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Nickel hydroxide [Ni(OH)2] is an electrochemically-active material used for rechargeable batteries, electrochemical capacitors, and electrochromic devices. Although there have been some studies on Ni(OH)2 thin films deposited by sputtering, the Ni(OH)2 formation has not been fully confirmed. In this study, a Ni metal target was reactively sputtered in atmospheres of O2 and Ar + H2O at substrate temperatures of RT (RT, around 20 °C), −80 °C, and −170 °C, and the aging treatment effects in the air at RT were studied. From optical, X-ray diffraction, and IR absorption measurements, β-Ni(OH)2 thin films were found to be formed after aging the films deposited at −80 °C in Ar + H2O, however, NiO thin films were formed at RT. These results corresponded well with a thermodynamic consideration of Ni(OH)2. At −170 °C, mixed metal and oxide films were formed, presumably because of insufficient Ni oxidation.

Organic light-emitting diodes (OLEDs) have been widely used, particularly in display applications. OLEDs are easily degraded without stringent encapsulation owing to their susceptibility to water vapor and oxygen. Therefore, establishing an effective protection method for these devices is essential. In this study, we demonstrate the device protection performance and improvement in color purity by introducing CaF

Nanowire-net and nanosheet-structured cobalt hydroxide (Co(OH)2) was prepared directly on a fluorine-doped tin oxide (FTO)-coated glass substrate using aqueous solutions of cobalt nitrate hexahydrate (10 mM) and hexamethylenetetramine (HMT, 2–30 mM), synthesized at 60 °C. With increasing HMT amount, the morphology changed from nanowire-net to nanosheet, resulting from the promotion of growth under sufficient OH− ions provided by the HMT. The binder-free Co(OH)2 sample prepared with 30 mM HMT showed a good areal specific capacitance of ∼60 mF/cm2 at a scan rate of 2 mV/s, as well as excellent capacity retention (∼84% over 5000 cycles). The proposed facile method allows the morphological engineering of Co(OH)2 nanostructures with superior electrochemical performance.

Tungsten oxide (WO3) and nickel oxide (NiO) are typical inorganic electrochromic (EC) materials. The color of WO3 changes from transparent to blue by reduction, whereas that of NiO changes from transparent to brown by oxidation. This study fabricated EC devices with an indium tin oxide (ITO)/WO3/NiO/ITO/Nafion/ITO structure. The WO3/NiO double layer and Nafion were used as the EC layer and electrolyte, respectively. The color of the device changed from blue to transparent and then to brown by varying the applied potential from −2.5 to +1.0 V and then to +2.0 V. The WO3 and NiO films were reduced at −2.5 V; the WO3 film was oxidized at +1.0 V, and both were oxidized at +2.0 V. The transmittance in the visible and near-infrared regions changed independently. Hence, the devices are considered applicable for dual-band EC smart windows.

Cobalt hydroxide (Co(OH)2) nanostructures were prepared on fluorine-doped tin oxide (FTO) substrates via an inexpensive and simple wet-chemical method. At a growth temperature of 60 °C, heterogeneous nucleation caused the nanowire-net structured Co(OH)2 to form a compact bottom layer on the surface of FTO substrate, and homogeneous nucleation resulted in the growth of a porous nanowire-net layer in the solution as the top layer. At 90 °C, vertically well-aligned Co(OH)2 nanosheets were grown from the heterogeneous nucleation on the surface of FTO substrate. Cyclic voltammetry (CV) revealed that the entirely binder-free Co(OH)2 prepared at 60 °C had a high capacitance of 254F/g (38.08 mF/cm2) at a scan rate of 2 mV/s and good rate capability compared to the nanosheet-structured Co(OH)2 prepared at 90 °C. Furthermore, it had excellent long-term electrochemical stability of ∼97% after 1000 cycles at a scan rate of 50 mV/s. These results suggested that the nanowire-net structured Co(OH)2 had significant application potential in the field of energy storage.

We report on the enhancement effect of metal nanotriangles (NTs) on the photoluminescence and its time-resolved dynamics of tris(8-quinolinolato) aluminum (Alq3). Regularly arranged Al NTs arrays were fabricated on the quartz substrate by means of nanosphere lithography. The absorption peaks corresponded to the localized surface plasmon (LSP) resonance of Al NTs were observed within a visible light region, and it was significantly shifted towards longer wavelength as increasing refractive index of the covering medium. The typical resonance wavelength of LSP of Alq3/Al NTs fabricated with 350 nm-PSt beads was 600 nm. From the PL measurement 2.6-fold PL enhancement was observed in Alq3 with Al NTs at room temperature, whereas the 4.4-fold PL enhancement was observed for Ag NTs with same size. According to the time-resolved PL data, the coupling of LSP with the excitation light field mainly contribute to the observed emission enhancement for the Al NTs, whereas the emission enhancement by Ag NTs can be originated from the direct coupling of LSP and emission which was suggested from the large contribution of short lifetime component.

