Platinum-coated Silicon Substrates Research Articles

Synthesis and characterization of strontium-doped barium titanate thin film by dip and dry technique

Thin films of polycrystalline (Ba[Formula: see text][Formula: see text]TiO3 ([Formula: see text] = 0.2 and 0.3) with Perovskite structure were prepared by a dip and dry technique on a platinum-coated silicon substrate. The good quality thin films with uniform microstructure and thickness were successfully produced by dip-coating techniques annealed at 730[Formula: see text]C for 1 h. The resulting thin film shows a well-developed dense polycrystalline structure with more uniform grain size distribution. The BST thin films were characterized for their structural, Raman spectroscopy, morphological properties, and complex impedance properties. The dielectric constant-frequency curve showed the good dielectric constant and loss dielectric loss with low-frequency dispersion. The BST 0.3 thin film reveals that the dielectric constant and dielectric loss at a frequency of 1 kHz were 578 and 0.02, respectively. The obtained results on dielectric properties can be analyzed in terms of the Maxwell–Wagner model.

Ferroelectric and photoluminescence properties of (Ca, Eu)Bi2Ta2O9 thin films prepared by pulsed laser deposition

Thin films of CaBi2Ta2O9 (CBT) and Eu3+ doped CaBi2Ta2O9 (CEBT) were deposited on platinum-coated silicon substrates via the pulsed laser deposition technique. The microstructural, leakage current, ferroelectric behavior and photoluminescence properties of CBT/CEBT films were systematically studied. The CBT/CEBT films form single phase with a polycrystalline perovskite structure is confirmed by X-ray diffraction, and the CEBT films exhibit better crystallinity when doped with a number of Eu3+ ions. Meantime, the ferroelectric hysteresis loops show that enhanced ferroelectric property with a remnant polarization 2Pr = 8 μC/cm2 are obtained from CEBT film when x = 0.15. Leakage current density curves show that the Eu3+ doping could lead to the increase of leakage current of CBT film. Furthermore, under the excitation of 394 nm and 464 nm light, the thin films exhibit yellow and red emission peaks centered at 592 nm and 613 nm, which attributes to the f–f electronic transition of 5D0 → 7F1 and 5D0 → 7F2 of Eu3+ ions. This study suggests that Eu3+ doped CaBi2Ta2O9 films have a potential application in the new multifunctional photoluminescence ferroelectric thin-film devices.

Optical properties of spin coated Co0.6Zn0.4Mn0.3Fe1.7O4 thin films deposited on silicon and platinum coated silicon substrates

ABSTRACTThis work presents optical properties of Zn and Mn co-doped CFO (Co0.6Zn0.4Mn0.3Fe1.7O4) films deposited on Si and Pt coated Si substrates by spin coating technique. X-ray diffraction pattern of the films exhibited spinel cubic structure with polycrystalline phase. Optical characteristics of the CZFMO films are studied using photoluminscence and UV-visible spectroscopy. With the rise in annealing temperature, quenching in PL emission was observed for films grown on silicon; whereas a marginal enhancement in emission was observed for films deposited on the Pt / Si substrate. Optical band gap of the films are found to vary between 2.3 – 2.7 eV range.

Study on leakage current properties of BiFeO3 thin films with Pb(Zr,Ti)O3 buffer layer

ABSTRACTA lead zirconate titanate (PZT) buffer layer was introduced for bismuth ferrite (BFO) thin films on platinum-coated silicon substrate, fabricated by sol-gel process. The enhanced crystallization has been obtained and explained by constraint stress contributed by the PZT buffer layer. The decreased leakage current has also been gained compared with the BFO thin film directly deposited on platinum electrode. The asymmetry of leakage current characteristic was exhibited and analyzed for this structure, which can be attributed to the differences of Schottky barrier height, because it has been proved that the leakage current mechanism is dominated by Schottky emission.

