Chemical Solution Deposition Approach Research Articles

Metal nanoparticles layer boosted resistive switching property in NiFe2O4-based memory devices

Metal nanoparticles layer (Ag and Cu) derived NiFe 2 O 4 thin films have been synthesized on Pt/Ti/SiO 2 /Si substrates via a facile chemical solution deposition approach. The influence of metal nanoparticles layer on resistive switching performance of NiFe 2 O 4 -based devices has been investigated. The multilayer devices exhibit low power, low Set/Reset voltage, low resistance fluctuation, high ON/OFF ratio, and superior retention performance compared to the majority of reported NiFe 2 O 4 -based resistance random access memory devices. Such improvement is ascribed to metal nanoparticles layer providing controllable paths to the growth/fracture of conductive filaments and suppressing the randomness of filaments based on Current transport conduction mechanisms and temperature dependence of resistance analysis. The hybrid metal conducting filaments and oxygen vacancies conducting filaments model has been proposed to clarify the behavior.

An Evaluation of Nanoparticle Distribution in Solution-Derived YBa2Cu3O7−δ Nanocomposite Thin Films by XPS Depth Profiling in Combination with TEM Analysis

This work discusses the development of an analysis routine for evaluating the nanoparticle distribution in nanocomposite thin films. YBa2Cu3O7−δ (YBCO) nanocomposite films were synthesized via a chemical solution deposition approach starting from colloidal YBCO solutions with preformed nanoparticles. The distribution of the nanoparticles and interlayer diffusion are evaluated with X-ray photoelectron spectroscopy (XPS) depth profiling and compared with cross-sectional transmission electron microscopy (TEM) images. It is shown that the combination of both techniques deliver valuable information on the film properties as nanoparticle distribution, film thickness and interlayer diffusion.

Tuning the defects and luminescence of ZnO:(Er, Sm) nanoflakes for application in organic wastewater treatment

A series of ZnO nanoflakes modified with rare earth ions of Er and Sm were prepared by a simple chemical solution deposition approach. It was found that the doping content of rare-earth ions was dominant for the defects in the nanoflakes and the ability of photocatalytic degradation for rhodamine B (RhB). The ZnO:(Er, Sm) nanoflakes exhibited a superior photocatalytic activity compared to undoped ZnO mainly due to the longer lifetime of photogenerated electrons-hole pairs in the process of photocatalytic reaction, and Zn0.98Sm0.01Er0.01O nanoflakes could degrade 96.5% RhB within 60 min under UV light irradiation. PL results provided a strong evidence for the existence of VO defect, which was also found to be responsive for the enhanced photocatalytic activity of ZnO:(Er, Sm) nanoflakes. And the peaks at 515 nm and 550 nm could be attributed to the transitions of $$^{2} H_{11/2} \to^{4} I_{15/2}$$ and $$^{4} S_{3/2} \to^{4} I_{15/2}$$ from Er3+ ions, indicating the realization of green luminescence.

Rapid Pyrolysis of YBa2Cu3O7-δ Films by Fluorine-Free Polymer-Assisted Chemical Solution Deposition Approach

A rapid pyrolysis heat treatment was proposed to prepare YBa2Cu3O7-δ (YBCO) films by a self-developed fluorine-free polymer-assisted chemical solution deposition (PA-CSD) approach. Metal acetates and polyvinyl butyral (PVB) in YBCO wet films were pyrolyzed within 30 min, which is less than one-twentieth the pyrolysis time for conventional fluorine–free CSD methods. The influence of the rapid decomposition on the microstructures of YBCO precursor films was investigated compared to conventionally pyrolyzed films. Based on the rapidly pyrolyzed films, high-temperature firing process was further optimized to fabricate epitaxially grown YBCO films. The results demonstrate that most of the defects generated in the rapid pyrolysis process can nearly be eliminated by extending firing time to 2 h, and thus the textured YBCO films with denser and smoother morphologies were obtained with superconducting transition temperature Tc of 93.3 K and critical current density Jc of 3.1 MA/cm2 at 77 K and self-field. This is almost three times of the Jc of the conventionally pyrolyzed film.

