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We report the development of an efficient imprinting process for the formation of metal (Au) nanodot arrays using a square-patterned medium substrate. Solid-state dewetting is induced by differences in the surface energy of the metal film and the interface energy between the substrate and the metal film. Thus, uniform metal nanodot arrays were transferred to the desired substrate by controlling the interfacial surface free energy between the metal film and the substrate. Optical extinction measurements showed an intense extinction peak at 550 nm, corresponding to the simulated result. Imprinting of the Au-nanodot arrays on the substrate enhanced the light trapping function and supported the electrical properties of a polymer electrode. In addition, the combination of a transparent conducting oxide-free device with the Au-nanodot arrays and a polymer electrode resulted in enhanced performance. This can be attributed to the fact that the Au-nanodot arrays allowed higher charge extraction, as confirmed by electrical analyses. Finally, a next-generation approach of imprinting metal nanodot arrays was introduced through the controlled solid-state dewetting mechanism in a specific area, which can be applicable not only in the development of optoelectronic devices but also in semiconductor processes requiring metal nanostructures.

A photoelectric cantilever-based current sensing methodology, mainly composed of a cantilever, a magnet, an analyzer, and a photodiode, for passive measuring diverse multiline cables with diverse currents, is proposed for the desirable application of a Wireless Sensor Node (WSN) in Internet of Things (IoT). The basic idea is to achieve a synchronous vibration of both the analyzer and the cantilever to modulate the natural light signal incident on the photodiode. In this Letter, the magnet, fixed at the end of the cantilever, is used to passively convert the applied current induced magnetic force into a cantilever vibration, which is further converted to a polarization angle variation via the above synchronous vibration. The natural light signal is accordingly modulated and a varied voltage, as a function of the applied current, is thus output from the photodiode. A two-wire DC electric current is used to verify the validity of the sensing mechanism. The measurement error can be decreased to less than half of the theoretical one by calibration, and the linear range can be further adjusted by changing a value on the host computer. Compared to the piezoelectric cantilever-based one, the proposed photoelectric cantilever-based methodology can achieve a continuous measurement of DC and its variation with a higher resolution, and both a faster response and a higher resolution for AC, and thus is more suitable for IoT applications.A photoelectric cantilever-based current sensing methodology, mainly composed of a cantilever, a magnet, an analyzer, and a photodiode, for passive measuring diverse multiline cables with diverse currents, is proposed for the desirable application of a Wireless Sensor Node (WSN) in Internet of Things (IoT). The basic idea is to achieve a synchronous vibration of both the analyzer and the cantilever to modulate the natural light signal incident on the photodiode. In this Letter, the magnet, fixed at the end of the cantilever, is used to passively convert the applied current induced magnetic force into a cantilever vibration, which is further converted to a polarization angle variation via the above synchronous vibration. The natural light signal is accordingly modulated and a varied voltage, as a function of the applied current, is thus output from the photodiode. A two-wire DC electric current is used to verify the validity of the sensing mechanism. The measurement error can be decreased to less than half...

We demonstrate significantly enhanced performance of 2.1 μm InGaAsSb quantum well lasers using Sb as a surfactant. The lasers are grown on an InP substrate by metal-organic vapor-phase epitaxy. Following the introduction of Sb, a double-channel waveguide laser, with uncoated facets, shows a remarkably increased continuous-wave output power of 330 mW, compared with 160 mW for a Sb-free InGaAs quantum well laser, measured at 10 °C. Moreover, the introduction of Sb improves the temperature performance of the device and doubles its wall-plug efficiency. In addition, the active region material and interface quality are investigated by transmission electron microscopy, which help to elucidate the basic physical mechanism of the Sb surfactant effect.

Broadband spectrum electrically pumped InP-based superluminescent diodes with high output power in continuous-wave (CW) mode are reported. The optimized active region and high quality of quantum wells are guaranteed for controlling the wavelength and acquiring large mode gain. Three kinds of cavity structures were designed to provide strong suppression of reflections allowing strong amplified spontaneous emission without any sign of lasing modes. All device spectrums are centered around 2.1 μm, and at low injection current, the full width at half maximum (FWHM) of the widest spectrum is 99 nm. After the optimization of the waveguide structure for higher output power, the maximum CW output power is lifted up to 30 mW with the two lobe far field pattern in a single output facet at 300 K and still the FWHM of 41 nm. This work is of great importance to pave the way for demonstrating compact and efficient light sources based on InP material systems. Considering the InP material compatibility with the mature device fabrication process, especially the buried heterostructure, device characteristics would be better improved and be more promising for applications.

