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A direct Z-scheme heterojunction via decorating Ag3PO4 quantum dots on SnS2 nanosheets results in highly selective and efficient solar-driven CO2-to-CO photoreduction.

The present investigation mainly addresses the open circuit voltage (Voc) issue in kesterite based Cu2ZnSn(S,Se)4 solar cells by simply introducing alkali metal fluoride nanolayers (~ several nm NaF, or LiF) to lower the work functions of the front ITO contacts without conventional hole-blocking ZnO layers. Kelvin probe measurements confirmed that the work function of the front ITO decreases from 4.82 to 3.39 and 3.65 eV for NaF and LiF, respectively, resulting in beneficial band alignment for electron collection and/or hole blocking on top electrodes. Moreover, a 10.4% power conversion efficiency (~ 11.5% in the cell effective area) CZTSSe cell with improved Voc of up to 90 mV has been attained. This demonstration may provide a new direction of further boosting the performance of copper chalcogenide based solar cells as well.

Cu2ZnSnS4 (CZTS) nanoparticles (NPs) were prepared in a one-step microwave-assisted synthesis using a mixture of trioctylphosphine oxide (TOPO) and oleylamine (OLA) as solvent. The reaction medium was optimized by varying the TOPO and OLA ratios to control the CZTS NPs formation. The synthesized CZTS NPs were characterized by X-ray diffraction, Raman spectroscopy, UV–vis spectroscopy, and transmission electron microscopy techniques. High quality CZTS NPs with composition of Cu1.8Zn1.4SnS3.6, optimum size distribution in the range of 22±4 nm and band gap of around 1.5 eV were obtained using microwave assisted synthesis method with OLA:TOPO (1:1) as co-solvent. In the microwave assisted process, the reaction temperature and time has been reduced significantly to 165 °C and 10 min respectively, as compared with other wet chemical solvothermal hot injection/ surfactant based methods. Finally, CZTSSe solar cell fabricated from the selenized microwave-assisted CZTS NPs yielded an efficiency of 4.48%; therefore, the low cost of synthesis of this high quality CZTS NPs ink and the capability of spraying for large solar cell area is very attractive.

In this study, we proposed a 4-step selenization process for the RF-sputtered Cu–Zn/Sn metallic stack to prepare Cu2ZnSnSe4 (CZTSe) absorber. We applied a pre-heating treatment for the metal stack under vacuum prior to the selenization, which plays an important role to form a well inter mixed alloy with relatively smooth thin film morphology. The nucleation temperatures were controlled precisely from 150 °C to 500 °C during 4-step selenization to avoid the formation of secondary phases and to improve the crystal quality of CZTSe with a greater homogeneity in the composition. The formation of various phases during each step in 4-step selenization process were studied by X-ray Diffraction, Raman analysis and we proposed a possible reaction mechanism of the CZTSe formation with binary and ternary compounds as intermediates. We also performed optical analysis, including Uv–Visible absorption and low temperature photoluminescence, and scanning transmission electron microscope analysis for the CZTSe samples. Finally, an efficiency of 5.8% CZTSe solar cell is fabricated with an open circuit voltage of 370 mV, short circuit current of 31.99 mA/cm2, and a fill factor of 48.3%.

We synthesized a bismuth-rich bismuth sulfide (Bi2+xS3) to improve the electrical conductivity. A percolated composite was obtained by mixing Bi2+xS3 with commercial Bi2S3 so that the other thermoelectric parameters were not compromised. The Bi2+xS3 acted as a conductive percolating channel within the Bi2S3 matrix. This percolation approach retained the high Seebeck coefficient of the Bi2S3 matrix while improving the electrical conductivity. A dimensionless figure of merit (zT) up to five times that of the pure Bi2S3 sample was achieved.

The development of earth-abundant and efficient electrocatalysts for the hydrogen evolution reaction (HER) is one of the keys to success for future green energy systems using hydrogen fuel. Nanostructuring of electrocatalysts is a promising way to enhance their electrocatalytic performance in the HER. In this study, pure pyrite-type beaded stream-like cobalt diselenide (CoSe2) nanoneedles are directly formed on flexible titanium foils through treating a cobalt oxide (Co3O4) nanoneedle array template with selenium vapor. The beaded stream-like CoSe2 nanoneedle electrode can drive the HER at a current density of 20 mA cm−2 with a small overpotential of 125 mV. Moreover, the beaded stream-like CoSe2 nanoneedle electrode remains stable in an acidic electrolyte for 3000 cycles and continuously splits water over a period of 18 hours. The enhanced electrochemical activity is facilitated by the unique three-dimensional hierarchical structure, the highly accessible surface active sites, the improved charge transfer kinetics and the highly attractive force between water and the surface of the nanoneedles that exceeds the surface tension of water.

