Metalorganic Chemical Deposition Research Articles

Reductive Segregation During the Synthesis of Sb−SnO2-Supported Iridium Electrocatalysts for the Oxygen Evolution Reaction

A metal-organic chemical deposition approach using an Ir(acac)3 precursor was employed to synthesise oxide−supported iridium-based electrocatalysts for the oxygen evolution reaction (OER) in acidic media. Inert and oxidising deposition conditions were explored in two temperature regimes, and the influence of these parameters on the physicochemical and electrochemical properties of catalysts consisting of IrOx supported on Sb–SnO2 (ATO) were studied. Surprisingly, it was found that increasing the deposition temperature up to 620 °C favoured the formation of reduced iridium phases even in the presence of an oxidising reaction environment. This was explained by a thermodynamic preference for reduced phases at high temperatures, as well as the presence of acetylacetonate ligand decomposition products serving as reducing agents. Similarly, the reductive segregation of Sb from the ATO support at high temperatures leads to the loss of conductivity of the support, and the formation of Ir–Sb–Sn alloyed nanoparticles. These processes resulted in a loss of OER performance for the materials prepared under high-temperature conditions. Our findings highlight the importance of carefully selecting the temperature range during the synthesis of oxidic support materials and electrocatalysts for the OER.

(Invited) Towards the Development of High-Performance Crystalline Rutile Iridium Dioxide Electrocatalysts for the Oxygen Evolution Reaction

Proton exchange membrane water electrolysis (PEMWE) offers a promising route for the production of green hydrogen from renewable energy sources and could be the master key to unlocking a future sustainable energy system (1). One of the main barriers delaying the wide-spread adoption of PEMWE technologies is the slow kinetics of the oxygen evolution reaction (OER) occurring at the anode and the need for high-cost, low-abundance precious metal electrocatalysts. Iridium-based oxides are still considered the only feasible option for practical applications due to their high activity and considerable corrosion stability under the harsh electrochemical reaction conditions. To improve the overall efficiency of PEMWEs, future electrocatalyst development strategies must concomitantly address performance metrics in terms of activity, stability and material cost.Towards enhancing iridium utilisation, efforts are aimed at increasing the electrochemical surface area of the catalyst per mass of iridium, thereby increasing the number of available electrocatalytic surface sites. In this regard, amorphous iridium oxide (IrOx) nanoparticles have been shown to achieve a high intrinsic activity (2). However, this comes at the expense of catalyst stability (3) and a loss of intrinsic electronic conductivity (4) associated with the lower degree of crystallinity. By maximising the dispersion of Ir-based nanoparticles, the use of high surface area support materials have also been shown to improve OER performance (5, 6).However, to address long-term stability concerns for Ir-based OER catalysts, highly crystalline rutile iridium dioxide (IrO2) materials may still offer the best prospects. The drawback of using this approach is that the formation of crystalline IrO2 nanoparticles often involves high temperature thermal oxidative treatment causing particle growth and loss of surface area, ultimately leading to decreased OER activities (7). Therefore, novel synthesis methods that retain a high degree of crystallinity without a loss of surface area for IrO2 nanoparticles are required.In this talk, we discuss two synthesis strategies geared towards the preparation of highly crystalline IrO2 nanoparticles with high OER performance. Firstly, we present a novel wet-chemistry synthesis method that avoids the use of reducing agents and eliminates the need for high temperature thermal oxidative treatment. The resultant nano-sized IrO2 nanoparticles were found to have excellent Ir mass-specific OER activity and durability attributed to the small nanoparticle size and high degree of crystallinity.Secondly, we present a novel metalorganic chemical deposition process as a simple, one-step preparation method for highly crystalline IrO2 nanoparticles supported on Sb-doped tin oxide (ATO) (8). The superior OER performance was attributed to the epitaxial anchoring of well dispersed, crystalline IrO2 nanoparticles onto the ATO support. We further discuss the versatility of the method to the application of other conductive oxide support materials such as indium tin oxide and F-doped tin oxide, with the ability of tuning the chemical state of the Ir-based nanoparticles by changing the reaction conditions, i.e., temperature and gas environment as well as the nature of the support.Finally, using a series detailed physico-chemical characterisation techniques to elucidate the nature the iridium phase, composition, morphology and structure, we relate these properties to the electrochemical activity and stability of the prepared materials for the OER. Herein, we highlight some of the challenges often encountered with the analysis of physical and electrochemical characterisation data for IrO2 nanoparticles, particularly when supported on other oxide materials. Acknowledgements This work is funded by the Department of Science and Innovation (DSI, South Africa) Impala Platinum Holdings Limited (Implats) and the Federal Minister of Education and Research (BMBF, Germany). References K. Ayers, Current Opinion in Electrochemistry, 18, 9 (2019). T. Reier, I. Weidinger, P. Hildebrandt, R. Kraehnert and P. Strasser, ECS Transactions, 58, 39 (2013). T. Binninger, R. Mohamed, K. Waltar, E. Fabbri, P. Levecque, R. Kötz and T. J. Schmidt, Scientific Reports, 5, 12167 (2015). M. Bernt, C. Schramm, J. Schröter, C. Gebauer, J. Byrknes, C. Eickes and H. A. Gasteiger, Journal of The Electrochemical Society, 168, 084513 (2021). H.-S. Oh, H. N. Nong, T. Reier, A. Bergmann, M. Gliech, J. Ferreira de Araújo, E. Willinger, R. Schlögl, D. Teschner and P. Strasser, Journal of the American Chemical Society, 138, 12552 (2016). A. Hartig-Weiss, M. Miller, H. Beyer, A. Schmitt, A. Siebel, A. T. S. Freiberg, H. A. Gasteiger and H. A. El-Sayed, ACS Applied Nano Materials, 3, 2185 (2020). J. Quinson, Advances in Colloid and Interface Science, 303, 102643 (2022). Z. S. H. S. Rajan, T. Binninger, P. J. Kooyman, D. Susac and R. Mohamed, Catalysis Science & Technology, 10, 3938 (2020).

