Thermodynamics of charged Brans–Dicke AdS black holes

It is well known that in four dimensions, black hole solution of the Brans–Dicke–Maxwell equations is just the Reissner–Nordstrom solution with a constant scalar field. However, in n4 dimensions, the solution is not yet the (n+1)-dimensional Reissner–Nordstrom solution and the scalar field is not a constant in general. In this Letter, by applying a conformal transformation to the dilaton gravity theory, we derive a class of black hole solutions in (n+1)-dimensional (n4) Brans–Dicke–Maxwell theory in the background of anti-de Sitter universe. We obtain the conserved and thermodynamic quantities through the use of the Euclidean action method. We find a Smarr-type formula and perform a stability analysis in the canonical ensemble. We find that the solution is thermally stable for small α, while for large α the system has an unstable phase, where α is a coupling constant between the scalar and matter field.     

Degradation behavior and products of malathion and chlorpyrifos spiked in apple juice by ultrasonic treatment

Apple juice (13 °Brix) spiked with malathion and chlorpyrifos (2–3 mg l⁻¹ of each compound) was treated under different ultrasonic irradiations. Results showed that ultrasonic treatment was effective for the degradation of malathion and chlorpyrifos in apple juice, and the output power and treatment time significantly influenced the degradation of both pesticides (p < 0.05). The maximum degradations were achieved for malathion (41.7%) and chlorpyrifos (82.0%) after the ultrasonic treatment at 500 W for 120 min. The degradation kinetics of both pesticides were fitted to the first-order kinetics model well (R²  0.90). The kinetics parameters indicated that chlorpyrifos was much more labile to ultrasonic treatment than malathion. Furthermore, malaoxon and chlorpyrifos oxon were identified as the degradation products of malathion and chlorpyrifos by gas chromatography–mass spectrometry (GC–MS), respectively. The oxidation pathway through the hydroxyl radical attack on the PS bond of pesticide molecules was proposed.     

Understanding of a-Si:H(p)/c-Si(n) heterojunction solar cell through analysis of cells with point-contacted p/n junction

We fabricated point-contacted a-Si:H(p)/c-Si(n) heterojunction solar cells using patterned SiO₂ and investigated their electrical properties using the light current–voltage (I–V) curve and Suns-V_oc measurements. The light I–V curves showed bias-dependent changes according to the applied voltage in the point-contacted cells, especially in the samples with a long distance between the point-contacted junctions. The Suns-V_oc measurements showed that the bias-dependence of the light I–V curves did not originate from the recombination in the SiO₂/Si or a-Si:H(p)/c-Si(n) interface, but from the series resistances. It is possible to explain the bias-dependent light I–V curve in terms of the conductivity of a-Si:H(p) and difference in the electrical contact properties between a-Si:H(p), ZnO and c-Si(n). These results mean that the electrical properties of the a-Si:H(p) layer and the contact properties with this layer are also critical to obtain a high J_sc and fill factor in n-type based Si heterojunction solar cells.     

Double-quantum NMR spectroscopy of P species submitted to very large CSAs

We introduce an original pulse sequence, , which is a block super-cycled sequence employing as basic element a π pulse sandwiched by ‘window’ intervals. This homonuclear dipolar recoupling method allows the efficient excitation of double-quantum coherences between spin-1/2 nuclei submitted to very large chemical shift anisotropy. We demonstrate that this technique can be employed in double-quantum ↔ single-quantum ³¹P homonuclear correlation experiment at high magnetic field (B₀  14 T) and high MAS frequencies (ν_R  30 kHz). The performances of are compared to those of the double-quantum recoupling methods, such as BABA and bracketed fp-RFDR, which were already employed at fast MAS rates. The sequence displays a higher robustness to CSA and offset than the other existing techniques.     

Effect of p-μc-Si1−xOx:H layer on performance of hetero-junction microcrystalline silicon solar cells under light concentration

Preparation of p-type hydrogenated microcrystalline silicon oxide thin films (p-μc-Si_1−xO_x:H) by 13.56 MHz RF-PECVD method for use as a p-layer of hetero-junction μc-Si:H solar cells is presented. We investigated effects of wide-gap p-μc-Si_1−xO_x:H layer on the performance of hetero-junction μc-Si:H solar cells under various light intensity. We observed that a wide-gap p-μc-Si_1−xO_x:H was effective in improving the open-circuit voltage (V_oc) of the solar cells. We also confirmed that the V_oc logarithmically increased with increasing light intensity, and the enhancement of V_oc became larger with increasing band gap of p-layer. These results indicate that wide-gap p-μc-Si_1−xO_x:H is a promising material for use as window layer in hetero-junction μc-Si:H solar cells.     

