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Device dimension scaling down to be comparable to the domain size of polycrystalline ferroelectric HfZrO2 (HZO) is evaluated for subthreshold swing (SS) and drain-induced barrier lowering (DIBL) by numerical simulation. The proposed multi-domain modeling involves polarization random location in HZO and probability with Gaussian distribution, as well as being integrated with the Landau–Khalatnikov equation. A small device with a few domains exhibits steep SS compared with large dimension with many domains. The N-DIBL (negative-DIBL) is also estimated by using this model, and the negative capacitance effect retards the short-channel effects significantly. The trend of the experimental data and simulation results of fin field-effect transistors and planar field-effect transistors is consistent with nano-scale and micro-scale devices, respectively.

This work aimed to use waste cooking oil as a greener replacement for the petroleum-based solvents in removing methylene blue (MB) from aqueous solutions by solvent extraction. The effects of different extraction parameters such as equilibrium pH, aqueous to organic phase ratio, and initial MB concentration on the extraction of MB from aqueous solutions by waste cooking oil were investigated. The back-extraction of MB from MB-loaded waste cooking oil was also explored. The maximum extraction (∼90%) and back-extraction (>90%) of MB were attained at equilibrium pH of 8, aqueous to organic phase ratio of 1:1, initial MB concentration of 20 mg/L, and with 1 M of sodium bicarbonate as the back-extraction agent.

This research aimed to extract copper ions from aqueous solutions with oleic acid as a green solvent. The effects of pH equilibrium, temperature, and sodium sulphate (Na2SO4) concentration were investigated and the optimum conditions for maximum extraction of copper ions were determined. The findings revealed that the extraction of copper ions increased with equilibrium pH and temperature before it reached a plateau, while it increased and achieved a peak before it decreased with sodium salt concentration. The highest extraction of copper ions was achieved at 94% under the following optimum conditions: equilibrium pH of 4, temperature 55°C and 400 mM of Na2SO4. Therefore, it can be concluded that oleic acid is a potential green solvent for extracting copper ions from aqueous solutions.

Commercial epoxides available in the market are mainly petroleum and animal based which are non-environmental friendly and often non-halal. Oleic acid (C18:1) derived from palm kernel oil contains the unsaturation double bond (C=C) in its long alkyl chain makes it an attractive fatty acid for the production of eco-friendly epoxide. The epoxidation of oleic acid was carried out by using in situ generated performic acid (HCOOOH) to produce epoxidized oleic acid. Performic acid was formed by mixing formic acid (as oxygen carrier) and hydrogen peroxide (as oxygen donor). The results indicated that optimum conditions occurred at moderate agitation speed 300 rpm and by using 30% hydrogren peroxide. Sulfuric acid was found to be the most efficient catalyst. It was found that a maximum relative conversion to oxirane (RCO) achieved was 87.61 % at optimal condition.

Epoxidized oleic acid is often regarded as a high value oleochemical due to the wide range of industrial applications including cosmetics, personal care and pharmaceutical products. Epoxidized oleic acid also extensively chosen by industry due to its advantages on the good performance as intermediate chemicals and can be obtained from renewable sources. Synthesis and physicochemical properties of oleic acid palm oil was analyzed for further reaction of epoxidation. In this study, the epoxidation of oleic acid was investigated with performic acid generated in situ from hydrogen peroxide in H2O2 (30%) with formic acid. The characterization of oleic acid through iodine value, viscosity, acid value, saponification number and refractive index were 130, 146. 190.0, 206.1 and 1.47 respectively. On the other hand, the characterization of epoxidized oleic acid were 109.8, 156, 192.6, 219.9 and 1.38 of the same analysis. The chemical structures of the products were confirmed by 1H-NMR and 13C-NMR spectral analysis.

The design of CSNS MEBT has two objectives: (1) to match the beam both in the transversal direction and the longitudinal direction from RFQ into DTL; (2) to further chop the beam into the required time structure asked by RCS. It is very difficult and critical to control well the emittance growth and in the meantime to match and chop the beam. Firstly, the optical design is done and optimized, and the multi-particle simulations show that the maximum emittance growth is successfully controlled within 14%. Secondly, based on the different beam envelopes obtained by TRACE-3D and PARMELA, the least deflecting angle of the chopper is determined by TRACE-3D. At last, the field of steering magnet is determined through simulations.