A non-toxic sol–gel spin coating approach is one of the attractive routes to achieve high atom economy, good quality Cu2ZnSnS4 (CZTS) thin films. In this paper, we introduce 1,3-dimethyl-2-imadazolidinone as a solvent for the preparation of highly viscous, homogeneous, nontoxic CZTS ink that eliminates the need for the use of additional binders or additives to disperse the precursors. In addition, we further report the annealing of the spin coated CZTS thin film in 6% diluted H2S gas with an externally supplied tin and sulfur environment to suppress the loss of tin from the thin-film surface and to enhance the device performance. CZTS grain sizes greater than 0.7 μm have been achieved with no detectable presence of carbon rich layers or layers containing fine grain sizes at the Mo/CZTS interface. An efficiency of 5.67% for the champion device fabricated here has been achieved with an open circuit voltage of 0.58 V, a short current density of 18.48 mA cm−2, and a fill factor of 53.14%.

Germanium antimony telluride (GeSbTe or GST), a popular material in optical and non-volatile memory devices, attracted renewed attention due to its potential for thermoelectric applications. In this study, we have employed a two-stage engineering process to enhance the thermoelectric properties of GeTe-rich GeSbTe. First, we introduced vacancy into the material by modifying the germanium content without disrupting the crystal structure. This influenced the electronic properties of the GeTe-rich GeSbTe and improved the overall dimensionless figure of merit, zT, from 0.7 to 1.1. Second, we rapidly cooled the material after annealing, further enhancing the zT value from 1.1 to 1.48 – one of the highest values reported for this material. In-depth studies suggest that disorder in the crystal structure was created via rapid cooling enhanced phonon scattering and effectively reduced the thermal conductivity, which, in turn, enhanced the thermoelectric performance.

One of the key challenges in artificial photosynthesis is to design a photocatalyst that can bind and activate the CO

A new multifunctional blue-emitting terfluorene derivative ( TFDPA ) featured with triphenylamine groups for hole-transportation and long alkyl chains for solution processability on the conjugation inert bridge centers was reported. TFDPA can give homogeneous thin film by solution process and exhibits high hole mobility ( μ h ≈ 10 −3 cm 2 V −1 s −1 ) and suitable HOMO for hole injection. Particularly, TFDPA performs efficient deep-blue emission with high quantum yield (∼100% in solution, 43% in thin film) and suitable triplet energy ( E T = 2.28 eV), making solution-processed OLED devices of using TFDPA as blue emitter and as host for iridium-containing phosphorescent dopants feasible. The solution-processed nondoped blue OLED device gives saturated deep-blue electroluminescence [CIE = (0.17, 0.07)] with EQE of 2.7%. TFDPA -hosted electrophosphorescent devices performed with EQE of 6.5% for yellow [(Bt) 2 Ir(acac)], 9.3% of orange [Ir(2–phq) 3 ], and 6.9% of red [(Mpq) 2 Ir(acac)], respectively. In addition, with careful control on the doping concentration of [(Bt) 2 Ir(acac)], a solution-processed fluorescence–phosphorescence hybrided two-color-based WOLED with EQE of 3.6% and CIE coordinate of (0.38, 0.33) was successfully achieved.

Rapid formation of radial p–n junctions on electroless-etched silicon nanowires (SiNWs) was successfully demonstrated. With a low-cost objective, a homemade nonhazardous diffusion source of high phosphor concentration annealed at a small thermal budget was used. The SiNW solar cell, with Au electrodes, has shown a power conversion efficiency of 8.41%, which is higher by 30% compared with its planar counterpart. The SiNW solar cell incorporates an inherent antireflection property, reduced diffusion length requirement, and broad-band spectral quantum efficiency. The evidence of a successful radial p–n junction formation in the NWs has been revealed through the help of a conducting atomic force microscope (AFM) scanning for the photogenerated currents on the fractured surfaces of the NWs. The demonstrated radial junction fabrication technique is believed to reduce the cost of production and promote widespread use of them.