Preparation of biaxially textured Ce1-x(Y0.2Zr0.8)xOδ buffer layers on RABiTS NiW tapes by chemical solution deposition

Highly (100)-oriented Ce1-x(Y0.2Zr0.8)xOδ (CYZO) films were prepared on biaxially textured NiW substrates by a chemical solution deposition approach using metal inorganic salts as starting materials. It has been found that both the preferential orientation and surface roughness of CYZO films decrease gradually with increasing of the doping percentage of Y3+ and Zr4+ ions. The epitaxial growth relationship of (220)CYZO//(200)NiW and [00 l]CYZO//[001]NiW was demonstrated by XRD texture measurement as well as atomic resolution STEM observation. XRD, Raman and XPS spectra results indicate that Y3+ and Zr4+ ions were indeed introduced into CeO2 lattice to substitute Ce4+ ions and form cubic fluorite CYZO solid solution. Moreover, CeO2 buffer layer can be endowed a strong enough capability to prevent element diffusion through co-doping of yttrium and zirconium, provided that an optimal doping ratio of them is adopted. This will provide a new approach to fabricating strong-barrier single buffer layer for coated conductor.

The effect of heat treatment temperature on superconductivity of Bi-2212/YBCO heteroepitaxial structure fabricated by chemical solution deposition approach

A planar-type heteroepitaxial junction with high-Tc superconducting YBa2Cu3O7−δ(YBCO) and Bi2Sr2CaCu2O8+δ(Bi-2212)electrodes has been prepared. Bi-2212/YBCO heteroepitaxial structure without an insulating layer was deposited on LaAlO3 (LAO) monocrystalline substrates by an all chemical solution deposition approach. Furthermore, the effect of heat treatment temperature on the superconductivity of Bi-2212/YBCO planar-type junction has been studied. Two superconducting transition steps in the R-T curves of Bi-2212/YBCO bilayer films prepared at 780 ℃ were clearly observed. The superconducting critical transition temperatures (Tc) of lower YBCO and upper Bi-2212 were about 91 K and 80 K, respectively. It was found that the critical current(Ic) was about 0.4 mA at 10 K and the superconductivity of planar-type junction strongly depend on the heat treatment temperature.

YBa2Cu3O7-z superconducting coated conductors by chemical solution deposition approach

YBa2Cu3O7-δ (YBCO) superconducting coated conductors were prepared on SmBiO3 (SBO) buffered substrates by chemical solution deposition approach. In this work, SBO buffer layers with a rapid decomposition process were heat treated less than 2 h. The SBO buffer layers deposited on LaAlO3, yttria-stabilised zirconium and NiO-buffered NiW substrates possess pure SBO (l00) X-ray diffraction peaks and dense as well as smooth surface microstructures. And YBCO superconducting layers with c-axis texture and dense morphology were successfully fabricated on different SBO-buffered substrates, with superconducting transition temperature Tc of 90 K and critical current density (77 K, self-field) above 1 MA cm−2. This could offer a promising alternative to low cost and high-performance preparation of YBCO superconducting coated conductors.

The Effect of Sintering Oxygen Partial Pressure on a SmBiO3 Buffer Layer for Coated Conductors via Chemical Solution Deposition

The application of high-temperature YBa2Cu3O7−δ (YBCO) superconducting material is a considerable prospect for the growing energy shortages. Here, SmBiO3 (SBO) films were deposited on (100)-orientated yttrium-stabilized zirconia (YSZ) simple crystal substrates via the chemical solution deposition (CSD) approach for coated conductors, and the effects of sintering oxygen partial pressure on SBO films were studied. The crystalline structures and surface morphologies of SBO films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscope (AFM). The optimized growth temperature, the intensity ratios of the SBO (200) peak to the SBO (111) peak, and the crystallinities of SBO films increased with the sintering oxygen partial pressure. The SEM and AFM images displayed a smooth and well-distributed surface in the argon atmosphere. The subsequent YBCO films with superconducting transition temperatures (Tc = 89.5 K, 90.2 K, and 86.2 K) and critical current densities (Jc = 0.88 MA/cm2, 1.69 MA/cm2, and 0.09 MA/cm2; 77 K, self-field) were deposited to further check the qualities of the SBO layer. These results indicated that sintering oxygen partial pressure had an effect on the epitaxial growth of the SBO buffer layer and YBCO superconducting properties. The experimental results may be a usable reference for the epitaxial growth of YBCO-coated conductors and other oxides.