This work demonstrates the use of lithium fluoride (LiF) as a passivation layer and a newly developed UV glue for encapsulation on the LiF passivation layer to enhance the stability of organic light-emitting devices (OLEDs). Devices with double protective layers showed a 25-fold increase in operational lifetime compared to those without any packaging layers. LiF has a low melting point and insulating characteristics and it can be adapted as both a protective layer and pre-encapsulation film. The newly developed UV glue has a fast curing time of only 6 s and can be directly spin-coated onto the surface of the LiF passivation layer. The LiF thin film plus spin-coated UV glue is a simple packaging method that reduces the fabrication costs of OLEDs.

At least two bunchers are needed in the 3 MeV H- Medium Energy Beam Transport (MEBT) line located between RFQ and DTL for the CSNS (China Spallation Neutron Source). A nose-cone geometry has been adopted as the type of buncher cavity for its simplicity, higher impedance and lower risk of multipacting. By making use of the results got from the simulations on the buncher with two-dimension code SUPERFISH, the thermal and structural analyses have been carried out, the process and results to determine the resulting frequency shift due to thermal and structural distortion of the cavity are presented, the water-cooling channel position and the optimum cooling water temperature as well as the tuning method by adjusting the cooling water temperature when the cavity is out of resonance are also determined through the analyses.

The phase transformations involved in Na2 SO4 (Na2 SO4 10H2 O as starting material) and predried Na2 SO4 in a dynamic thermal process of heating from 30 to 500 °C and then cooling down to 30 °C, with a heating/cooling rate of 2 °C min-1 in two consecutive thermal cycles, were monitored at 1 °C intervals by thermo-Raman spectroscopy (TRS). The transformations were characterized on the basis of the disappearance of the bands, appearance of new bands, splitting in the internal modes, change in the spectral profile, intensity (area) changes in the internal modes, full width at half maximum (FWHM) of the totally symmetric stretching mode and even the variations observed in the background during the thermal process. This thermo-Raman investigation provided some evidence for the existence of an intermediate phase between phase V and phase I and also for the changes observed in the phase I structure at higher temperatures, in addition to the dynamic transformations between the well known phase V, phase I, phase II and phase III. The intensity study on the 3 mode of SO2- 4 clearly demonstrated the thermal hysteresis involved among the phases during the heating and cooling process. The differences observed in the polymorphisms of Na2 SO4 (Na2 SO4 10H2 O as starting material) and predried Na2 SO4 were also discussed.

Recently, exciplex had drawn attention because of its potential for efficient electroluminescence or for use as a host in organic light-emitting diodes (OLEDs). In this study, four kinds of hole transport material/electron transport material combinations were examined to verify the formation of exciplex and the corresponding energy bandgaps. We successfully demonstrated that the combination of tris(4-carbazoyl-9-ylphenyl)amine (TCTA) and 3,5,3′,5′-tetra(m-pyrid-3-yl)phenyl[1,1′]biphenyl (BP4mPy) could form a stable exciplex emission with an adequate energy gap. Using exciplex as a host in red, green, and blue phosphorescent OLEDs with an identical trilayer architecture enabled effective energy transfer from exciplex to emitters, achieving corresponding efficiencies of 8.8, 14.1, and 15.8%. A maximum efficiency of 11.3% and stable emission was obtained in white OLEDs.

For use in lighting applications, white organic light-emitting devices (WOLEDs) must operate at higher biases to ensure an ample flux. However, stressed operation voltages often result in poor performance and limited device lifetime. This could be addressed by modifying the inherent optical properties of OLEDs. This study proposes a gradient refractive index (GRIN) substrate to adjust the ratio of the light-waveguided modes as well as the radiation mode. An embedded nanocomposite film consisting of titanium dioxide (TiO2) nanoparticles (NPs) was inserted between ITO and glass to create an internal light-extraction structure (IES). The high refractive index of TiO2 is essential for increasing the refractive index of the photoresist film and thus diminishing the total internal reflection between the interfaces. In addition, the silicon dioxide NPs mixed poly(dimethylsiloxane) was used to form an external light-extraction structure (EES). The refractive indices of the IES and EES were adjusted to form a GRIN substrate. Compared with a control device, this sophisticated substrate produced a 1.6 fold efficiency improvement. Furthermore, the experiment results indicates that the size of NPs in the nanocomposite layer affects the efficiency enhancement of OLEDs with different emission colors.

