In-plane dielectric characterization of sol–gel derived PLZT (9/65/35) thin films using an interdigital electrode configuration

Lead lanthanum zirconate titanate (PLZT 9/65/35) thin films were deposited on MgO (00l) substrates using a sol–gel method. X-ray diffraction measurements reveal that the PLZT film has epitaxially grown on the substrate and has a pure perovskite structure. Using gold interdigital electrodes the in-plane dielectric properties of the films were measured as a function of frequency (1 kHz to 10 GHz), temperature (293–435 K) and dc electric field (0–20 MV/m). The PLZT (9/65/35) thin film exhibits a diffuse phase transition, which indicates a relaxor-like ferroelectric behavior. The temperature dependence of the characteristic relaxation time was analyzed in terms of the Vögel–Fulcher relation. The relative permittivity has a high tunability of 34–42% in the frequency range of 10 MHz to 1 GHz.     

Influence of the substrate on ferroelectric properties of 〈1 1 1〉 oriented rhombohedral Pb(Zr0.6Ti0.4)O3 thin films

〈1 1 1〉-oriented Pb(Zr_0.6Ti_0.4)O₃ thin films were elaborated in the same run by RF multitarget sputtering on Si/SiO₂/TiO₂/Pt(1 1 1) and LaAlO₃/Pt(1 1 1) substrates. PZT thin films were textured, exhibiting 〈1 1 1〉 fibre texture on silicon substrates whereas epitaxial relationships were found when grown on LaAlO₃/Pt(1 1 1). On the latter substrate, values of spontaneous polarization and of dielectric permittivity were measured close to that calculated previously along the 〈1 1 1〉 direction of PZT rhombohedral single crystal. On the contrary, spontaneous polarization and dielectric permittivity measured on PZT thin films deposited on platinized silicon were found deviating from calculated values. These different electrical results are attributed to different ferroelectric domain configurations.     

Lead-free ferroelectric BaTiO3 doped-(Na0.5Bi0.5)TiO3 thin films processed by pulsed laser deposition technique

The difficulties in synthesizing phase pure BaTiO₃ doped-(Na_0.5Bi_0.5)TiO₃ are known. In this work, we reporting the optimized pulsed laser deposition (PLD) conditions for obtaining pure phase 0.92(Na_0.5Bi_0.5)TiO₃-0.08BaTiO₃, (BNT-BT_0.08), thin films. Dielectric, ferroelectric and piezoelectric properties of BNT-BT_0.08, thin films deposited by PLD on Pt/TiO₂/SiO₂/Si substrates are investigated in this paper. Perovskite structure of BNT-BT_0.08 thin films with random orientation of nanocrystallites has been obtained by deposition at 600 °C. The relative dielectric constant and loss tangent at 100 kHz, of BNT-BT_0.08 thin film with 530 nm thickness, were 820 and 0.13, respectively. Ferroelectric hysteresis measurements indicated a remnant polarization value of 22 μC/cm² and a coercive field of 120 kV/cm. The piezoresponse force microscopy (PFM) data showed that most of the grains seem to be constituted of single ferroelectric domain. The as-deposited BNT-BT_0.08 thin film is ferroelectric at the nanoscale level and piezoelectric.     

Elaboration of (1 1 1)-oriented La-doped PZT thin films on platinized silicon substrates

PLZT thin films with different thickness were deposited in situ on platinum coated silicon substrates using a multi-target sputtering system. The purpose was to grow (1 1 1)-textured PLZT films on Pt (1 1 1). To this aim, the role of some key parameters on both crystalline quality and electrical properties was investigated. An ultra-thin TiO₂ seeding layer was deposited, prior to PLZT, which strongly affected the crystallographic orientation of the films. The relation between temperature deposition and film crystallinity is analysed. TEM observations show the presence of some very small grains of Zr_0.9La_0.1O_1.95 at the film bottom interface. In the range of thickness investigated, the plot of the inverse capacitance as a function of the film thickness split up into two different curves, each with a linear shape, which however allows determination of a single value of interface capacitance. Above a thickness of 400-500 nm a saturation of the dielectric properties seems to be reached.     

