Solution Deposition Process Research Articles

Observation of 57Fe-Enriched BiFeO3 Thin Films Using Mössbauer Spectroscopic Microscope

57Fe-enriched BiFeO3 (BFO) thin films were produced from a stoichiometric precursor solution by chemical solution deposition process. The perovskite BFO thin film fabricated at 550 °C on a Pt/Ti/SiO2/Si substrate showed saturated polarization–electric field (P–E) hysteresis loops. The remanent polarization Pr and the coercive field Ec at room temperature were 89 µC/cm2 and 365 kV/cm, respectively. The Mössbauer spectra consisted of the antiferromagnetic perovskite BFO and a paramagnetic component at a fraction in the range of 11 to 14%. The secondary component was supposed to be due to Bi2Fe4O9 and/or an amorphous component, influencing the ferroelectric property at room temperature. The Bi2Fe4O9 thin film was also fabricated at 700 °C on a SiO2/Si substrate. Furthermore, we tried to measure the mapping images corresponding to the perovskite BFO and Bi2Fe4O9 components separately using a Mössbauer spectroscopic microscope. A mapping image showed the distribution of the perovskite BFO component on the film.

Mössbauer Spectra of <sup>57</sup>Fe-Enriched BiFeO<sub>3</sub> Thin Films Fabricated on SiO<sub>2</sub>/Si Substrates by Chemical Solution Deposition Process

sup>57Fe-enriched BiFeO3 (BFO) thin films were fabricated on SiO2/Si substrates from a stoichiometric precursor solution by chemical solution deposition process. The Bi/Fe molar ratio of the thin films decreased from 0.95 to 0.80 with increase in the sintering temperature. A perovskite phase and flat surface were obtained in the BFO thin films sintered at 500 and 600 °C. However, the 57Fe Mössbauer spectra showed a mixture phase due to amorphous and/or Bi2Fe4O9 phases in the BFO thin films. The valence state of Fe ions of the BFO thin films was confirmed to be only Fe3+ by the Mössbauer spectra.

Surface morphology and ferroelectric properties of compositional gradient PZT thin films prepared by chemical solution deposition process

A series of PbTiO3/PbZrxTil−xO3 (PT/PZT) and PbZrO3/PbZrxTil−xO3 (PZ/PZT) compositional gradient thin films are obtained by chemical solution decomposition (CSD) method. The influences of buffer layers on surface morphology are investigated. Thin films with buffer layer are able to maintain the perovskite structure with (111)-preferred orientation. The surface microstructure and ferroelectric properties of the PZT thin films differs significantly depending on the use of PT or PZ buffer layers. When the PT buffer layer has five layers, the root mean square roughness (RMS) [17.7nm] and remnant polarization (Pr) [35.83μC/cm2] are maximized. On the other hand, when PZ buffer layer has one layer, the RMS [3.67nm] and Pr [26.08μC/cm2] are also maximized. The down-graded (Zr composition varying from 0.6 at the bottom surface to 0.4 at top surface) thin films exhibit larger surface roughness and better ferroelectric property than up-graded (Zr composition varying from 0.4 at the bottom surface to 0.6 at top surface) thin films. Therefore, different buffer layer determines different surface morphology. It is concluded that the ferroelectric property of the gradient thin films not only depends on its composition structure, but can also be controlled by the surface morphology. The results indicate that the PZT films with better ferroelectric property should have larger surface roughness.

In situ measurement of crystallization of oxide thin films during irradiation with pulsed UV laser in chemical solution deposition process

The epitaxial and polycrystalline growth of lanthanum strontium manganite films on single crystalline strontium titanate and lanthanum aluminate substrates, respectively, under the irradiation with XeCl lasers in the excimer laser-assisted metal organic deposition (ELAMOD) process have been previously reported. In order to investigate the growth phenomena, we monitored the thermal radiation from the sample surfaces irradiated with a pulsed ultraviolet laser in situ with near-infrared sensors. The cooling of the lanthanum strontium manganite films on strontium titanate substrates was significantly slower than that of films on lanthanum aluminate substrates. A similar behavior was also observed by the numerical simulation study. This difference in the cooling decay curves may play an important role in the mode by which crystal growth occurs in the ELAMOD process.

Preparation and Photoelectrochemical Properties of TiO<sub>2</sub> Nanotube Arrays Modified with Nano-Scaled CdSe

Highly ordered TiO2 nanotube arrays (TNTAs) with smooth walls and uniform diameter were prepared by electrochemical anodization. And then solution deposition process was adopted for the modification of the TNTAs with nanoscaled CdSe. The materials obtained were characterized by field emission scanning electron microscopy, UVvisible spectroscopic and photoelectrochemical techniques. The results revealed that the morphologies and growth mechanism for CdSe/TNTAs composites varied with the reaction time in Se2- solutions (c=1.2 mol/L) when nanotubes were firstly imported with Cd2+ ions. Optical absorption behavior of the CdSe/TNTAs composites increased with more CdSe nanoparticles. And the photo-response of the obtained nanomaterials was first strengthened and then declined with the sustained increase of the deposited CdSe.