The morphological and electrochemical properties of nickel–cobalt double hydroxide (Ni-Co DH), cobalt hydroxide [Co(OH)2], and nickel hydroxide [Ni(OH)2] prepared directly on a transparent conductive oxide substrate via a simple one-pot wet-chemical method have been investigated and compared. All samples were composed of nanosheets vertically aligned on the substrate. Comparison of the results showed that Ni-Co DH with submicrometer-scale pores had more compact structure than Ni(OH)2 or Co(OH)2. Moreover, the highly symmetric cyclic voltammetry (CV) curves of Ni-Co DH indicated its good electrochemical reversibility. The specific capacitance value of Ni-Co DH was ∼ 286 F/g and ∼ 210 F/g at scan rate of 2 mV/s and 100 mV/s, respectively, indicating its better rate capability, particularly at high scan rate, than Ni(OH)2 or Co(OH)2. In addition, after CV cycling test, the Ni-Co DH nanosheets showed no noticeable morphological change. Furthermore, the electrochromic performance of Ni-Co DH was sustained over 10000 s. Thus, Ni-Co DH prepared via a facile one-step process exhibited promising characteristics as a cost-effective functional material for use in electrochemical devices.

We successfully synthesized copper oxide (CuO) nanostructures using an aqueous solution of copper acetate monohydrate without any surfactant at 90°C, and analyzed their morphological evolutions and electrochemical properties with different growth times. All samples consisted of polycrystalline single-phase monoclinic CuO. The CuO directly grown on transparent conductive oxide (TCO) substrates had a bilayered structure, with the bottom layer consisting of compact nanostructures formed from heterogeneous nucleation on the surface of the TCO substrate and the top layer comprising microspheres formed from homogeneous nucleation in the solution. The entirely binder-free bilayered CuO nanostructures prepared by the simple wet-chemical method exhibited an impressive specific capacitance with good cycling stability over 1000 cycles.

To assess whether serum albumin concentration measured upon hospital arrival was useful as an early prognostic biomarker for neurologically favorable outcome in out-of-hospital cardiac arrest (OHCA) patients treated with target temperature management (TTM). This prospective, multicenter observational study (The CRITICAL Study) carried out between July 1, 2012 and December 31, 2014 in Osaka Prefecture, Japan involving 13 critical care medical centers (CCMCs) and one non-CCMC with an emergency department. This study included patients ≥18 years of age who underwent an OHCA, for whom resuscitation was attempted by Emergency Medical Services personnel and were then transported to participating institutions, and who were then treated with TTM. Based on the serum albumin concentration upon hospital arrival, involved patients were divided into four quartiles (Q1-Q4) defined as Q1 (3.0 g/dL), Q2 (≥3.0,3.4 g/dL), Q3 (≥3.4,3.8 g/dL), and Q4 (≥3.8 g/dL). The primary outcome of this study was 1-month survival with neurologically favorable outcome defined by cerebral performance category 1 or 2. During the study period, a total of 327 were eligible for our analysis. The overall proportion of neurologically favorable outcome was 33.0% (108/327). The Q4 group had the highest proportion of neurologically favorable outcome (52.5% [48/91]), followed by Q3 (34.5% [30/87]), Q2 (27.3% [21/77]), and Q1 (12.5% [9/72]). The multivariable logistic regression analysis demonstrated that the proportion of neurologically favorable outcome was significantly higher in the Q4 group than that in the Q1 group (adjusted odds ratio 10.39; 95% confidence interval 3.36-32.17). The adjusted proportion of neurologically favorable outcome increased in a stepwise fashion across increasing quartiles (p 0.001). In this study, higher serum albumin concentration upon hospital arrival had a positive association with neurologically favorable outcome after OHCA in a dose-dependent manner.

Enhancement of 4.4-fold photoluminescence (PL) of tris(8-hydroxyquinolinato)aluminum (Alq3) thin film was observed in the presence of 50-nm thick Ag nanotriangles (NTs) compared with bare Alq3 film at room temperature. According to the temperature dependence of integrated PL intensity and the PL lifetime obtained from time-resolved PL measurements, an increase in radiative recombination rate was observed over a wide temperature range. Because the absorption peak originated from localized surface plasmon (LSP) states and the emission spectra are well overlapped, the observed enhancement can be explained by efficient coupling of the LSP of the Ag NTs with the emission from the Alq3.

Surface plasmon resonance (SPR) of Ag nanoparticles (NPs), and its emission enhancement properties are investigated by time-resolved photoluminescence spectroscopy using tris(8-hydroxyquinolinato)aluminium (Alq3), which is generally applied in organic light-emitting diode, as the emitter. 5-nm-thick Ag island-films were fabricated, and annealed at various temperatures to vary the size of the Ag NPs. The peak position of the SPR band in the absorption spectra of Ag NPs blue-shifts with increasing annealing temperature, that is, the SPR frequency is controlled by the NP size. Comparison of the photoluminescence (PL) spectra of Alq3 with and without Ag NPs annealed at 150 °C indicates 1.2-fold enhancement of PL for Alq3 with Ag NPs compared to the reference Alq3. From the temperature dependence of the PL intensity and lifetime of Alq3 with Ag NPs, we evaluated the degree of enhancement of the radiative recombination rate in the presence of the localized surface plasmon of Ag NPs, in comparison with the competitive non-radiative quenching process.

Curved and nanolayered structures of nickel hydroxide (Ni(OH)2) were synthesized via a facile wet-chemical process. After nanoparticles of less than 100 nm formed during the initial reaction stage, two-dimensional (2D) nanosheets were obtained. With increasing reaction times, the nanosheets became interconnected with each other, resulting in the formation of nanolayered structures. Moreover, semi-transparent self-supporting Ni(OH)2 films with areas on the order of square centimeters were obtained after drying at 90 °C. Annealing at 500 °C caused the dehydration of hydroxide phase (Ni(OH)2), leading to the formation of oxide phase (NiO). During this phase transition, the curved and nanolayered structures maintained their shape, while each individual nanosheet was embedded with sub-level nanoparticles.