La掺杂浓度对PLZT薄膜红外光学性质的影响

采用溶胶-凝胶法在Pt/Ti/SiO2/Si衬底上制备了不同La掺杂浓度PLZT(x/40/60)薄膜- x射线衍射分析表明制备的PLZT(x/40/60)薄膜是具有单一钙钛矿结构的多晶薄膜- 通过红外椭圆偏振光谱仪测量了波长为2-5—12-6μm范围内PLZT薄膜的椭偏光谱，采用经典色 散模型拟合获得PLZT薄膜的红外光学常数，同时也拟合获得PLZT薄膜的厚度- 随着La掺杂浓 度的增大，折射率逐渐减小- 而消光系数除PLZT(4/40/60)薄膜外，呈现逐渐增大的趋势- 分析表明这些差异主要与PLZ 关键词： PLZT薄膜 红外光学性质 红外椭圆偏振光谱     

Low dielectric loss Ba0.6Sr0.4TiO3/MgTiO3 composite thin films prepared by a sol–gel process

The dielectric properties of Ba_0.6Sr_0.4TiO₃ (BST)/MgTiO₃ (MT) composite thin films deposited on Pt(1 1 1)/Ti/SiO₂/Si(1 0 0) substrates by the sol–gel method were investigated. The X-ray pattern analysis indicates that the thin films exhibit good crystalline quality with perovskite phase and that insertion of MT layer does not obviously affect the phase structure of BST thin films. The characterization of dielectric properties demonstrates that configuration of BST/MT/BST thin films is an effective approach to obtain low dielectric loss and dielectric tunability of BST thin films. At room temperature, the tunability of pure BST60 films and BST/MT (15 nm)/BST composite thin films is 47% and 36%, respectively, at the frequency of 1 MHz with an applied electric field of 400 kV/cm. For BST/MT/BST composite thin films, considerable reduction in the dielectric loss values is observed, which renders them attractive for tunable microwave device applications.     

Substrate and orientation influence on electrical properties of sputtered La-doped PZT thin films

Pb_1−2y/3La_yZr_xTi_1−xO₃ (PLZT) thin films have been prepared “in situ” by multi-target sputtering on Silicon, LaAlO₃ (LAO) and MgO substrates covered with a Pt bottom electrode. The purpose was to grow tetragonal PLZT films (Zr/Ti = 28/72 with different La contents) on these various substrates and to compare their electrical properties. To this aim, Pt was first deposited on the three different substrates to get (1 1 1)Pt/Si, (1 1 1)Pt/LAO and (2 0 0)Pt/MgO. Then PLZT was deposited in a same run on these three kinds of substrates and the influence of La contents and film orientation on electrical properties was investigated. The La content was varied from y = 0 to y = 32 in order to explore the phase transition between ferroelectric and paraelectric phases as a function of the substrate. For large amount of Lanthanum, relaxor behavior has been observed and studied.     

Lead-free ferroelectric thin films obtained by pulsed laser deposition

Na_0.5Bi_0.5TiO₃-BaTiO₃ (NBT-BT) thin films grown by pulsed laser deposition have been investigated by X-ray diffraction, scanning electron microscopy, and dielectric spectroscopy in order to clarify the role of substrate temperature on crystalline structure, grain morphology, and dielectric properties. We have shown that the structural and dielectric properties of NBT-BT thin films with composition at morphotropic phase boundary (6% BT) critically depend on the substrate temperature: small variations of this parameter induce structural changes, shifting the morphotropic phase boundary toward tetragonal or rhombohedral side. Higher deposition temperature (1000 K) favor the formation of rhombohedral phase, films deposited at 923 K and 973 K have tetragonal symmetry at room temperature. Grains morphology depends also on the deposition temperature. Atomic force micrographs show grains with square or rectangular shape in a compact structure for films grown at lower temperatures, while grains with triangular shape in a porous structure are observed for films grown at 1000 K. Dielectric spectroscopy measurements evidenced the phase transition between ferroelectric and antiferroelectric phase at 370 K. Films grown at 1000 K shown low electrical resistivity due to their porous structure. High dielectric constant values (about 800 at room temperature and 2700 at 570 K) have been obtained for films grown at temperatures up to 973 K.     

