Influence of an In2O3 buffer layer on the properties of ITO thin films

In the present study, an indium oxide (In₂O₃) thin film was deposited as a buffer layer between ITO (indium tin oxide) and PES (polyestersulfone) by RF (radio frequency) magnetron sputtering at room temperature, and X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) were conducted to characterise the structural variation. The random texture of the ITO/In₂O₃ multilayered film favoured the (2 2 2) crystallographic plane rather than the (4 0 0) plane, which was favoured in single-layer ITO films. Transmission electron microscopy (TEM) observations further indicated that the buffer layer of In₂O₃ film was amorphous, while the ITO film was characterised by a columnar structure that was oriented perpendicular to the substrate surface. The electrical and optical properties of ITO/In₂O₃ multilayered films were enhanced due to the superior crystallinity and larger grain size of the material, as observed by XRD and FESEM. The multilayered film presented an electrical resistivity of 3.1 × 10⁻⁴ Ω cm, which is significantly better than that of a single-layer ITO film without an In₂O₃ buffer layer (4.7 × 10⁻⁴ Ω cm). In addition, optical transmission through the multilayered film increased by 2-4% due to the widening of the band gap by 0.2 eV, which was attributed to a Burstin-Moss shift.     

Hydrothermal synthesis and characterization of In2O3-ZnGa2O4 nanocomposites and their application in IGZO ceramics

Poly-crystalline In₂O₃-ZnGa₂O₄ nanocomposites were successfully synthesized by hydrothermal method with a mixed solution of In, Ga and Zn nitrates with equal mole ratio (In: Ga: Zn=1:1:1) and the ammonia was used as the precipitant. The effects of hydrothermal temperature and pH value of the mixed solution on the properties of the nanocomposites were investigated. The microstructure of the prepared In₂O₃-ZnGa₂O₄ nanocomposites was characterized by SEM and TEM, respectively. The growth mechanisms of In₂O₃-ZnGa₂O₄ nanocomposites were also preliminarily discussed in this study. Results reveal that the IGZO ceramics prepared by In₂O₃-ZnGa₂O₄ nanocomposites own a high relative density of 99.5% and low resistivity of 1.2?mΩ·cm, which can be applied to the preparation of IGZO thin film with superior performance.     

Semiconducting properties of In2O3 nanoparticle thin films in air and nitrogen

Oil soluble In₂O₃ nanoparticles were synthesized via the decomposition of indium acetylacetonate in organic solution. In₂O₃ nanoparticle thin films were prepared by spin-coating the dichloromethane solution of In₂O₃ on SiO₂/Si substrates and annealing at various temperatures. X-ray diffraction and scanning electron microscopy show that the In₂O₃ nanoparticles are spherical and the quality of thin film surface varies with annealing temperature and time. Field-effect transistor devices of the In₂O₃ nanoparticles were fabricated and their electronic characteristics were studied in air and nitrogen. The semiconducting properties can be tuned by modifying exposing time of the In₂O₃-based devices in air. The electron mobility and on–off current ratio have a dramatic change in the starting stage exposed in air, suggesting the device is sensitive to air due to the presence of nanostructures in the In₂O₃ thin films. The results suggest that the In₂O₃ thin film device may find applications in gas sensors.     

Structure deformation of indium oxide from nanoparticles into nanostructured polycrystalline films by in situ thermal radiation treatment

A microstructure deformation of indium oxide (In₂O₃) nanoparticles by an in situ thermal radiation treatment in nitrous oxide plasma was investigated. The In₂O₃ nanoparticles were completely transformed into nanostructured In₂O₃ films upon 10 min of treatment time. The treated In₂O₃ nanoparticle sample showed improvement in crystallinity while maintaining a large surface area of nanostructure morphology. The direct transition optical absorption at higher photon energy and the electrical conductivity of the In₂O₃ nanoparticles were significantly enhanced by the treatment.     

