Search

This article aims at exploring translation competence (TC) from the perspective of higher-order thinking skills (HOTS), and developing a HOTS-oriented TC model accordingly. The underlying assumption is that the translation competence needed to solve ill-structured translation problems is highly integrated HOTS in essence. Based on this assumption, a framework for HOTS-oriented TC is presented, using features from the PACTE group’s TC model, and combining it with HOTS-specific features. Subsequently, a HOTS-oriented TC model is constructed, which consists of three interrelated parts: HOTS (i.e., translation problem-solving ability, translation decision-making ability, translation creative-thinking ability, and translation critical thinking ability); translation knowledge, and translation thinking dispositions. Additionally, two other assumptions are made as scaffolding to support our HOTS-oriented TC model. Finally, implications for TC studies and translation pedagogy are provided.

As the portal of plants, rhizosphere microorganisms play an essential role in controlling the species, transformation, and bioavailability of heavy metals, yet the potential passivation mechanism is still unclear. In this study, two heavy metal resistant and growth-promoting rhizosphere bacteria were screened, and their mechanisms in dealing with external stress and immobilizing heavy metal were explored. The results showed that heavy metals inhibited the ability of Pseudomonas sp. H13 and Brevundomonas sp. H16 to promote plant growth, but stimulated the production of extracellular polysaccharides and inorganic labile sulfide, and enhanced biofilm formation, thereby significantly improved the removal efficiency of Cu2+, Zn2+, Cd2+, and Pb2+. Compared with H16, the biofilm of H13 disintegrated rapidly in the later stage, so more metal ions were adsorbed on the planktonic cells. The C–OH and P O groups related to polysaccharides play a crucial role in heavy metal adsorption, and the immobilization mechanism of the planktonic cell is mainly ion exchange and group complex, but for H16, intracellular enrichment cannot be ignored. Functional group complexes played a dominant role in biofilm, and the immobilized heavy metals were more difficult to release into the environment. This study highlighted the potential application prospects of biofilm bacteria in heavy metal remediation and explained the reactive barrier of rhizosphere bacteria to heavy metals.

The off-state leakage (I off ) properties of the AlGaN/GaN high electron mobility field-effect transistors (HEMTs) was analyzed by fabricating metal-semiconductor (MES)-HEMTs and metal-insulator-semiconductor (MIS)-HEMTs. The experimental results show that off-state gate leakage (I g-off ) for MES-HEMTs is larger than the corresponding off-state drain leakage (I d-off ), which suggests that I d-off is a branch of I g-off . I off by the ion implantation isolation is nearly an order of magnitude lower than that by the ICP-etching isolation, which suggests the side wall under the gate electrode caused by the etching isolation can increase the I g-off and planar structure formed by ion implantation isolation can suppress gate leakage efficiently. A linear relationship of I d-off and I g-off for MES-HEMTs with the gate length implies that the gate area is proportional to the I g-off . This indicates that the edge effect on the I g-off can be negligible. At the same time, the estimated current with L g of 0 μm is not zero, indicating the gate metal covered isolation region participates in conduction. MIS-HEMTs can suppress I off significantly, indicating that the existence of the insulation layer can not only reduce the leakage current from effective gate electrode, but also suppress the leakage current from gate metal-covered isolation area.

The equipment which has not been operated, maintain, and switched beyond a specified interval is called three-no equipment. As the three-no equipment will cause some danger power network operation, a quick survey technology is proposed in this paper. The technique simulates artificial retrieval in the third subarea of the secondary security protection system. The technique works in a self-adaptive, divided-period, no-repeat way. Meanwhile, new equipment doesn't need to access and original network settings don't need to change. After the last action time of equipment is obtained by the computer in a short time, the difference between the last active time of equipment and the current time is used to take advice for check operation. An artificial equipment survey can be taken by computer automatically. The results of the actual case also show that the proposed technique is effective.