Enhanced ferroelectric photovoltaic response of BiFeO3/BaTiO3 multilayered structure

The present work is based on the photovoltaic properties of multilayered structure of Bismuth ferrite (BFO) and Barium titanate (BTO) thin films prepared by pulsed laser deposition technique on platinum coated silicon substrate. The multilayered structure possesses enhanced ferroelectric properties and shows a remarkable increase in photocurrent (from 1.56 × 10−7 A to 6.96 × 10−5 A) upon illumination with laser light of wavelength 405 nm at an intensity of 160 mW/cm2. The values of short circuit photocurrent and open circuit voltage were found to be 0.3184 mA/cm2 and −1.25 V, respectively, with a light-to-electricity conversion efficiency of 0.067%. A relatively high efficiency calculated at 405 nm for the developed multilayered BFO/BTO structure highlights its practical application in ferroelectric photovoltaics.

Study of the optical properties of lead zirconate–titanate layers obtained by magnetron sputtering

Lead zirconate–titanate films to be used as the active and adhesion layers in a ferroelectric structure have been studied. The layers are obtained by magnetron sputtering on platinum-coated silicon substrates, and spectral ellipsometry is used to determine their optical characteristics. The ellipsomeric angles were measured in the 250–900-nm wavelength range, and the thicknesses (213 and 54 nm) and the dispersion of the optical constants (the refractive and absorption indices) were determined on the basis of two optical models of the layers.

Measurements of Nonlinear Dielectric Constants of Pb(Zr,Ti)O3 Thin Films Using a Dynamic Measuring Method

The nonlinear dielectric constants of Pb(Zr,Ti)O3 (PZT) thin films were studied using a dynamic measuring method. The 111-oriented PZT thin films with various Zr/Ti ratios were deposited on platinum-coated silicon substrates using a sol–gel method. The ε333 of the films increased with the Zr concentration in the tetragonal region and reached a maximum value of 280 aF/V close to the morphotropic phase boundary (Zr/Ti= 52/48). This measured value is 400 times larger than that of LiTaO3 single crystals.

Ferroelectric and structural instability of (Pb,Ca)TiO3 thin films prepared in an oxygen atmosphere and deposited on LSCO thin films which act as a buffer layer

Structural, microstructural and ferroelectric properties of Pb0.90Ca0.10TiO3 (PCT10) thin films deposited using La0.50Sr0.50CoO3 (LSCO) thin films which serve only as a buffer layer were compared with properties of the thin films grown using a platinum-coated silicon substrate. LSCO and PCT10 thin films were grown using the chemical solution deposition method and heat-treated in an oxygen atmosphere at 700°C and 650°C in a tube oven, respectively. X-ray diffraction (XRD) and Raman spectroscopy results showed that PCT10 thin films deposited directly on a platinum-coated silicon substrate exhibit a strong tetragonal character while thin films with the LSCO buffer layer displayed a smaller tetragonal character. Surface morphology observations by atomic force microscopy (AFM) revealed that PCT10 thin films with a LSCO buffer layer had a smoother surface and smaller grain size compared with thin films grown on a platinum-coated silicon substrate. Additionally, the capacitance versus voltage curves and hysteresis loop measurement indicated that the degree of polarization decreased for PCT10 thin films on a LSCO buffer layer compared with PCT10 thin films deposited directly on a platinum-coated silicon substrate. This phenomenon can be described as the smaller shift off-center of Ti atoms along the c-direction 〈001〉 inside the TiO6 octahedron unit due to the reduction of lattice parameters. Remnant polarization (Pr) values are about 30μC/cm2 and 12μC/cm2 for PCT10/Pt and PCT10/LSCO thin films, respectively. Results showed that the LSCO buffer layer strongly influenced the structural, microstructural and ferroelectric properties of PCT10 thin films.

