Temperature-Dependent Properties of Spray-Deposited ITO Thin Films

Sprayed indium tin oxide (ITO) thin films are synthesized by mixing adequate quantities of ethanolic solutions of indium trichloride and stannic chloride at different substrate temperatures. The pyrolytic decomposition temperature affects the properties and morphology of ITO samples. X-ray diffraction results showed that the films are polycrystalline with cubic structure and exhibit preferential orientation along (222) plane. The SEM and AFM studies indicated that the surface morphology of the samples increases with substrate temperature. The typical I₅₀₀ sample is composed of cubic grains and has carrier concentration of 3.26 × 10²⁰ cm^?3 and mobility of 9.77 cm²/V s. The electrical resistivity of ITO films decreased with increasing deposition temperature. The highest figure of merit of film is 4.4 × 10^?3 Ω^?1. Optical absorption studies reveal that films are highly transparent in the visible region and band gap increases with substrate temperature owing to Moss-Burstein effect.     

Aqueous chemical growth of ZnO disks, rods, spindles and flowers: pH dependency and photoelectrochemical properties

Suitable morphology for fast electron transportation is a crucial requirement for photoelectrochemical (PEC) solar cells. Highly oriented and well defined zinc oxide (ZnO) nano/micro-scale structures were grown on the glass and FTO coated glass substrates. The grown nanostructures have been characterized by X-ray diffraction pattern (XRD), scanning electron microscope (SEM) and optical absorption techniques. XRD patterns confirm high crystalline quality of ZnO with hexagonal wurtzite structure. SEM micrographs show the formation of disk, rod, spindle and flower-like morphologies at different pH values ranging from 5 to 10. The PEC solar cell configuration of ZnO/0.5 M Na₂SO₄/graphite has been used to record the current voltage (I-V) and capacitance voltage (C-V) characteristics of the films. The junction ideality factor (n_l), series and shunt resistance (R_s and R_sh), flat-band-potential (V_fb), donor concentration (N_D), fill factor (FF) and efficiency (η) have been estimated. Energy band diagram of ZnO and Na₂SO₄ electrolyte has been constructed.     

Electrical Properties of Ag/Tl–Ba–Ca–CuO/CdSe Heterostructures

Tl₂Ba₂Ca₂Cu₃O superconducting films are electrochemically deposited onto Ag-substrate followed by the semiconducting CdSe. The metal–superconducting-semiconductor heterostructure has been imprinted and the electrical properties of the junctions implied have been analyzed and the outcomes are reported in this paper for the first time. The formation of metal–insulator–superconductor (N–I–S) and superconductor–insulator–semiconductor (S–I–Sm) junctions are affirmed. capacitance–voltage (C–V) characteristics manifest the utilitarian tool for the junctional dimensions exploration. The consequences of laser irradiation on the electrical properties are also depicted.     

Thermoluminescence of CaS:Bi:Dy phosphors

Calcium sulphide phosphors co-activated with varying concentration of bismuth & dysprosium have been prepared and their thermoluminescence has been studied systematically. The thermoluminescence intensity curves are analysed to determine the activation energy & frequency factor. The conclusion regarding the type of kinetics involved in the thermoluminescence has been discussed. The dependence of thermoluminescence intensity with irradiation dose has been studied by plotting the build-up curve. Measurements are made on sulphurised and unsulphurised samples and the conclusions are drawn regarding the nature of electron traps.     

Heterogeneity in aerosol characteristics at the semi-arid and island AERONET observing sites in India and Maldives

