Films Of Pt Research Articles

The interplay of electronic structure, molecular orientation and charge transport in organic semiconductors: Poly(thiophene) and poly(bithiophene)

Ultrathin films of poly(thiophene) (PT) and poly(bithiophene) (PBT) were prepared by electrochemical route using ionic liquid (BFEE) as medium and electrolyte. Distinct morphologies and electrical properties were observed in these materials. To evaluate its response in photovoltaics, these films were used as active layer in bilayer geometry solar cells with the electron acceptor molecule C60. The best performance was observed for PT films. In order to probe the differences in molecular dynamics and structural order, ultrafast electron dynamics in the low-femtosecond regime was evaluated by resonant Auger spectroscopy using the core–hole clock method at the sulfur K absorption edge. Electron delocalization times for the different polymeric films were derived as a function of the excitation energy. Photoabsorption measurements were conducted and molecular orientation derived. These results corroborated with the morphology found for these films and thus the performance of PT and PBT in the devices, and with the proposed conduction mechanism.

Vertically-Oriented Polymer Electrolyte Nanofiber Catalyst Support for Fuel Cells

This paper presents fabrication and characterization of a novel extended surface electrode with a high surface area catalyst support made of a polymer electrolyte composite. The degradation and high Pt loading of conventional carbon-supported Pt electrodes still present challenges for polymer electrolyte fuel cells (PEFCs). The electrode presented here is based on a high surface area Nafion composite membrane featuring vertically oriented nanofibers. Nanofibers were fabricated from solution casting SiO2/Nafion composite ionomer onto a porous polycarbonate template. A thin film of Pt was vacuum deposited directly on the surface of the nanofibers to form the electrode. Two different electrodes were fabricated: one with Pt sputtered onto the template before casting and the other with a non-sputtered template. Sputtered template electrode outperformed the non-sputtered template electrode. The structural and electrochemical characterizations show that this electrode is a viable approach.

Electromodulation of monomer and excimer phosphorescence in vacuum-evaporated films of platinum (II) complexes of 1,3-di(2-pyridyl)benzenes

Electric field-modulated photoluminescence (EML) measurements are presented for vacuum-evaporated films of cyclometallated Pt (II) complexes of 1,3-di(2-pyridyl) benzenes used as triplet emitters in organic light-emitting diodes (OLEDs). The excimer phosphorescence is quenched by the external electric field of 2.5MV/cm up to 25% but the same effect on monomer phosphorescence is one order of magnitude smaller. The higher quenching effect for triplet excimers than triplet monomers in solid films of Pt complexes is rationalized assuming excimers to be populated within excimer-active domains of the films through an intermediate stage of geminate (e–h) pairs derived from dissociated monomer excitons. The EML data for excimers are successfully described in the framework of Sano–Tachiya–Noolandi–Hong (STNH) theory of geminate (e–h) pair recombination where the final recombination step (e–h capture) proceeds on a sphere of finite radius (a) with a finite speed. The conventional Onsager theory (a=0) is sufficient to explain the EML quenching effect for monomers. The results are important for explaining the decrease of electroluminescence quantum efficiency observed in OLEDs working under high electric fields.

Large ferroelectric polarization of chemical solution processed BiFeO3–PbTiO3 thin films

We report unusually high ferroelectric polarization in chemical solution processed thin films of BiFeO3–PbTiO3 (BF–xPT) of compositions near the morphotropic phase boundary (MPB). Saturated hysteresis loops were obtained showing a large remnant polarization of 80μC/cm2 in thin films of composition BF–0.25PT with polarization decreasing for BF–0.30PT and BF–0.35PT. Structural analysis revealed single phase region with monoclinic Cm space group for composition x=0.25 while a two phase region of monoclinic (Cm) and tetragonal (P4mm) phase exists at x=0.30–0.35. The large polarization in BF–0.25PT films is attributed to superior polarizability of the monoclinic Cm phase.