High temperature failure modes of In2O3 thin films and improved thermal stability using Al2O3/ZrO2 protective layers

The limiting temperature of an In₂O₃ thin film sensor is much lower than its melting point. Herein, the failure modes of In₂O₃ thin films at high temperatures, including sublimation and changes in composition, have been studied. The edge and surface layer sublimation rates increased dramatically at 1350 °C, indicating that it is the limiting temperature of no-protection In₂O₃ films. In addition, oxygen atoms will escape from In₂O₃ thin films at high temperatures, forming oxygen vacancies. As the main current carrier type in In₂O₃, the increasing number of oxygen vacancies affects the resistance of In₂O₃ thin film sensors. To solve these problems and promote the high temperature performance of In₂O₃ thin films, protection methods based on Al₂O₃ and ZrO₂ layers have been investigated. The ZrO₂ protective layer alleviated the serious considerable sublimation of In₂O₃ thin films at high temperatures, and the Al₂O₃ protective layer was beneficial for reduction the escape of oxygen atoms. Finally, different protection layers were evaluated by in-situ resistivity measurements of In₂O₃ thin films at high temperatures. The resistance of the In₂O₃ thin film resistor with a protective multilayer consisting of Al₂O₃ and ZrO₂ remained stable at 1360 °C, verifying the protection method effectively increased the thermal stability of In₂O₃ thin films.     

Hydrogen plasma reduction induced oxygen vacancies in cubic In2O3 particles with enhanced photocatalytic performance

The impacts of oxygen vacancies on the photocatalytic performance of In₂O₃ particles were never investigated previously. In this paper, cubic shape In₂O₃ particles were synthesized by hydrothermal method, and different concentrations of oxygen vacancies were generated in In₂O₃ particles by controlling the H₂ gas flow rate in hydrogen plasma reduction. The SEM images confirmed that the hydrogen plasma reduction did not change the particle morphology. The existence of oxygen vacancies was determined by electron paramagnetic resonance spectrum. Finally, the photocatalytic performance of In₂O₃ particles with different concentration of oxygen vacancies was investigated by the degradation of Methylene Blue (MB) solution under visible light irradiation. It was observed that when the hydrogen flow rate is 2?mL/min, the sample showed the highest photocatalytic performance, a further increased flow rate resulted in a decreased photocatalytic performance, which could be attributed to the over reduction of In₂O₃.     

V-doped In2O3 nanofibers for H2S detection at low temperature

Pristine and vanadium-doped In₂O₃ nanofibers were fabricated by electrospinning and their sensing properties to H₂S gas were studied. X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to investigate the inner structure and the surface morphology. The H₂S-sensing performances were characterized at different temperatures ranging from 50 to 170 °C. The sensor based on 6 mol% V-doped In₂O₃ nanofibers exhibit the highest response, i.e. 13.9–50 ppm H₂S at the relatively low temperature of 90 °C. In addition, the fast response (15 s) and recovery (18 s) time, and good selectivity were observed.     

Synthesis of Bi2O3/TiO2 nanostructured films for photocatalytic applications

Dendritic growth of bismuth oxide nanostructured films was accomplished by reactive magnetron sputtering. The deposition of the Bi₂O₃ template layers was adapted to abide a vapour-liquid-solid mechanism in order to develop a 3D growth morphology with high surface area templates for photocatalytic applications. TiO₂ photocatalytic thin films were deposited at a later stage onto Bi₂O₃ layers. The obtained heterostructured films were characterized by scanning electron microscopy, X-ray diffraction and atomic force microscopy. Additionally, the photocatalytic efficiency was assessed by conducting an assay using methylene blue dye as testing pollutant under a UV-A illumination. The photocatalytic tests revealed that the Bi₂O₃ layers functionalized with TiO₂ thin films are more efficient at degrading the pollutant, by a factor of 6, when compared with the individual layered films.     