Systematic investigations of photoelectrochemical behavior between Au nano-particle modified n- and p-GaN were reported in this study. With Au nanoparticles sputtered on the surface, strong Fermi level pinning caused by the creation of metal induced gap states alters the behavior of electrolyte/GaN interface. Under illumination, the photocurrent of p-GaN at zero bias exhibited 25 times enhancement, whereas that of n-GaN showed slight decrease. The overall hydrogen generation efficiency of p-GaN in HCl solution was increased from 0.02% to around 0.59%. The enhancement can be attributed to the different energy shift of the surface band edge at the interface according to the doping of GaN. Keywords: Photoelectrochemistry, Water splitting, GaN, Gold nanoparticle, Hydrogen generation

A simple growth technique capable of growing a variety of zinc oxide (ZnO) nanostructures with record growth rates of 25 μm/s is demonstrated. Visible lengths of ZnO nanowires, nanotubes, comb-like and pencil-like nanostructures could be grown by employing a focused CO2 laser-assisted heating of a sintered ZnO rod in ambient air, in few seconds. For the first time, the growth process of nanowires was videographed, in-situ, on an optical microscope. It showed that ZnO was evaporated and presumably decomposed into Zn and oxygen by laser heating, reforming ZnO nanostructures at places with suitable growth temperatures. Analysis on the representative nanowires shows a rectangular cross-section, with a [0 0 0 1] growth direction. With CO2 laser heating replacing furnace heating used conventionally, and using different reactants and forming gases, this method could be easily adopted for other semiconducting inorganic nanostructures in addition to ZnO.

The optical properties of tetrodotoxin (TTX), a scarce toxin with anesthetic properties, were studied using nanoparticle arrays-assisted surface-enhanced Raman scattering (SERS). The nanoparticles arrays were fabricated using nanosphere lithography and a metallic lift-off process to control the particle size, shape, and spacing in the arrays. Using density functional methods, the Raman spectrum of TTX was also calculated with Gaussian03 software. The main peaks of the spectrum are originated from the vibration of the NH2 molecule group. In the SERS experiment, we were able to measure the Raman spectrum with a TTX concentration as less as 0.9 ng/mL. This sensitivity is comparable to that from high performance liquid chromatography.

[*] Dr. K. H. Chen, M. H. Wu, W. C. Chen Institute of Atomic and Molecular Sciences, Academia Sinica No. 1, Sec. 4, Roosevelt Rd., Taipei 106 (Taiwan) E-mail: chenkh@pub.iams.sinica.edu.tw Dr. L. C. Chen, Dr. C. H. Chen, Dr. K. H. Chen Center for Condensed Matter Sciences, National Taiwan University No. 1, Sec. 4, Roosevelt Rd., Taipei 106 (Taiwan) E-mail: chenlc@ntu.edu.tw C. H. Lin, Prof. J. H. Lee Graduate Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University No. 1, Sec. 4, Roosevelt Rd., Taipei 106 (Taiwan)

A set of In 2 Se 3 films was grown on (1 1 1) Si substrate with AlN buffer by metalorganic chemical vapor deposition (MOCVD) using H 2 Se as the metalogramic precursors for Se. The In 2 Se 3 films on (1 1 1) Si substrate were pinhole-free with homogeneous and lamellar structures. It was found that by properly controlling the substrate temperatures, single-phase γ-In 2 Se 3 films with fairly good optical properties can be well fabricated. Photoluminescence spectra of single-phase γ-In 2 Se 3 show exciton emissions at 2.140 eV at 10 K. The band gap of single-phase γ-In 2 Se 3 at room temperature is estimated at 1.943 eV.

This paper introduces a photo-assisted atomic force microscope (AFM) local oxidation technique which is capable of producing highly smooth oxide patterns with heights reaching several tens of nanometres on both n- and p-types of GaN (and in principle on most semiconductors) without the use of chemicals. The novel methodology relies on UV illumination of the surface of the substrate during conventional AFM local oxidation. A low 1.2 V threshold voltage for n-type GaN was obtained, which can be explained by UV photo-generation of excess electron–hole pairs in the substrate near the junction, thereby reducing the electric field required to drive carrier flow through the tip–sample Schottky barrier. It was demonstrated that the presence or absence of light alone was sufficient to switch the growth of the oxide on or off. The photo-assisted AFM oxidation technique is of immediate interest to the semiconductor industry for the fabrication of GaN-based complementary metal–oxide–semiconductor devices and nanodevices, improves chances for AFM-type data storage, and presents new degrees of freedom for process control technique.