As the reuse of agricultural and forestry waste, leaf biochar can remove heavy metals from the environment, avoid secondary pollution while creating economic and environmental benefits for society. Our research presents an innovative approach to preparing efficient adsorbents for the first time using natural bioaugmentation (decay) pretreatment of fallen leaves biomass followed by pyrolysis to biochar. Compared with the pristine biochar derived from leaf (BC), the natural bioaugmentation biochar (NBC) characterization showed that the enhancement of microstructure increased the specific surface area, the change of surface composition increased the oxygen-containing functional groups and active adsorption sites, and the increase of porosity improved the mass transfer rate, resulting in a 2-fold increase of Cd(II) fixation capacity. Langmuir and pseudo-second-order models demonstrated that Cd(II) adhered to the NBC core sites through chemical reaction sites by a spontaneous process. The release of nutrients and changes in soil pH after NBC addition to contaminated soil enhanced the stability of the ecosystem and promoted plant growth. This study illustrates for the first time the great potential of natural bioaugmentation (decay) leaf-derived biochar for heavy metal adsorption and provides a new idea to explore the reuse of cellulose waste resources.

Heavy metal pollution restricts the intensification of land and endangers human health through the food chain. Surface adsorption of heavy metals by soil natural minerals affects their mobility and biotoxicity, yet little is known about the fate of heavy metals after microorganisms affect the surface structure of minerals. Our study shows that ureolytic microbes corrode the surface of phosphate minerals through carbonate modification without changing their crystal structure but significantly enhancing their specific surface area. Compared with natural phosphate rock (PR), the concave surface of the flora-phosphate rock (FPR) exposes more Ca2+ exchange sites, more active functional groups, and more straightforward to release phosphates that co-precipitate with Cd2+, resulting in an approximately tenfold increase in Cd2+ adsorption. The adsorption of Cd2+ by FPR is a spontaneous endothermic single-layer adsorption, which can quickly remove Cd2+ in wastewater. FPR can also obviously change the pH of the soil by releasing phosphate to increase the stabilization effect of Cd2+. These results provide a sustainable approach to developing novel, cost-effective minerals for environmental remediation and contribute to understanding the function and role of microorganisms in immobilizing heavy metals at the mineral interface.

The causes and processes of personal accidents in the distribution network have extremely complicated factors. Due to the lack of scientific understanding of the basic laws of safety risks, personal accidents are repeatedly happened, leading to vicious electric shock accidents. In addition, if faults cannot be handled quickly and in a timely manner, ground faults can easily cause device overvoltage, causing equipment burnout and even causing fire accidents. Single phase grounding fault and power failure will reduce the reliability of power supply and directly affect industrial production and people’s living standards. This article is mainly based on the international advanced safety management concept. By identifying the influencing factors of single-phase grounding in distribution networks and closely integrated with power grid enterprises actual field operations, using the “5M safety risk factor” theory to analyze the personal safety and equipment safety influencing factors in power supply operations, extract six major influence factors that have a greater impact on the distribution network operation and personal safety. Based on the above points, a quantitative assessment model, index, and method system for single-phase fault processing based on security protection are proposed to effectively improve the person and device safety in power grid companies. Pre-control ability has very important practical value and promotion significance. It can provide a strong reference for the primary and secondary equipment and structure design of the new distribution network and the adjustment of the operating mode of the distribution network in operation, and effectively guide the operation and maintenance of the distribution network.

This research demonstrates a p-GaN gate AlGaN/GaN high electron mobility transistor with beta-Ga2O3 back barrier and investigates the electric characteristics of the device. The simulated results show that the threshold voltage of the device will increase with the use of the Ga2O3 back barrier. Moreover, the off-state leakage current level is one order of magnitude lower than the device without back barrier, which can be attributed to the rise of the conduction band diagram in the buffer layer and the decrease of the electron current density released by ionized accept traps. In addition, the impacts of the beta-Ga2O3 back barrier thickness are investigated, and the results show that with increasing Ga2O3 thicknesses, the threshold voltage of the device decreases while the leakage current of the device increases.

