To reduce power consumption of transparent oxide‐semiconductor thin film transistors, a gate dielectric material with high dielectric constant and low leakage current density is favorable. According ...to previous study, the bulk TiNb2O7 with outstanding dielectric properties may have an interest in its thin‐film form. The optical, chemical states and surface morphology of sol‐gel derived TiNb2O7 (TNO) thin films are investigated the effect of postannealing temperature lower than 500°C, which is crucial to the glass transition temperature. All films possess a transmittance near 80% in the visible region. The existence of non‐lattice oxygen in the TNO film is proposed. The peak area ratio of non‐lattice oxygen plays an important role in the control of leakage current density of MIM capacitors. Also, the capacitance density and dissipation factor were affected by the indium tin oxide (ITO) sheet resistance at high frequencies. The sample after postannealing at 300°C and electrode‐annealing at 150°C possesses a high dielectric constant (>30 at 1 MHz) and a low leakage current density (<1 × 10−6 A/cm2 at 1 V), which makes it a very promising gate dielectric material for transparent oxide‐semiconductor thin film transistors.
The microwave dielectric properties and the microstructures of (Mg1−xCox)2TiO4 ceramics prepared by the conventional solid‐state route were investigated. Lattice parameters were also measured for ...specimens with different x. The formation of solid solution (Mg1−xCox)2TiO4 (x=0.02–0.1) was confirmed by the X‐ray diffraction patterns, energy dispersive X‐ray analysis, and the lattice parameters measured. By increasing x from 0 to 0.05, the Q×f of the specimen can be tremendously boosted from 150 000 GHz to a maximum of 286 000 GHz. A fine combination of microwave dielectric properties (ɛr∼15.7, Q×f∼286 000 GHz at 10.4 GHz, τf∼−52.5 ppm/°C) was achieved for (Mg0.95Co0.05)2TiO4 ceramics sintered at 1390°C for 4 h. Ilmenite‐structured (Mg0.95Co0.05)TiO3 was detected as a second phase. The presence of the second phase would cause no significant variation in the dielectric properties of the specimen because it possesses compatible properties compared with that of the main phase. In addition, only a small deviation in the dielectric properties was monitored for specimens with x=0.04–0.05 at 1360°–1420°C. It not only provides a wide process window but also ensures an extremely reliable material proposed as a very promising dielectric for low‐loss microwave and millimeter wave applications.
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•TAgNPs and AgNDs were fabricated by photochemical reduction method.•Light-scattering property for AgNDs is much higher than that for TAgNPs.•HTL was doped with AgNDs or TAgNPs at the ...same concentration and made into PLED.•Higher light-scattering for metal NPs can induce a relatively strong LSPR effect.
This study used photochemical reduction to successfully synthesize triangular silver nanoplates (TAgNPs) and silver nanodecahedrons (AgNDs) with higher light-absorption and higher light-scattering properties, respectively, for the same wavelength. To analyze the contribution of light-absorption and light-scattering of silver nanoparticles to the localized surface plasmon resonance (LSPR) effect, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate was doped with TAgNPs or AgNDs at the same concentration (1.17 μg/cm2) and made into polymer light-emitting diodes (PLEDs). According to the current density-voltageluminance characteristics and electroluminescence (EL) spectra, the enhancement factors for current efficiency and EL intensity for AgND-containing PLEDs were found to be higher than those for PLED with TAgNPs by 24.9% and 138%, respectively. This shows that the metal nanoparticles with higher light-scattering property can induce a relatively strong LSPR effect, which possibly gives a hint to design plasmonic photovoltaic in future.
Plasmonic photocatalysis, combing noble metal nanoparticles (NMNPs) with semiconductors, has been widely studied and proven to perform better than pure semiconductors. The plasmonic effects are ...mainly based on the localized surface plasmon resonance (LSPR) of NMNPs. The LSPR wavelength depends on several parameters, such as size, shape, the surrounding media, and the interdistance of the NMNPs. In this study, graphene-modified plate-like BiVO4 composites, combined with silver nanoplates (AgNPts), were successfully prepared and used as a photocatalyst for CO2 photoconversion. Triangular silver nanoplates (TAgNPts), icosahedral silver nanoparticles (I-AgNPs), and decahedra silver nanoparticles (D-AgNPs) were synthesized using photochemical methods and introduced to the nanocomposites to compare the shape-dependent plasmonic effect. Among them, T-AgNPts/graphene/BiVO4 exhibited the highest photoreduction efficiency of CO2 to CH4, at 18.1 μmolg−1h−1, which is 5.03 times higher than that of pure BiVO4 under the irradiation of a Hg lamp. A possible CO2 photoreduction mechanism was proposed to explain the synergetic effect of each component in TAgNPts/graphene/BiVO4. This high efficiency reveals the importance of considering the compositions of photocatalysts for converting CO2 to solar fuels.
The microwave dielectric properties and the microstructures of (Mg1−xZnx)2TiO4 ceramics prepared by the conventional solid‐state route were investigated. Lattice parameters were also measured for ...samples with different x. As x increased from 0 to 0.05, the Q×f of the specimen can be promoted from 150 000 GHz to a maximum 275 300 GHz. It also showed a remarkable lowering in the sintering temperature (∼100°C). Ilmenite‐structured (Mg0.95Zn0.05)TiO3 was detected as a second phase. The coexistence of the second phase, however, is not harmful to the dielectric properties of the specimen because it possesses compatible ones. A fine combination of microwave dielectric properties (ɛr∼15.48, Q×f∼275 300 GHz, τf∼−34 ppm/°C) was obtained for (Mg0.95Zn0.05)2TiO4 specimen sintered at 1330°C for 4 h. It is proposed as a very promising dielectric material for low‐loss microwave and millimeter wave applications.