Investigation of Ta2O5 and TaSixOy thin films obtained by radio frequency plasma assisted laser ablation for gate dielectric applications

Pulsed laser deposition was employed for the growth of tantalum oxide and tantalum silicate thin films. Ta2O5 thin films were obtained following the ablation of a metallic Ta target by the 3rd (355nm) and 4th (266nm) harmonics of a Nd:YAG laser. For the deposition of TaSixOy thin films, a composite target consisting of Si (25%) and Ta (75%) sectors was ablated and the resulted material was collected on platinum coated silicon substrates. The influence of different experimental parameters, such as substrate temperature (from 200 to 400°C) and laser wavelength, on the morphology and electrical properties of the thin films was investigated. We find that although the addition of the RF plasma to the PLD procedure increases surface roughness, it improves the electrical properties of the resulting structures, leading to lower leakage currents and wider range of the electric field.

Control over Memory Performance of Layer-by-Layer Assembled Metal Phthalocyanine Multilayers via Molecular-Level Manipulation

We herein report on the nonvolatile memory properties of iron phthalocyanine multilayers prepared using an electrostatic layer-by-layer assembly method. Cationic poly(allylamine hydrochloride) (PAH) and anionic iron(III) phthalocyanine-4, 4,′ 4″, 4′″-tetrasulfonic acid (Fe-TsPc) were alternately deposited onto quartz glass, indium tin oxide (ITO), or platinum-coated silicon substrates via electrostatic interactions. The electrochemical response of the PAH/Fe-TsPc, which was obtained from cyclic voltammograms (CV) in solution, indicated that redox reactions occurred at the phthalocyanine unit and at the metallic center. It was found that these redox reactions of the PAH/Fe-TsPc multilayer films in solution could be extended to resistive switching nonvolatile memory based on a charge trap/release mechanism in air. The PAH/Fe-TsPc multilayers sandwiched between the bottom (platinum) and top (Ag or tungsten) electrodes exhibited the characteristics of a resistive switching memory at a relatively low operating...

Thickness-dependent piezoelectric behaviour and dielectric properties of lanthanum modified BiFeo3 thin films

Bi0.85La0.15FeO3 (BLFO) thin films were deposited on Pt(111)/Ti/SiO2 /Si substrates by the soft chemical method. Films with thicknesses ranging from 140 to 280 nm were grown on platinum coated silicon substrates at 500?C for 2 hours. The X-ray diffraction analysis of BLFO films evidenced a hexagonal structure over the entire thickness range investigated. The grain size of the film changes as the number of the layers increases, indicating thickness dependence. It is found that the piezoelectric response is strongly influenced by the film thickness. It is shown that the properties of BiFeO3 thin films, such as lattice parameter, dielectric permittivity, piezoeletric coefficient etc., are functions of mis?t strains.

Structural and Electrical Properties of Lead Zirconate Titanate 0–3 Composite Films

Modified sol-gel method alongwith the infilteration process have been used to deposit dense, crack-free ferroelectric lead zirconate titanate (PZT) 0–3 ceramic/ceramic composite films of composition Pb(Zr0.52Ti0.48)O3 and thickness greater than 10 μm onto a platinum coated silicon substrate. PZT powder with the same composition was dispersed using a dispersant ESL400 in PZT sol to obtain a slurry. The slurry and the sol were alternatively deposited on the substrate followed by drying, pyrolysis and final annealing at 750°C to get single phase perovskite structure of the film. Thickness of the film was determined by SEM. Surface morphology of the film was studied by AFM. Raman spectrum of the film depicts coexistence of rhombohedral and tetragonal phases. Temperature dependence of dielectric constant shows that the films exhibit diffused phase transition rather than relaxor behavior. The remanant polarization (Pr) and coercive field (Ec) of the resulting film are 13.5 μC/cm2 and 57 kV/cm respectively.