A temperature compensation methodology comprising a negative temperature coefficient thermistor with the temperature characteristics of a piezoelectric material is proposed to improve the measurement accuracy of piezoelectric sensing based devices. The piezoelectric disk is characterized by using a disk-shaped structure and is also used to verify the effectiveness of the proposed compensation method. The measured output voltage shows a nearly linear relationship with respect to the applied pressure by introducing the proposed temperature compensation method in a temperature range of 25–65 °C. As a result, the maximum measurement accuracy is observed to be improved by 40%, and the higher the temperature, the more effective the method. The effective temperature range of the proposed method is theoretically analyzed by introducing the constant coefficient of the thermistor (B), the resistance of initial temperature (R0), and the paralleled resistance (Rx). The proposed methodology can not only eliminate the ...

A position and orientation correction scheme for current sensing based on magnetic piezoelectric cantilevers is proposed in this letter, offering an insight for the improvement of measurement accuracy. In this scheme, an array of magnetic piezoelectric cantilevers, converting mechanical vibration generated by current induced magnetic force applied on magnets at the ends of cantilevers into output voltages, is utilized. A system of nonlinear equations is established in terms of amplitude of objective current, position, and orientation errors. They are derived by solving the system of equations treated as variables, instead of parameters. As a result, the measurement error caused by position and orientation errors decreased substantially. Experiments of passive current sensing for two-wire appliances prove the validity of the proposed position and orientation correction scheme. The application of the proposed scheme can be further extended to sensors based on the magnetic field sensing mechanism, for achiev...

This paper proposes a method for passive sensing a two-wire DC current without using any cord separator. In this method, a piezoelectric thin-film cantilever with a micro-magnet on its end is positioned near a power cord. The DC current in the power cord induces a magnetic field, which generates a magnetic force acting on the micro-magnet. Consequently, the piezoelectric cantilever is bent and induces an output voltage that is sensitive to small variations of DC currents. A prototype device has been fabricated and experimentally studied. It was found that the initial peak amplitude of the piezoelectric output voltage increases linearly with the DC current value upon “ON-OFF” switching. Compared to the Hall-effect based sensing, this method has the advantages of no need of driving voltage or cord separators even for two-wire appliance cords. Apart from the conventional consumer electronics, this method may have a wide application foreground in the new emerging fields, such as energy vehicles, lithium ion battery, or smart power grid.

The nanomechanical properties of single-crystalline silicon cantilevers as resonating elements are investigated in ultra-high vacuum. Flash heating the single-crystalline silicon cantilever at 1000 °C in ultra-high vacuum dramatically reduced the mechanical energy dissipation of the oscillating cantilever due to the removal of contaminants and natural oxide and reconstruction of the silicon surface. However, the reconstructed silicon surface is not stable and mechanical properties change depending on the surface state. The Q-factor and influence of gas adsorption on ultrathin single crystalline silicon resonators having (100) and (111)-oriented surfaces are presented.

The influence of crystallographic orientation on the nanomechanical properties of 50 nm thick (100)-oriented single-crystal silicon resonators was investigated by examining the effects of surface treatments, such as flash-heating, on the mechanical quality factors (Q-factors) and resonant frequencies. The measured Q-factors were found to vary periodically with crystallographic orientation and were shown to have higher values in the 〈110〉 direction. A 1500 nm thick (100)-oriented cantilever array was also studied for comparison, for which no obvious periodic change was observed. Since the energy dissipation in vibrating resonators cannot be explained by the support loss or thermoelastic loss, a surface-related mechanism should be considered.

The metalorganic decomposition-derived SrBi2Ta2O9 (SBT) ferroelectric thin films were annealed in forming gas (5%H2+95%N2), and their fatigue characteristics were investigated. Although the hysteresis loops of these films had an unacceptable degradation under such a H2-containing reducing atmosphere, no obvious polarization fatigue with electric field cycling could be observed. However, an increase of P*r was observed over the initial period of the fatigue test. It could be viewed as a competition between the increase of P*r due to the leakage current and the decrease of P*r due to switching polarization. H2 played an important role in the increasing in the leakage current of SBT thin films, forming more weak pinning centers of domain walls, and degradation in the fatigue characteristics.

An enhanced anomalous Hall effect (AHE) is observed via interface modification in MgO/[Co/Pt]2/Co/MgO multilayers, due to the insertion of a Hf metal layer at the Co/MgO interface. It is shown that the saturation anomalous Hall resistivity is 215% larger than that in the multilayers without Hf insertion. More importantly, thermally stable AHE and perpendicular magnetic anisotropy features are obtained in MgO/[Co/Pt]2/Co/Hf/MgO multilayers. The AHE is improved for sample MgO/[Co/Pt]2/Co/Hf/MgO by annealing, which is attributed to the enhancement of the side jump contribution.