To improve the performance of the conventional p-GaN gate AlGaN/GaN high electron mobility transistors (HEMTs), we propose an improved design for e-mode AlGaN/GaN HEMT with a gate stack β-Ga2O3/p-GaN structure. The simulated results show that the proposed device increases the threshold voltage and the gate breakdown voltage in comparison with the conventional p-GaN gate HEMT due to the use of the β-Ga2O3 layer, which has an additional β-Ga2O3/p-GaN heterojunction and decreases the strength of electric field in the gate region. Moreover, the proposed device exhibits a lower off-state leakage current, which can be attributed to the less donor ionized density. In addition, the impacts of the β-Ga2O3 layer thickness are investigated. There is a trade-off between β-Ga2O3 layer thickness and the performance of the proposed device, including threshold voltage, gate breakdown, and saturation drain current.

This research investigates electrical properties of E-mode AlGaN/GaN HEMTs with n-type β-Ga2O3/p-GaN gate stack under different gate work functions of 4.6, 5.1 and 5.7 eV, respectively. The simulated results show that the device with gate work function of 5.7 eV exhibits the largest threshold voltage of 2.8 V while having the lowest saturation drain current of 0.15 A mm−1, which can be ascribed to the device having the highest Schottky barrier, leading to the least electrons collected at the AlGaN/GaN interface. Moreover, the device with gate work function of 5.7 eV shows the largest gate breakdown voltage as well as the lowest off-state gate leakage, which can be attributed to the least strength of electric field in the Ga2O3 layer. Additionally, the Fowler–Nordheim equation was used to study the mechanisms of off-state leakage.

GaN-based light emitting diodes (LEDs) have been grown by metalorganic chemical vapor deposition on Si(111) substrate with and without 3C-SiC intermediate layer (IL). Structural property has been characterized by means of atomic force microscope, X-ray diffraction, and transmission electron microscope measurements. It has been revealed that a significant improvement in crystalline quality of GaN and superlattice epitaxial layers can be achieved by using 3C-SiC as IL. Regarding of electrical and optical characteristics, it is clearly observed that the LEDs with its IL have a smaller leakage current and higher light output power comparing with the LEDs without IL. The better performance of LEDs using 3C-SiC IL can be contributed to both of the improvements in epitaxial layers quality and light extraction efficiency. As a consequence, in terms of optical property, a double enhancement of the light output power and external quantum efficiency has been realized.

Electric vehicle charging station is the infrastructure to provide electric energy for electric vehicles (EV). Reasonable location of charging station is of great significance to promote the popularization of EVs. Firstly, the ownership of EVs in the selected area is forecasted. According to the ownership and driving characteristics of various types of EVs, the total charging demand of EVs and the charging demand of each network node are obtained. Secondly, the location model of charging station is established to minimize the sum of operation and maintenance costs of charging station and user loss costs. Finally, weighted Voronoi diagram and adaptive particle swarm optimization are used. The results show that this method can optimize the annual average comprehensive cost of charging station. Graphic user interface (GUI) is designed to display the result of location, which makes the location scheme more intuitive.

The influence of quantum-well (QW) number on electroluminescence properties was investigated and compared with that of AlN electron blocking layer (EBL) for deep ultraviolet light-emitting diodes (DUV-LEDs). By increasing the QW number, the band emission around 265 nm increased and the parasitic peak around 304 nm was suppressed. From the theoretical calculation, the electron current overflowing to the p-type layer was decreased as the QW number increased under the same injection. Correspondingly, the light output power also increased. The increment of output power from 5 QWs to 10 QWs was less than that from 10 QWs to 40 QWs, which was very different from what has been reported for blue and near-UV LEDs. The parasitic peak was still observed even when the QW number increased to 40. However, it can be suppressed efficiently by 1 nm AlN EBL for LEDs with 5 QWs. The simulation showed that the insertion of a thin EBL increased the barrier height for electron overflow and the electron current in p-type layers decreased significantly. The results contributed to the understanding of behavior of electron overflow in DUV-LEDs.