Design and fabrication of infrared detectors based on lattice-matched InAs0.91Sb0.09 on GaSb

The InAs_0.91Sb_0.09 ternary compound grown on GaSb substrates is a promising alloy for light detection in the 3–5 μm window. Nevertheless, its development is still limited due to difficulties occurring during device processing. For example, the use of dry etching for the processing of InAs_0.91Sb_0.09 p–i–n photovoltaïc detectors induces a strong leakage current along the mesa edge. In this letter, we show an improvement of the R₀A characteristic by several orders of magnitude at low temperature by using an ion beam etching (IBE) followed by a wet chemical etching. This optimized and reliable device processing allows us to demonstrate that the detector performance is actually limited by the diffusion current of holes. Finally, we discuss the ability of an n-type barrier made of the InAs/AlSb super-lattice to prevent hole diffusion and to improve the R₀A characteristic of these detectors.     

Antireflective properties of disordered Si SWSs with hydrophobic surface by thermally dewetted Pt nanomask patterns for Si-based solar cells

We have theoretically and experimentally investigated the antireflective properties of the disordered subwavelength structures (SWSs) with a hydrophobic surface on silicon (Si) substrates by an inductively coupled plasma (ICP) etching in SiCl₄/Ar plasma using thermally dewetted platinum (Pt) nanopatterns as etch masks for Si-based solar cells. The Pt thin films on the SiO₂/Si surface were properly changed into the optimized dot-like nanopatterns via the thermal dewetting by rapid thermal annealing process. The antireflection properties were definitely affected by the etched profile of SWSs which can be controlled by the conditions of etching process. For the tapered Si SWS with a high average height of 724 ± 78 nm, the reflectance was significantly reduced below 5% over a wide wavelength range of 350-1030 nm, leading to a relatively low solar weighted reflectance of 2.6%. The structure exhibited reflectances less than 14.8% at wide incident angles of 8-70°. The hydrophobic surface with a water contact angle of 113.2° was obtained. For Si SWSs, the antireflective properties were also analyzed by the rigorous coupled-wave analysis simulation. These calculated results showed similar behavior to the experimental results.     

Pulsed laser synthesis of titanium silicides using a Q-Switched Nd: Glass laser

Titanium films 120 nm thick deposited on single-crystalline silicon (c-Si) as well as poly-Si/SiO₂/c-Si substrates were subjected to Nd: glass laser irradiation. Laser fluences of 1,1.5, and 2 J/cm² were used at the pulse duration of 30 ns. From RBS analysis it follows that on c-Si substrate titanium suicide is formed using one pulse of 1.5 J/cm² energy density. On the substrate with surface overlayers lower fluence (1 J/cm²) was sufficient. Under these conditions the sheet resistance of the samples decreased from the initial value 5 / to 2–3 /. The smaller threshold density of energy for suicide formation in Ti/polySi/SiO₂/c-Si structure is shown to be a consequence of the SiO₂ underlayer, which is a poorer heat conductor than silicon. The experimental results of the suicide synthesis are in semi-quantitative accordance with the numerical computations of the temperature vs time evolution and depth temperature distribution in our samples.     

Influence of H2O/DEZ ratio on LPCVD ZnO:B films for application in a-Si:H/μc-Si:H tandem solar cells

In this study, boron doped zinc oxide (ZnO:B) films were prepared at different water to diethyl zinc (H₂O/DEZ) flow ratios from 0.6 to 1.4 by a low pressure chemical vapor deposition (LPCVD) technique. It is found that the morphology of ZnO:B films varies from small leaf-like to pyramidal surface structures with the increasing H₂O/DEZ flow ratio. The rough ZnO:B films deposited at a relatively H₂O/DEZ flow ratio such as 1.2 or 1.4 show a high haze value of up to 28 % at 600 nm and $\mathrm{a} (11\overline{2}0)$ preferential crystallographic orientation. All ZnO:B films were applied in hydrogenated amorphous silicon/microcrystalline silicon tandem solar cells (a-Si:H/μc-Si:H) as front electrodes. The efficiency of the solar cells increases with the increasing H₂O/DEZ flow ratio, which is attributed to a high spectral response mainly in the long-wavelength range and the consequent enhancement of short-circuit current. A high-efficiency a-Si:H/μc-Si:H tandem solar cell of 10 % was achieved. The H₂O/DEZ ratio is an important process parameter to tune the material properties of LPCVD ZnO:B films and the performances of corresponding silicon thin film solar cells.     