ABSTRACT

Multi-year Aerosol Robotic Network (AERONET) direct Sun retrieved and inversion algorithm derived aerosol products at a semi-arid, urban site, Jaipur (26.90° N, 75.80° E) and island observing site, Maldives Climate Observatory-Hanimaadhoo (MCO-Hanimaadhoo, 6.74° N, 73.17° E) are analysed to investigate heterogeneity in aerosol optical and microphysical properties. Results reveal the existence of a large seasonal diversity in the frequency distributions of aerosol optical depth (AOD_500 nm, AOD_1020 nm) and Ångström exponent (AE_{440–870 nm}) during different seasons at Jaipur and MCO-Hanimaadhoo. These are indicative of the advection of different aerosol types (viz., black carbon (BC) aerosol, organic aerosol, sulfate particle, dust, sea salt, nitrate particle, and mixtures thereof) from a variety of production mechanisms influenced by strong seasonal changes of anthropogenic activities as well as modulations induced by the climatic condition. The cumulative frequency analysis of the single scattering albedo (SSA) difference (i.e. ΔSSA = SSA_440 nm – SSA_1020 nm) shows that at Jaipur ΔSSA is predominantly negative (around 88% days) while at MCO-Hanimaadhoo it is positive (around 74% days). The positive and negative values of ΔSSA are respectively linked to a stronger absorption by BC mixed anthropogenic pollution aerosols at 1020 nm and to a stronger absorption by mineral dust containing iron oxide at 440 nm. The spectral behaviour of SSA, thus, facilitates investigation of the existence of iron oxide or BC in aerosols. The ‘Bivariate Kernel density’ plots of SSA versus fine-mode fraction (FMF) of AOD_440 nm/AE_{440–870 nm} reveal that at Jaipur the aerosol ensemble consists of coarse-mode particles (AE and FMF cluster in the range 0.2–0.4), a dominant category along with significant fine-mode and much less mixed category. At MCO-Hanimaadhoo fine-mode particle category (with FMF and AE cluster in the range 0.90–0.95 and 1.2–1.6 respectively) is the only dominant category. The persisting log-normal bimodal feature in aerosol volume size distribution (AVSD) is observed both at Jaipur and MCO-Hanimaadhoo. The modal volume concentration of coarse-mode aerosol decreases from FMF of AOD_675 nm = 0.25 (inherently belonging to the coarse-mode regime) to FMF of AOD_675 nm = 0.95 (inherently belonging to the fine-mode regime). This transformation in coarse-to fine-mode volume concentration is associated with a steady rise in AE_{440–874 nm} supporting this changeover.     

Effect of zinc composition on properties on PEC cells based on sprayed Cd1−x Zn x S films

Polycrystalline Cd_1−x Zn _x S films were prepared by spray pyrolysis technique, both on conducting and non-conducting glasses. These films were used as photoanodes in photoelectrochemical cells. The optical and electrical properties of these cells are studied and the effect of zinc composition on these properties is revealed.     

Cobalt Iron Hydroxide as a Precious Metal‐Free Bifunctional Electrocatalyst for Efficient Overall Water Splitting

Highly efficient and stable electrocatalysts from inexpensive and earth‐abundant elements are emerging materials in the overall water splitting process. Herein, cobalt iron hydroxide nanosheets are directly deposited on nickel foam by a simple and rapid electrodeposition method. The cobalt iron hydroxide (CoFe/NF) nanosheets not only allow good exposure of the highly active surface area but also facilitate the mass and charge transport capability. As an anode, the CoFe/NF electrocatalyst displays excellent oxygen evolution reaction catalytic activity with an overpotential of 220 mV at a current density of 10 mA cm^?2. As a cathode, it exhibits good performance in the hydrogen evolution reaction with an overpotential of 110 mV, reaching a current density of 10 mA cm^?2. When CoFe/NF electrodes are used as the anode and the cathode for water splitting, a low cell voltage of 1.64 V at 10 mA cm^?2 and excellent stability for 50 h are observed. The present work demonstrates a possible pathway to develop a highly active and durable substitute for noble metal electrocatalysts for overall water splitting.     

A compact and grounded comb‐shaped microstrip antenna: A key to realize enhanced radiation performance

A compact grounded comb‐shaped single‐element microstrip antenna is proposed with wide beam width and symmetrical radiation pattern in both principal and diagonal planes. The proposed antenna exhibits excellent isolation of around 35 dB between co‐polarized and cross‐polarized radiation while the same for a conventional patch is only 15 dB. Around 105°‐110° of 3 dB beamwidth is achieved in both principal and diagonal (skew) planes at the center frequency. Around 1.5 dB of front‐to‐back radiation isolation is found from the proposed patch. Most importantly, the proposed antenna produces 65% and 35% broader beam in H‐ and E‐planes, respectively, than that of a classical microstrip antenna. Furthermore, in all principal and diagonal planes, the radiation pattern is found to be symmetrical in a wide angular region (?125° to +125°).     

Flow feature and mixing performance analysis of RB-TSAR and EB-TSAR micromixers

Three-dimensional CFD simulations carried to evaluate mixing performance of two designs of micromixers namely RB-TSAR and EB-TSAR. The results of flow physics analysis indicate that the interfacial area between the two flow fluids can be enhanced by creating a flow in transverse direction with the help of split and recombination of fluid streams by placing baffles in diffuser shaped mixing elements along the axial direction. Further, the simulation results indicate that at inlet Reynolds number below 1, the molecular diffusion is the most dominant mechanism of mixing, and the mixing index is almost the same for all cases. However at Re > 5, the secondary flow influencing the mixing process dramatically and thus mixing index is increased. The results also reveal that baffles can break the fluid streams, produce fluid convection and increase the contact area of the fluid by folding and deflecting which in turn helps to improve the mixing index. The split and recombination of the fluid streams and separation vortices play vital role in enhancing the mixing performance. The design configurations studied here showed mixing index higher than 0.85 for the Re in the range from 10 to 50.