Porous nanosheet-structured nickel oxide (NiO) films were directly prepared on conductive oxide substrates using a cost-effective and simple one-pot solution method. By incorporating cobalt (Co) dopant, the growth of vertically aligned nanosheet was promoted. However, zinc (Zn)-doped NiO film had the loose-packed nanosheet-structure with relatively low coverage on the surface of the substrate compared to the NiO and Co-NiO films. All the NiO films exhibited electrochromic properties. In the colored state, the NiO, Co-NiO, and Zn-NiO films were dark brown, black, and brown, respectively. In the bleached state, the NiO, Co-NiO, and Zn-NiO films were pale gray, pale yellow, and transparent, respectively. The switching time of the Co-NiO film (tc ~ 2 s, tb ~ 6 s) was slightly slower than those of the NiO (tc ~ 1 s, tb ~ 1 s) and Zn-NiO (tc ~ 1 s, tb ~ 2 s) films. However, it had better transmittance modulation (~58% at 700 nm) with excellent memory durability (increased by ~2% after 3,000 s) than the NiO and Zn-NiO films. Dopants could easily and effectively modify the electrochromic performance of NiO films.

Ag thin-films with thicknesses of 5, 10, 15, 20, and 25 nm are deposited by thermal vacuum evaporation, and the obtained films are subsequently annealed at 400 °C for 1 h to form the Ag nanoparticles (NPs). The averaged diameters of the resultant Ag NPs are increased from 50 to 300 nm as increasing the initial Ag deposition thickness, according to the morphological observation using scanning electron microscopy (SEM). The significant red-shift of the extinction peak depending on the particle size of the Ag NPs, which can be assigned to the localized surface plasmon resonance of the Ag NPs. The organic emitter, tris(8-hydroxyquinolinato)aluminum (Alq3) film is overcoated on the Ag NPs. About 4-fold enhancement of the photoluminescence of Alq3 was observed in combination with the larger size Ag NPs fabricated from the 15–25 nm thick Ag films, which can be applied for the improvement of the light-extraction efficiency of the organic light-emitting devices.

We report the ellipsometric and photoluminescence (PL) properties of Indium zinc oxide (IZO) films, which were grown by radio frequency sputtering under Ar and O2 atmospheres. IZO films grown under an O2 atmosphere (IZO (O2)) showed enhanced PL properties when compared to the films grown under an Ar atmosphere (IZO (Ar)), particularly with respect to the band-edge emission. The enhancement of band-edge emission can be attributed to the reduction in the non-emissive defect states related to oxygen vacancies, which were repaired by sputtering under O2 atmosphere, whereas the PL enhancement in green region is probably due to the formation of the different types of defects under the excess oxygen environment. This was also supported by the results of time-resolved PL measurements, where the band-edge emission of IZO (Ar) showed rapid decay with a 50 ps lifetime, which indicates the dominance of the relaxation pathway to underlying defect states. In contrast, the PL decay profiles of IZO (O2) for band-edge and emissive defect states showed moderate decay with time-constants of 2.3 ns and 5.7 ns, respectively. The exciton relaxation dynamics were sensitive to the presence and its kinds of defect states, which were controlled by the growth conditions.

Porous zinc oxide (ZnO)-nickel oxide (NiO) nanocomposites were fabricated via a one-pot process using aqueous solutions of zinc nitrate hexahydrate (Zn(NO), 10 mM), hexamethylenetetramine (HMT, 10 mM), and nickel acetate tetrahydrate (Ni(Ac), 7 mM (7NZO), 10 mM (10NZO)). The structural and morphological properties of these nanocomposites were investigated and compared to those of pure ZnO nanostructures. Rod-type nanostructures were observed in the pure ZnO sample, while porous sphere-like structures and continuous nanolayered structures were observed in the 7NZO and 10NZO samples, respectively. This difference in morphology might be due to the growth of the non-polar plane instead of the polar plane of ZnO in the clusters. The nanocomposites were composed of Ni, Zn, and O, which were homogeneously distributed. Distinct morphologies of the ZnO-NiO nanocomposites were obtained via a facile one-pot solution process.

Three-dimensional (3D) sphere-like structured zinc oxide (ZnO) – nickel oxide (NiO) nanocomposites were prepared via a simple one-pot solution process. Their morphological properties were investigated as a function of the annealing temperature in the range 300–700 °C. Metal hydroxides (Zn(OH)2 and Ni(OH)2) were completely decomposed to metal oxides (ZnO and NiO), respectively, after annealing at 500 °C. Field emission scanning electron microscopy (FESEM) images revealed that the sphere-like structures maintained their shapes during the annealing treatment. The interwoven nanowalls that constituted sphere-like structures were themselves a sheet-like assembly of nanoparticles, which increased in size with increase in annealing temperature. After annealing at 700 °C, a network of interconnected nanoparticles could be observed.