Fabrication and Application of 1653.7 nm Methane Sensor

In industries such as coal mining, natural gas transportation and waste-to-energy, methane detection is an essential step. In order to reduce the risk and improve accuracy, laser sensors are used to detect methane. Aiming at the characteristics of the absorption peak of methane gas at 1653.7 nm, the 1653.7 nm distributed feedback laser was obtained from the multi quantum well materials design and ridge-wide pattern design to device packaging by using metal-organic chemical vapor epitaxial deposition, holographic exposure, and nanoimprint lithography. The laser performance achieves a side-mode suppression ratio of 54 dB, a slope efficiency of 0.372 W/A, a threshold current not greater than 12 mA, a saturated optical power greater than 20 mW, and stable optical and electrical properties. Based on this laser, for methane gas with a concentration of 0% to 3%, the loss is stable with the change of gas concentration, and the absorption sensitivity to methane is 0.20237 dB/%.

Low-Vacuum Pyrolysis of YBCO Films by Using Fluorine-Free Metal Organic Chemical Deposition

The preparation of YBCO superconducting films by using metal organic chemical deposition (MOD) involves low-temperature pyrolysis and high-temperature treatment. The former process generally requires the introduction of water vapor and other gases. The study on pyrolysis in a low vacuum environment and non-carrier gas atmosphere has never been reported. In this work, we explored a low vacuum pyrolysis scheme with simple Argon gas decompression and a carrier-free atmosphere. The effects of heating rate on the microstructure of pyrolysis films were investigated, and the high-temperature treatment temperature (Th) was also optimized. Compared with conventional pyrolysis, the present low-vacuum pyrolysis does not employ the flowing dry or wet gases, facilitating the internal gas release during film decomposition. More importantly, the efficiency was greatly improved with reduced pyrolysis time. The obtained film surface is free of CuO particle, which leads to a lower roughness. We also investigated the effect of Th on the final YBCO film texture and superconductivity. As Th increased from 810 °C to 815 °C, the BaCuO2 phase decreased with enhanced c-axis orientation being evident by XRD and Raman spectra. As a result, the critical current density (Jc) increased from 0.38 MA/cm2 to 1.2 MA/cm2 (77 K, self-field).