Influence of intermediate Ag layer on the structure and magnetic properties of Pt/Ag/Fe thin films

Layered films of Pt(15 nm)/Ag(x)/Fe(15 nm) with various Ag layer thicknesses (0 nm, 3 nm, 30 nm) were deposited at room temperature onto SiO2(100 nm)/Si(001) substrates. The films were post-annealed in the temperature range of 100 °C–900 °C for 30 s in high vacuum. The influence of the Ag interlayer on the L10-FePt phase formation, as well as its structure and magnetic properties were investigated by X-ray diffraction, electrical resistance measurements, secondary neutral mass spectrometry and SQUID magnetometry. It is illustrated that the limited solubility of Ag in the FePt lattice as well as its grain boundary segregation and diffusion results in magnetic isolation of the FePt grains and in increase of the coercivity of the film. Sufficient distinctions of L10 phase formation in Pt/Ag/Fe films compared to the FePt/Ag/FePt films were shown. The presence of the Ag interlayer, as compared to the Pt/Fe bilayer, did not change the transformation temperatures, but the increase of the Ag interlayer thickness up to 30 nm resulted in the slowing down of the transformation kinetics: the Ag interlayer acts as diffusion barrier against of the intermixing of the Pt and Fe layers.

Adaptive Optics Integrated Surface Roughness Measurement of Sputtered PT Film on Silicon Substrate

ABSTRACTA new optical inspection system for in situ surface roughness measurement of sputtered Pt film on silicon is developed. In this study, we present an in‐process measurement of surface roughness by combining an optical probe of laser‐scattering phenomena and adaptive optics (AO) for aberration correction. The aim of this study was to demonstrate the necessity for AO compensation in regions containing turbulences. Measurement results of eight Pt film on top of P‐type silicon wafer samples with a roughness ranging from 58 to 83 nm demonstrate excellent correlation between the peak power and average roughness with a correlation coefficient (R2) of 0.9963. The proposed AO‐assisted system is in good agreement with stylus method and less than 0.70% error values are obtained for the aforementioned average sample roughness. The proposed system can be used as a rapid in‐process roughness monitor to further improve the stability of thin film–sputtering processes in situ. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2055–2059, 2013

High–Energy‐Storage Density Capacitors of Bi(Ni1/2Ti1/2)O3–PbTiO3 Thin Films with Good Temperature Stability

High–energy‐storage density capacitors with thin films of 0.5Bi(Ni1/2Ti1/2)O3–0.5PbTiO3 (BNT–PT) were fabricated by chemical solution deposition technique on Pt/Ti/SiO2/Si substrates. The dense thin films with pure‐phase perovskite structure could be obtained by annealing at 750°C. High capacitance density (~1925 nF/cm2 at 1 kHz) and extremely high‐energy density (~45.1 J/cm3) under an electric field of 2250 kV/cm were achieved at room temperature. The energy‐storage density and efficiency varied little in a wide temperature range from −190°C to 250°C. The high–energy‐storage density and good temperature stability make BNT–PT films promising candidates for high power electric applications.

The (100) orientation evolution and temperature-dependent electrical properties of Bi(Zn1/2Ti1/2)O3–PbTiO3 ferroelectric films

The 0.2Bi(Zn1/2Ti1/2)O3–0.8PbTiO3 (0.2BZT–0.8PT) ferroelectric thin film was successfully fabricated on Pt(111)/Ti/SiO2/Si substrates by a sol–gel method. The result indicates that the film exhibits the (100) preferred orientation and has a relatively dense and uniform microstructure with a thickness of ~230 nm. The formation mechanism of the oriented films was ascribed to the growth of the (100) oriented PbO layer at ~450 °C during a layer-by-layer crystallization process. Temperature-dependent electrical properties of the 0.2BZT–0.8PT films were investigated, showing that the film has a potential for high temperature applications.

A novel nanomachined flow channel glucose sensor based on an alumina membrane

In the present study, the construction of a nanomachined flow channel sensor based on a nanoporous alumina membrane (NAM) together with information on its kinetic biosensing for real-time electrochemical detection of glucose are described. Firstly, the enzyme glucose oxidase was covalently immobilized on nanochannels of NAM as active biosensing elements, and a thin film of Pt was sputtered at the end of the nanochannels as an electrochemical detector. When the glucose solutions flowed through the nanochannels at a certain flux, the hydrogen peroxide (H2O2) produced as a result of enzymatic conversion was detected by an amperometric method at the end face of the Pt film sputtered membrane. The results showed that the H2O2produced in the nanochannels was completely collected at the Pt film electrode due to the unique nanoscale channels. Thus, the detection sensitivity of glucose was significantly improved to as high as 86.62 μA mM−1 cm−2 at a flow rate of 20 μL min−1. It was also found that the amperometric signal of glucose was directly related to the imposed flow rate. The increased sensitivity of the sensor at a faster flow rate was at the cost of a reduction of the dynamic range of glucose. The present nanochannel sensor exhibited excellent stability and reproducibility even with a usage time of ten days. The proposed sensor was used to detect glucose in wine samples, and the results obtained were in good agreement with the values obtained by a spectrophotometric enzyme method.