We report on a photoluminescence (PL) enhancement in IZO/Ag/IZO sandwiched structure via surface plasmonic effects of 14 nm-thick Ag film. In the presence of Ag thin film, the 2–8-fold enhancement was observed for the broad PL around 2.34 eV, which can be originated from defect states in amorphous IZO film. The results of time-resolved PL spectra suggested that the increase in radiative recombination rate, and the maximum Purcell factor of 19 was estimated from the analysis of the PL decay profiles. The comparison between the results of static- and dynamic-PL measurement suggests that the non-radiative process after the excitation of the surface plasmon of the silver film also affects the total efficiency of the emission enhancement.

Previously, we developed a highly stable silver thin film where surface and interface Al nanolayers were used to suppress agglomeration by annealing. In this study, we focus on reflectance of the silver film. The Al and Ti surface layers were deposited on silver films by RF magnetron sputtering. The surface morphology and reflectance of Ag, Al/Ag and Ti/Ag films were measured using an atomic force microscope and a spectrophotometer, respectively. It is found that the surface roughness of all the films is very small and it decreased by deposition of Al and Ti layers. We found 1-nm-thick Al or Ti layer deposited Ag films showed the same reflectance as silver single film. But a decrease of the reflectance was observed when the thickness of the Al or Ti layer was increased to 3 nm. Consequently, it is found that the optimum thickness of Al or Ti layer deposition is 1 nm in highly stable silver thin films. Their optical properties were influenced by both metal and metal oxide of the surface layer.

Ni oxide is well known electrochromic (EC) materials. And nickel hydroxide (Ni (OH)2) and oxyhydroxide (NiOOH) are considered to be electrochemically more active than nickel oxide (NiO). Reactive sputtering is one of the most commonly used techniques for obtaining compound thin films, however, deposition rate of compound thin film is low. We have reported that the deposition rate of sputtered nickel oxide thin film increased remarkably by substrate cooling using a liquid nitrogen and injection of water vapor (H2O) onto the target surface in argon (Ar) atmosphere [1]. In this study, we studied the effect of the direction of water vapor injection and the substrate temperature on deposition rate, composition and EC characteristics of the Ni oxide thin films. Ni oxide thin films were prepared by an RF magnetron sputtering system at substrate temperatures (Ts) of -80 °C and -170 °C. Ar and H2O were used as sputtering gas, and the flow rates of Ar and H2O were kept constant at 2.5 cc/min. H2O was injected onto the substrate or target surface. RF power and sputtering gas pressure were constant at 50 W and 50 mTorr, respectively. Film thickness was measured using a stylus profiler, and deposition rate was calculated using the film thickness and sputtering time. Crystal structure and chemical bonding state of the films were characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR), respectively. Optical and electrical properties of the films were studied by UV-Vis spectroscopy and four probe method. EC properties of the films were evaluated using cyclic voltammetry (CV) and chronoamperometry (CA) in a 1 M KOH aqueous electrolyte. Figure 1 shows the deposition rate of Ni oxide thin films deposited at Ts=-80 °C and -170 °C with the H2O injection onto the substrate or target surface. At Ts=-80 °C, high deposition rates of 30-35 nm/min were obtained regardless of the direction of H2O injection. The deposition rates are much higher than that obtained by conventional reactive sputtering at room temperature (4nm/min) [1]. In contrast, the deposition rate varied from 21 nm/min for H2O injection to substrate 38 nm/min (the highest deposition rate) for H2O injection to target at Ts=-170 °C. Highly transparent films with a transmittance above 80% were obtained regardless of the direction of H2O injection at Ts=-80 °C, however, the transmittances of the films deposited at Ts=-170 °C were low. From the four probe method measurement, the thin film deposited at Ts=-170 °C with H2O injection to substrate was found to be a mixed film of metal Ni and Ni oxide with a resistivity of 3.3×10-4Ωcm. The films deposited at Ts=-80 °C with H2O injection to substrate or target and the film deposited at -170 °C with H2O injection to target were considered to be NiO or Ni(OH)2. CV and CA measurements showed that the film deposited at Ts=-80 °C with H2O injection to target had good cycle stability and large transmittance change of 58% at a wavelength of 600nm. In summary, the deposition rate, chemical composition, and EC properties of the Ni oxide films were found to be strongly dependent on the substrate temperature and the direction of H2O injection. The films deposited with H2O injection to target at Ts=-170 °C showed the highest deposition rate and that deposited at Ts=-80°C with H2O injection to target showed the largest transmittance change. REFERENCES [1] Y. Yokoiwa et al, Jpn. J. Appl. Phys. 58 (2019) 055504. Figure 1