Interrelation between electronic structure and interatomic distances for compounds

The heat capacity was studied for LaMn₂Si₂, La_0.75Y_0.25Mn₂Si₂, La_0.7Y_0.3Mn₂Si₂, YMn₂Si₂ and LaFe₂Si₂ isostructural intermetallic compounds in the temperature range 1.8–360 K. The electronic, magnetic and lattice contributions to the heat capacity of the compounds were determined and analyzed. The interrelation was found between values of the electronic contribution to the heat capacity (density of states at the Fermi level) and crystal lattice parameters of R(Mn,Fe,Ni)₂Si₂ compounds. The electronic contribution and the density of states at Fermi level increase with increasing lattice parameters of the compounds. The change of interlayer Mn–Mn exchange interactions with change of Y concentration in La_1-xY_xMn₂Si₂ compounds is not accompanied by considerable changes in the electronic contribution to the heat capacity and density of states at the Fermi level. The performed analysis of the magnetic contribution shows that no essential differences exist between the behavior of the heat capacity of the compounds with d_Mn–Mnd_c and with d_Mn–Mn<d_c upon various types of the magnetic phase transitions.     

Improvement of solar cell efficiency by applying Si3N4 nanopattern on glass substrate

A cylindrical Si₃N₄ nanopattern whose heights was 200 nm was fabricated on a glass substrate, and an aluminum-doped zinc oxide (AZO) layer was grown on the nanopatterned glass substrate. The nanopattern was applied to an amorphous silicon solar cell in order to increase the light-scattering effect, thus enhancing the efficiency of the solar cell. The reflectance of the solar cell on the Si₃N₄ nanopattern decreased and its absorption increased. Compared to a flat substrate, the short-circuit current density (J_sc) and conversion efficiency of a solar cell on the Si₃N₄ nanopatterned substrate were improved by 17.9% and 24.2%, respectively, as determined from solar simulator measurements.     

Improvement in electrical and photovoltaic properties of a-Si/c-Si heterojunction with slanted nano-columnar amorphous silicon thin films for photovoltaic applications

The flat a-Si and slanted nanocolumnar (S-nC) a-Si thin films were prepared on c-Si and corning glass substrates by e-beam physical vapor deposition (EB-PVD) technique. The structural properties of all the grown thin films were determined by X-Ray Diffraction (XRD) analysis and Raman spectroscopy. Surface and cross-sectional morphology of a-Si/c-Si and S-nC a-Si/c-Si heterojunctions were investigated by Field Emission Scanning Electron Microscopy (FE-SEM). Sculptured thin films demonstrate potential for significant nanoscale applications in the area of thin film technology. The electrical and photovoltaic properties of these heterojunctions have been investigated by means of dc current–voltage (I–V) measurements at room temperature in dark and light conditions. The S-nC STFs' performance has been found to be improvable on changing the morphology of the thin film. We have found that, the porous morphology of this structure improves the photosensitivity features in photovoltaic devices and solar cell technology. We gained a high open voltage value, such as 900 mV in S-nC a-Si/c-Si thin film, without any doping process.     

The enhanced conductivity and stability of AZO thin films with a TiO2 buffer layer