Bulk heterojunction all-polymer solar cells, fabricated with poly{[4,8-bis-(2-ethyl-hexyl-thiophene-5-yl)-benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl]-alt-[2-(2-ethyl-hexanoyl)-thieno[3,4-b′]thiophen-4,6-diyl]} (PBDTTT-CT) as a donor polymer, and a acceptor polymer, poly{[N,N′-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′-bithiophene)} (P(NDI2OD-T2)), have been demonstrated and have achieved a power conversion efficiency exceeding 3.7% by using 1,8-diiodooctane (DIO) as a processing additive. Based on the analysis of charge carrier dynamics (charge generation, separation, and extraction), we found that the appropriate ratio of processing solvent additive (5 vol. % DIO) leads to enhanced device performance and favorable morphological characteristics. This research, therefore, indicates that the incorporation of a DIO additive in all-polymer blends is an effective way to form a morphologically ideal heterojunction network and thereby improve charge carrier kinetics for effi...

Thermal oxides on p-type silicon carbide exhibit high densities of interface states and fixed charge. Understanding the effect of the oxide composition on the electrical properties is imperative to improve the quality of oxides on p-type silicon carbide. In this work, we use angle resolved x-ray photoelectron spectroscopy to profile the oxide composition. The result is a direct correlation between the carbon content in the oxide and the density of interface states and fixed charge as determined by electrical capacitance–voltage measurements.

In this research, the enhanced power conversion efficiency of PBnDT-FTAZ:PC70BM bulk-heterojunction (BHJ) solar cells (over 7%), fabricated with a solvent additive (1,8-diiodooctane, 3%), was demonstrated. The appropriate ratio of solvent additive leads to a device with increased JSC, fill factor, and favorably controlled nanomorphology phase separation. Furthermore, the device with BHJ film fabricated with the solvent additive exhibited improved charge collection and simultaneously reduced charge recombination from a systematic light intensity analysis. The lack of Shockley-Read-Hall recombination at open circuit, the dominance of bimolecular recombination only when approaching open circuit, and an improved charge collection probability (95.5%) at short circuit contribute to high performance organic photovoltaic cells.

We report a field-effect approach to enhance the electroluminescence (EL) from a model Si nanocrystal light-emitting device (Si-NC LED). The field effects are established within the carrier injection regions of the LEDs via introducing an i-type Si layer on the top of active layer and an Al2O3 layer between the active layer and the Si substrate. The fields are consistent in polarity with the forwardly biased electric field within the LEDs. One order of magnitude increases in the EL intensity from Si-NC LED are readily achieved after introducing the field effects.

We present a study of electron and hole mobility in blends of the solution-processed small molecule (DTS(PTTh2)2):fullerene as a function of the fullerene content. The mobilities are measured using the Field–Effect Transistor device configuration with the blend as the material in the channel. The hole mobility of the small molecule increases when about 10% of [6-6]-phenyl C71 butyric acid methyl ester (PC70BM) is added and then decreases at higher fullerene content. The electron mobility always increases as the fullerene content increases. Balanced charge transport occurred at 70:30 and 60:40 donor to acceptor ratios in the DTS(PTTh2)2:PC70BM system. The observation of balanced charge mobility agrees well with the reported solar cell performance.

A reusable metallic substrate of surface-enhanced-Raman-scattering (SERS) was fabricated with field-enhancement property. Silver nanoparticles spread on a glass substrate and covered with a graded SiO2 coating were employed to enhance and to modulate the Raman scattering signal of probed samples. In the study, the Raman scattering enhancement of the crystal violet dye depended on the thickness of the SiO2 coating and the optimal Raman signal occurred as the SiO2 coating thickness was around 8.7 nm. Moreover, the SiO2 coating that functioned as a protector, maintaining the activity of the Ag nanoparticles, led to a reusable SERS-active substrate.

When the cross-sectional size of structural elements reduces to nanometers, surface effects become quite important in their mechanical behaviors. In this letter, a theoretical model is proposed to account for surface effects through both surface energy and core-shell model. Through the principle of minimum potential energy, a refined analytical solution is derived for the stiffness of nanosprings. It is shown that surface energy evidently affects the stiffness of nanosprings. The present model provides an efficient tool to analyze the mechanical performance of various nanosized helixes and is also helpful to design nanospring-based devices.

We demonstrated a simple and nonlithographic method that enlarges the active layer/metal electrode contact area in polymer solar cells by adding the thermal initiator 2,2′-azobisisobutyronitrile (AIBN) as a nanohole generating agent. From diffused light spectra and x-ray diffraction measurements, it is found that device performance enhancement comes not from a change in the charge carrier generation or transportation characteristics but from increased charge carrier collection due to the reduced contact resistance and shortened pathway to the electrode caused by enlarged interface area.