This paper investigates the performance of AlGaN/gallium nitride (GaN) MIS high electron mobility transistors (MIS-HEMTs). The gate dielectric layer and the surface passivation layer are formed by the low-pressure chemical vapor deposition (LPCVD) Si3N4. The LPCVD-Si3N4 MIS-HEMTs exhibit a high breakdown voltage (BV) of 1162 V at $I_{\mathrm{ DS}}= 1~\mu \text{A}$ /mm, a low OFF-state leakage of $7.7 \times 10^{-12}$ A/mm, and an excellent ON/OFF-current ratio of $\sim 10^{11}$ . Compared with the static ON-resistance of 2.88 $\text{m}\Omega \cdot \textrm {cm}^{2}$ , the dynamic ON-resistance after high OFF-state drain bias stress at 600 V only increases to 4.89 $\text{m}\Omega \cdot \textrm {cm}^{2}$ . The power device figure of ${\mathrm{ merit}} = \textrm {BV}^{{\vphantom {R^{l}}{2}}}/R_{{{\mathrm{\scriptscriptstyle ON}.{\mathrm{ sp}}}}}$ is calculated to be 469 $\textrm {MW}\cdot \textrm {cm}^{-2}$ . The LPCVD-Si3N4/GaN interface state density is in the range of (1.4–5.3) $\times 10^{{\vphantom {R^{l}}{13}}}$ eV $^{-1}$ cm $^{-2}$ extracted by the conventional conductance method. Finally, the gate insulator degradation of GaN-based MIS-HEMTs is analyzed by time-dependent dielectric breakdown test. The lifetime is extrapolated to 0.01% of failures after ten years at 300 K by fitting the data with a power law to a gate voltage of 10.1 V.

The influence of quantum-well (QW) width on electroluminescence properties of AlGaN deep ultraviolet light-emitting diodes (DUV LEDs) was studied at different temperatures. The maximum external quantum efficiency (EQE) ratios of LED with 3.5 nm QW to that with 2 nm increased from 6.8 at room temperature (RT) to 8.2 at 5 K. However, the ratios for LED with 3.5 nm QW to that with 5 nm QW decreased from 4.8 at RT to 1.6 at 5 K. The different changes of EQE ratios were attributed to the decrease of non-radiative recombination and the increase of volume of the active region. From theoretical analysis, the LED with 2-nm wells had a shallowest barrier for electron overflow due to the quantum-confined effect, whereas the LED with 5-nm wells showed the least overlap of electron and hole due to the large internal field. Therefore, the LED with 3.5 nm QW had the highest maximum EQE at the same temperature. As temperature decreased, the current for maximum EQE decreased for all the LEDs, which was believed to be due to the increase of electron which overflowed out of QWs and the decrease of hole concentration. The results were helpful for understanding the combination of polarization effect and electron overflow in DUV LEDs.

The thermal stability of F ion-implanted isolated AlGaN/GaN heterostructures was investigated, with B ion-implanted isolation shown for comparison. The sheet resistance of as-implanted samples with F ions was lower than that with B ions due to enhanced hopping conduction. The leakage current for both implanted samples initially decreased and then increased with increases in post-annealing temperature, indicating a damage-induced isolation mechanism. Leakage reached a minimum value after 400oC annealing, which was over 108 times lower than the saturated current ( I sat) of the as-grown structure, suggesting a successful isolation. After relatively high-temperature annealing, the leakage for F implantation showed a small change, whereas that for B implantation showed significant increase, suggesting that F-implanted isolation exhibited excellent thermal stability. Leakage current measured at 300oC for F ion-implantation was 103 times lower than the I sat of the as-grown structure, demonstrating that F ion isolation was applicable up to 300oC. Differences in current and activation energy ( E a) between the high-resistance GaN layer and F or B ion-implanted samples indicated that the leakage current originated from the region above the high-resistance GaN layer. Variation in E a revealed that the optimal contributing states for conduction changed with operating temperature, annealing temperature, and ion species.