Thermal processing of aqueous AZO inks towards functional TCO thin films

Aluminium doped zinc oxide is considered an interesting, earth abundant alternative to the transparent conductor indium tin oxide. In this respect, we synthesized Al-ZnO (AZO) thin films by a chemical solution deposition approach. Using water-based inks, the AZO thin films were printed in one single step on glass substrates in non-vacuum conditions. The drying process and the humidity of the atmosphere proved to be crucial during the thermal processing of the wet deposited thin films. To improve the understanding of the phenomena involved, the influence of these processing parameters on the final properties of the AZO thin films are investigated by FTIR, XRD, SEM, 1H and 27Al NMR and resistivity measurements. Optimal conditions were obtained by drying the wet thin film at 120 °C, followed by heating in a tube furnace until 500 °C under a 200 ppm O2/N2 atmosphere with a humidity controlled by bubbling the gas flow through 2 glass bottles containing water at 20 °C. AZO thin films with an resistivity of 2.54 × 10−2 Ω cm were obtained.

Disentangling Epitaxial Growth Mechanisms of Solution Derived Functional Oxide Thin Films

This study investigates the mechanisms of epitaxial development and functional properties of oxide thin films (Ce0.9Zr0.1O2−y, LaNiO3, and Ba0.8Sr0.2TiO3) grown on single crystal substrates (Y2O3:ZrO2, LaAlO3, and SrTiO3) by the chemical solution deposition approach. Rapid thermal annealing furnaces are very powerful tools in this study providing valuable information of the early stages of nucleation, the kinetics of epitaxial film growth, and the coarsening of nanocrystalline phases. Advanced transmission electron microscopies, X‐ray diffraction, and atomic force microscopy are employed to investigate the film microstructure and morphology, microstrain relaxation, and epitaxial crystallization. This study demonstrates that the isothermal evolution toward epitaxial film growth follows a self‐limited process driven by atomic diffusion, and surface and interface energy minimization. All investigated oxides experience a transformation from the polycrystalline to the epitaxial phase. This study unequivocally evidences that the film thickness highly influences the epitaxial crystallization rate due to the competition between heterogeneous and homogeneous nucleation barriers and the fast coarsening of polycrystalline grains as compared to epitaxial growth. The investigated films possess good functional properties, and this study successfully confirms an improvement at long annealing times that can be correlated with grain boundary healing processes. Thick epitaxial films can be crystallized by growing sequential individual epitaxial layers.

Epitaxial growth of CSD modified lanthanum zirconium oxide buffer layer for coated conductors

Texture and morphology evolution of modified Lanthanum Zirconium oxide (LaZr1.1Oy) films grown on biaxially textured Ni5%W tapes by chemical solution deposition (CSD) method at different heat-treatment conditions has been investigated. Results show that both the growth orientation and surface morphology of films are dependent on the heating rate and annealing temperature during heat-treatment process. Compared with the annealing temperature, heating rate shows a greater influence on the orientation growth of CSD-LaZr1.1Oy film. Slow heating rate is beneficial to a single (00l) orientation growth of LaZr1.1Oy grains on textured Ni-5at.%W (Ni5W) substrate. However, the surface morphology analysis reveals a minor effect of heating rate on the grain size and surface roughness of LaZr1.1Oy film. We consider that a slow heating rate would lead to the homogeneity nucleation of LaZr1.1Oy grains and eventually forming the great textured film due to the narrow temperature interval of the complete decomposition for LaZr1.1Oy precursor gel. In any case, high-quality LaZr1.1Oy film has been achieved at annealing temperature of 900 °C with heating rate of 2 °C/min. Moreover, we have grown epitaxial CeO2 film on the textured Ni5W substrate covered by LaZr1.1Oy film using CSD approach. CeO2 precursor solution was spin-coated on short sample of Ni5W/LZO and then heat-treated at 1000 °C for 30 min in Ar-4%H2. Detailed XRD and AFM studies indicate that CeO2 film has sharp bi-axial texture and smooth surface. These results demonstrate that a low-cost CSD LaZr1.1Oy film can act as a planarization template for the further production high Jc YBCO-superconducting film.

Integration of functional complex oxide nanomaterials on silicon

The combination of standard wafer-scale semiconductor processing with the properties of functional oxides opens up to innovative and more efficient devices with high value applications that can be produced at large scale. This review uncovers the main strategies that are successfully used to monolithically integrate functional complex oxide thin films and nanostructures on silicon: the chemical solution deposition approach (CSD) and the advanced physical vapor deposition techniques such as oxide molecular beam epitaxy (MBE). Special emphasis will be placed on complex oxide nanostructures epitaxially grown on silicon using the combination of CSD and MBE. Several examples will be exposed, with a particular stress on the control of interfaces and crystallization mechanisms on epitaxial perovskite oxide thin films, nanostructured quartz thin films, and octahedral molecular sieve nanowires. This review enlightens on the potential of complex oxide nanostructures and the combination of both chemical and physical elaboration techniques for novel oxide-based integrated devices.