Structure and electrical properties of Mn doped Bi(Mg1/2Ti1/2)O3-PbTiO3 ferroelectric thin films

The Mn doped 0.63Bi(Mg1/2Ti1/2)O3–0.37PbTiO3 (BMT–0.37PT–xMn, x=0–0.01) thin films were deposited on Pt(111)/Ti/SiO2/Si substrates by a sol–gel method. The effect of the Mn doping concentration on the structure and electrical properties of BMT–0.37PT thin films was studied. The X-ray diffraction data indicate that the B-site Mn substitution does not change the perovskite structure of the films. The X-ray photoelectron spectra show that Mn ions mainly exist as Mn3+ except for a few as Mn2+ for the 1mol% Mn doped BMT–0.37PT film. Moreover, it was found that the addition of a small amount of Mn effectively reduces the dielectric loss and improves the resistivity of the films. The BMT–0.37PT–0.005Mn film exhibits lower leakage current density than the undoped BMT–0.37PT film such that saturated hysteresis loops can be achieved. As a result, the BMT–0.37PT–0.005Mn film exhibits the largest permittivity (ɛr∼1271 at 1kHz) and remanent polarization (Pr∼17.4μC/cm2 at 100Hz) in all studied compositions.

Synthesis of Pt doped TiO2 nanoparticles: Characterization and application for electrocatalytic oxidation of l-methionine

a b s t r a c t In this research, we reported a novel method for synthesis of Pt doped TiO2 nanoparticles (Pt-TiO2) by sol-gel assisted method. The synthesized Pt doped TiO2 nanoparticles were characterized using X- ray diffraction (XRD), transmission electronic microscopy (TEM) and FT-IR techniques. To investigate the catalytic efficiency of Pt-TiO2 nanoparticles, the electrooxidation of l-methionine (l-Met) using the deposited film of Pt doped TiO2 nanoparticles and carbon nanotubes composite on glassy carbon electrode (Pt-TiO2/CNT/GCE) was studied in buffer solution (pH 7.00) using cyclic voltammetry (CV). Bare GCE shows an ill-defined oxidation wave around 1.4 V for l-Met whereas Pt-TiO2/CNT/GCE shows a well- defined oxidation peak at 1.1 V. The modified electrode does not show any fouling effect toward the oxidation of l-Met. Amperometry method was used to determine l-Met in the concentration range of 0.5-100 M with a detection limit of 0.1 M (S/N = 3). The selectivity of the reaction has been assessed with no interference from tyrosine, lysine, cysteine, tryptophan, alanine and glutathione. The present modified electrode shows good recovery results for spiked l-Met in human blood serum sample. © 2012 Published by Elsevier B.V.

Gas sensing properties of surface acoustic wave NH3 gas sensor based on Pt doped polypyrrole sensitive film

In this paper, we demonstrated the fabrication and gas sensing properties of room temperature surface acoustic wave (SAW) NH3 gas sensors based on polypyrrole (PPy) film of different layers and Pt doped 2 layer PPy film. The PPy film was deposited on the photolithography patterned sensitive area by layer-by-layer (LBL) self-assembly method. The doping of Pt was conducted by immersing substrates with PPy film in the solution of H2PtCl6 and then reduced by NaBH4. Gas sensing properties of SAW devices with different layer of PPy films and Pt doped 2 layer PPy film were investigated and compared. We found that device with 2 layer PPy film shows best performance among devices with different layers of PPy films. Response and stability of device with 2 layer PPy could be further improved by the doping of Pt. Gas sensing properties of our device in different carrier gases (air and N2) were also investigated. Fourier transform infrared (FTIR) spectroscopy, energy dispersive X-ray spectrometry (EDS) and scanning electron microscopy (SEM) techniques were used for the characterization of each sensitive film. Besides, the sensing mechanism was also discussed.