Aluminum doped zinc oxide (AZO) films were substitutes of the SnO₂:F films on soda lime glass substrate in the amorphous thin-film solar cells due to good properties and low cost. In order to improve properties of AZO films, the TiO₂ buffer layer had been introduced. AZO films with and without TiO₂ buffer layer were deposited on soda lime glass substrates by r.f. magnetron sputtering. Subsequently, one group samples were annealed in vacuum (0.1 Pa) at 500 °C for 120 s using the RTA system, and the influence of TiO₂ thickness on the properties of AZO films had been discussed. The XRD measurement results showed that all the films had a preferentially oriented (0 0 2) peak, and the intensity of (0 0 2) peak had been enhanced for the AZO films with TiO₂ buffer layer. The resistivity of TiO₂ (3.0 nm)/AZO double-layer film is 4.76×10⁻⁴ Ω cm with the maximum figure merit of 1.92×10⁻² Ω⁻¹, and the resistivity has a remarkable 28.7% decrease comparing with that of the single AZO film. The carrier scattering mechanism of TiO₂ (3.0 nm)/AZO double-layer film had been described by Hall measurement in different temperatures. The average transmittance of all the films exceeded 92% in the visible spectrum. Another group samples were heat treated in the quartz tube in air atmosphere, and the effect of TiO₂ thickness on thermal stability of AZO films had been discussed.     

Room-temperature deposition of transparent conductive Al-doped ZnO thin films using low energy ion bombardment

Al-doped zinc oxide (AZO) films are prepared on quartz substrates by dual-ion-beam sputtering deposition at room temperature (∼25°C). An assisting argon ion beam (ion energy E _i =0–300 eV) directly bombards the substrate surface to modify the properties of AZO films. The effects of assisted-ion beam energy on the characteristics of AZO films were investigated in terms of X-ray diffraction, atomic force microscopy, Raman spectra, Hall measurement and optical transmittance. With increasing assisting-ion beam bombardment, AZO films have a strong improved crystalline quality and increased radiation damage such as oxygen vacancies and zinc interstitials. The lowest resistivity of 4.9×10⁻³Ω cm and highest transmittance of above 85% in the visible region were obtained under the assisting-ion beam energy 200 eV. It was found that the bandgap of AZO films increased from 3.37 to 3.59 eV when the assisting-ion beam energy increased from 0 to 300 eV.     

Hybrid system of iron porphyrin on aminosilanized c-Si

Adsorption of iron porphyrin (Fe^IIITPPS₄) Fe(III)meso-tetra(4-sulfonatophenyl) porphine on aminosilanized surface of crystalline Si (c-Si) was investigated. Formation of nanometric structures of Fe^IIITPPS₄ on c-Si, the surface of which has been modified by various silanization procedures, was studied. Aqueous, ethanol and acetone solutions of 3-aminopropyltrietoxysilane (APTES) were prepared for deposition on c-Si by spinning or immersion techniques. Smooth homogeneous APTES films of thickness 100–500 nm were produced by multiple spin coating procedure. Thin APTES films of thickness 2.5 nm were fabricated by dipping technique followed by washing procedure. Hybrid system of Fe^IIITPPS₄/APTES/Si was prepared from a drop of Fe^IIITPPS₄ aqueous solution put on aminosilanized Si surface or by dipping the Si wafer in Fe^IIITPPS₄ aqueous solution. Nanostructures of size 50–250 nm were formed along with large rings of Ø50–100 μm which have been observed at chemisorption of highly concentrated (1 mM) Fe^IIITPPS₄ aqueous solution. Spectroscopic ellipsometry was used to characterize the APTES layer and to investigate the aggregation state of Fe^IIITPPS₄. The studies provided allowed one to presume that covalent bonds were formed between amino-groups of APTES and functional groups of sulfonic acid in porphyrin leading to immobilization of Fe^IIITPPS₄ on Si substrate.     

PECVD制备AZO（ZnO:Al）透明导电薄膜

采用PECVD（等离子体增强化学气相沉积）工艺在普通玻璃和Si基上制备出了方块电阻低至89 Ω,可见光透过率高达79%,对基体附着力强的多晶态的AZO（ZnO:Al）薄膜.采用PECVD法制备AZO薄膜是一种有益的尝试,AZO透明导电薄膜不仅具有与ITO（透明导电薄膜,如In₂O₃:Sn）可比拟的光电特性,而且价格低廉、无毒,在氢等离子体环境中更稳定,所获结果对实际工艺条件的选择具有一定借鉴作用和参考价值. 关键词： AZO（ZnO:Al） 等离子体增强化学气相沉积 透明导电薄膜     

Calculation of axial optical forces exerted on medium-sized particles by optical trap

Optical trapping has become an efficient technique of trapping and manipulating micrometer and sub-micrometer dimension particles. Particles in the range between the applicable regime of ray optics theory (ROT) and the Rayleigh regime (so-called medium-sized particles) are focused on. By using ROT and the generalized Lorenz–Mie theory (GLMT), axial optical forces and their dependences on particle sizes and beam waists are presented. Furthermore, by comparing the numerical results of these two theories, the applicability of the GLMT to particles of arbitrary size and the limit of ROT in the region of small particles are analyzed. A new criterion of the applicable region of ROT is obtained, i.e. the relative particle size β=2πa/λ20, where a is the particle radius and λ is the wavelength of light. The theoretical results will be of great help to the design and optimization of the most efficient optical trap.     