AlGaN/GaN metal–insulator–semiconductor high-electron-mobility transistors (MIS-HEMTs) on a silicon substrate were fabricated with silicon oxide as a gate dielectric by sputtering deposition and electron-beam (EB) evaporation. It was found that the oxide deposition method and conditions have great influences on the electrical properties of HEMTs. The low sputtering temperature or oxygen introduction at higher temperature results in a positive equivalent charge density at the oxide/AlGaN interface (Nequ), which induces a negative shift of threshold voltage and an increase in both sheet electron density (ns) and drain current density (ID). Contrarily, EB deposition makes a negative Nequ, resulting in reduced ns and ID. Besides, the maximum transconductance (gm-max) decreases and the off-state gate current density (IG-off) increases for oxides at lower sputtering temperature compared with that at higher temperature, possibly due to a more serious sputter-induced damage and much larger Nequ at lower sputtering temperature. At high sputtering temperature, IG-off decreases by two orders of magnitude compared to that without oxygen, which indicates that oxygen introduction and partial pressure depression of argon decreases the sputter-induced damage significantly. IG-off for EB-evaporated samples is lower by orders of magnitude than that of sputtered ones, possibly attributed to the lower damage of EB evaporation to the barrier layer surface.

An AlGaN/GaN metal-insulator-semiconductor high electron mobility transistor (MIS-HEMT) on Si substrate was obtained with 18 nm silicon nitride (Si3N4) grown by low-pressure chemical vapour deposition (LPCVD) as the gate insulator. The D-mode MIS-HEMT shows a high I-dss of 16.8 A at V-g = 3 V, a high breakdown voltage (BV) of 600 V and a low-specific on-resistance of 2.3 m Omega.cm(2). The power device figure of merit (FOM = BV2/R-on,R-sp) is calculated as 157 MW.cm(-2). The good insulation effects of LPCVD-Si3N4 were also demonstrated by the low gate leakage current of 154 nA at V-ds = 600 V and V-gs = -14 V. Furthermore, an E-mode device was realised by a low-voltage silicon metal-oxide-semiconductor field-effect transistor in series; the V-th was determined to be 2.6 V. The high I-dss, low-specific on-resistance, high BV and positive V-th show the potential and advantages of GaN MIS-HEMTs for power switching applications.

An AlGaN/GaN metal-oxide semiconductor (MOS) high-electron mobility transistor (HEMT) on silicon substrate was obtained with 8 nm Al2O3 gate dielectric films grown using atomic layer deposition. The MOS-HEMT shows a low specific on-resistance of 0.57 Omega.mm(2), a large maximum saturate drain current of 12.5 A and a minimal threshold hysteresis of 0.05 V. Low specific on-resistance, large maximum saturate drain current and minimal threshold hysteresis show that the fabricated MOS-HEMT is very suitable for power switching applications.

A porphyrin ‘‘Mille-Feuilles” photo-electrode is fabricated layer-by-layer by deposition of anionic [zinc meso-tetrakis(p-sulfonato phenyl) porphyrin]4- (ZnTPPS4−) and positively charged polypeptides on a 11-mercaptoundecanoic acid-modified gold electrode to form a photoactive film. This work demonstrates that it is possible to form 3D structures having regularly spaced layers of redox molecules. UV–visible spectra of the multilayer films display the characteristic absorption bands of the porphyrins and the absorbance increases linearly with the number of bilayers. The cyclic voltammetric response of the films in contact with 1,2-dichloroethane (DCE) varies from that of a modified electrode to that of a supported liquid film. Under illumination, a large photocurrent response for oxygen reduction with a maximum for a 5-bilayer film is observed.

Titanium oxide (Ti(O)) xerogel films functionalized by protoporphyrin IX (PPIX) and ferrocene carboxylic acid (FCA) were deposited on indium tin oxide (ITO) electrodes following a sol–gel synthesis. PPIX and FCA were first complexed to titanium oxide precursors, which were then subjected to hydrolysis to obtain a homogenous Ti(O) polymeric network gel doped with PPIX and FCA. The Ti(O) film cast on the ITO electrode has been characterized by UV–Vis absorption, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy and cyclic voltammetry. Illumination of the PPIX doped Ti(O) films on the ITO electrode immersed in aqueous electrolytes onsets photoinduced electron transfer reactions, and a cathodic photocurrent was observed in most cases. This photocurrent response was investigated in detail using a kinetic model. Preliminary investigations of oxygen reduction, lithium and proton insertion into the Ti(O) film have also been carried out.