Effect of PbTiO3 seed layer on the orientation behavior and electrical properties of Bi(Mg1/2Ti1/2)O3–PbTiO3 ferroelectric thin films

Abstract High Curie-temperature 0.63Bi(Mg 1/2 Ti 1/2 )O 3 –0.37PbTiO 3 (BMT–PT) films were fabricated on Pt(111)/Ti/SiO 2 /Si substrates by the sol–gel spin-coating method. The oriented growth behavior of thin films was controlled by introducing a PT seed layer onto the platinum electrode surface. The effect of the annealing method of the PT seed layer on the orientation behavior and electrical properties of BMT–PT films was investigated. It was found that BMT–PT thin film exhibits higher (100) orientation degree when the PT seed layer was treated by rapid thermal annealing. The dielectric permittivity increases while the remanent polarization and coercive field decrease with increasing the (100) orientation degree. These results were explained according to the relationship between the preferential orientation and the spontaneous polarization directions of the films.

Inelastic energy loss of medium energy H and He ions in Au and Pt: Deviations from velocity proportionality

Electronic energy loss of light ions in nm films of Au and Pt has been studied at keV ion energies. For H the electronic stopping power $S$ is found to exhibit the expected velocity proportionality at low ion velocities, which confirms the anticipated excitation mechanisms responsible for the energy transfer between ions and the electrons in the solid. In contrast, for He, $S$ shows a clear deviation from velocity proportionality for both materials at ion velocities below 0.8 atomic units, i.e., 64 keV. This result indicates a change in the interaction mechanisms active at the investigated ion velocities, which cannot exclusively be interpreted from the density of states of the target. Instead, the more complex electronic structure of the He ion enables an additional energy loss channel due to charge exchange by atomic level promotion. Associated energy losses together with a changed equilibrium charge state permit an explanation of the observed phenomenon.

Ferroelectric and dielectric properties of 0.62Pb(Mg1/3Nb2/3)O3–0.38PbTiO3 thin films on La0.6Sr0.4CoO3 buffered Si substrates

0.62Pb(Mg1/3Nb2/3)O3–0.38PbTiO3 (0.62PMN–0.38PT) thin films were deposited on La0.6Sr0.4CoO3 (LSCO) buffered Si substrates by radio-frequency magnetron sputtering. It has been found that the 0.62PMN–0.38PT films show a (100) preferred oriented perovskite phase on (100) preferred oriented LSCO layer while they show a (110) preferred perovskite phase on (110) preferred oriented LSCO layer. The formations of such preferred orientations are attributed to co-contribution of the surface energy and lattice-match interface energy. The (110) preferred oriented 0.62PMN–0.38PT film exhibits a relatively low remnant polarization of 12.1μC/cm2 while a low coercive field of 27kV/cm compared with (100) preferred oriented one (13.9μC/cm2, 56kV/cm). Moreover, the (110) preferred oriented film shows a larger dielectric constant of ∼2260 and a lower dielectric loss of 0.09 at 1kHz than those of (100) preferred oriented one (1050 and 0.19). The results demonstrate that the enhanced ferroelectric and dielectric properties are achieved for (110) preferred oriented film, which is correlated with large anisotropy in the texture films induced by LSCO buffer layers.

Processing Optimization of Lead Magnesium Niobate‐Lead Titanate Thin Films for Piezoelectric MEMS Application

We report processing conditions and electromechanical properties of highly textured, 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 (PMN–PT) films, processed via chemical solution deposition on platinized silicon substrates. Textured perovskite seed layers, optimization of heat treatment conditions and Pb content control were studied to obtain pure perovskite PMN–PT films with dense, columnar grains. Highly (100)‐ and (111)‐oriented films, with Lotgering factors between 91% and 97%, and average grain size up to ~430 nm were synthesized on thin PbTiO3 and Pb(Zr,Ti)O3 seed layers. Overall, (100)‐textured films showed higher dielectric permittivity and saturated d33,f piezoelectric coefficients. Dense, submicron‐thick, (100)‐oriented films showed low‐field, relative dielectric permittivity of up to ~2850 (tan δ = 0.02) at 1 kHz, and remnant polarization values up to 17.5 μC/cm2. The films showed saturated d33,f piezoelectric coefficients as high as 210 pm/V.