Effect of annealing on thermal stability and morphology of pulsed laser deposited Ir thin films

Iridium (Ir) thin films, deposited on Si (1 0 0) substrate by pulsed laser deposition (PLD) technique using Ir target in a vacuum atmosphere, were annealed in air ambient and the thermal stability was investigated. The crystal structure and surface morphology of Ir thin films before and after being annealed were studied by X-ray diffraction, Raman scattering, scanning electron microscope, and atomic force microscopy. The results showed that single-phase Ir thin films with (1 1 1) preferred orientation could be deposited on Si (1 0 0) substrate at 300 °C and it remained stable below 600 °C, which showed a promising bottom electrode of integrated ferroelectric capacitors. Ir thin films got oxidized to IrO₂ at temperatures from 650 to 800 °C.     

Enhanced dielectric properties of lead barium zirconate thin films by manganese doping

(Pb_0.5Ba_0.5)ZrO₃ (PBZ) and 1 mol% Mn-doped (Pb_0.5Ba_0.5)ZrO₃ (Mn-PBZ) sol were successfully fabricated, and corresponding thin films were deposited on Pt(1 1 1)/TiO₂/SiO₂/Si(1 0 0) substrates by spin-coating method. Effects of Mn doping on the microstructure and electrical properties of PBZ thin films were investigated systemically. X-ray diffraction patterns showed that both films had a polycrystalline perovskite structure, and that the degree of (1 1 1) orientation were increased by Mn doping. Dielectric measurements illustrated that Mn-doped PBZ thin films not only had a larger dielectric constant, but also possessed a smaller dielectric loss. Accordingly, the tunability and the figure of merit of PBZ films were improved by Mn doping.     

Piezoelectric non-linearity in PbSc0.5Ta0.5O3 thin films

Epitaxial (001)-oriented PbSc_0.5Ta_0.5O₃ (PST) thin films were deposited by pulsed laser deposition. Local piezoelectric investigations performed by piezoelectric force microscopy show a dual slope for the piezoelectric coefficient. A piezoelectric coefficient of 3 pm/V was observed at voltages up to 0.8 V. However, at voltages above 0.8 V, there is a steep increase in piezoelectric coefficient mounting to 23.2 pm/V. This nonlinear piezoelectric response was observed to be irreversible in nature. In order to better understand this nonlinear behavior, voltage dependent dielectric constant measurements were performed. These confirmed that the piezoelectric non-linearity is indeed a manifestation of a dielectric non-linearity. In contrast to classical ferroelectric systems, the observed dielectric non-linearity in this relaxor material cannot be explained by the Rayleigh model. Thus the dielectric non-linearity in the PST films is tentatively explained as a manifestation of a percolation of the polar nano regions.     

Microstructure of microwave dielectricthin films by RF magnetron sputtering

The article describes the microstructure and morphological properties of microwave dielectric ceramic thin films. These thin films were successfully prepared on SiO₂ (1 1 0) single-crystal substrates by radio frequency magnetron-sputtering system. The microstructure and morphology of the thin films were characterized by X-ray diffraction, scanning electron microscopy, atomic force microscopy, and transmission electron microscopy. The results show that the main phase is Ba_0.5Sr_0.5Nb₂O₆,which has a tetragonal perovskite structure, a long strip pattern, and uniform crystal-grain size of about 2-3 μm in length when annealed under 1150 °C for 30 min in an O₂ atmosphere. These thin films are of excellent crystallization quality, with a polycrystalline and dense structure.     