Aging-induced change of photoluminescence in yttria-fully-stabilized ZrO2 with Sc2O3 or In2O3 doping

We report on the photoluminescence properties of Sc₂O₃- or In₂O₃-doped yttria-fully-stabilized zirconia (YSZ) by sub-bandgap photo-excitation to localized electronic states of oxygen vacancies, in order to clarify the mechanism for the aging-induced decrease of ionic conductivity via vacancies known in YSZ and suppressed by such doping. A new band emerged at 2.70 eV and remained even after the aging for the Sc₂O₃-doped samples at the doping concentration whereof the conductivity decrease was suppressed. On the other hand, a sharp and singular increase of the photoluminescence intensity was observed for the In₂O₃-doped samples at the range of the dopant concentration wherein a singular conductivity drop was observed and the suppression of conductivity decrease started. It is suggested that the suppression mechanism is different between Sc₂O₃-doped YSZ (Sc-YSZ) and In₂O₃-doped YSZ (In-YSZ).     

Nucleant layer effect on nanocolumnar ZnO films grown by electrodeposition

Different ZnO nanostructured films were electrochemically grown, using an aqueous solution based on ZnCl₂, on three types of transparent conductive oxides grow on commercial ITO (In₂O₃:Sn)-covered glass substrates: (1) ZnO prepared by spin coating, (2) ZnO prepared by direct current magnetron sputtering, and (3) commercial ITO-covered glass substrates. Although thin, these primary oxide layers play an important role on the properties of the nanostructured films grown on top of them. Additionally, these primary oxide layers prevent direct hole combination when used in optoelectronic devices. Structural and optical characterizations were carried out by scanning electron microscopy, atomic force microscopy, and optical transmission spectroscopy. We show that the properties of the ZnO nanostructured films depend strongly on the type of primary oxide-covered substrate used. Previous studies on different electrodeposition methods for nucleation and growth are considered in the final discussion.     

Preparation and optical properties of nanostructured ZnS:Cu films

Electrochemical deposition of nanostructured films of zinc sulfide with the addition of copper (ZnS:Cu) has been developed. This article discusses the surface morphology, structure, and phase composition of the films deposited on glass and sitall substrates with In₂O₃, a tunnel transparent layer. The spectral distribution of the transmittance and reflection coefficients are obtained, based on which the absorption spectra and widths of the band gap of ZnS:Cu in the form of film have been calculated as a function of the treatment temperature. The study of the optical properties of the films has made it possible to calculate the band gap and specify the phase compositions of the obtained films.     

Optical band gap modulation by Mg-doping in In2O3(ZnO)3 ceramics

In this study, different amounts of Mg were doped in In₂O₃(Zn_1−xMg_xO)₃ and their thin films were grown by using the RF magnetron sputtering method. The optical and electrical characteristics of the films revealed that the lattice constant decreased while the optical band gap increased as the Mg content increased, showing an inverse proportional relationship with each other. Therefore, it was found that Mg doping in indium zinc oxide (IZO) is also effective for band gap modulation as it was reported in a Mg-doped ZnO system. When IZO thin films were grown in a more reducing ambient, the carrier concentration increased which resulted in the increase of band gap energy. This was explained due to the Burstein–Moss effect.     

CuInSe2 films prepared by three step pulsed electrodeposition. Deposition mechanisms, optical and photoelectrochemical studies