Local oxidations of InN and GaN were realized using an atomic force microscope (AFM). InN was oxidized easily by traditional AFM oxidation to ~40?nm oxide height. The same AFM methodology was applied to GaN, which exhibited only minimum oxidation even at 10?V and high humidity. However, further experimentation led to successful nano-oxidation of GaN by two different techniques. In the first technique, a ~10?nm gold film was deposited by sputtering onto the clean GaN substrate. The gold film reduced the AFM oxidation circuit resistance and increased the oxyanion driving current (oxidation current), thereby allowing AFM oxidation with heights reaching ~25?nm at a humidity of 70%, but with a danger of gold contamination of the oxide. To eliminate this danger, additional experiments were performed in which the gold film on the GaN was removed in a small area, after which AFM oxidation was successfully performed in the area with gold removed with oxidation heights comparable to those of the gold-covered GaN. The techniques in this study make possible fast, chemical-free and contamination-free AFM nano-oxidation for metal?oxide?semiconductor field effect transistors based on two important nitrides.

Well-aligned nanotip arrays were fabricated via a self-masking dry etching technique in an electron cyclotron resonance (ECR) plasma process. Nanotip arrays of Si , poly silicon, GaN , GaP , sapphire, and Al were fabricated. Simultaneous etching of the substrate and formation of silicon carbide ( SiC ) protecting caps are attributed to the nanotip formation. The ultra-low turn-on field for electron field emission as well as the surface enhanced Raman Spectroscopic study of Si nanotips is also demonstrated.

Well-aligned nanotip arrays were fabricated by electron cyclotron resonance (ECR) plasma process using gas mixtures of silane, methane, argon, and hydrogen. The resultant tips have nanoscale apexes...

One of the key challenges in artificial photosynthesis is to design a photocatalyst that can bind and activate the CO2 molecule with the smallest possible activation energy and produce selective hydrocarbon products. In this contribution, a combined experimental and computational study on Ni-nanocluster loaded black TiO2 (Ni/TiO2[Vo] ) with built-in dual active sites for selective photocatalytic CO2 conversion is reported. The findings reveal that the synergistic effects of deliberately induced Ni nanoclusters and oxygen vacancies provide (1) energetically stable CO2 binding sites with the lowest activation energy (0.08 eV), (2) highly reactive sites, (3) a fast electron transfer pathway, and (4) enhanced light harvesting by lowering the bandgap. The Ni/TiO2[Vo] photocatalyst has demonstrated highly selective and enhanced photocatalytic activity of more than 18 times higher solar fuel production than the commercial TiO2 (P-25). An insight into the mechanisms of interfacial charge transfer and product formation is explored.

The conversion of atmospheric carbon dioxide (CO2) into solar fuels by imitation of a natural photosynthesis using only water vapor and sunlight for energy has attracted widespread attention recently. One of the key challenges is to design a photocatalyst that can bind and activate the CO2 molecule with smallest possible activation energy and produce selective solar fuel production. In this contribution, we report a combined experimental and computational studies on Ni nanocluster loaded black TiO2 (Ni@TiO2[Vo]) with built-in dual active sites for selective photocatalytic CO2 conversion. Our findings reveal that, the synergistic effect of deliberately induced unsaturated Ni nanocluster and oxygen vacancies provide (1) energetically stable CO2 binding sites with lowest activation energy (0.08eV), (2) highly reactive sites, (3) fast electron transfer pathway, (4) enhanced light harvesting by lowering the band gap. The Ni@TiO2[Vo] photocatalyst has demonstrated highly selective and enhanced photocatalytic activity of more than 18 times higher solar fuel production than the commercial TiO2 (P-25). An insight to the mechanism of interfacial charge transfer and product formation mechanism are explored. The proposed approach to adsorb and activate CO2 molecule on dual active sites can be applied to design other catalysts for photocatalytic CO2 reduction.