Preparation of perovskite Fe-doped Na0.5Bi0.5TiO3 thin film from polyethylene glycol-modified solution precursor on LaNiO3/Si substrate

A (100)-oriented Fe-doped NBT Na0.5Bi0.5TiO3 (NBTFe) thin film was fabricated on LaNiO3(100)/Si substrate using a chemical solution deposition process, in which the solution precursor was modified by polyethylene glycol with a molecular weight of 600 (PEG600). The effects of PEG600 for crystalline structure, morphology, and electrical properties of NBTFe thin film were characterized. It is observed that with the PEG600 additive, phase-pure perovskite can be obtained for NBTFe thin film at a relatively lower annealing temperature of 500°C. Moreover, in NBTFe thin film with PEG600 modification, enhanced ferroelectricity is achieved with a larger remanent polarization (Pr) of 21.9μC/cm2, and the values of the dielectric constant and dissipation loss at 100kHz are estimated to be 411 and 0.153, respectively.

Raman spectroscopy of nanocrystalline Mn-doped BiFeO3 thin films

Enhancement of magnetic and electric properties in multiferroic Mn-substituted BiFeO3 thin films (BiFe1− x Mn x O3 with x = 0.00–0.05) grown via the low-temperature chemical solution deposition process on low-cost substrates like indium tin oxide (ITO)/glass and silicon is reported in this work. A detailed structural analysis by high-resolution X-ray diffraction and Raman spectroscopy indicates that the grown films exhibit rhombohedral distorted perovskite structure without any impure phase. Raman spectroscopic analysis shows all 13 Raman active (4A1 + 9E) phonon modes corresponding to distorted rhombohedral BFO R3c structure. BFO thin film with 5% Mn substitution showed maximum saturation and remnant magnetisation (M s = 16.70 emu/g and M r = 2.58 emu/g) and remarkably reduced leakage current due to distortion in the spin cycloid structure and suppression of oxygen vacancies due to partial replacement of Fe3+ ion by Mn3+ ion, respectively. These enhanced multifunctional properties highlight the potential applications of BFMO system in thin film devices which can couple magnetic and ferroelectric order parameters.

Enhanced ferroelectric properties of highly (100) orientedPb(Zr0.52Ti0.48)O3thick films prepared by chemical solution deposition

Ferroelectric Pb ( Zr0.52Ti0.48) O3(PZT) thick films with highly (100) preferential orientation have been prepared by chemical solution deposition process on Pt / Ti / SiO2/(100) Si substrates and pyrolyzed at 350°C–450°C, then annealed at 650°C. The typical thickness of the films is 3.9 μm. Effects of the pyrolysis temperature and excess PbO on the orientation, dielectric and ferroelectric properties of PZT thick films have been discussed. Domain switching and depoling process were studied by piezoelectric force microscopy. (100) oriented PZT films exhibit enhanced electrical properties. The dielectric constant and loss tangent of the films are 1444 and 0.022 at 1 kHz, respectively. The remnant polarization increases from 27.6 to 34.6 μC/cm2, and the coercive field decreases from 61.4 to 43.5 kV/cm, when the orientation of the films changes from the random orientation to the preferential (100) orientation. The leakage current density is 10-8A/cm2at dc field of 0.25 kV/cm, and then increases to 10-6A/cm2at 40 kV/cm. The piezoelectric response of the oriented films is investigated by Piezoelecric Force Microscopy (PFM).

Evolution of low fluorine solution in decomposition and crystallization for YBa2Cu3Oy film growth

A new chemical solution deposition process for YBCO films based on a low fluorine content solution has been developed. The total content of fluorine in this solution is about 50% of that in all TFA solution, the amount of corrosive fluorine-containing gas released can be greatly reduced and the acute decomposition in a short time can be suppressed. A smooth and homogeneous surface have been achieved at the heating rate of 5K/min by using this low fluorine solution. During the crystallization process, the composition of intermediated phases (BaYF, CuO) are changed with the annealing temperature. The reaction of nanocrystal Y2O3 and CuO is accompanied with the nucleation of YBCO phase, which indicates that there may be less second phase formation in the crystallization process. The traces of intermediate phase (BaYF–Ba(O,F)2) are observed. It demonstrates that the growth mechanism of the low fluorine solution is still “ex situ BaF2” process. The YBCO films with a fast pyrolysis process has been demonstrated high performance with Jc (77K, self field)=∼3.2MA/cm2.