Simulation study on the diversity and characteristics of twin structures in GaN

Gallium nitride (GaN) is a promising material for high-frequency and high-power electronics owing to its high thermal stability, wide bandgap, and high breakdown voltage. Monocrystalline GaN films are usually produced by metal organic chemical vapor phase deposition using Si, SiC, or Al 2 O 3 as the substrate. However, the difference in lattice constants and thermal expansion coefficients causes many defects in GaN epilayers . In particular, the formation of twins will strongly influence the electronic properties of GaN-based devices. In this study, the solidification process of GaN was simulated by molecular dynamics at a cooling rate of 10 12 K/s, and the twin structures in GaN were discussed. The results of this simulation showed two types of twins, including coherent twin and rotating twin, which were analyzed by visualization technology. The formation of twins was related to the coexistence of zinc blende and wurtzite phases. Furthermore, the types of twins were closely associated to the stacking ways of zinc blende and wurtzite structures. In general, it is essential to study the microstructure and the structural evolution of twin GaN, in order to give references to experiments about the growth and characteristics of twins. • Zinc blende and wurtzite nucleated randomly and formed lots of complex structures at the beginning of crystallization. • Coherent and rotating twins were formed according to different stacking methods of zinc blende and wurtzite structures. • The rules for the combination of twin structures in GaN crystals have been summarized and it can be generalized. • An error in the stacking sequence can cause the metastable phase c-GaN to start seeding the h-GaN phase.

Photoconductivity and Photovoltaic Studies on Polycrystalline Bi1−xM′xFe1−yM″yO3−δ (M′ = K+ and Cs+; M″ = Ti4+; x = y = 0 and 0.1) Thin Films

The recent surge of interest in using all-inorganic materials like CsPbI3 for photovoltaic devices has brought significant interest in exploring the properties of BiFeO3 (BFO) by substituting Cs+ and K+ at the Bi3+ site. The aim of the present work is to study the parameters like controlling the lattice and surface oxygen vacancy (VO) defects which can significantly improve the photovoltaic device performances. Monovalent substituted and aliovalent co-substituted Bi1−xM'xFe1−yM"yO3−δ (M′ = K+ and Cs+; M" = Ti4+; x = y = 0 and 0.1) are grown on fluorine-doped tin oxide (FTO)/glass substrates by metal-organic chemical solution deposition method. Photoconductivity and photovoltaic properties of these films are studied in FTO/Bi1−xM'xFe1−yM"yO3−δ/Au capacitor configuration. Aliovalent substitution (for M' = K+ and Cs+, BK10FO and BCs10FO, respectively) at Bi3+ sites create VO in BFO thin films. Further, grain size reduction from 100 nm to 30 nm also results in the creation of surface VO defects. Tauc plot shows a reduction in the bandgap (Eg) values from 2.32 eV to 2.26 eV due to the formation of mid-bandgap VO defect states. Consequently, ferroelectric properties also get diminished. Aliovalent K+-Ti4+ co-substitution in BFO thin films brings back the Eg values to 2.3 eV, i.e., similar to pristine BFO thin films suggesting suppression of VO. This results in the revival of ferroelectric nature in aliovalent co-substituted thin films. Photoconductivity studies show two order enhancement in conductivity for BK10FO thin film devices compared to pure BFO. This enhancement is attributed to the mid-bandgap VO defect states due to aliovalent substitution. On the other hand, photoconductivity observed in BCs10FO devices is comparable with pristine BFO devices. Contrary to this, aliovalent co-substituted thin films show a decreasing trend of photoconductivity compared to M'+ substituted BFO suggesting that VO defects get suppressed due to charge compensation. Photoconductivity and photovoltaic device studies show similar behavior. BK10FO devices exhibit short circuit current density (JSC) ~0.45 µA/cm2, which is larger than that observed in BFO devices (JSC ~0.3 µA/cm2). But, BCs10FO devices show lesser JSC 0.07 µA/cm2. Open circuit voltage (VOC) observed in BFO devices is around 3 V which decreases to 0.1 V and 0.06 V for BK10FO and BCs10FO devices, respectively. This decrease in VOC is attributed to the reduction of the ferroelectric nature of the films. BFO, BK10FO, and BCs10FO devices show photovoltaic switching upon poling the films. Co-substituted thin films show a reduction in the JSC and betterment in the VOC compared to the monovalent substituted BFO thin films. This happens due to the suppression of VO defects by partial charge compensation in aliovalent co-substituted BFO films. This study explicitly brings out the role of VO on the photovoltaic and photoconductivity properties of BFO thin films.