Heterojunctions of TiO2 nanoparticle film and c-Si with different Fermi level positions

The photovoltaic properties of heterojunctions of titanium dioxide (TiO₂) nanoparticle films with single crystal silicon (c-Si) substrates with different Fermi level (E _f) positions were studied. The TiO₂ nanoparticles of rutile and anatase structures were studied without any sintering process. To clarify the photovoltaic properties, the characteristics of the heterojunction solar cells of TiO₂ nanoparticle films with p-Si and n-Si substrates were investigated, where several Si substrates with different resistivities were used. The I–V characteristics of p-Si/TiO₂ heterojunction showed the rectifying behavior and photovoltaic effect. The n-Si/TiO₂ heterojunction also showed good rectifying characteristics; however, the conversion efficiency was extremely lower than that of p-Si/TiO₂ heterojunction. The conversion efficiencies of various Si/TiO₂ (rutile) heterojunction solar cells against the Fermi level E _f of c-Si showed the maximum in the p-doped region. The photovoltaic properties of the Si/TiO₂ heterojunction also depended on the crystal structure of TiO₂, and the conversion efficiency of anatase is higher than that of rutile, which was attributed to the higher carrier mobility of anatase.     

Wet-chemical passivation of atomically flat and structured silicon substrates for solar cell application

Special sequences of wet-chemical oxidation and etching steps were optimised with respect to the etching behaviour of differently oriented silicon to prepare very smooth silicon interfaces with excellent electronic properties on mono- and poly-crystalline substrates. Surface photovoltage (SPV) and photoluminescence (PL) measurements, atomic force microscopy (AFM) and scanning electron microscopy (SEM) investigations were utilised to develop wet-chemical smoothing procedures for atomically flat and structured surfaces, respectively. Hydrogen-termination as well as passivation by wet-chemical oxides were used to inhibit surface contamination and native oxidation during the technological processing. Compared to conventional pre-treatments, significantly lower micro-roughness and densities of surface states were achieved on mono-crystalline Si(100), on evenly distributed atomic steps, such as on vicinal Si(111), on silicon wafers with randomly distributed upside pyramids, and on poly-crystalline EFG (Edge-defined Film-fed-Growth) silicon substrates.The recombination loss at a-Si:H/c-Si interfaces prepared on c-Si substrates with randomly distributed upside pyramids was markedly reduced by an optimised wet-chemical smoothing procedure, as determined by PL measurements. For amorphous-crystalline hetero-junction solar cells (ZnO/a-Si:H(n)/c-Si(p)/Al) with textured c-Si substrates the smoothening procedure results in a significant increase of short circuit current I_sc, fill factor and efficiency η. The scatter in the cell parameters for measurements on different cells is much narrower, as compared to conventional pre-treatments, indicating more well-defined and reproducible surface conditions prior to a-Si:H emitter deposition and/or a higher stability of the c-Si surface against variations in the a-Si:H deposition conditions.     

Properties of ITO–AZO bilayer thin films prepared by magnetron sputtering for applications in thin-film silicon solar cells

In this paper we study the electro-optical behavior and the application of indium–tin oxide (ITO) and aluminum-doped zinc oxide (AZO) bilayer thin films for silicon solar cells. ITO–AZO bilayer thin films were deposited on glass substrates using radio-frequency magnetron sputtering. The experimental results show that a decrease in the electrical resistivity of the ITO–AZO bilayer thin films has been achieved without significant degradation of optical properties. In the best case the resistivity of the bilayer films reached a minimum of 5.075×10^?4 Ω?cm when the thickness of the AZO buffer layer was 12 nm. The ITO–AZO bilayer films were applied as the front electrodes of amorphous silicon solar cells and the short-circuit current density of the solar cells was considerably increased.