The Influence of Ni Doping on the Properties of BST Ferroelectric Thin Film

Undoped and Ni-doped barium strontium titanate (BST) thin films have prepared by sol-gel method on a platinum-coated silicon substrate. The structure and dielectric properties of Ni-doped BST thin films were investigated. Results show that grain size of the BST thin films decrease with the increase of Ni content. Dielectric constant and dielectric loss also decrease. As the content of Ni-doped reaches 10 mol%, the dielectric constant, dielectric loss, tunability and FOM are 230.25, 0.015, 30.8% and 20.53, respectively. Ni-doped BST thin films were suitable for tunable microwave devices.

The Influence of Ni Doping on The Properties of BST Ferroelectric Thin Film

Undoped and Ni-doped barium strontium titanate(BST) thin films have prepared by sol-gel method on a platinum-coated silicon substrate. The structure and dielectric properties of Ni-doped BST thin films were investigated. Results show that grain size of the BST thin films decrease with the increase of Ni content. Dielectric constant and dielectric loss also decrease. As the content of Ni-doped reaches 10mol%, the dielectric constant, dielectric loss, tunability and FOM are 230.25, 0.015, 30.8% and 20.53, respectively. Ni-doped BST thin films were suitable for tunable microwave devices.

ZnO nanocrystalline thin films: a correlation of microstructural, optoelectronic properties

The compositional, structural, microstructural, dc electrical conductivity and optical properties of undoped zinc oxide films prepared by the sol–gel process using a spin-coating technique were investigated. The ZnO films were obtained by 5 cycle spin-coated and dried zinc oxide films followed by annealing in air at 600 °C. The films deposited on the platinum coated silicon substrate were crystallized in a hexagonal wurtzite form. The energy-dispersive X-ray (EDX) spectrometry shows Zn and O elements in the products with an approximate molar ratio. TEM image of ZnO thin film shows that a grain of about 60–80 nm in size is really an aggregate of many small crystallites of around 10–20 nm. Electron diffraction pattern shows that the ZnO films exhibited hexagonal structure. The SEM micrograph showed that the films consist in nanocrystalline grains randomly distributed with voids in different regions. The dc conductivity found in the range of 10−5–10−6 (Ω cm)−1. The optical study showed that the spectra for all samples give the transparency in the visible range.

In situ investigation of thermally influenced phase transformations in (pb0.92sr0.08) (zr0.65ti0.35)o3 thin films using micro-raman spectroscopy and x-ray diffraction

Thin films of ferroelectric strontium-doped lead zirconate titanate [PSZT, (Pb(0.92)Sr(0.08))(Zr(0.65)Ti(0.35))O(3)] deposited by RF magnetron sputtering have been analyzed by in situ analysis techniques. The in situ techniques employed for this study include micro-Raman spectroscopy and X-ray diffraction (XRD), and variations in thin film structure and orientations for temperatures up to 350 degrees C and 750 degrees C for the respective techniques have been studied. The samples analyzed were PSZT thin films deposited on platinum-coated silicon substrates at either room temperature or at 750 degrees C. In situ measurements using micro-Raman spectroscopy and XRD techniques have been used to identify the Curie point for poly-crystalline PSZT thin films and to determine the temperature-activating significant grain growth for room-temperature-deposited PSZT thin films. To study the presence of hysteresis, analysis was carried out during both temperature ramp-up and ramp-down cycles. Raman measurements showed expected bands (albeit weak), and the in situ measurements have detected variations in the crystal structure of the thin film samples, with negligible variations between the heating and cooling cycles. A combination of the Raman and XRD results has shown that the temperature-activating significant grain growth for the room-temperature-deposited films is about 275 degrees C and the Curie point lies between 325 and 400 degrees C. This relatively high Curie point makes these films suitable for wide temperature range applications.

