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Photovoltaic (PV) conversion of solar energy appears to be the most promising way of meeting the increasing energy requirements of the future, at a time when conventional sources of energy are bein...

In the present study, crystallization of amorphous-Si (a-Si) in Al/a-Si bilayer thin films under thermal annealing and ion irradiation has been investigated for future solar energy materials applications. In particular, the effect of thickness ratio (e.g. in Al : a-Si, the ratio of the Al and a-Si layer thickness) and temperature during irradiation on crystallization of the Si films has been explored for the first time. Two sets of samples with thickness ratio 1 : 1 (set-A: 50 nm Al/50 nm a-Si) and thickness ratio 1 : 3 (set-B: 50 nm Al/150 nm a-Si) have been prepared on thermally oxidized Si-substrates. In one experiment, thermal annealing of the as-prepared sample (of both the sets) has been done at different temperatures of 100 °C, 200 °C, 300 °C, 400 °C, and 500 °C. Significant crystallization was found to initiate at 200 °C with the help of thermal annealing, which increased further by increasing the temperature. In another experiment, ion irradiation on both sets of samples has been carried out at 100 °C and 200 °C using 100 MeV Ni7+ ions with fluences of 1 × 1012 ions per cm2, 5 × 1012 ions per cm2, 1 × 1013 ions per cm2, and 5 × 1013 ions per cm2. Significant crystallization of Si was observed at a remarkably low temperature of 100 °C under ion irradiation. The samples irradiated at 100 °C show better crystallization than the samples irradiated at 200 °C. The maximum crystallization of a-Si has been observed at a fluence of 1 × 1012 ions per cm2, which was found to decrease with increasing ion fluence at both temperatures (i.e. 100 °C & 200 °C). The crystallization of a-Si is found to be better for set-B samples as compared to set-A samples at all the fluences and irradiation temperatures. The present work is aimed at developing the understanding of the crystallization process, which may have significant advantages for designing crystalline layers at lower temperature using appropriate masks for irradiation at the desired location. The detailed mechanisms behind all the above observations are discussed in this paper.

Sol-gel (SG) and direct precipitation (DP) routes were employed to synthesize zinc oxide (ZnO) nanoparticles. Al doping and Al-Cu dual doping in ZnO nanoparticles were performed. The structural, mo...

The subject of nanofriction having its origins in the late 19th century has slowly but surely started picking up lately. With rapid advancements in science and technology throughout the last century, understanding nanofriction has been gaining prominence. In this context, and in the current 21st century of nanotechnology, it is expected that nanofriction will play a predominant role, as we try moving forward to solve the most pressing medical and biological problems with the usage of nanobots. It is important to understand the challenges we have to encounter in order to solve these problems for the benefit of the human race. The availability of high speed computers and smart algorithms has made it possible to investigate the problems (as outlined above and many more) without compromising on the complexities involved. The focus of the present review is to bring together major theoretical/mathematical models and computational approaches to study friction at nanoscale. The role of adhesion in the estimation of force of friction at nanoscale has also been clearly outlined. A critical discussion on the significance of single and multiple asperity models towards estimating friction at nanoscale has also been provided. At the end, a short description on scanning probe microscopy in estimating nanofriction has been provided for the completeness of the review.

Metallic nanowires show great potential for applications in miniaturization of electronic devices due to their extraordinary mechanical strength and electrical properties. Experimental investigations of these properties are difficult due to their size and complications in performing experiments at such length scales. Computational techniques based on classical molecular dynamics simulations (using LAMMPS) provide an effective mean to understand the mechanical deformation behaviour of such nanowires with considerable accuracy and predictability. In the present investigation, we have discussed the deformation behaviour of Au nanowires due to tensile loading using classical molecular dynamics simulations (LAMMPS). The effect of strain rate and temperature on the yield strength of the nanowire has been studied in detail. The deformation mechanisms have also been discussed.