We report the simultaneous electrochemical detection of dopamine (DA), uric acid (UA) and ascorbic acid (AA) on three dimensional (3D) unmodified ‘as-grown’ epitaxial graphene nanowall arrays (EGNWs). The 3D few layer EGNWs, unlike the 2D planar graphene, offers an abundance of vertically oriented nano-graphitic-edges that exhibit fast electron-transfer kinetics and high electroactive surface area to geometrical area (EAA/GA≈134%), as evident from the Fe(CN)63−/4− redox kinetic study. The hexagonal sp2-C domains, on the basal plane of the EGNWs, facilitate efficient adsorption via spontaneous π–π interaction with the aromatic rings in DA and UA. Such affinity together with the fast electron kinetics enables simultaneous and unambiguous identification of individual AA, DA and UA from their mixture. The unique edge dominant EGNWs result in an unprecedented low limit of detection (experimental) of 0.033 nM and highest sensitivity of 476.2 µA/µM/cm2, for UA, which are orders of magnitude higher than comparable existing reports. A reaction kinetics based modeling of the edge-oriented 3D EGNW system is proposed to illustrate the superior electro-activity for bio-sensing applications.

Indium nitride (InN) film was successfully grown on sapphire (0 0 0 1) substrate using a simple resistive heated metalorganic chemical vapor deposition (MOCVD) system by utilizing a pyrolytic boron nitride (PBN) heater with a precise temperature control within 1°C. Structural studies and optical property measurement by scanning electron microscope (SEM), X-ray diffraction (XRD), Raman spectroscopy and photoluminescence of the films were presented. An improved epitaxy was achieved in films grown at a high substrate temperature (540°C). The room temperature photoluminescence spectrum of the InN film showed a strong peak at 1.8 eV. Further high resolution transmission electron microscopy (HRTEM) investigation revealed some inclusion of nanocrystalline phase, which might be responsible for the strong photoluminescence signal.

Electron beam induced formation of carbon nanorods was realized in situ under high resolution scanning electron microscopy (HRSEM). When a CVD deposited carbon nanotube sample was irradiated with an electron beam in an HRSEM, progressive etching of the sample, expanding of the nanotubes, and formation of additional nanorods have been observed. Transmission electron microscopy study revealed typical nanorods of 20 nm in diameter and with amorphous structure. The direct observation of the synthesis of nanorods under electron microscopy manifests the possibility of nano-machining of such nanomaterials using electron beams. This may lead to future integration and networking of nanostructures of different functionalities, which is crucial for nanotechnology.

In this study, we use X-ray diffraction and Raman scattering techniques to study the structure and phase transition of lithium sodium niobate crystal. Raman scattering experiments on these ceramics have been performed in the temperature range from 300 to 77 K. All the spectral lines in the Raman spectra can be assigned as the transitional modes of cations Li+ and Na+ and the internal modes of NbO6 octahedron. From the evolution of the spectral line in the Raman spectra at various temperatures, we conclude that phase transition of all three crystals of x=0.1,0.12,0.15 occurs over a temperature range from 200 to 180 K on the cooling process and at 280 K in the heating process. The phase transition of other compositions is also similar to the pure sodium niobate, but the transition temperatures are different. The lattice structure at room temperature was also studied by X-ray diffraction. The study shows that the crystal demonstrates a single phase of orthorhombic structure for x≤0.15 , two phases above x=0.2 , and then changes to LiNbO3 structure until x=0.9 . These results agree well with the results from x-dependent Raman scattering experiments. From temperature-dependent Raman scattering study, we have shown that the Raman spectra of LixNa1−xNbO3 exhibit a phase transition below room temperature that is similar to that observed in NaNbO3. The transitional motion of the Na+ cation may be involved in the structural phase transition of lithium sodium niobate.

The magnetic-phase diagram of the system is studied by specific-heat, magnetic-susceptibility and electrical resistance measurements (x = 0.1, 0.2, 0.3, 0.6, 0.8, 0.9, 1.0). The susceptibility was measured by zero-field-cooling (ZFC) and field-cooling (FC) methods. If x 0.1, starts to deviate from at . This suggests a spin-glass state below . In the range , the specific-heat measurements of show multiple magnetic phase transitions. There are three phase transitions in and . Except for x = 0, below 30 K, electrical resistivity increases continuously up to a temperature of 10 K. The drastic drop of below 10 K is due to magnetic ordering. The multiple phase transitions of are not observed in the resistance measurements. However, the slope of of changes at , which further supports multiple phase transitions in .