Indium tin oxide (ITO) thin films have been incorporated into electrochromic (EC) devices as a transparent conductive film. It is highly desirable that EC devices applied to a smart window can control both visible and infrared light, because infrared light accounts for about half of the energy of sunlight. In this study, we fabricated WO3 thin film on ITO thin films with different sheet resistances and studied their EC properties in visible and near-infrared region. ITO thin films deposited on glass were used as substrates. Tungsten oxide (WO3) thin films were deposited using RF magnetron sputtering system. Crystal structure was characterized by X-ray diffraction. Optical properties of the prepared samples were measured using UV-VIS-NIR spectrophotometer. The electrical resistance of the ITO thin films was measured by a four probe method. EC properties of the WO3 thin film were measured by cyclic voltammetry (CV) and chronoamperometry (CA) in a 0.01 M H2SO4 aqueous electrolyte. The transmittance of the high sheet-resistance ITO thin film (177 Ω/sq) decreased at a short wavelength region below 455 nm. However, it showed high transmittance above 70% in the visible and near-infrared region (455-2050 nm). In contrast, the low sheet-resistance ITO thin films showed high transmittance above 70% in a wavelength region of 335-1350 nm and its transmittance decreased above 1350 nm. The differences of the transmittance in short and long wavelength regions are considered to be caused by the Burstein-Moss effect and Drude model, respectively. Fig. 1 shows the transmittance spectra of the WO3 thin film with a thickness of 200 nm deposited on the ITO/glass substrates measured in air. Lines (1) and (2) show the transmittance spectra of colored and bleached states of WO3 thin film deposited on high sheet-resistance ITO thin film, and lines (3) and (4) show those of colored and bleached states of WO3 thin film deposited on low sheet-resistance ITO thin film. The WO3 thin film deposited on the high sheet-resistance ITO thin film showed a larger transmittance change and higher transmittance in bleached state in the near-infrared region than those of the WO3 thin film deposited on the low sheet-resistance ITO thin film. From these results, it was found that the selection of appropriate ITO electrodes is very important to obtain good EC property of WO3 thin films in visible and near-infrared region. Figure 1

Hierarchical cobalt oxyhydroxide (CoOOH) nanostructures were directly grown on flexible stainless steel (SS) mesh substrates via a cost-effective, facile chemical solution method. The nanostructures were grown at 90 °C with different time intervals, and their morphological evolution and electrochemical performance were investigated. Initially, the nanowires and nanoparticles were randomly distributed on the surface of the SS mesh substrate. With increasing growth times, the nanowire-like structures were assembled as nanosheet-like structures having widths of ~20 nm. The small nanoparticles between the nanosheet-like structures agglomerated into large nanoparticles with a diameter of ~130 nm. The mixed nanosheet-like- and nanoparticle-structured CoOOH grown on the SS mesh substrate exhibited mass specific capacitances of ~383 F/g at 2 mV/s and ~176 F/g at 100 mV/s with excellent cycling stability (~96%, 3000 cycles).

We discussed the morphological properties of Al-doped zinc oxide (Al–ZnO) microrods grown on a ZnO seed layer and precipitation particles and compared them with undoped ZnO samples. The ZnO nanorods grown on a ZnO seed layer were dense and perpendicular to the surface of the substrate, i.e., fluorine-doped tin oxide (FTO). In contrast the Al–ZnO grew as larger microrods, and the rods were sparsely and obliquely arranged. Precipitation particles synthesized in the ZnO solution through homogeneous nucleation had flower-like structures assembled from the rods and individual rods with lengths of several micrometers. Al–ZnO precipitation particles consisted of rods with length of several micrometers and hexagonal nanoplates. Fourier transform infrared (FTIR) analysis results showed that the rods and precipitation particles had the good chemical properties of ZnO. Both size and morphology of the rods could be effectively controlled by adding aluminum nitrate (Al(NO 3 ) 3 ) as dopant in the ZnO rod solution.

Amorphous rhodium (Rh) oxide thin films ranging in thickness from 50 to 400 nm were prepared by reactive sputtering at −20 °C in either an oxygen (O2) or water (H2O) vapor atmosphere. Their electrochemical and electrochromic (EC) properties were investigated in an aqueous KOH electrolyte solution. The transferred charge density increased linearly with increasing film thickness, and a 400 nm-thick H2O-deposited film displayed the highest transferred charge density of 60 mC/cm2. Electrochemically active Rh atoms comprised approximately 20% and 50% of the Rh atoms in the O2- and H2O-deposited films, respectively. Transmittance by the bleached and colored films decreased with increasing film thickness in accordance with Lambert's law. The 400 nm-thick H2O-deposited film exhibited the largest change in transmittance (57%) at 700 nm. In contrast, the maximum change in transmittance by an O2-deposited film (16%) was observed at a thickness of 200 nm. The molar absorption coefficients of the bleached H2O-deposited films were much smaller than those of the O2-deposited films. However, the molar absorption coefficients of the colored H2O- and O2-deposited films were very similar. The Rh oxide thin films prepared by sputtering in a H2O vapor atmosphere exhibited low molar absorption coefficients in the bleached state and exhibited excellent EC properties and stable transmittance through 25,000 cyclic voltammetry cycles.

We studied a reactive sputtering technique that involves substrate cooling with liquid nitrogen and water vapor injection into the substrate surface to deposit Ta2O5 solid electrolyte thin films. The ion conductivities of the tantalum oxide films increased upon substrate cooling, and the maximum conductivities of approximately 10−3 S/m were obtained at substrate temperatures of −120°C and −80°C. The deposition rate increased by substrate cooling and high deposition rates of 30–50 nm/min were obtained at substrate temperatures of −80 °C to −170 °C. According to these results, this sputtering technique is highly effective for improving ion conductivity and the deposition rate of Ta2O5 films.