p-Type semiconducting copper indium diselenide thin films have been prepared onto In₂O₃:Sn substrates by a recently developed pulse electrodeposition method that consists in repeated cycles of three potential application steps. The Cu–In–Se electrochemical system and the related single component electrolytes were studied by cyclic voltammetry to identify the electrode processes and study the deposition processes. In situ atomic force microscopy measurements during the first 100 deposition cycles denote a continuous nucleation and growth mechanism. Particles removed by film sonication from some of the films were characterized by transmission electron microscopy and determined to consist in nanoscopic and crystalline CuInSe₂. The remaining film is still crystalline CuInSe₂, as assessed by X-ray diffraction.The chemical characterization by combined X-ray photoelectron spectroscopy, X-ray fluorescence and inductively coupled plasma optical emission spectroscopy, showed that films were Cu-poor and Se-poor. Raman characterization of the as-grown films showed that film composition varies with film thickness; thinner films are Se-rich, while thicker ones have an increased Cu–Se content. Different optical absorption bands were identified by the analysis of the UV–NIR transmittance spectra that were related with the presence of CuInSe₂, ordered vacancy compounds, Se, Cu_2−xSe and In₂Se₃. The photoelectrochemical activity confirmed the p-type character and showed a better response for the films prepared with the pulse method.     

CO2 laser-assisted preparation of transparent Eu2Ti2O7 thin films

We present a laser-assisted preparation of transparent europium-titanate Eu₂Ti₂O₇ thin films with tailored structural and optical properties. We have evaluated the effects of the irradiation time on the structural and the optical properties of the films. This approach allows the preparation of nanocrystalline crack-free films and micro patterns. The amorphous thin films were prepared by a sol-gel method. The films were annealed by a CO₂ laser beam for various time intervals. The laser irradiation induced a crystallization process that resulted in the formation of Eu₂Ti₂O₇ nanocrystals. The nanocrystals regularly grew with increasing irradiation time reaching the size from 25?nm to 45?nm. A film of a thickness 480?nm exhibited an optical transmission of 91.9% that is close to the maximal theoretical limit. The film's refractive index at 632?nm was 2.26. A micrometric pattern was prepared by a direct laser writing followed by a wet chemical etching. Feasibility of the demonstrated approach, together with the high film's quality, and europium-titanate chemical resistivity open up many opportunities for advanced applications. The approach can be used for a preparation of protective coatings and integrated photonic devices such as planar optical waveguides and couplers.     

A diffusion kinetics study of Li-ion in LiV3O8 thin film electrode

The kinetic behaviors of Li-ion insertion/extraction in LiV₃O₈ thin film have been investigated using cyclic voltammetry (CV), potentiostatic intermittent titration (PITT) and electrochemical impedance spectroscopy (EIS) method. This LiV₃O₈ thin film with a mixed amorphous-nanocrystalline microstructure was fabricated by RF sputtering. For the first time, the intrinsic kinetics of LiV₃O₈ thin film electrode is obtained. The DLi+ value is about 10⁻¹³ cm²/s in mixed amorphous-nanocrystalline microstructure LiV₃O₈ thin film. Different to crystalline LiV₃O₈ thin film, the DLi+ values do not change a lot with the increase of cell potential which is due to the absence of structural phase transition behavior in mixed microstructure LiV₃O₈ thin film during Li⁺ insertion/extraction process. This is also the reason for excellent capacity retention performance of LiV₃O₈ film with a mixed microstructure.     

Preparation and characterization of single crystalline In2O3 films deposited on MgO (110) substrates by MOCVD

Epitaxial indium oxide (In₂O₃) films have been prepared on MgO (110) substrates by metal-organic chemical vapor deposition (MOCVD). The deposition temperature varies from 500 °C to 700 °C. The films deposited at each temperature display a cube-on-cube orientation relation with respect to the substrate. The In₂O₃ film deposited at 600 °C exhibits the best crystalline quality. A clear epitaxial relationship of In₂O₃ (110)|MgO (110) with In₂O₃ [001]|MgO [001] has been observed from the interface area between the film and the substrate. The average transmittance of the prepared films in the visible range is over 95%. The band gap of the obtained In₂O₃ films is about 3.55–3.70 eV.     