We report the first demonstration of cobalt phosphate (Co-Pi)-assisted molybdenum-doped zinc oxide nanorods (Zn(1-x)Mo(x)O NRs) as visible-light-sensitive photofunctional electrodes to fundamentally improve the performance of ZnO NRs for photoelectrochemical (PEC) water splitting. A maximum photoconversion efficiency as high as 1.05% was achieved, at a photocurrent density of 1.4 mA cm(-2). More importantly, in addition to achieve the maximum incident photon to current conversion efficiency (IPCE) value of 86%, it could be noted that the IPCE of Zn(1-x)Mo(x)O photoanodes under monochromatic illumination (450 nm) is up to 12%. Our PEC performances are comparable to those of many oxide-based photoanodes in recent reports. The improvement in photoactivity of PEC water splitting may be attributed to the enhanced visible-light absorption, increased charge-carrier densities, and improved interfacial charge-transfer kinetics due to the combined effect of molybdenum incorporation and Co-Pi modification, contributing to photocatalysis. The new design of constructing highly photoactive Co-Pi-assisted Zn(1-x)Mo(x)O photoanodes enriches knowledge on doping and advances the development of high-efficiency photoelectrodes in the solar-hydrogen field.

The built-in electric fields in a MBE grown δ-doped GaAs homojunction have been investigated by the techniques of photoreflectance and phase suppression. Two Franz-Keldysh oscillation features originating from two different fields in the structure superimpose with each other in the photoreflectance spectrum. By properly selecting the reference phase of the lock-in amplifier, one of the features can be suppressed, thus enabling us to determine the electric fields from two different regions. We have demonstrated that only two PR spectra, in-phase and out-phase components, are needed to find the phase angle which suppresses one of the features. The electric field in the top layer is 3.5 ± 0.2 × 10 5 V cm −1 , which is in good agreement with theoretical calculation. The electric field in the buffer layer is 1.2 ± 0.1 × 10 4 V cm −1 , which suggests the existence of interface states at the buffer/substrate interface.

We report magnetic-susceptibility, specific-heat, and electrical resistivity measurements of ${\mathrm{Pr}}_{2}{\mathrm{CuSi}}_{3}.$ This compound exhibits ferromagnetism at ${T}_{c}=10$ K and upon further cooling shows spin-glass properties below about ${T}_{f}=8$ K. The coefficient of the term linear in temperature in the specific heat \ensuremath{\gamma} of ${\mathrm{Pr}}_{2}{\mathrm{CuSi}}_{3}$ is 0.505 ${\mathrm{J}\mathrm{}\mathrm{mol}}^{\mathrm{\ensuremath{-}}1}{\mathrm{}\mathrm{K}}^{\mathrm{\ensuremath{-}}2}$ which is much larger than that of normal metals. This compound might be classified as a nonmagnetic atom-disorder spin glass.

We have investigated the effects of annealing on the uranium intermetallic compound UAu 2 Si 2 . The physical properties of both the annealed and as-cast samples were studied from 5 to 300 K. Both the resistivity ϱ ( T ) and low-field magnetic susceptibility χ ( T ) of the as-cast sample show anomalies at 18 K and at 82 K; whereas the heat capacity C ( T ) shows only an anomaly at 20.5 K. The ϱ ( T ) and χ ( T ) of the annealed sample displays a low-temperature anomaly around 20 K; and a complex magnetic phase transition between 48 K and 55 K was observed. A sharp anomaly of C ( T ) in the annealed UAu 2 Si 2 can be seen at 21.5 K. The annealed sample shows Fermi-liquid behavior below 10 K with a coefficient of the quadratic term in the temperature dependence of the resistivity being 11.5 μΩ-cm K −2 . The low temperature electronic specific heat coefficient γ of the annealed sample is 92 mJ mol K −2 . We infer that UAu 2 Si 2 has heavy-fermion behavior with ferromagnetic ground state, which is an uncommon behavior in the uranium intermetallic compounds.

We present magnetic, electric and thermal properties of SmCuAl3. An antiferromagnetic transition is observed at 7 K. The hysteresis loops exhibit both ferromagnetic and antiferromagnetic properties at low temperature. SmCuAl3 displays large specific heat C(T) values at low temperatures. The specific heat C(T) is interpreted as a result of the small crystal-field splitting.