In situ study through electrical resistance of growth rate of trifluoroacetate-based solution-derived YBa2Cu3O7 films

In this work, we have studied by means of in situ electrical measurements the nucleation, growth and sintering stages of epitaxial YBa2Cu3O6+δ (YBCO) superconducting thin films prepared using a chemical solution deposition approach based on metal-organic trifluoroacetate-based (TFA) precursors. Single crystal substrates (LaAlO3 and CeO2/YSZ) were used in this study. Analysis of isothermal time dependences, at different temperatures, of in situ electrical resistance of films allowed to evidence that the growth rate G is strongly temperature dependent, i.e. G is enhanced by a factor ∼15 when going from 700 to 810 °C. Additionally, we demonstrate that adding Ag-TFA in the solution may enhance the growth rate by as much as 50%, as compared to pure YBCO, thus confirming previous assessments of the strong influence of Ag doping on YBCO film growth and microstructure. In situ electrical resistance measurements show as well that an incubation time exists and we infer the origin of its temperature dependence. Finally, a thermodynamic analysis allows proposing a single equation for the growth rate of YBCO films integrating all the relevant processing parameters. Our analysis has validated the solid-gas reaction-diffusion model describing the growth of YBCO films from TFA precursors and thus enlarges the knowledge required to enhance the control of the microstructure and superconducting properties of solution-derived YBCO films.

Preparation of High-Performance SmBa2Cu3O7−x Superconducting Films by Chemical Solution Deposition Approach

Pure and Co3+-doped SmBa2Cu3O7−z (SmBCO) superconducting films were prepared on (00l) LaAlO3 single crystal substrate by self-developed fluorine-free chemical solution deposition approach. According to the X-ray diffraction and SEM observation, SmBCO films with biaxial texture possess dense, smooth, and microcrack-free surface microstructures. However, critical transition temperature (Tc) of a Co3+-doped SmBCO film is lower than that of pure SmBCO film, which may be attributed to the Co3+ doping decreasing the concentration of hole carriers for doped film. In addition, the Co3+-doped film has higher normalized critical current densities (Jc) in the whole magnetic fields, indicating better magnetic flux pinning properties. These results show that Co3+ doping by this chemical method is one of the promising ways to prepare high-performance SmBCO films.

Chemical solution route to self-assembled epitaxial oxide nanostructures

Self-assembly of oxides as a bottom-up approach to functional nanostructures goes beyond the conventional nanostructure formation based on lithographic techniques. Particularly, chemical solution deposition (CSD) is an ex situ growth approach very promising for high throughput nanofabrication at low cost. Whereas strain engineering as a strategy to define nanostructures with tight control of size, shape and orientation has been widely used in metals and semiconductors, it has been rarely explored in the emergent field of functional complex oxides. Here we will show that thermodynamic modeling can be very useful to understand the principles controlling the growth of oxide nanostructures by CSD, and some attractive kinetic features will also be presented. The methodology of strain engineering is applied in a high degree of detail to form different sorts of nanostructures (nanodots, nanowires) of the oxide CeO2 with fluorite structure which then is used as a model system to identify the principles controlling self-assembly and self-organization in CSD grown oxides. We also present, more briefly, the application of these ideas to other oxides such as manganites or BaZrO3. We will show that the nucleation and growth steps are essentially understood and manipulated while the kinetic phenomena underlying the evolution of the self-organized networks are still less widely explored, even if very appealing effects have been already observed. Overall, our investigation based on a CSD approach has opened a new strategy towards a general use of self-assembly and self-organization which can now be widely spread to many functional oxide materials.

Direct Monolithic Integration of Vertical Single Crystalline Octahedral Molecular Sieve Nanowires on Silicon

We developed an original strategy to produce vertical epitaxial single crystalline manganese oxide octahedral molecular sieve (OMS) nanowires with tunable pore sizes and compositions on silicon substrates by using a chemical solution deposition approach. The nanowire growth mechanism involves the use of track-etched nanoporous polymer templates combined with the controlled growth of quartz thin films at the silicon surface, which allowed OMS nanowires to stabilize and crystallize. α-quartz thin films were obtained after thermal activated crystallization of the native amorphous silica surface layer assisted by Sr2+- or Ba2+- mediated heterogeneous catalysis in the air at 800 °C. These α-quartz thin films work as a selective template for the epitaxial growth of randomly oriented vertical OMS nanowires. Therefore, the combination of soft chemistry and epitaxial growth opens new opportunities for the effective integration of novel technological functional tunneled complex oxides nanomaterials on Si substrates.