Generally, Ag thin films on glass substrates grow three-dimensionally because of the high Ag/glass interface free energy. However, flatter growth has been reported to be achieved by introducing an appropriate interlayer between the substrate and Ag film. With flatter growth, enhanced optical properties are expected. In the present study, very thin Ag films were deposited on an Al interlayer and their optical properties over a wide wavelength range from the visible-light region to the infrared region were investigated. Ag/Al films and Ag films were formed on substrates via resistance-heating vacuum evaporation. The Al interlayer thickness was fixed at 1 nm, and the Ag thickness was varied from 6 to 15 nm. The surface morphology was observed by atomic force microscopy, and the sheet resistance was measured by the four-point-probe method. The visible-light transmittance was evaluated using a spectrophotometer, and the infrared reflectance was evaluated using Fourier transform infrared spectroscopy. The surface roughness of a 6 nm-thick Ag film was found to be reduced from 1.0 nm to 0.6 nm by the introduction of the interlayer. In the absence of the interlayer, the sheet resistance was too high to be measured; however a sheet resistance of 16.2 Ω/sq. was obtained when the interlayer was present. Similar effects were observed for a 10 nm-thick Ag film. Ag films with thicknesses of 6 and 10 nm showed improved visible-light transmittance and infrared reflectance upon introduction of the interlayer. However, when the thickness of the Ag film was 15 nm, no difference in the sheet resistance or optical properties was observed between samples with and without the interlayer. As a consequence, we found that introducing an Al interlayer is effective for two-dimensional-like growth of Ag films, leading to enhanced visible-light transmittance and infrared reflectance.

We investigated the characteristics of Ag films with and without an Al surface layer deposited by radio frequency magnetron sputtering in different gases. Using Kr gas, the films showed a lower electrical resistivity and larger crystallite size than those sputtered in Ar gas. An Al/Ag film with an Al thickness of 1 nm had a reflectance equivalent to that of a non-coated Ag film because the surface Al layer was fully transformed into a transparent Al oxide layer. To investigate the durability of the films, an environmental test was conducted at a temperature of 55 °C and a relative humidity of 90% for 16 h. It was found that the Al/Ag films suffered no degradation during this test.

Ag/ZnS/Ag (AZA) multilayer films with various ZnS interlayer thicknesses were deposited on glass substates by thermal vacuum evaporation. The transmittance, reflectance, and sheet resistance of the films were investigated for their use as the transparent electrode of an organic light-emitting diode (OLED). A transmittance peak and reflectance valley showed red-shift by changing the interlayer thickness and thus corresponded well. The sheet resistance of the AZA multilayer films was lower than that of indium tin oxide, which is suitable for usage as a transparent electrode for OLED. Next, the OLED devices with AZA multilayer films of different interlayer thicknesses were fabricated, and the device performance and electroluminescence (EL) spectra were evaluated. Unexpectedly, the emission color of AZA-OLED changed from yellow to sky blue when the thickness of ZnS interlayer went from 30 nm to 60 nm. According to the correspondence between EL and reflectance spectra, the observed color change can be attributed to the dominance of a microcavity effect rather than plasmon-induced color filtering. The calculated external quantum efficiency was the highest when the ZnS interlayer thickness was 30 nm compared to the other AZA-OLEDs and conventional OLEDs.

We fabricated alternately multilayered films using CaF2 and ZnS with a different number of pairs by thermal evaporation method and evaluated their reflectance as a distributed Bragg reflector (DBR). A 7-pair CaF2/ZnS multilayered film had an enough high reflectance for use as DBR in the wavelength region of 400–600 nm, which is good agreement with the theoretically calculated reflectance. The fabricated CaF2/ZnS multilayered film was incorporated to the organic light-emitting diode (OLED) devices. We found that the inversed-type OLED (iOLED) structure is suitable for achieving the working device. From the result of electroluminescence (EL) measurement, the spectral linewidth of EL of inversed OLED with DBR (μ-cavity iOLED) was significantly narrowed compared to that of conventional OLED (cOLED). The EL peak wavelength of μ-cavity iOLED was centered around 520 nm, which was well corresponded to the designed cavity length. The observed narrowing of EL spectra for μ-cavity iOLED was originated from the microcavity effect. Color coordinate of the emission were changed from cOLED: (0.31, 0.54) to μ-cavity iOLED (0.20, 0.72), which indicates a significant improvement of color purity of green emission.

The use of water vapor as a reactive gas under metallic mode for high rate sputter deposition of chromium oxide thin films have been studied in the course of this research. Chromium oxide (Cr2O3) thin films were deposited by an RF magnetron sputtering system with chromium metal as a target and argon (Ar) and water vapor (H2O) as the sputtering gas. Water was injected to the target or substrate surface at an H2O flow ratio of H2O/(H2O + Ar), varied from 0 to 100%. A liquid nitrogen cold trap was placed in the sputtering chamber to adsorb non-reacted H2O molecules. When the cold trap was inactive, the deposition rate and discharge voltage dropped and the transmittance of the films increased above an H2O flow ratio of 10%. Discharge voltage and plasma emission measurements showed that Cr2O3 films were deposited under compound target mode. In contrast, when the cold trap was active, the deposition rate increased with increase in H2O flow ratio and also a gradual increase in the transmittance of the films was observed. Hence, the target surface was considered to be almost in a metallic state and the oxidation proceeded gradually. Results of this study indicate that H2O sputtering using cold trap is a promising method for the formation of chromium oxide thin films at high deposition rates under metallic target mode.