A new method that fits the whole temperature response of a heat-pulse calorimeter for heat capacity is developed. Analyzing the thermal response of a heat-pulse calorimeter on a model that was used by the relaxation method, the authors derived some useful relations and further utilized the numeric method of the general linear least squares to determine the heat capacity of a sample. Absolute accuracy of the proposed method was verified by determining the heat capacity of a 0.249 76 g copper sample (purity 99.999%) on a self-designed and fully automated calorimetric system from 4.5 to 80 K. Comparing the result with the literature, the deviation in average was 1.2% from 4.5 to 20 K and 2.0% from 20 to 80 K. It is found that the proposed method is capable of measuring heat capacity regardless if the sample is adiabatically or nonadiabatically isolated. The size of the specimen is not critical for the application of the method and the temperature range of measurement can be expanded. It also deals with the τ...

Temperature dependences of the specific heat, electrical resistivity and magnetic susceptibility of single-phased AlB2-type compound Ce2CuSi3 as well as its nonmagnetic counterpart La2CuSi3 are reported. La2CuSi3 is Pauli paramagnetic whereas Ce2CuSi3 shows complex magnetic properties. An antiferromagnetic ordering at 2.1 k is observed by low field (50 Oe) susceptibility measurement on Ce2CuSi3. Magnetic susceptibility measured under 2000 Oe, however, appears to be saturated below 2.1 K. Heat capacity measurement down to 4.5 K reveals an upturn in C(T) of Ce2CuSi3 which could be correlated with magnetic transition at 2.1 K. The electronic specific heat in Ce2CuSi3 is obtained, indicating an enhanced temperature-independent γ of 76mJK−2 mol−1 Ce. A negative contribution to the enhanced γ that could be due to spin fluctuation, is observed. The resistivity data of Ce2CuSi3 shows the typical behavior of a Kondo compound, which might be responsible for the enhanced effective mass.

The applications of TiO2/graphene nanocomposite as a compact layer for ZnO-based dye-sensitized solar cell (DSSC) have been studied. It was shown that the role of bifunctional graphene flakes in TiO2 compact layer not only suppressed the electron recombination between indium-doped tin oxide and electrolyte, but also reduced the resistance of compact layer. In addition, compared to typical compact layers, TiO2/graphene nanocomposite without blocking effect in optical transmittance could further boost the power conversion efficiency in DSSC. TiO2/graphene nanocomposite was demonstrated the potential to be an alternative of compact layer to typical dense TiO2 for ZnO-based DSSCs.

Magnetic properties of UPd 2 Ge 2 have been studied at 4.2–300 K and in an applied field up to 55 kG. The magnetic state of the compound is different in three temperature regions. At 140 K UPd 2 Ge 2 transforms from para- to antiferromagnetic state, and in H ext = 0 the material is antiferromagnetic in the range 140-80 K. The strong field H ext > 14 kG can induce a ferromagnetic component in this region. Below 80 K a small ferromagnetic component appears spontaneously, and it is strongly enhanced by the applied field. In the range 80-20 K the magnetic state can be considered as a coexistence of antiferromagnetic and ferromagnetic states, or as a ferrimagnetic state. In high H ext the antiferromagnetic state can be suppressed and ferromagnetic phase dominates. Below 20 K the ferromagnetic component is small and the antiferromagnetic phase dominates.

Silicon nanotips with tip diameter and height measuring 1 nm and 1 μm, respectively, and density in the range of 109–3×1011 cm−2, were fabricated monolithically from silicon wafers by electron cyclotron resonance plasma etching technique at a temperature of 200 °C. Field emission current densities of 3.0 mA/cm2 at an applied field of ∼1.0 V/μm was obtained from these silicon nanotips. High-resolution transmission electron microscope and Auger electron spectroscopy analyses concluded that the nanotips are composed of monolithic silicon and nanometer-size SiC cap at the top. A 0.35 V/μm turn-on field to draw a 10 μA/cm2 current density was demonstrated, which is much lower than other reported materials. The excellent field emission property demonstrated by these nanotips, which were fabricated by a process integrable to the existing silicon device technology at low temperatures, is a step forward in achieving low-power field emission displays and vacuum electronic devices.

We present magnetic, electric and thermal properties of UPd2Ge2. In UPd2Ge2, a paramagnetic to antiferromagnetic transition is observed at 140 K. Below 100 K, the magnetization oscillates with temperature and the hysteresis loops exhibit ferromagnetic properties. The magnetic properties of UPd2Ge2 can be understood by incommensurate phases.