Fabrication of YBCO Thin Films by Fluorine-Free MOCSD Method: Influence of Sintering Near the Melting Point

YBa 2 Cu 3 O 7-δ thin films were deposited by a fluorine-free metal-organic chemical solution deposition method using metal acetates as the starting materials. In this article, influence of different sintering temperatures (770-800 °C) on structural and superconducting properties of the films was investigated. Using a mixture of argon with 100 ppm oxygen as the atmosphere of the sintering process, some grain melting was observed at this temperature range, which favors to obtain a more c-axis epitaxial films with a higher critical current density. The decomposition mechanism of organic components of precursor powder was studied by Thermal Gravimetric Analysis (TGA)/Differential Scanning Calorimetry (DSC) analysis. The structural and morphological properties of the films were investigated by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Atomic Force Microscopy (AFM) analysis. Four-point probe and inductive third-harmonic voltage measurements were carried out to determine transition temperature and critical current density, respectively. The film sintered at 790 °C showed a superconducting transition temperature at 91.5 K with a width of 1.2 K and a critical current density of 2 MA/cm 2 .

A quick and versatile one step metal-organic chemical deposition method for supported Pt and Pt-alloy catalysts.

A simple, modified Metal–Organic Chemical Deposition (MOCD) method for Pt, PtRu and PtCo nanoparticle deposition onto a variety of support materials, including C, SiC, B4C, LaB6, TiB2, TiN and a ceramic/carbon nanofiber, is described. Pt deposition using Pt(acac)2 as a precursor is shown to occur via a mixed solid/liquid/vapour precursor phase which results in a high Pt yield of 90–92% on the support material. Pt and Pt alloy nanoparticles range 1.5–6.2 nm, and are well dispersed on all support materials, in a one-step method, with a total catalyst preparation time of ∼10 hours (2.4–4× quicker than conventional methods). The MOCD preparation method includes moderate temperatures of 350 °C in a tubular furnace with an inert gas supply at 2 bar, a high pressure (2–4 bar) compared to typical MOCVD methods (∼0.02–10 mbar). Pt/C catalysts with Pt loadings of 20, 40 and 60 wt% were synthesised, physically characterised, electrochemically characterised and compared to commercial Pt/C catalysts. TEM, XRD and ex situ EXAFS show similar Pt particle sizes and Pt particle shape identifiers, namely the ratio of the third to first Pt coordination numbers modelled from ex situ EXAFS, between the MOCD prepared catalysts and commercial catalysts. Moreover, electrochemical characterisation of the Pt/C MOCD catalysts obtained ORR mass activities with a maximum of 428 A gPt−1 at 0.9 V, which has similar mass activities to the commercial catalysts (80–160% compared to the commercial Pt/C catalysts).

Scalable BEOL compatible 2D tungsten diselenide

Low-temperature synthesis of two-dimensional (2D) transition metal dichalcogenides (TMDs) is a key challenge for their integration with complementary metal-oxide-semiconductor (CMOS) technology at ‘back-end-of-line (BEOL)’. Most low-temperature synthesis utilizes alkali salts, oxide-based metals, and methyl-group based chalcogen precursors which do not meet current BEOL requirements for contaminant-free manufacturing and process scalability. In this study, we benchmark a carbon and alkali salt-free synthesis of fully coalesced, stoichiometric 2D WSe2 films on amorphous SiO2/Si substrates at BEOL- compatible temperatures (475 °C) via gas-source metal-organic chemical deposition. This work highlights the necessity of a Se-rich environment in a kinetically limited growth regime for successful integration of low-temperature 2D WSe2. Atomic-scale characterization reveals that BEOL WSe2 is polycrystalline with domain size of ~200 nm and band gap of 1.8 eV. Back-gated and electrolyte double layer gated field-effect transistors (FETs) exhibit increased ON currents as high as 4 µA µm−1 and ON/OFF ratios of ~106, demonstrating a 100× improvement compared to previously reported BEOL compatible TMDs.