Investigation of carbon nanotube webs as counter electrodes in a new organic electrolyte based dye sensitized solar cell

A new organic electrolyte system composed of 1-methyl-3-propylimidazole-2-thione (T) and 2,2′-dithiobis(1-methyl-3-propyl-2-imidazolinium) ditriflate (DT) has been formulated and used in dye sensitized solar cells (DSSCs). The electroactivity of different counter electrodes (CEs) has been evaluated by means of measuring J–V curves, Tafel plots and impedance spectroscopy. The CEs investigated were thin films of Pt and CoS on FTO, where CoS showed much better electroactivity towards the regeneration of the electrolyte at the cathode. In addition, electroactive layers of multi-walled carbon nanotube webs (MWCNT webs) have been investigated, for the first time, as CEs in a DSSC. CEs made with 20 layers of the webs showed great performance towards the reduction of DT. An efficiency of η = 4.12% has been attained in a DSSC with 20 layers of MWCNT webs, whereas by using a CoS based CE a slightly lower efficiency (η = 3.99%) was measured. These results were attributed to the high surface area and electrocatalytic activity of the MWCNT webs.

Fabrication and Properties of High Curie Temperature xBiZn1/2Ti1/2O3–(1−x)PbTiO3 Piezoelectric Films by a Sol–Gel Process

The xBiZn1/2Ti1/2O3–(1−x)PbTiO3 (BZT–PT, x = 0.1–0.3) thin films were fabricated on Pt(111)/Ti/SiO2/Si substrates via an aqueous sol–gel method. Highly (100) oriented BZT–PT films with thickness of 600 nm were obtained by introducing PbO seeding layers. Dense uniform microstructures with average grain size of about 50 nm were observed for these films. The dielectric, ferroelectric, and piezoelectric properties of the BZT–PT thin films were investigated. The curie temperature of the BZT–PT films was about 535°C for x = 0.2, and higher than 600°C for x = 0.3. The local effective piezoelectric coefficient of the (100) oriented BZT–PT films was approximately 40 pm/V for x = 0.3.

A novel route to Pt–Bi2O3 composite thin films and their application in photo-reduction of water

A novel homoleptic bismuth(III) β-diketonate (dibenzoylmethane – dbm) complex [Bi(dbm)3]2 has been used as a precursor to thin films of crystalline β-Bi2O3, and hexachloroplatinic acid (H2PtCl6·6H2O) has been demonstrated as a suitable precursor for deposition of platinum nanoparticles, both deposited via aerosol-assisted chemical vapour deposition (AACVD). Thin films of Pt–Bi2O3 were co-deposited from a mixture of [Bi(dbm)3]2 and H2PtCl6·6H2O; the introduction of Pt particles into β-Bi2O3 causes hydrogen to be evolved during photolysis of water over the composite material, a property not found for Pt particles or β-Bi2O3 alone.

Rotating disk electrode study of Cs 2.5H 0.5PW 12O 40 as mesoporous support for Pt nanoparticles for PEM fuel cells electrodes

The catalytic activity of Pt nanoparticles supported by zeolite-type mesoporous Cs 2.5H 0.5PW 12O 40 solid super-acid towards oxygen reduction has been explored. Pt(IV) impregnated Cs 2.5H 0.5PW 12O 40 was prepared by titration of an aqueous solution of phosphotungstic acid and a known quantity of H 2PtCl 6 with a solution of cesium carbonate. The H 2PtCl 6 impregnated insoluble salt was subsequently chemically or electrochemically reduced to form supported Pt nanoparticles. HRTEM micrographs show that the reduced composites Pt–Cs 2.5H 0.5PW 12O 40 (Pt–Cs 2.5PW 12) contains Pt nanoparticles of average dimensions 2–5 nm, embedded into the porous structure of the insoluble salt. RDE and RRDE studies and fuel cell polarization data performed using thin layer composite films of Pt–Cs 2.5PW 12 chemically or electrochemically reduced show that the catalyst is very stable and rather efficient for oxygen reduction (ORR). The oxygen reduction wave is shifted by 60–70 mV towards more positive potentials with respect to the one obtained using electrodes prepared with a standard catalyst such as E-Tek 20% Pt–Vulcan. Analysis of the voltammetric curves demonstrates that the electrocatalytic activity of the composite electrodes is higher than that of the standard catalyst. This indicates that the solid state super-acid Cs 2.5H 0.5PW 12O 40 acts as co-catalyst by providing a proton rich environment in the vicinity of the Pt nanoparticles that enhances their catalytic activity towards oxygen reduction.