A thin aqueous film prepared by layer-by-layer assembly of oppositely charged polypeptides on 4-aminobenzoic acid modified porous reticulated vitreous carbon (RVC) electrodes was used with the aim of forming a 3D-ITIES. The film containing a redox mediator, namely ferri/ferrocyanide, was placed in contact with an organic solution 1,2-dichloroethane containing an electron acceptor, 7,7′,8,8′-tetracyanoquinodimethane (TCNQ). The reduction of TCNQ was studied to characterise the electrochemical properties of the supported ITIES. When the film is dye-sensitised, a reduction photocurrent was observed upon illumination. This photocurrent was an order of magnitude larger than that measured on a planar electrode.

Micro/nano-composite TiO2 porous films are prepared in a nutshell by the electro-hydrodynamic (EHD) method, and are applied to dye sensitized solar cells (DSSCs) successfully. Considering that micro/nano-composite structures based on the EHD technique are better for the filling of ionic liquid and quasi-solid-state electrolytes than liquid state electrolytes, a fill factor (ff) of 78.9% and a total photoelectric conversion efficiency (?) of 6.4% for ionic liquid electrolyte and an ff of 75.3% and an ? of 5.3% for quasi-solid-state electrolyte are obtained. Moreover, this kind of composite hierarchical structure may be of benefit for light collection because of strong light scattering. In order to obtain optimized devices, we probe into the influence of adding an amount of polymer on the photovoltaic performance, and find that by changing the concentration of the polymer during the EHD process the specific surface area of the films changes, which leads to different photovoltaic behaviour of solar cells.

Solid-state dye-sensitized solar cells (DSSCs) were fabricated using 4-dodecylbenzenesulfonic acid-doped polyaniline (PANI−DBSA) blended with LiI and 4-tert-butylpyridine (tBP) as hole conductors. The introduction of LiI and tBP into the polymer improves the photovoltaic behavior of solid-state DSSCs significantly. Compared with a DSSC only using PANI−DBSA as a hole conductor, one with LiI added at the optimum concentration gives an overall solar-to-electric energy conversion efficiency (ηe) increased by a factor of 5.13, whereas one with both LiI and tBP added at the optimum concentrations gives an ηe increased by a factor of 6.6 and a maximum value of the incident photon to current conversion efficiency increased 100%. In addition, the photovoltage and photocurrent transients are determined to investigate the influence of LiI and tBP in PANI−DBSA on the photovoltaic performance of solid-state DSSCs.

This paper describes the preparation and properties of porous carbon by a technique which consists of mixing a carbon precursor (furfuryl resin and furfural alcohol), a pore-forming agent and a solvent (glycol), polymerizing the resin mixture, and pyrolyzing the hybrid of resin and glycol. The properties of porous carbons have been systematically investigated as a function of composition and heat treatment, with emphasis on understanding and controlling their morphology and pore size distribution. The results seem to indicate that by varying the ratios of the constituents in the polymer system, porous carbons with a wide variation in pore size distribution and morphology can be obtained. Three types of morphologies were observed: interconnected carbon with secondary spherical pores, discrete carbon particulates, and a crosslinked carbon network. Porous carbons with a very narrow pore size distribution have been obtained and the average pore size was controlled between 5 and 0.008 μm. The microstructure of porous carbon formed as a result of phase separation of resin-rich phase and glycol-rich phase, rather than a result of the pyrolysis process. Heat treatment had little effect on the properties of the porous carbons.

The electroluminescent (EL) properties of AlGaN deep ultraviolet light-emitting diodes (DUV LEDs) are improved by increasing the Al composition of the barriers in the active region and decreasing the thickness of the p-cladding layer, respectively. Under 1.5 A cm−2 direct current (DC) injection, the intensity of the parasitic peak around 320 nm is 43 times more than that of the band-to-band peak at 265 nm in the LED with a lower Al-composition (55%) barrier, while the parasitic peak is suppressed efficiently in the LED with a higher Al-composition (70%) barrier. By increasing the Al composition from 55% to 70% and decreasing the thickness of the p-cladding layer from 25 to 10 nm, the light output power of the DUV LEDs improved 305 and 61 times at DC injection of 1.5 and 15 A cm−2, respectively. The band structure and the vertical conductivity were calculated. It was found that the increase of Al composition not only enhanced the barrier height for quantum wells but also decreased the barrier for hole injection. On the other hand, the thickness decrease of p-type cladding layers to some extent resulted in the improvement of both hole concentration and vertical tunneling conductivity. All of these contributed to the improvement of the EL properties of the LEDs.

