Effect of balanced and unbalanced magnetron sputtering processes on the properties of SnO2 thin films

A comparative study has been carried on the role of balanced magnetron (BM) and unbalanced magnetron (UBM) sputtering processes on the properties of SnO₂ thin films. The oxygen partial pressure, substrate temperature and deposition pressure were kept 20%, 700 °C and 30 mTorr, respectively and the applied RF power varied in the range of 150–250 W. It is observed that the UBM deposition causes significant effect on the structural, electrical and optical properties of SnO₂ thin films than BM as evidenced by X-ray diffraction, C-V, Spectroscopic Ellipsometer and Photoluminescence measurements. The value of band gap (E_g) of the films deposited at 150 W in UBM is found as E_g = 3.83 eV which is much higher than the value of E_g = 3.69 eV as observed in BM sputtering indicating that UBM sputtering results in good crystalline quality. Further, the C-V measurements of SnO₂ thin films deposited using UBM at high power 250 W show hysteresis with large flat band shift indicating that these thin films can be used for the fabrication of memory device. The observed results have been attributed to different mechanisms which exist simultaneously under unbalanced magnetron sputtering due to ion bombardment of growing SnO₂ thin film by energetic Ar+ ions.     

Thermally Stimulated Depolarisation Currents in Urea and Thiourea

Thermally stimulated depolarisation currents (TSDC) are observed in Urea and Thiourea. Urea gives a single TSDC peak at 278° K, while for Thiourea there is a prominent peak at 290°K and the spectrum below 290°K is little complicated. The prominent peaks are interpreted in terms of molecular relaxations. For Urea, space charge polarisation peak above RT was also observed.     

Fully Developed Mixed Convection Flow in a Vertical Channel Containing Porous and Fluid Layer with Isothermal or Isoflux Boundaries

An analysis of fully developed combined free and forced convective flow in a fluid saturated porous medium channel bounded by two vertical parallel plates is presented. The flow is modeled using Brinkman equation model. The viscous and Darcy dissipation terms are also included in the energy equation. Three types of thermal boundary conditions such as isothermal–isothermal, isoflux–isothermal, and isothermal–isoflux for the left–right walls of the channel are considered. Analytical solutions for the governing ordinary differential equations are obtained by perturbation series method. In addition, closed form expressions for the Nusselt number at both the left and right channel walls are derived. Results have been presented for a wide range of governing parameters such as porous parameter, ratio of Grashof number and Reynolds number, viscosity ratio, width ratio, and conductivity ratio on velocity, and temperature fields. It is found that the presence of porous matrix in one of the region reduces the velocity and temperature.     

Trends in Emission and Utilization of CO2: Sustainable Feedstock in the Synthesis of Value-Added Fine Chemicals

Catalysis Surveys from Asia - At this moment the major challenge for the human beings is to address uninterrupted raise in CO2 emissions and their consequences. The demands of globalization...     

Development of polycrystalline silicon films on flexible metallic substrates by aluminium induced crystallization

Thin film silicon solar cells on low cost foreign substrates could be attractive for highly efficient and low cost production of photovoltaic electricity. An attempt has been made to synthesise high-quality continuous polycrystalline silicon (pc-Si) layers on flexible metallic substrates using aluminium induced crystallization (AIC) for the first time. Amorphous silicon films deposited by ECR-PECVD were crystallized on diffusion barrier coated metallic substrates at lower temperatures (<577°C). The crystallization was studied using Raman as well as UV reflectance spectroscopy. The as-grown AIC pc-Si films were found to be continuous and densely packed without amorphous phase. The migration of impurities from the substrate to the pc-Si films and the conformability of the barrier layer with the substrate and pc-Si films were studied systematically in terms of chemical and stress level analysis, which are the important aspects to be considered when metallic foils are used as substrates. It was observed that the barrier layer also serves as a buffer layer to minimise the stress level enormously in the AIC grown pc-Si layer, though the supporting material has a thermal expansion coefficient of higher order at higher annealing temperatures. The present investigation proves the possibility to grow better-quality polycrystalline silicon films on flexible metallic foils and further demonstrates the steps that need to be considered to improve the quality of AIC pc-Si films as well as the strength of the barrier layer.     

Effect of the organic solvent on the formation and stabilization of CdS and PbS nanoclusters

Nanoclusters of CdS and PbS were prepared using two different organic solvents as stabilizers in order to understand the factors affecting their formation and stabilization. Growth of the nanoclusters was monitored by optical absorption spectroscopy at regular intervals of time. Mean cluster size was characterized by X-ray diffraction (XRD). The surface structure of nanoclusters was analyzed using infrared (IR) spectroscopy. Spectroscopic studies under identical experimental conditions reveal interesting correlations between the stability of the nanoclusters formed, the nature of the solvent and the size of metal ion involved, leading to a better understanding of nanocluster formation.     

Large amplitude flexural vibration of stiffened plates

The large amplitude free flexural vibration of thin, elastic orthotropic stiffened plates is studied. The boundary conditions considered are either simply supported on all edges or clamped on all edges and the in-plane edge conditions are either immovable or movable. The governing dynamic equations are derived in terms of non-dimensional parameters describing the stiffening achieved, and the solutions are obtained on the basis of an assumed one-term vibration mode shape for various stiffener combinations. In all cases, the non-linearity is found to be of the hardening type (i.e., the period of non-linear vibration decreases with increasing amplitude). Some interesting conclusions are drawn as to the effect of the stiffening parameters on the non-linear behaviour. A simple method of predicting the postbuckling and static large deflection behaviour from the results obtained in this analysis is included.     

Chemometrics Assisted Formulation of Glimepiride Nanosuspension for Solubility Enhancement in Diabetic Therapy—A Systematic Approach

Glimepiride (GLM), a third-generation sulfonylurea oral hypoglycemic medication, is used to treat type II diabetes. Admittedly, it has a low bioavailability, a relatively short half-life (t_1/2), and high toxicity. To address the issue, a nanosuspension of poorly soluble GLM is designed using a Quality-by-Design (QbD) method, to enhance its solubility. Prospective risk factors are identified and assessed using Critical Material Attribute (CMAs) and Critical Processing Parameter (CPPs) to evaluate the targets by Taguchi orthogonal array (OA) design and to study the effects of formulation and process variables on dependent variables. The amount of Polyvinylpyrrolidone (PVP) (X2), agitation time (X5), and concentration of Poloxamer (X7) are found as significant parameters (p < 0.05), and are further optimized using the Box Behnken Design as response surface methodology model. The optimized GLM nanosuspension 1) has mean particle size (PS), zeta potential, viscosity (VS), and percentage cumulative drug release (CDR%) of 258.17 nm, −25.2 mV, 1.087cPs, and 98.52%, respectively. The pattern of drug release is fitted to Non-Fickian kinetics. The study results in an economic and efficient nano formulation with enhanced solubility.