Polymeric precursor method to the synthesis of XWO 4 (X = Ca and Sr) thin films—Structural, microstructural and spectroscopic investigations

Stoichiometric XWO 4 (X = Ca, and Sr) thin films were synthesized using the polymeric precursor method. In this soft chemical method, soluble precursors such as strontium carbonate, calcium carbonate and tungstic acid, as starting materials, were mixed in an aqueous solution. Through the polyesterification reaction, evidences of the formation of the W-citrate complex and the strontium were obtained by 13C NMR and FT-Raman spectroscopy. The thin films were deposited on silicon and platinum-coated silicon substrates through the spinning technique. The surface morphology and crystal structure of the thin films were investigated using atomic force microscopy (AFM), X-ray diffraction (XRD), specular reflectance infrared Fourier transform spectroscopy, and micro-Raman spectroscopy. Nucleation stages and surface morphology evolution of the thin films on silicon substrates were studied by atomic force microscopy. X-ray diffraction characterization of these films showed that the XWO 4 (X = Ca, and Sr) thin film phases crystallize at 500 °C from an inorganic amorphous phase, given that no intermediate crystalline phase was identified.

Effect of strontium addition on ferroelectric phase transition of PZT thin films prepared by chemical route

The dependence of ferroelectric phase transition temperature as a function of strontium substitution in lead titanate zirconate thin films (referred here as PSZT) on platinum-coated silicon substrates was investigated. The dielectric study reveals that the material undergoes a diffuse type ferroelectric phase transition that depends on the substitution of Sr for Pb in PZT. At 100 kHz, the phase transition temperatures were 633, 613 and 516 K for PSZT10, PSZT20 and PSZT30 thin films, respectively. On the other hand, the results showed that the dependence of the dielectric constant upon the frequency does not reveal any relaxor behavior. The diffusivity increases with increasing Sr contents in the studied composition range. The experimental data obtained from measurements of the dielectric constant as a function of temperature and frequencies showed a classical behavior of ferroelectric phase transition in PSZT thin films, rather than a relaxor ferroelectric phase transition. The transition temperature decreases with increasing Sr contents due to the decrease in grain size, lattice decrease and local structural disorder.

Pyro, Ferro and Dielectric Properties of Ba0.8Sr0.2TiO3 Films Deposited by Sol-Gel on Platinized Silicon Substrates

We report on the deposition by a sol-gel process of Ba 0.8 Sr 0.2 TiO 3 films on platinum coated silicon substrates. X-Ray diffraction patterns show that the films are (111) preferentially oriented. The surface morphology is smooth, without cracks and the grain size is about 50 nm as determined by AFM and SEM. The dielectric constant measured from 10 2 to 10 6 Hz decreases slightly and is around 400 at 10 4 Hz. The losses are constant in a first approximation for a 1.5 μ m thick film with a value of 0.03 at 10 kHz. The existence of an hysteresis cycle attests that the films, whatever their thickness, are in a ferroelectric state. Pyroelectric coefficients have been determined and the best figure of merit obtained at 293 K and 10 kHz is 40 μ C/m 3 /K.

Improvement of electrical properties of Sr-modified (Pb,Ca)TiO 3 thin films grown by soft chemistry route

Strontium and calcium-modified lead titanate (Pb 0.70Ca 0.15Sr 0.15)TiO 3 soft chemistry-derived thin films were prepared on platinum-coated silicon substrate by spin-coating method. Investigations were made on the structure, surface morphology and electrical properties of the film. The results by XRD and FE-SEM showed that the film exhibits a pure tetragonal perovskite phase and an average grain size of about 50–60 nm, respectively. Electrical measurements of a metal–ferroelectric–metal type capacitor exhibited a stable and switchable electrical polarization in the film. The structure of the Au/PCST/Pt capacitor showed well-saturated hysteresis loops at an applied voltage of 300 kV/cm with remanent polarization and coercive field values of 22 μC/cm 2 and 100 kV/cm, respectively. At 100 kHz, the dielectric constant and the dielectric loss of the (Pb 0.70Ca 0.15Sr 0.15)TiO 3 thin film with thickness 240 nm were 528 and 0.05, respectively.