It is essential to understand which mechanism of localized surface plasmon (LSP) emission enhancement is to be utilized when combining plasmonic metal nanostructures with an emissive material to produce an optoelectronic device. Herein, we report on the size dependence and time-resolved dynamics of photoluminescence (PL) enhancement using three sizes of aluminum nanotriangles (Al NTs) on emission by tris(8-hydroxyquinolinato)aluminum (Alq3) for elucidating its enhancement mechanism. Al nanostructures were fabricated using a nanosphere lithography technique. Two-dimensionally aligned polystyrene (PSt) beads with different diameters were used as mask templates for obtaining the Al NTs. The absorption peaks red-shifted with increasing Al NT size, and hence, were attributed to the LSP resonance. From PL of Alq3 with and without Al NTs, 2–3 fold PL enhancements were observed among the samples with different Al NTs sizes. The significant shortening of the PL lifetime was observed only in Alq3/Al NTs using Ps500, indicating the effective coupling of LSP of Al NTs and the emission, which is also evidenced from the overlapping the PL peak and the LSP absorption. In contrast, the PL emission enhancement due to LSP coupling with the absorption process of Alq3 was dominant in Alq3/Al NTs using Ps200, suggested from the similarity of the PL decay curve with that of bare Alq3, and the excitation energy matching with LSP resonance. From these observation, we can distinguish the LSP coupling process (absorption or emission) from the presence or absence of lifetime enhancement in the time-resolved PL measurements, offering a guideline for designing the optical devices incorporating the metal nanostructures.

We investigated the optical, morphological, and electrochemical characteristics of nanostructured samples that were directly prepared on fluorine doped tin oxide (FTO) by a simple wet-chemical method with an aqueous solution of copper acetate monohydrate, at different growth temperatures. At room temperature, the nanostructured sample exhibited ribbon-like structures composed of sheets. With increasing temperature (40 °C), it had mixed crystalline phases of ribbon-like-structured copper carbonate hydroxide (Cu2CO3(OH)2) and sphere-like-structured copper oxide (CuO). With a further increase in the growth temperature to 50 °C, a bilayer-structured CuO sample was obtained, that comprised a bottom layer with compact nanoparticles and a top layer with sphere-like structures. The bilayer-structured CuO sample had excellent UV–Vis. light filtration efficiency. In addition, the entirely binder-free CuO sample grown at 60 °C exhibited a specific capacitance of ~23 F/g at a scan rate of 2 mV/s with good rate capability.

Recently, we found that Ag thin films with low electrical resistivity could be produced by DC sputtering using Kr gas, whose atomic mass is closer to that of Ag than Ar gas is. In contrast, sputtering using Ar caused trapping of Ar atoms in the film, leading to higher resistivity. In addition, the films sputtered using Kr gas had a much larger crystallite size than those sputtered using Ar gas. In the present study, we clarified the relation between the resistivity and crystallite size by data fitting using an equation proposed in the literature. Ag thin films with a thickness of 150 nm were deposited on glass substrates via DC magnetron sputtering in Ar or Kr gas at a pressure of 2 mTorr. The sputtering voltage was varied from 300 to 1000 V. By fitting the experimental data, we found that the model curves reproduced the experimental results for films sputtered in either Ar or Kr gas, and the electron reflection coefficient at the grain boundaries was the same for both types of film. Thus, the resistivity depends on the crystallite size, and the electron scattering behavior is basically the same for both films. Therefore, it is considered that the main reason for the lower resistivity of the film produced by sputtering in Kr is enhanced grain growth due to suppression of energetic neutral Kr bombardment of the film surface. Although it is known that the Ar gas pressure affects the characteristics of thin films, the effects of pressure have not been well investigated for Kr gas. In the present study, we examined the effect of the Kr gas pressure on the resistivity and crystallite size for sputtered Ag films. The results indicated that there was no significant effect.

We investigated the effects of Ni dopant on structural properties of zinc oxide (ZnO) nanorods. All rods had a ZnO hexagonal wurtzite structure. Upon incorporation of Ni in ZnO, the length and width of the nanorods decreased and increased, respectively. Furthermore, the Ni-doped ZnO (Ni-ZnO) nanorods exhibited overall superior crystalline quality and orientation without showing lattice distortion, as determined by XRD (X-ray diffraction) and electron backscattering diffraction (EBSD) analyses. Both rod types had a hydrophilic surface, whilst, the only polar surface energy slightly decreased after Ni doping. Display Omitted We investigated the effects of Ni dopant on structural properties of ZnO nanorods.Ni-ZnO nanorods exhibited overall superior crystalline quality and orientation.Both rod types had a hydrophilic surface.

We investigated the structural properties of zinc oxide (ZnO) nanorods with various Ni doping amounts. The length and diameter of the nanorods decreased and increased, respectively, with increasing Ni doping amount to 5 mM. Ni-doped ZnO (Ni-ZnO) nanorods exhibited better crystalline quality than undoped ZnO nanorods. In the visible wavelength region, the optical transmittance of Ni-ZnO nanorods was slightly lower than that of ZnO nanorods. Upon further increasing the Ni doping amount (7 mM), the morphology of Ni-ZnO dramatically changed from that of nanorods to a sphere-like structure assembled with interwoven nanowalls. Ni incorporation is a facile strategy for tuning growth behavior and morphology of ZnO nanostructures.

