.03, respectively, exhibiting polarization-electric field hysteresis with a remanent polarization of 5.1 μC/cm² and a coercive field of 21 kV/cm.     

Microstructural Developments and Dielectric Properties of Rapid Thermally Processed PZT Thin Films Derived by Metallo-organic Decomposition

Microstructural developments and dielectric properties of lead zirconate titanate thin films (0.22 4mUm) with the composition Pb(Zr_0.53Ti_0.47)O₃ were studied. The films were prepared by metallo-organic decomposition (MOD) and rapid thermal processing (RTP) in the temperature range 475–825°C for 2 min in an oxygen gas flow with and without post-annealing. An amorphous–pyrochlore–perovskite phase transformation is indicated at or below 525°C RTF temperatures while a direct amorphous-to-perovskite phase transformation is indicated at higher RTP temperatures. A decrease in grain size with increasing temperature is correlated with an increase in and dominance of nucleation of perovskite sites. The best dielectric and fatigue properties were exhibited by films processed in the temperature range 725–775°C. Hysteresis loops tended toward squareness and polarization charges increased with increased temperature. Furthermore, 45% of the initial charge remained after 10⁹switching reversals. A degradation, however, was observed in both properties at higher temperatures.     

Properties of Boron Nitride (BxNy) Films Produced by the Spin-Coating Process of Polyborazine

Boron-rich boron nitride (BN) films have been prepared on Si and SiO₂/Si substrates by the vacuum pyrolysis of spin-coated polyborazine films. Physical properties of the prepared films such as film strength, thermal conductivity, and dielectrics were determined. The BN films vacuum-pyrolyzed at 900°C showed residual N–H bonds with a 0.75 N/B ratio, interdiffusion phenomena, and preferred orientation at the interfacial zone. Hardness and the elastic modulus of the film increased to 1.6 GPa and 50 GPa by nanoindentation loading. It had a thermal conductivity of 134 W/(m·K) at 296.5 K, and a dielectric constant in the range of 5–7, with tan ∂ between 0.01 and 0.47, depending on the film thickness.     

Effect of Substrate Texture on Orientations of rf-Sputtered Ba2Si2TiO8 Thin Films

Radio-frequency-sputtered barium silicon titanate, Ba₂Si₂TiO₈ (BST), thin films were grown on various substrates at substrate temperatures ranging from 750° to 955°C. The asdeposited films were characterized using X-ray diffraction, optical microscopy, and scanning electron microscopy (SEM). The results of the morphology analysis and X-ray diffraction analysis show no crystalline structure for films deposited on the fused quartz and unetched Si (100) substrates at temperatures lower than 865°C. At a substrate temperature of 900°C, tiny tetragon-like grains were observed for the film grown on the fused quartz, and the grains grew at a rate of 0.18 μm/min in the initial deposition stage. Optical and SEM micrographs reveal (001)-oriented, tetragon-like grains grown on HF-etched Si (100) wafers in the initial deposition stage and in later stages at substrate temperatures from 822° to 865°C. The results of X-ray diffraction analysis show a high (001) orientation for the thicker films, which corresponds to the tetragon-like configuration of the grains in the initial stage. Triangle-like grains were observed on the films deposited on etched Si (111) substrates in a temperature range from 822° to 899°C, but the grain configuration changed from the initial triangle shape to a tetragon shape as the films grew thick. The X-ray diffraction spectra show a high (001) orientation for the thicker films, which indicates an orientation transformation during the deposition due to a very low interfacial energy between the (001)-oriented BST overgrowth and the BST substrates in the later stage of deposition. Both the tetragon-like and the triangle-like grains have quasi-two-dimensional polygon shapes and have nonliquid-like characteristics in coalescence, which suggests a strong interaction between the BST deposits and the Si substrates.     

A New Compound with Ultra Low Dielectric Loss at Microwave Frequencies

A new ultra low loss microwave dielectric ceramic, Mg(Sn_0.05Ti_0.95)O₃ (MSnT), was found and investigated. The compounds were prepared by the conventional solid-state route, and sintered at 1360°–1480°C for 2–6 h. The investigations show that the MgTi₂O₅ secondary phase was observed. Moreover, the dielectric properties were correlated with the formation second phase. The excellent microwave dielectric properties of Q × f =322 000 (GHz), ɛ_r=17.4, and τ_f=−54 ppm/°C were obtained from the new MSnT ceramics sintered at 1390°C for 4 h.     

Characterization of Photoluminescent (Y1–xEux)2O3 Thin Films Prepared by Metallorganic Chemical Vapor Deposition

The purpose of this study was to identify and correlate the microstructural and luminescence properties of europium-doped Y₂O₃ (Y_{1– x} Eu _x )₂O₃ thin films deposited by metallorganic chemical vapor deposition (MOCVD), as a function of deposition time and temperature. The influence of deposition parameters on the crystallite size and microstructural morphology were examined, as well as the influence of these parameters on the photoluminescence emission spectra. (Y_{1– x} Eu _x )₂O₃ thin films were deposited onto (111) silicon and (001) sapphire substrates by MOCVD. The films were grown by reacting yttrium and europium tris(2,2,6,6-tetramethyl–3,5-heptanedionate) precursors with an oxygen atmosphere at low pressures (5 torr (1.7 × 10³ Pa)) and low substrate temperatures (500°–700°C). The films deposited at 500°C were smooth and composed of nanocrystalline regions of cubic Y₂O₃, grown in a textured [100] or [110] orientation to the substrate surface. Films deposited at 600°C developed, with increasing deposition time, from a flat, nanocrystalline morphology into a platelike growth morphology with [111] orientation. Monoclinic (Y_{1– x} Eu _x )₂O₃ was observed in the photoluminescence emission spectra for all deposition temperatures. The increase in photoluminescence emission intensity with increasing postdeposition annealing temperature was attributed to the surface/grain boundary area-reduction effect.     

Dielectric Characteristics of Nd(Zn1/2Ti1/2)O3 Ceramics at Microwave Frequencies

The microwave dielectric properties and the microstructures of Nd(Zn_1/2Ti_1/2)O₃ (NZT) ceramics prepared by the conventional solid-state route have been studied. The prepared NZT exhibited a mixture of Zn and Ti showing 1:1 order in the B-site. The dielectric constant values (ɛ_r) saturated at 29.1–31.6. The quality factor ( Q × f ) values of 56 700–170 000 (at 8.5 GHz) can be obtained when the sintering temperatures are in the range of 1300°–1420°C. The temperature coefficient of resonant frequency τ_f was not sensitive to the sintering temperature. The ɛ _r value of 31.6, the Q × f value of 170 000 (at 8.5 GHz), and the τ_f value of −42 ppm/°C were obtained for NZT ceramics sintering at 1330°C for 4 h. For applications of high selective microwave ceramic resonators, filters, and antennas, NZT is proposed as a suitable material candidate.