Effects of Mn,Cl co-doping on the structure and photoluminescence properties of novel walnut-shape MAPb0.95Mn0.05I3-xClx films

The novel walnut shape MAPb_0.95Mn_0.05I_3-xCl_x film was successfully synthesized by a one-step method followed by chlorobenzene anti-solvent treatment. The bandgap energy and PL intensity of perovskite film can be effectively tuned by Mn and Cl co-doping. The enlarged bandgap energy is mainly attributed to the synergistic effect of strengthened Pb-I interaction, Cl incorporation and smaller electronegativity of Mn dopants. The stronger coupling between the Mn d- and Pb p-bands, extended carriers diffusion length and more emitting defect-associated states caused by Mn and Cl co-doping are the main reasons for the enhancing PL intensity of MAPb_0.95Mn_0.05I_3-xCl_x walnut shape film. This work not only helps to in-depth understand the correlation between co-doping elements and optical properties of nanostructured perovskite films, but also provides important strategy for future designing the lower-toxic nanostructured perovskite materials with enhanced electrical and optical properties.     

Rational design of binder-free ZnCo2O4 and Fe2O3 decorated porous 3D Ni as high-performance electrodes for asymmetric supercapacitor

The development of hierarchical, porous film based current collector has created huge interest in the area of energy storage, sensor, and electrocatalysis due to its higher surface area, good electrical conductivity and increased electrode-electrolyte interface. Here, we report a novel method to prepare a hierarchically ramified nanostructured porous thin film as a current collector by dynamic hydrogen bubble template electro-deposition method. At a first time, we report a porous 3D-Ni decorated with ZnCo₂O₄ and Fe₂O₃ by simple, low-cost electrochemical deposition method. The fabricated porous 3D-Ni based electrodes showed an excellent electrochemical property such as high specific capacitance, excellent rate capability, and good cycle stability. The asymmetric solid-state supercapacitor device was fabricated using porous, 3D Ni decorated with ZnCo₂O₄ and Fe₂O₃ as the positive and negative electrodes. The fabricated ZnCo₂O₄//Fe₂O₃ asymmetric device delivered an areal capacitance of 92?mF?cm^?2 at a current density of 0.5?mA?cm^?2 with a maximum areal power density of 3?W?cm^?2 and areal energy density of 28.8?mWh?cm^?2. The higher performances of porous, 3D current collector have a huge potential in the development of high performance supercapacitor.     

Improved electrochromic performance of hierarchically porous Co3O4 array film through self-assembled colloidal crystal template

A hierarchically porous cobalt oxide (Co₃O₄) array film, in which the skeleton is composed of ordered non-close-packed bowl array possessing nanoporous walls, is successfully prepared by electrodeposition through self-assembled monolayer polystyrene sphere template. As an anodic coloring material for electrochromic application, the hierarchically porous Co₃O₄ array film exhibits enhanced electrochromic properties with higher optical modulation, faster switching speed and better cycling performance, compared to dense Co₃O₄ film. The porous Co₃O₄ array film presents a quite good transmittance modulation with 42% in the visible range and also shows good reaction kinetics with fast response time of about 2 s, much higher than those of the dense film (25% and 4.5 s). The better electrochromic performances of the porous film are attributed to its highly porous morphology, which shortens the ion diffusion paths and provides bigger surface area.     

An approach to Y2O3:Eu optical nanostructured ceramics

Y₂O₃:Eu³⁺ (1 at.%) translucent nanostructured ceramics with total forward transmission achieving ∼70% of the theoretical limit has been obtained by the transformation-assisted consolidation of custom-made cubic Y₂O₃:Eu³⁺ nanopowders under high pressure (HP). Sintering under the pressure of 7.7 GPa and temperatures in the 100-500 °C range leads to the partial cubic-to-monoclinic phase transition that results in two-phase Y₂O₃:Eu³⁺ nanoceramics. The average grain size of ceramics d ≤ 50 nm for both Y₂O₃:Eu³⁺ polymorph is comparable with crystallite size of initial nanopowders (d ∼ 40 nm), indicating that the grain growth factor is near unity. The phase compositions, morphology, densities, preliminary optical and luminescent properties of synthesized nanostructured ceramics have been studied.