Space-charge forces acting in mismatched beams have been identified as a major cause of beam halo. In this paper,we describe the beam halo experimental results in a FODO beam line at IHEP. With this beam transport line, experiments are carried out to compare the measured data with the multi-particle...

Cu-metallized interconnects for GaN high-electron-mobility transistors (HEMTs) on Si substrate using a Pt/Cu diffusion barrier layer are investigated. Auger electron spectroscopy (AES) depth profiles indicate that the GaN/Au/Ti/Pt/Ti/Cu thin metal structure is thermally stable up to 350 °C. The Cu-metallized devices using the proposed metal scheme exhibited DC characteristics comparable to those of conventional Au-metallized GaN devices even after annealing at 350 °C for 30 min. No degradation in current with time was observed when the device was tested under 28 V high-voltage stress for 24 h at room temperature. These results indicate that the Cu-metallized airbridges with the Ti/Pt/Ti/Cu diffusion barrier layer can be used for GaN HEMT fabrication.

2.2-µm-thick crack-free GaN films were grown on patterned Si substrates. The crack-free GaN films were obtained by patterning Si substrate and optimizing the graded Al x Ga1-x N layers. With the increase of the graded Al x Ga1-x N layer thickness, the GaN crystal quality improved as judged from the X-ray diffraction data. By applying multi-Al x Ga1-x N layers on the patterned Si substrate, a 31% reduction of tensile stress for the GaN film was obtained as measured by micro-Raman. For the AlGaN/GaN high electron mobility transistor grown on 1×1 cm2 larger patterns, the device exhibits maximum drain current density of 776 mA/mm and maximum transconductance of 101 mS/mm.

The electrical characteristics of molecular-beam-deposited HfO2/n-InAs/InGaAs metal–oxide–semiconductor capacitors with different postdeposition annealing (PDA) temperatures (400–550 °C) are investigated. Results show that the sample with the PDA temperature of 500 °C exhibits the best capacitance–voltage (C–V) behavior with small frequency dispersion and small hysteresis. The X-ray photoelectron spectroscopy (XPS) spectra show the reduction of the amount of As-related oxides to below the XPS detection level when the PDA temperature is up to 500 °C. As the PDA temperature was increased to above 500 °C, As and In atoms seem to diffuse significantly into HfO2, resulting in the degradation of C–V behavior.

In this study, slice-type GaN-based light-emitting diodes (µ-slice LEDs) scaled down to a few micrometers using focused ion beam (FIB) process were demonstrated. Electroluminescence peak wavelengths (λp) of the single µ-slice LEDs were nearly independent of driving current density due to the fact that the effects of joule heating and band filling on the shift of λp compete with each other. The smaller full width of half maximum of electroluminescence peaks observed from the µ-slice LEDs could result from the effect of strain release after the FIB process and thermal annealing during the FIB process on sliced structures.

The derivatives of C60, [6,6]-phenyl C61-butyric acid methyl ester (PCBM), and 3-hexylthiophene (P3HT) were dissolved in o-dichlorobenzene (DCB) solvent, and then spin-coated as an active layer for polymer solar cells. The experimental parameters including the spin-coating speed and drying conditions for the active layer, were studied carefully to obtain the optimum power conversion efficiency (PCE). In the active layer drying procedure, the DCB solvent saturated/unsaturated vapor pressure was adjusted by controlling the amount of solvent at a half-open capacity. The DCB solution was used to enhance the self-organization of the active layer of P3HT and to reduce the number of pure PCBM clusters. In the DCB optimum solution, the PCE of a polymer solar cell can be increased from 1.36 to 1.79%. The structure corresponds to a nano-to-micron scale ordering in the unsaturation-treatment films. In the optimum unsaturation procedure, the PCE of a polymer solar cell can be increased from 1.79 to 2.53%. Using two steps with optimum rotation speeds in the active layer spin-coating, the surface uniformity can be improved, with the PCE increased from 2.53 to 3.13%.