This letter reports the synthesis of indium nitride (InN) nanowires on gold-patterned silicon substrates in a controlled manner using a method involving thermal evaporation of pure indium. The locations of these InN nanowires were controlled by depositing gold in desired areas on the substrates. Scanning electron microscopy and transmission electron microscopy investigations showed that the InN nanowires are single crystals with diameters ranging from 40 to 80 nm, and lengths up to 5 μm. Energy dispersive x-ray spectrometry showed that the ends of the nanowires are composed primarily of Au, and the rest of the nanowires were InN with no detectable Au incorporations. The Raman spectra showed peaks at 445, 489, and 579 cm−1, which are attributed to the A1(transverse optical), E2, and A1(longitudinal optical) phonon modes of the wurtzite InN structure, respectively. Photoluminescence spectra of the InN nanowires showed a strong broad emission peak at 1.85 eV.

We introduce a platform, comprised of silver nanoparticle decorated silica nanowires (SiONWs) dispersed on fused quartz substrates, for high sensitivity surface-enhanced Raman scattering (SERS) measurements using both frontal (through the analytes) and back-face (through the transparent substrate) excitation. Quasi-quantitative SERS performances on the specialized substrate, vis-a-vis a silver deposited bare fused quartz plate, showed: (i) the suitability of the Ag modified SiONW substrate for frontal as well as back-face excitation; (ii) a wider detection range with high sensitivity to Rhodamine 6G; and (iii) good underwater metal-oxide adhesion of the specialized substrates. Capable of surviving ultrasonic cleaning, the substrate introduced is one of the few reusable low-cost Ag-based nanostructured SERS substrates, requiring only a simple silver reload process (the silver mirror reaction).

Defect inspection plays a critical role in thin film transistor liquid crystal display (TFT-LCD) manufacture, and has received much attention in the field of automatic optical inspection (AOI). Previously, most focus was put on the problems of macro-scale Mura-defect detection in cell process, but it has recently been found that the defects which substantially influence the yield rate of LCD panels are actually those in the TFT array process, which is the first process in TFT-LCD manufacturing. Defect inspection in TFT array process is therefore considered a difficult task. This paper presents a novel inspection scheme based on kernel principal component analysis (KPCA) algorithm, which is a nonlinear version of the well-known PCA algorithm. The inspection scheme can not only detect the defects from the images captured from the surface of LCD panels, but also recognize the types of the detected defects automatically. Results, based on real images provided by a LCD manufacturer in Taiwan, indicate that the KPCA-based defect inspection scheme is able to achieve a defect detection rate of over 99% and a high defect classification rate of over 96% when the imbalanced support vector machine (ISVM) with 2-norm soft margin is employed as the classifier. More importantly, the inspection time is less than 1 s per input image.

Silica nanowires decorated with silver nanocrystals on quartz substrate were employed as SERS substrates. The substrates features reusablity, backside measurement, and wide measuring range from >0.1M to near single molecule detection, tested on Rhodamine 6G.

The optical properties of tetrodotoxin (TTX), a scarce toxin with anesthetic properties, were studied using nanoparticle arrays-assisted surface-enhanced Raman scattering (SERS). The nanoparticles arrays were fabricated using nanosphere lithography and a metallic lift-off process to control the particle size, shape, and spacing in the arrays. In the SERS experiment, we were able to measure the Raman spectrum with a TTX concentration as less as 0.9 ng/mL. This sensitivity is comparable to that from high performance liquid chromatography.

Nonlinear optical absorption of InN epitaxial films in the range of 720-790 nm were investigated by Z-scan measurements. The optical absorption cross-sections of the InN films were estimated, and the values are found in good agreement with band-filling model.

The technique of photoreflectance was employed to investigate the interband transitions (E0, E0 + Δ0, E1 and E1 + Δ1) of GaSb as well as their temperature dependence over the range of 83 to 300 K. The parameters which describe the temperature dependence in terms of the Varshni expression were also evaluated. Through examination of the spectral lineshapes, it was concluded that band to band transition is the main mechanism of E0 + Δ0 transition, while excitonic transition is responsible for E1 and E1 + Δ1 transitions. Both Raman and photo- reflectance spectra were also used to study the damage resulting from ion implantation, as well as the induced “healing” caused by a range of differing thermal annealing temperatures and/or time. Both techniques provide a convenient, powerful and contactless tool in investigating the above-mentioned studies.