Investigation of Composition Uniformity in Thickness of GaInAsP Layers Grown on InP Substrates by Vapor-Phase Epitaxy

GaInPAs/InP heterostructures grown by metalorganic chemical vapor-phase deposition at a temperature of 600°C and pressure of 0.1 bar are investigated. The thicknesses of the grown GaInAsP layers amount to about 1 μm. For Ga1 –xInxP1 –yAsy solid solutions with average compositions of x = 0.77–0.87 and y = 0.07–0.42, the variation in the content y of V-group atoms over the epitaxial-layer thickness by a value of Δy up to 0.1 atomic fractions in the sublattice of the V-group elements is revealed by secondary ion mass spectrometry. In most cases, a change in y occurs in the GaInAsP layer over a length to 200 nm from the InP heterointerface. In certain cases, y varies throughout the entire GaInPAs-layer thickness. For the epitaxial layers with satisfactory crystalline perfection, the value of Δy is less in the case of better lattice-matching between the GaInPAs epitaxial layer and the substrate. For GaInPAs layers strongly lattice-mismatched with the substrate and characterized by a low degree of crystalline perfection, the value of Δy is close to zero. All these facts enable us to assume that it is elastic deformations arising in the forming monolayer lattice-mismatched with the growing surface that affect the incorporation of V-group atoms into the forming crystalline lattice.

Influence of chemical solution growth and vacuum annealing on the properties of (100) pseudocubic oriented BiFeO3 thin films

BiFeO3 (BFO), a Pb-free perovskite oxide, is being explored for its potential use in a multitude of applications. We report on the oriented growth of BFO thin films using a facile metal-organic chemical solution deposition. Unlike the growth characteristics observed in Si/SiO2 and glass/FTO substrates, the solution growth process on sapphire (0001) is found to yield highly oriented thin films along (100)pc planes. Furthermore, annealing in air (BFO-A) and high-vacuum (BFO-V) ambients are done to explore the tunable limits of its physical properties. Temperature-dependent Raman studies highlight the high quality of thin films with sharp changes in Raman modes around transition temperatures. In addition, the films exhibit a hitherto unreported anomalous shift in A1(TO) and E(TO) modes around 450 K. The bandgap of BFO-V (Eg = 2 eV) is lower than that of BFO-A (Eg = 2.12 eV) and exhibits an increased defect photoluminescence emission. The magnetization (M) is twofold higher for BFO-V [M ≈ 42 (67) emu/cm3 at 300 K (5 K)]. In-plane and out-of-plane M vs H plots show larger anisotropy and hard hysteresis for BFO-A compared to BFO-V. Piezoelectric switching with d33 values of 5–10 pm/V is the characteristic of BFO ferroelectric materials. Photoconductivity measurements show a one order increase due to vacuum annealing. Carrier generation and recombination lifetimes are twofold faster in BFO-V as compared to BFO-A thin films. The controllable physical properties of oriented BiFeO3 thin films will be useful in magnetoelectrics and photoferroelectrics applications.

MoS2 coating on CoSx-embedded nitrogen-doped-carbon-nanosheets grown on carbon cloth for energy conversion

Designing low-cost and highly efficient electrocatalysts has become a critical aspect to achieve sustainable energy production. Herein, we report the preparation strategy of MoS2 on Co-oxide nanoparticles embedded nitrogen-doped carbon nanosheets (Co-NC) those derived by ZIF-L anchored on a carbon cloth as an electrode for hydrogen evolution reaction (HER). The hybrid electrode denoted as MoS2/Co-NC/CC was synthesized in sequence of the growth of the leaf-like zeolitic imidazolate framework (Co-ZIF-L) on a carbon cloth (CC), the carbonization of the Co-ZIF-L and deposition of MoS2 by metal organic chemical deposition (MOCVD). The hierarchical porous catalyst presented remarkable electrochemical activity towards the HER in acidic solution, exhibiting great stability and fast kinetics with a small Tafel slope of 51 mV dec−1. Moreover, to produce a current density of 10 mA cm−2 (η10), MoS2/Co-NC/CC required a low overpotential of 111 mV, which is comparable with Pt.

Effects of 3D structure on electrochemical oxygen reduction characteristics of Pt-nanoparticle-supported carbon nanowalls

For polymer electrolyte fuel cell applications, effects of Pt-nanoparticle-supported 3D carbon nanostructures, i.e. carbon nanowalls (Pt/CNWs), on electrochemical characteristics were determined by alternating current impedance analysis of resistive elements, which contribute to the oxygen reduction reaction. CNWs were fabricated by radical-injection plasma-enhanced chemical vapor deposition (RI-PECVD), and Pt catalysts were formed on the template of CNWs by supercritical fluid metalorganic chemical fluid deposition. CNWs of different wall densities were synthesized during RI-PECVD by varying the deposition pressure. The resistive elements can be consisted of three regions with different corresponding frequencies, and the resistive elements of mass diffusion, which showed up in the lowest frequency region of less than 100 Hz, increased as the wall density of CNWs increased. It was found that the wall density of CNWs was one of the essential parameters of Pt/CNWs for the electrochemical reaction involving the fluid flow and the mass transfer of active materials.