The microstructures and the microwave dielectric properties of the (1–x)(Mg0.95Zn0.05)TiO3–xSrTiO3 ceramic system were investigated. (Mg0.95Zn0.05)TiO3 possesses high dielectric constant (ɛr∼17.05), ...high quality factor (Q×f value∼264 000 at 9 GHz), and negative τf value (−40.31 ppm/°C). In order to achieve a temperature‐stable material, SrTiO3, having a large positive τf value of 1700 ppm/°C, was added to (Mg0.95Zn0.05)TiO3. Two‐phase system was confirmed by the X‐ray diffraction patterns and the measured lattice parameters. Evaporation of Zn occurred at temperatures higher than 1300°C and caused an increase in the dielectric loss of the system. As the x value varies from 0 to 0.1, (1–x)(Mg0.95Zn0.05)TiO3–xSrTiO3 ceramic system has the dielectric properties as follows: 17.05<ɛr<26.35, 20 000<Q×f<264 000, and −41<τf<140. By appropriately adjusting the x value in the (1–x)(Mg0.95Zn0.05)TiO3–xSrTiO3 ceramic system, zero τf value can be achieved. A new microwave dielectric material, 0.96(Mg0.95Zn0.05)TiO3–0.04SrTiO3 applicable in microwave devices is suggested and possesses the dielectric properties of a dielectric constant ɛr∼20.96, a Q×f value∼135 000 GHz (at 9 GHz), and a τf value ∼0 ppm/°C. A compact band‐pass filter using two open‐loop ring resonators with asymmetric tapping feed lines is designed and fabricated using the proposed dielectric to study its performance.
Field emission (FE) devices are advanced lighting devices that have a 2-D planar configuration, different from the 0-D (dot) and 1-D (line) configurations of light-emitting diode (LED) and ...fluorescent lighting, respectively. The purpose of this study is to develop a FE lighting device with a lateral-cathode triode. Carbon nanotubes (CNTs) are used as emitters and ZnS particles are used as a green phosphor. The materials were screen-printed onto two soda lime glass substrates. To increase the device lifetime and performance, we applied pulsewidth modulation (PWM) to the gate electrode. A high luminance of 12 690 cd/m 2 and a good luminance uniformity of 84% were achieved for a lighting device with a lateral-cathode structure.
Novel ultra-low firing (Mg
1-x
Zn
x
)V
2
O
6
(x = 0-0.09) ceramics have been investigated and systematically designed as promising dielectrics for ultra-low temperature co-fired ceramics ...applications. The X-ray diffraction patterns indicated that all samples crystallized in a monoclinic structure with a space group of C
2/m
. Microstructures and lattice parameters are presented and correlated with the microwave dielectric properties of the ceramics. The MgV
2
O
6
specimen can be well-sintered at 610°C, the resulting ceramic of which featured an ε
r
~ 8.8, a Q × f ~ 10,300 GHz and a τ
f
~ - 29.7 ppm/°C. The tunable τ
f
value can be adjusted to near zero along with a great promotion in the Q × f of MgV
2
O
6
by using a small Zn substitution. In addition, excellent microwave dielectric properties (ε
r
~ 9.3, Q × f ~ 15,300 GHz @15.5 GHz and τ
f
~ - 3.4 ppm/°C) were obtained for the (Mg
0.93
Zn
0.07
) V
2
O
6
specimen sintered at 610°C for 4 h. The specimen is chemically compatible with Al electrodes and could be an ideal ultra-low temperature co-fired ceramics dielectric. Possible applications include the 5 G system, particularly with high frequency regions.
With the resistive random access memory (ReRAM) devices based on the Al/BaTiO3 (BTO)/ITO structure fabricated at hand, by cross-analyzing the resistive memory characteristics in terms of various ...barium titanate (BTO) film thicknesses, it is found that the device with 60 nm thick BTO can be switched more than 425 times, while the corresponding SET/RESET voltage, the on-off ratio, and the retention time are −0.69 V/0.475 V, 102, and more than 104 seconds, respectively. Furthermore, the aforementioned ReRAM with a low switching voltage and low power consumption is further integrated with a waveguide resonator in the form of a dual microdisk aligned in a parallel fashion. As the separation gap between the two microdisks is fixed at 15 μm, the ReRAM-mediated dual disk resonator would render a 180° phase reversal between the spectral outputs of the through-port and drop-port. If the gap is shortened to 10 and 5 μm, the expected phase reversal could also be retrieved due to the selective combinations of different memory states associated with each of the two ReRAM microdisks as witnessed by a series of characterization measurements.
Solid solutions of (Mg1−xNix)Al2O4 (x=0–1) have been prepared using the solid‐state reaction method and their dielectric properties were measured at microwave frequencies. Formation of single‐phase ...spinel‐structured solid solutions was confirmed by X‐ray diffraction analysis throughout the entire compositional range, and the measured lattice parameters varied linearly from 8.0810 Å at x=0 (MgAl2O4) to 8.0445 Å at x=1 (NiAl2O4) leading to a linear decrease in the unit cell volume from 527.71 to 520.59 Å3. The ionic polarizability obtained, however, increased with the increase of x to a maximum at x=0.25 and decreased thereafter. It shows only a small variance in the ɛr with Ni substitution for Mg and a maximum ɛr of 8.21 was achieved for (Mg0.75Ni0.25)Al2O4 in response to the highest ionic polarizability and relative density. However, the Q×f value can be significantly promoted up to a maximum value of 130 000 GHz (measured at 15.4 GHz) at x=0.25. In addition, substitution of Mg by Ni also helps to decline the τf value from −65 ppm/°C at x=0 to −53.5 ppm/°C at x=0.25.
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