Ga-doped ZnO (GZO) films were deposited onto low-temperature-grown (LTG) GaN/i-GaN (PD-I) and i-GaN (PD-II) epitaxy layers to form Schottky barrier UV band-pass photodetectors (PDs). The UV PDs exhibited a narrow band-pass spectral response ranging from 330 to 380 nm. It was also found that by using an LTG GaN layer on top of conventional nitride-based UV PDs, the leakage current was significantly reduced and a much larger photocurrent-to-dark-current contrast ratio was achieved. The short-wavelength cutoff at around 330 nm can be attributed to the marked absorption of the GZO top contact layer. The zero-bias peak responsivities were estimated to be 0.13 and 0.08 A/W at 360 nm for PD-I and PD-II, respectively. When the reverse bias was below -10 V, the dark current of PD-I was considerably below 20 pA.

Substrate leakage current in InGaP/GaAs heterojunction bipolar transistors (HBTs) has been observed. For a substrate thickness of 100 µm and an emitter area of 60 µm2, the parasitic current is on the order of 10-8 A. The current flowing between the collector terminal and the substrate can be decomposed into linear and parabolic components. The parabolic dependence is also observed in Medici simulation. A theoretical derivation based on electron drift in the substrate shows parabolic dependence on applied voltage, consistent with our measurement and Medici simulation. In addition, it has been found that the current is inversely proportional to the cube of substrate thickness. To account for this substrate parasitic effect, a modification of the vertical bipolar inter-company (VBIC) model is proposed.

The microscopic visco-elastic motion of a quasi-2D dusty plasma liquid confined to a width of about 15 interparticle distances under square stress pulses shorter than thermal relaxation time from a chopped laser beam is investigated experimentally. The stress-enhanced excitations of hopping vortices are responsible for particles in the laser driven zone reaching, after a higher initial velocity, a constant nonzero terminal forward velocity and partial plastic deformation through the loss of the structure memory. The driven particles around domains with caged shear motion still partially keep the structural memory and demonstrate partial elastic backwards motion with exponential relaxation after turning off the laser.

Y-128° LiNbO3 is a well-known high-electromechanical-coupling Surface Acoustic Wave (SAW) material, but its usefulness is limited because of its poor temperature-stablility property. AlN films have some excellent characteristics, such as high SAW velocity, stable chemical properties, and high-temperature stability. In this research, the c-axis-oriented AlN films were successfully prepared on Y-128° LiNbO3 by the sputtering method and a SAW delay line oscillator under various temperatures was used to measure the temperature coefficient of frequency (TCF) value of this structure. For Y-128° LiNbO3 with an AlN layer, the TCF value was from -76.32 (ppm/°C) to -39.04 (ppm/°C) and the improved quantity was 48.8%. The oscillator frequency at 25°C also increased from 40.0909 MHz up to 41.6221 MHz. It exhibited Y-128° LiNbO3 with an AlN layer that will effectively improve the poor temperature stability and enhance the SAW velocity.

The stress induced microscopic responses of dust particles in strongly coupled dusty plasma liquids suspended in plasma traps are investigated experimentally. Narrow laser beams are used to generate stress on dust particles through optical pressure. Assisted by background thermal fluctuations, chaotic micro-vortices with decaying intensities from the laser beam are generated. The forward transport and transverse diffusion rate are enhanced and show nonlinear reponse to the external stress. Visco-elastic response is observed for an elongated liquid cluster driven by a periodically chopped laser beam. The shear wave is damped.

A novel method is developed to investigate the localized states in the band gap of a-Si:H films by analyzing the photoluminescence spectra. A model of phonon emission process among localized states in long band tail is proposed to interpret the periodic oscillations in the sideband of photoluminescence spectra. For pure film samples of short band tail, thermalization of excited carriers in extended states gives a Gaussian-like photoluminescence spectrum. Rutherford backscattering spectrometry and d.c. conductivity measurement are also performed and analysis on these data conforms the above proposed model.