Infrared spectroscopic ellipsometry of (Pb, La)(Zr, Ti)O3 thin films on platinized silicon

Lead lanthanum zirconate titanate (PLZT) thin films with different La concentrations (x), whose composition is x/40/60, have been grown directly on Pt/Ti/SiO₂/Si (100) substrates by a modified sol-gel method. X-ray diffraction analysis shows that the PLZT thin films are polycrystalline. The infrared optical properties of the PLZT thin films have been investigated using the infrared spectroscopic ellipsometry in the spectral range of 2.5–12.5 μm. By fitting the measured ellipsometric spectra (Ψ and Δ) with a three-phase model (air/PLZT/Pt), and a derived classical dispersion relation for the thin films, the optical constants and thicknesses of the thin films have been obtained. The refractive index of the PLZT thin films decreases with increasing La concentrations, however, the extinction coefficient increases with increasing La concentrations except for the PLZT(4/40/60) thin films. The values of the effective static charge calculated for the PLZT thin films, which state that PLZT belongs to a mixed ionic-covalent compound, decrease with increasing La concentrations. Moreover, the refractive index at the wavelength of 2.5 μm changes linearly with the effective static charge. The plot of the calculated infrared optical absorption versus wavelength for the Ni/PLZT/Pt multilayer structures with various La concentrations is given and indicates that the PLZT thin films are excellent candidates for ferroelectric infrared detectors and focal plane arrays.     

Effect of deposition temperature on orientation and electrical properties of (K0.5Na0.5)NbO3 thin films by pulsed laser deposition

Lead-free ferroelectric K_0.5Na_0.5NbO₃ (KNN) thin films have been prepared on Pt/TiO₂/SiO₂/Si substrates by pulsed laser deposition process. The structures, crystal orientations and electrical properties of thin films have been investigated as a function of deposition temperature from 680 °C to 760 °C. It is found that the deposition temperature plays an important role in the structures, crystal orientations and electrical properties of thin films. The crystallization of thin films improves with increasing deposition temperature. The thin film deposited at 760 °C exhibits strong (0 0 1) preferential orientation, large dielectric constant of 930 and the remnant polarization of 8.54 μC/cm².     

Effect of annealing temperature on microstructure of chemically deposited calcium modified lead titanate thin films

Thin ferroelectric films of calcium modified lead titanate Pb_1−xCa_xTiO₃(PCT) have been prepared by chemical deposition process. The as deposited amorphous films were thermally treated for crystallization and formation of perovskite structure. Characterization of these films by X-ray diffraction (XRD) have been carried out for various amounts of calcium (Ca)-doping (0.20, 0.24, and 0.28) on indium tin oxide (ITO) coated corning glass substrates. For a better understanding of the crystallization mechanism, the investigations were carried out at various annealing temperatures (450, 550, and 650 °C). Characterization of these films by XRD shows that the films exhibit tetragonal phase with perovskite structure. Atomic force microscope images (AFM) are characterized by slight surface roughness with a uniform crack-free, densely-packed structure. Also, Fourier transform infrared spectra (FT-IR) of the as deposited film and annealed thin films (x=0.24) at 650 °C on silicon (Si) substrates were taken to get more information about the film formation. Dielectric studies of the films were carried out and reported.     

Characterization of bicrystalline epitaxial LaNiO3 films fabricated on MgO (1 0 0) substrates by pulsed laser deposition

A series of metallic LaNiO₃ (LNO) thin films were deposited on MgO (1 0 0) substrates by pulsed laser deposition (PLD) under the oxygen pressure of 20 Pa at different substrate temperatures from 450 to 750 °C. X-ray diffraction (XRD) was used to characterize the crystal structure of LNO films. θ-2θ scans of XRD indicate that LNO film deposited at a substrate temperature of 700 °C has a high orientation of (l l 0). At other substrate temperatures, the LNO films have mixed phases of (l l 0) and (l 0 0). Furthermore, pole figure measurements show that LNO thin films, with the bicrystalline structure, were epitaxially deposited on MgO (1 0 0) substrates in the mode of LNO (1 1 0)//MgO (1 0 0) at 700 °C. Reflection high-energy electric diffraction (RHEED) and atomic force microscopy (AFM) were also performed to investigate the microstructure of LNO films with the high (l l 0) orientation. RHEED patterns clearly confirm this epitaxial relationship. An atomically smooth surface of LNO films at 700 °C was obtained. In addition, bicrystalline epitaxial LNO films, fabricated at 700 °C, present a excellent conductivity with a lower electrical resistivity of 300 μ Ω cm. Thus, the obtained results indicate that bicystalline epitaxial LNO films could serve as a promising candidate of electrode materials for the fabrication of ferroelectric or dielectric films.     