The transfer properties of the ionic species involved in the Williamson ether synthesis by phase-transfer catalysis were investigated using electrochemical techniques developed for the study of polarised liquid/liquid interfaces. This approach allows the measurement of the apparent partition coefficients of the transferring species. From these data, it is proposed that the role of the phase-transfer catalyst salt in the reaction mechanism is to establish a Galvani distribution potential difference between the two phases which in turn acts as the driving force for transferring the reactive aqueous ions to the organic phase.

Novel carboxylated oligothiophenes with different thiophene units were designed and synthesized as photosensitizers in dye-sensitized solar cells (DSSCs) for efficient opto-electric materials. The introduction of -COOH into thiophene molecules can lead to a red shift of UV-visible absorption, increase light-harvesting efficiency, and enhance photoinduced charge transport by forming efficient covalent bonds to the substrate surface. A red shift of the absorption spectrum of oligothiophene is also achieved by the increase in the number of thiophene units. The DSSCs based on the oligomers have excellent photovoltaic performances. Under 100 mW cm - 2 irradiation a short-circuit current of 10.57 mA cm - 2 and an overall energy conversion efficiency of 3.36% is achieved when pentathiophene dicarboxylated acid was used as a sensitizer. The incident photo-to-current conversion efficiency (IPCE) has a maximum as high as 80%. In addition, photovoltage and photocurrent transients show that slow charge recombination in DSSCs is important for efficient charge separation and excellent photoelectric conversion properties of the oligomers. These initial and promising results suggest that carboxylated oligothiophenes are efficient photosensitizers.

The influence of polyanilines (PANIs) as hole conductors on the photovoltaic behaviors of dye-sensitized solar cells is studied. The current-voltage (I-V) characteristics and the incident photon to current conversion efficiency (IPCE) curves of the devices are determined as the function of different conductivities and morphologies of PANIs. The results show that the conductivity of PANIs affects the performance of the devices greatly, and PANI with the intermediate conductivity value (3.5 S/cm) is optimum. In addition, the effects of both the film formation property and the cluster size of polyanilines on the photovoltaic behaviors of the devices are also discussed.

Normally-off AlGaN/GaN metal-oxide-semiconductor high electron mobility transistors (MOS-HEMTs) on Si substrate were fabricated with the fluorine-based treatment technique. By employing a 20nm-thick Al2O3 gate dielectric deposited by atomic layer deposition, the fabricated MOS-HEMT exhibits a large positive threshold voltage of + 3.5V, a maximum gate input voltage of 15V, a maximum saturate drain current of 5.3A and an off-state breakdown voltage of 402V. The high threshold voltage and the large input voltage swing is expected to improve the electromagnetic interference immunity and safety of AlGaN/GaN MOS-HEMT power switches.

Influence of thickness and growth condition of AlN spacer on electrical properties of AlGaN/AlN/GaN high-electron-mobility transistors (HEMTs) grown on 4-in. Si substrate was studied. Hall measurements show the mobility of AlGaN/AlN/GaN heterostructure varies with different thickness of AlN spacer and a narrow high-mobility window was obtained. The surface and structure studies indicate that both increasing growth temperature and lowering pressure benefit the quality of AlN and AlGaN, which leads to improvement of Hall mobility, except the temperature higher than that of GaN growth. Drain current–voltage (Ids–Vds) characteristics of such HEMTs exhibit the maximum current density (Imax) and tranconductance (gmax) have the similar trend with the mobility due to different interface roughness and piezoelectric field induced by part relaxation of tensile strain in AlGaN grown on AlN. The optimum properties of HEMT (Imax = 807 mA/mm, gmax = 221 mS/mm) are obtained when 1 nm AlN spacer grown at 1130 °C and 100 Torr.

not Available.