Epitaxial Growth of LZO Film on NiW Substrate

La2Zr2O7 (LZO) oxide film is a good choose for buffer layer of coated conductors, especially for Chemical Solution Deposition route to fabricate coated conductors. In this paper, the influences of process parameters on texture of LZO films deposited by chemical solution deposition process on NiW substrate were studied, and results indicated that the heat-treatment temperature, dwell time and the oxygen content in the heat-treatment atmosphere were important to obtain a cube textured LZO film on NiW substrate. Based on our results, it was believed that inhibition of crystallite growth of LZO grains on the top layer of LZO film was the key to understand the epitaxial growth of LZO film on NiW substrate.

Effect of excess Pb on epitaxial growth of Pb(Mg<sub>1/3</sub>Nb<sub>2/3</sub>)O<sub>3</sub> thin films prepared by chemical solution deposition process

Effect of excess Pb on epitaxial growth of Pb(Mg<sub>1/3</sub>Nb<sub>2/3</sub>)O<sub>3</sub> thin films prepared by chemical solution deposition process

Thermal conductivity of nano-grained SrTiO3 thin films

We measure the thermal conductivities of nano-grained strontium titanate (ng-SrTiO3) films deposited on sapphire substrates via time-domain thermoreflectance. The 170 nm thick oxide films of varying grain-size were prepared from a chemical solution deposition process. We find that the thermal conductivity of ng-SrTiO3 decreases with decreasing average grain size and attribute this to increased phonon scattering at grain boundaries. Our data are well described by a model that accounts for the spectral nature of anharmonic Umklapp scattering along with grain boundary scattering and scattering due to the film thickness.

Thin Film Yttria-Stabilized Zirconia (YSZ) Electrolyte Fabricated by a Novel Chemical Solution Deposition (CSD) Process for Solid Oxide Fuel Cells (SOFCs)

Thin Film Yttria-Stabilized Zirconia (YSZ) Electrolyte Fabricated by a Novel Chemical Solution Deposition (CSD) Process for Solid Oxide Fuel Cells (SOFCs)

Characterization of 57Fe-Enriched BiFeO3 Thin Films by Mössbauer Spectroscopy

57Fe-enriched BiFeO3 (BFO) thin films were fabricated on Pt/Ti/SiO2/Si substrates from a stoichiometric precursor solution by chemical solution deposition process. The Bi/Fe molar ratio of the BFO thin films was about 0.93. The crystallinity and surface morphology of the BFO thin films were improved by using a single-sintering technique. Mössbauer spectra of the BFO thin films were measured at room temperature, and the valence state of Fe ions was confirmed to be Fe3+ only. One of the BFO thin films fabricated by single-sintering at 550 °C showed a relatively saturated P–E hysteresis loop. The remanent polarization Pr and the coercive field Ec at 10 kHz were 59 µC/cm2 and 327 kV/cm, respectively, at room temperature.

Enhanced photovoltaic properties in polycrystalline BiFeO3 thin films with rhombohedral perovskite structure deposited on fluorine doped tin oxide substrates

Polycrystalline BiFeO3 thin films have been deposited on fluorine doped tin oxide substrates successfully through a modified chemical solution deposition process based on using N,N-dimethylformamide as solvent. Structural analyses show that, N,N-dimethylformamide is beneficial to reduce the structural strain, and hence rhombohedral BiFeO3 films rather than the conventional pseudocubic ones were obtained. Absorption spectrum indicates that the modified process derived rohombohedral BiFeO3 has a narrower band gap (2.54eV) than that of the conventional process derived pseudocubic BiFeO3 (2.76eV). The BiFeO3 shows good photovoltaic properties with indium tin oxide as top electrode. The short circuit current density and open circuit voltage of the heterojunctions are measured to be 0.13mA/cm2 and 0.65V, respectively, much higher than the reported values for the conventional process derived pseudocubic BiFeO3 based heterojunctions. Our results indicate that the modified process derived rhombohedral BiFeO3 can induce higher photovoltaic effect compared with the conventional process derived pseudocubic counterpart.

Orientation-dependent phase transition and dielectric properties of Ba0.85Ca0.15Ti0.9Zr0.1O3 thin films

Polycrystalline Ba0.85Ca0.15Ti0.9Zr0.1O3 (BCZT) thin films with (100) preferential and random orientation are prepared on the LaNiO3 electrodes coated on Si substrates by chemical solution deposition process. The results show that the two types of films stabilize in the pure perovskite structure. The ferro-paraelectric phase transitions of two types of films occur at the temperature ranges of 280.2-297.8 K and 278.4-287.6 K, respectively. The dielectric constant, relaxation time and tunability of the random orientation film are smaller than those of the (100) preferential film but both almost have the similar leakage current characteristics. The mechanism associated with the change of the electrical properties of the thin films is also discussed.