Optimized growth and dielectric properties of barium titanate thin films on polycrystalline Ni foils

Barium titanate(BTO) thin films were deposited on polycrystalline Ni foils by using the polymer assisted deposition(PAD) technique.The growth conditions including ambient and annealing temperatures were carefully optimized based on thermal dynamic analysis to control the oxidation processing and interdiffusion.Crystal structures,surface morphologies,and dielectric performance were examined and compared for BTO thin films annealed under different temperatures.Correlations between the fabrication conditions,microstructures,and dielectric properties were discussed.BTO thin films fabricated under the optimized conditions show good crystalline structure and promising dielectric properties with εr～ 400 and tan δ < 0.025 at 100 kHz.The data demonstrate that BTO films grown on polycrystalline Ni substrates by PAD are promising in device applications.     

Effects of deposition temperature on the structural and morphological properties of SnO2 films fabricated by pulsed laser deposition

Tin oxide (SnO₂) thin films were grown on Si (1 0 0) substrates using pulsed laser deposition (PLD) in O₂ gas ambient (10 Pa) and at different substrate temperatures (RT, 150, 300 and 400 °C). The influence of the substrate temperature on the structural and morphological properties of the films was investigated using X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM). XRD measurements showed that the almost amorphous microstructure transformed into a polycrystalline SnO₂ phase. The film deposited at 400 °C has the best crystalline properties, i.e. optimum growth conditions. However, the film grown at 300 °C has minimum average root mean square (RMS) roughness of 3.1 nm with average grain size of 6.958 nm. The thickness of the thin films determined by the ellipsometer data is also presented and discussed.     

Morphological and optical properties of silicon thin films by PLD

Silicon thin films have been prepared on sapphire substrates by pulsed laser deposition (PLD) technique. The films were deposited in vacuum from a silicon target at a base pressure of 10⁻⁶ mbar in the temperature range from 400 to 800 °C. A Q-switched Nd:YAG laser (1064 nm, 5 ns duration, 10 Hz) at a constant energy density of 2 J × cm⁻² has been used. The influence of the substrate temperature on the structural, morphological and optical properties of the Si thin films was investigated.Spectral ellipsometry and atomic force microscopy (AFM) were used to study the thickness and the surface roughness of the deposited films. Surface roughness values measured by AFM and ellipsometry show the same tendency of increasing roughness with increased deposition temperature.     

Structural and optical properties of YSZ thin films grown by PLD technique

We report on the structural and optical properties of yttria stabilized zirconia (YSZ) thin films grown by pulsed laser deposition (PLD) technique and in situ crystallized at different substrate temperatures (T_s = 400 °C, 500 °C and 600 °C). Yttria-stabilized zirconia target of ∼1 in. diameter (∼95% density) was fabricated by solid state reaction method for thin film deposition by PLD. The YSZ thin films were grown on an optically polished quartz substrates and the deposition time was 30 min for all the films. XRD analysis shows cubic crystalline phase of YSZ films with preferred orientation along 〈1 1 1〉. The surface roughness was determined by AFM for the films deposited at different substrate temperatures. The nano-sized surface roughness is found to increase with the increase of deposition temperatures. For the optical analysis, a UV-vis-NIR spectrophotometer was used and the optical band gap of ∼5.7 eV was calculated from transmittance curves.