Anomalous electroluminescent blue-shift behavior induced by well widths variance and localization effect in InGaN/GaN multi-quantum wells.

Twelve InGaN MQW LED samples with varying well thickness grown via metal-organic chemical vaper deposition (MOCVD) are investigated. It is observed from electroluminescence (EL) measurement that at low current densities, the peak energy shifts to blue with increasing current, and when the current change by fixed increment, the peak energy shifts to blue end to different extent among samples. This blue shift was expected to be stronger when the well thickness increases, however, for well widths above 5 nm we observe a decrease in emission energy. Since no relaxation was detected from reciprocal space mapping (RSM), the deteriorated homogeneity is found to be responsible for this phenomenon. Temperature dependent photoluminescence (TDPL) results analyzed by band-tail model fitting show that the localization effect gets more prominent with increasing well thickness. It is found that elevating the growth temperature of active region from 710°C to 750°C significantly improves the homogeneity of InGaN layer.

Effect of hexagonal hillock on luminescence characteristic of multiple quantum wells structure

GaN based ultraviolet multiple quantum well structures grown on a c-plane sapphire substrate by metal organic chemical deposition showed a microstructure with a large amount of huge hexagonal hillocks. The polarity of the sample is confirmed by etching with sodium hydroxide solution. The luminous intensity distribution of a typical hexagonal hillock was investigated by the phototluminescent mapping and the luminous intensity at hillock top regions was found to be 15 times higher than that of the regions around hillocks. The reduction of dislocations, the decreasing of the quantum confirmed stack effect caused by semipolar plane and the inclination of the sidewalls of the hexagonal hillock were responsible for the enhancement of luminous intensity.

Defect formation and optical activation of Tb implanted AlxGa1−xN films using channeled implantation at different temperatures

AlxGa1−xN (x = 0.20, 0.50, 0.63) films grown on (0001) sapphire substrates by metal organic chemical vapor phase deposition were implanted with Tb ions at 150 keV and a fluence of 7 × 1014 Tb cm−2. The implantation was carried out with the beam aligned with the c-axis and the implantation temperature was varied from room temperature (RT) to 550 °C. Additionally, post-implantation rapid thermal annealing was performed at 1200 °C during 120 s. The impact of implantation temperature on the damage accumulation is investigated. Rutherford backscattering spectrometry/channeling (RBS/C) measurements show that two damage regions are forming and the damage is not decreasing monotonically with the increase of implantation temperature. Bulk damage follows the same trend for all AlxGa1−xN compositions, increasing when the temperature is raised up to ~100 °C, and then decreasing for higher temperatures. A good agreement is observed between the damage accumulation obtained from RBS/C and the strain profile derived from symmetric (0002) 2θ-ω X-ray diffraction scans. Transmission electron microscopy results show the suppression of basal stacking faults after implantation at 550 °C. Tb lattice site location studies revealed two preferential sites: the substitutional cation site and a site displaced from that by 0.2 Å along the c-axis. A higher substitutional fraction of Tb ions is obtained for implantation temperature of 550 °C. The optical activity investigated by photoluminescence showed that after thermal annealing, the 5D4 → 7FJ intra-4f8 transition is detected in all the samples.

Fabrication and characterization of {110}-oriented Pb(Zr,Ti)O3 thin films on Pt/SiO2/Si substrates using PdO//Pd buffer layer

A strongly {110}-oriented perovskite-type thin film of tetragonal Pb(Zr0.4Ti0.6)O3 (PZT) was successfully obtained on a (100)Si substrate using a {101}PdO//{111}Pd thin film as a buffer layer. The {101}PdO//{111}Pd thin film buffer layer was obtained by oxidizing {111}Pd after depositing {111}Pd on a {111}Pt/TiOx/SiO2/{100}Si substrate. Using this buffer layer, a {110}c-oriented SrRuO3 (SRO) thin film was deposited by sputtering as a bottom electrode of PZT thin films. Subsequently, the {110}-oriented PZT thin film can be deposited on a (110)cSRO thin film by metal–organic chemical deposition (MOCVD) and its properties can be compared with those of PZT thin films with other orientations of {100} and {111}. Among the {100}, {110}, {111}-oriented PZT films, the {100}-oriented one showed the largest remnant polarization, which is in good agreement with those of the PZTs epitaxially grown in the 〈100〉, 〈110〉, and 〈111〉 directions. The other properties, i.e., piezoelectricity and dielectric constants, also showed similar anisotropic tendencies, which is in good agreement with the data reported in the epitaxially grown PZTs.