Investigation of Crystallization Behavior of CIG-Se Bi-Layer Thin Films

Copper indium gallium diselenide (CIGSe) thin film was fabricated via a thermal treatment of GIG-Se bi-layer thin films. A CIG layer was prepared first, by a chemical solution deposition (CSD) process. The Se layer was deposited separately on the CIG layer by evaporation. The GIG-Se bi-layer then underwent a thermal treatment to cause a reaction between the two layers. In order to investigate the mechanism of CIG-Se bi-layer crystallization, the thermal treatment temperature was varied. The properties of the prepared CIGSe2 thin films were analyzed using X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectrometry (EDS), and UV-visible spectrophotometry.

Highly Active and Stable Ni–Fe Bimetal Prepared by Ball Milling for Catalytic Hydrodechlorination of 4-Chlorophenol

A novel Ni-Fe bimetal with high dechlorination activity for 4-chlorophenol (4-CP) was prepared by ball milling (BM) in this study. Increasing Ni content and milling time greatly enhanced the dechlorination activity, which was mainly attributed to the homogeneous distribution of Ni nanoparticles (50-100 nm) in bulk Fe visualized by scanning electron microscopy/energy dispersive X-ray spectrometry (SEM/EDS) with image mapping. In comparison with the Ni-Fe bimetal prepared by a chemical solution deposition (CSD) process, the ball milled Ni-Fe bimetal possessed high dechlorination activity and stability before being used up. Dechlorination kinetics indicated that the dechlorination rates of 4-CP increased with increasing Ni-Fe dose but decreased with increasing solution pH. Solution pH had a significant effect on the dechlorination of 4-CP and the passivation of the Ni-Fe bimetal. The enhanced pH during the dechlorination process significantly accelerated the formation of passivating film on the bimetallic surface. The Ni-Fe bimetal at the dose of 60 g/L was reused 10 times without losing dechlorination activity for 4-CP at initial pH less than 6.0, but the gradual passivation was observed at initial pH above 7.0.

Using Sol–Gel Replications to Assess the Porosity of Block-Copolymer Derived Thin Films

In this paper, we report the use of a sol–gel replication method to prepare high fidelity SiO2 replicas of porous thin films obtained from microphase separated block-copolymer systems as an easy, robust, and rapid way to investigate their inner morphology. The cylinder-forming poly(styrene)-b-poly(lactide) (PS-b-PLA) block copolymer, containing a sacrificial block (PLA), was used to produce porous thin films with thicknesses above one periodical distance and bearing various internal organizations and orientations of the cylinders. The porosity was first infiltrated by silica precursors using a chemical solution deposition process, before being exposed to a brief thermal treatment to provoke inorganic condensation and elimination of the PS template. SEM observations of the obtained replica gave three-dimensional view of the internal topology of the porosity, which were then compared to structural characterizations obtained directly by AFM, SEM, or GISAXS on the parent block-copolymer films. It is shown that the replication provides an ideal tool to characterize the topology of porous networks in supported polymer thin films. This method can be generalized to any type of porous polymer media, offering a unique mode of visualization of the internal topology with valuable details at the substrate interface.

Multifunctional superhydrophobic composite films from a synergistic self-organization process

A synergistic self-organization method was proposed to prepare multifunctional superhydrophobic composite films, which combined well-exfoliated graphene nanosheets (GNs) with a conjugate polymer (poly(3-hexyl thiophene), P3HT) through a simple solution-deposition process. The composite film can be rapidly prepared on various substrates; typically only a few minutes were necessary when the P3HT-GN suspension was coated on a metal mesh. The 35 wt% P3HT composite film is superhydrophobic with a contact angle of 159.2°, an electrical conductivity up to 6560 S m−1 and specific electromagnetic interference shielding effectiveness (43.7 dB cm3 g−1) four times greater than solid copper. It has a porous structure with the bulk density of 0.76 g cm−3, separation efficiency of over 98% for the n-octane/water mixtures in volume ratios of 1 : 1–1 : 15, and good environmental stability with a capacity to endure thermal treatment at 200 °C and organic solvents such as methanol, acetone and DMFetc. This synergistic self-organization method was also applied to prepare superhydrophobic P3HT-montmorillonite (MMT) composite films with a contact angle of 161° and a high adhesion capacity to water droplets, proving a versatile method in fabricating functional superhydrophobic films suited to practical applications.