Fabrication of YBCO/CeO2/YBCO multilayer films through an all chemical solution deposition approach

In this paper, the growth characteristics and superconducting properties of YBCO/CeO2/YBCO multilayer films derived from an all chemical solution deposition process layer by layer are investigated. X-ray diffraction results show that the c-axis epitaxial growth feature of the bottom YBa2Cu3O7-δ (YBCO) film was perfectly inherited. Alternating epitaxial growth of YBCO/CeO2/YBCO multilayer films was confirmed by high resolution transmission electron microscopy in combination with selected area electron diffraction, which will lay the groundwork for preparation of SIS-type Josephson junctions. In addition, nanosized BaCeO3 particle rather than BaCeO3 transition layer was observed in the interface between YBCO and CeO2. The superconductivity measurement results show that the proposal method gives better superconducting properties only for high magnetic field and at low magnetic field it deteriorates the superconducting properties.

Preparation and Performance of the Sm0.2Ce0.8O1.9- Single Buffer Layer Fabricated with Dip-Coating

Abstract An epitaxial Sm 0.2 Ce 0.8 O 1.9- x (SCO) single buffer layer with thickness of about 250 nm has been deposited via dip-coating polymer-assisted chemical solution deposition (PACSD) approach for YBCO coated conductors on bi-axially textured Ni-5%W (200) alloy substrate. Flat, crack-free SCO films with sharp (200) c -axis orientation and texture have been obtained by carefully controlling the concentration of precursor solution, withdrawing speed, annealing temperature and dwelling time. Leaving other three factors unchanged, focuses on the influence of different withdrawing speeds on the performance of the SCO buffer layer has been focused on. YBCO superconducting layer has been deposited equally via dip-coating PACSD approach on the SCO-buffered NiW, showing a bi-axially texture. Micro-structural investigations revealed a homogeneous surface structure. Both of these indicate that SCO single buffer layer can function well as template. The approach has shown a promising way to fabricate long-length, low-cost YBCO coated conductors.

Chemical Solution Deposition of SrZrO3 Buffer Layers by Different Polymer Additives

A series of SrZrO3 (SZO) buffer layers were prepared on SrTiO3 (STO) single crystal substrate by a polymer-assisted chemical solution deposition (CSD) approach. Influence of different polymer additives on the properties of SZO buffer layers has been investigated. Compared with PVP (pyrrolidone)- and PEG (polyethylene glycol)-assisted SZO buffer layers, SZO buffer layer assisted by PVB (polyvinyl butyral) has better in-plane and out-of-plane texture as well as denser surface microstructure. The root mean square roughness of PVB-assisted SZO layer is around 3.68 nm over a surface cut-out of 5 μm×5 μm. In addition, the thickness of the SZO layer assisted by PVB is up to 230 nm. These results indicate that the polymer-assisted CSD method is promising to prepare the high-performance and single buffer layers for high-temperature superconducting coated conductors.

Aqueous CSD approach for the growth of novel, lattice-tuned LaxCe1−xOδ epitaxial layers

Lanthanum–cerium oxide (LCO) films were deposited on Ni-5%W substrates by chemical solution deposition (CSD) from water-based precursors. LCO films containing different ratios of lanthanum and cerium ions (from CeO2 to La2Ce2O7) were prepared. The composition of the layers was optimized towards the formation of LCO buffer layers, lattice-matched with the superconducting YBa2Cu3Oy layer, useful for the development of coated conductors. Single, crack-free LCO layers with a thickness of up to 140 nm could be obtained in a single deposition step. The crystallinity and microstructure of these lattice-matched LCO layers were studied by X-ray diffraction techniques, RHEED and SEM. We find that only layers with thickness below 100 nm show a crystalline top surface although both thick and thin layers show good biaxial texture in XRD. On the most promising layers, AFM and (S)TEM were performed to further evaluate their morphology. The overall surface roughness varies between 3.9 and 7.5 nm, while the layers appear much more dense than the frequently used La2Zr2O7 (LZO) systems, showing much smaller nanovoids (1–2 nm) than the latter system. Their effective buffer layer action was studied using XPS. The thin LCO layers supported the growth of superconducting YBCO deposited using PLD methods.