Room Temperature Sensing Achieved by GaAs Nanowires and oCVD Polymer Coating.

Novel structures comprised of GaAs nanowire arrays conformally coated with conducting polymers (poly(3,4-ethylenedioxythiophene) (PEDOT) or poly(3,4-ethylenedioxythiophene-co-3-thiophene acetic acid) display both sensitivity and selectivity to a variety of volatile organic chemicals. A key feature is room temperature operation, so that neither a heater nor the power it would consume, is required. It is a distinct difference from traditional metal oxide sensors, which typically require elevated operational temperature. The GaAs nanowires are prepared directly via self-seeded metal-organic chemical deposition, and conducting polymers are deposited on GaAs nanowires using oxidative chemical vapor deposition (oCVD). The range of thickness for the oCVD layer is between 100 and 200 nm, which is controlled by changing the deposition time. X-ray diffraction analysis indicates an edge-on alignment of the crystalline structure of the PEDOT coating layer on GaAs nanowires. In addition, the positive correlation between the improvement of sensitivity and the increasing nanowire density is demonstrated. Furthermore, the effect of different oCVD coating materials is studied. The sensing mechanism is also discussed with studies considering both nanowire density and polymer types. Overall, the novel structure exhibits good sensitivity and selectivity in gas sensing, and provides a promising platform for future sensor design.

Rapid fabrication of chemical-solution-deposited La0.6Sr0.4CoO3−δ thin films via flashlight sintering

This study demonstrates the sintering effectiveness of an intense pulsed light (IPL) sintering method for the fabrication of lanthanum strontium cobaltite (La0.6Sr0.4CoO3−δ, LSCO) thin films via xenon flashlight irradiation. LSCO thin film was coated on silicon (100) wafer via metal organic chemical solution deposition (MOCSD) methods and the flashlight irradiation process preceded instantly under ambient room temperature conditions. The properties of flashlight irradiated films were compared with thermally sintered ones as reference target. Electrical property, surface morphology, and crystallinity were observed to evaluate effectiveness of the flashlight sintering method by employing four-point probe apparatus, FE-SEM, and XRD, respectively. Considering that flashlight sintering process is procedurally accomplished in milliseconds under ambient room temperatures, this method may be able to circumvent several issues from the conventional thermal sintering process in realizing a convenient and available sintering process. The significance of this work lies in the demonstration of xenon flashlight sintering methods of perovskite oxides that are fabricated via wet chemical solution methods.

High haze textured surface B-doped ZnO-TCO films on wet-chemically etched glass substrates for thin film solar cells**Project supported by the State Key Development Program for Basic Research of China (Nos. 2011CBA00706, 2011CBA00707), the Tianjin Applied Basic Research Project and Cutting-Edge Technology Research Plan (No. 13JCZDJC26900), the Tianjin Major Science and Technology Support Project (No. 11TXSYGX22100), the National High Technology Research

Textured glass substrates with crater-like feature sizes of ∼5–30 μm were obtained using the chemical etching method through adjusting the treatment round (R). Pyramid-like boron-doped zinc oxide (ZnO:B) films with feature sizes of ∼300–800 nm were deposited on the etched glass substrates by the metal organic chemical deposition (MOCVD) technique using water, diethylzinc and 1%-hydrogen-diluted diborane. The ZnO:B films on the etched glass with micro/nano double textures presented a much stronger light-scattering capability than the conventional ZnO:B on the flat glass and their electrical properties changed little. Typical etched glass-3R/ZnO:B exhibited a high root mean square (RMS) roughness of ∼160 nm. The haze values at the wavelengths of 550 nm and 850 nm for etched glass-3R/ZnO:B sample were 61% and 42%, respectively. Finally, the optimized etched glass/ZnO:B was applied in the silicon (Si) based thin film solar cells. The high haze etched glass/ZnO:B substrates have potential merits for thin film solar cells.