We fabricated undoped zinc oxide (ZnO), Li-doped zinc oxide (LZO), and Cu-doped zinc oxide (CZO) nanorods (NRs) on fluorine-doped tin oxide (FTO)-coated glass substrates using chemical solution deposition and investigated their structural properties. With the incorporation of the Li dopant, the length and crystallinity of LZO NRs increased and improved, respectively, compared to that of the ZnO NRs. The average optical transmittance of LZO NRs was slightly lower than that of the ZnO NRs, but otherwise very similar over the visible wavelength region. With the incorporation of the Cu dopant, however, the morphology of the CZO sample was remarkably different from that of the pure ZnO NRs. Rods with a length of ∼12 μm and a diameter of 0.5–1.2 μm were randomly oriented on the substrate, and copper oxide (CuO) nanocrystals were uniformly grown on the surface of substrate. This paper presents a simple way to tune the growth behaviors of the ZnO NRs by adding dopants.

We investigated the structural properties of zinc oxide (ZnO) nanostructures grown on the glass substrates using the chemical solution deposition while being doped with Ag in different amounts. The undoped ZnO nanostructures were composed of flower-like bundles consisting of nanorods with a length of ~2.3 μm and hexagonal disks with a diameter of ~2.2 μm and thickness of ~350 nm. In these flower-like bundles, the diameter and density of the nanorods at the center were smaller and higher, respectively, than those of the nanorods at the edge. With addition of Ag in the ZnO, the Ag nanoparticles were formed on the substrate, which led to suppress the growth of the flower-like bundles and decrease the thickness of the disks. The intensities of the diffraction peaks corresponding to the ZnO and Ag phases decreased and increased, respectively, with an increase in the amount of Ag added. It was found that the Ag-doped ZnO nanostructures contained Ag particles, which formed a continuous thin film, resulting in low sheet resistance (~1 Ω/sq).

We demonstrated that the sequential structural control of nanoparticles of an open-framework coordination polymer, copper hexacyanoferrate (CuHCF). The structural control has been achieved by addin...

Zinc oxide (ZnO) nanorods were grown on a ZnO seed layer using chemical solution deposition, and their growth behavior over various timescales was investigated. The structural properties of the nanorods were investigated using x-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM), and the pH of the solution was measured both before and after the reaction process. It was observed that the nanorods grew in two stages, with the first stage from 0 to 6 h time and the second stage at 12–24 h of time. When they were given 24 h of reaction time, the length and aspect ratio of the nanorods reached ∼2.6 μm and ∼54, respectively. The pH value of the solution changed during the whole process, and on reaching a pH value ∼8.1 after 36 h, the nanorods exhibited very stable size dimensions. The most effective growth time to yield nanorods with high aspect ratios was determined to be 24 h.

We investigated the growth behavior of Al-doped zinc oxide (ZnO) microrods grown on ZnO seed layers at various growth times. During the initial 3 h (region I), the randomly oriented microrods grew on the surface of the substrate because of the weak acidity of the initial solution (pH ∼5.5). Between 3 h and 6 h (region II), when the pH was close to neutrality, a dominant growth of Al-doped ZnO (AZO) microrods with tapered shape occurred. After that the vertical growth of the microrods reached a certain equilibrium, a selective etching of the side nonpolar plane, rather than the top polar plane, dominantly occurred between 6 h and 12 h (region III), thus leading to the formation of the microrods of cylindrical shape. From 12 h to 24 h (region IV), the pH value was saturated, and the morphology of the microrods did not significantly change. As a result, owing to the change of the pH value, the growth behavior of the AZO microrods appeared significantly different when increasing the time.

Improvement of the color-switching response of an electrochromic device (ECD) is achieved using nanoparticles of Prussian blue (iron hexacyanoferrate, FeHCF-NPs) and of zinc hexacyanoferrate (ZnHCF-NPs) using size-control of ZnHCF-NP by the nanoparticle classification. Using the centrifuge method, ZnHCF is classified into three groups with average particle sizes of 59 nm, 71 nm, and 214 nm. The maximum transmittance contrast Δ T max of a FeHCF/ZnHCF ECD is blue-to-colorless with -ca. 60%, irrespective of the ZnHCF-NP used. However, the response time for coloration of the ECD with the smallest ZnHCF-NPs is only 13% of that of other ECDs with the largest ZnHCF-NPs, although the response time of the electrode with the smallest ZnHCF-NP electrode remains 65 % and 79 % of the largest case for oxidation and reduction, respectively. Because the applied voltage is limited to avoid the side reaction in the coloration of the ECD, the acceleration of the electrochemical response by the downsizing of ZnHCF-NPs leads the drastic change in the coloration speed.

We investigated structural and optical properties of Cu-, Ag-, and Al-doped zinc oxide (ZnO) nanorods grown on ZnO seed layers. Cu-doped ZnO (ZnO:Cu) nanorods showed increased length and improved crystallinity, compared to undoped ZnO nanorods, where the average transmittance in the visible region is lower than that of ZnO nanorods. Meanwhile, the Ag incorporation led to quite opposite behaviors: decreased length and crystallinity of nanorods. It was also found that Ag-doped ZnO (ZnO:Ag) nanorods exhibited high transparency. The incorporation of Al dopant led to a marked morphological variation, with randomly oriented microrods grown on the surface of the ZnO seed layer, instead of nanorods. Al-doped ZnO (ZnO:Al) microrods exhibited excellent transparency over the visible region. The present results thus show that incorporation of Cu, Ag, and Al dopants has a critical effect on structural and optical properties of ZnO nanorods.