High-efficiency heterojunction with intrinsic thin-layer (HIT) technology is a highly efficient module technology, whose performance depends upon the climatic conditions. In this investigation, performance of HIT module under various climatic conditions prevailing in India have been done with the help of logged sensor data at NISE (National Institute of Solar Energy, Gurugram). Five different climatic conditions have been considered: hot and humid, hot and dry, temperate, cold and composite. Chennai has been chosen Chennai for hot and humid conditions, Jodhpur for hot and dry condition, Bangalore for temperate condition, Leh for cold condition and Gurugram for composite climatic conditions. In all the cases, performance ratio (PR) of HIT modules has been calculated, which captures the PV system’s performance. IEC 61424 standard describes the performance ratio as the ratio of Energy Yield ( E y ) to reference yield ( E r ). The calculations show a PR value of 86.4 % for Leh, 82.9 % for Gurugram, 82.4 % for Bangalore, 82.0 % for Jodhpur and 81.9 % for Chennai. From these PR values we may say that the HIT module works comparatively better in cold climatic condition. The HIT modules employed in this study have a rating of 210 Wp.

The increasing demand for more compact electronic devices is stimulating the researchers to develop nanoscale circuit components. Nanowires are molecular-scale connection wires, which carry current inside these small circuits. The present work examines the deformation and melting behavior of silver nanowires with classical molecular dynamics simulations. Large Atomic/Molecular Massively Parallel Simulator (LAMMPS) has been used to simulate silver nanowires of different dimensions at selected temperatures. The deformation behavior is investigated by applying uniaxial stress to the nanowire, and recording the resulting strain in it. The nanowires are also subjected to incremental heating up to 1600 K to understand their melting characteristics. The change in the potential energy with temperature has been used to understand the melting properties of the silver nanowires. It has been found that the melting temperatures of all the nanowires, investigated in this exercise, are lower than their bulk counterparts.

The present study is focused on losses analysis of CdTe and micromorph PV modules installed in composite climate of India. A comprehensive module characterization with the related uncertainty analysis has been carried out by using the real electrical parameters measured at the operating field conditions. The impact of cracks in the PV module on the I-V curve has also been evaluated. A power drop of 49% has been recorded in micromorph PV modules as a result of 24% reduction in the panel area due to crack defects. The performance assessment of both the technology PV modules (CdTe and micromorph) has been initially carried out over a period of one year field exposure. Irradiance, temperature and spectral effects have been identified to quantify the corresponding losses/gain in power generation. The performance ratios of CdTe and micromorph PV modules have been found to be 80% and 65%, respectively. Spectral and temperature losses up to −29.2% and −10.1%, respectively have been recorded in the micromorph PV module. However, both PV module technologies’ results are found insensitive to the irradiance effects with negligible losses of approximately -1%. Overall, the CdTe module technology is found to be more efficient than the micromorph PV modules in composite climate of India.

Life cycle assessment for new emerging photovoltaic (PV) technology is an important tool to establish a PV system in field condition. In this paper, life cycle assessment of the 3.2 kW cadmium telluride (CdTe) PV system has been carried out on the basis of actual field performance data in a composite climate of India. Further, analysis has been performed on the basis of the energy metrics, life cycle assessment, per unit cost of electricity and carbon credit earned. The analysis of the PV system has been performed under the same environmental conditions likely solar irradiation, ambient temperature and wind speed, etc. Energy payback time (EPBT), energy production factor (EPF) and life cycle conversion efficiency (LCCE) of the PV system has been found to be 3.60 years, 0.27 and 0.0018 respectively. The unit cost of electricity of the PV system has been calculated as 9.85 INR/kW h for 5% interest rate and 30 years life span.

Electrochemical biosensors employing nano-transduction surfaces are considered highly sensitive to the morphology of nanomaterials. Various interfacial parameters namely charge transfer resistance, double layer capacitance, heterogeneous electron transfer rate and diffusion limited processes, depend strongly on the nanostructure geometry which eventually affects the biosensor performance. The present work deals with a comparative study of electrochemical impedance-based detection of L-tyrosine (or simply tyrosine) by employing carbon nanostructures (graphene quantum dots, single walled carbon nanotubes (CNTs) and graphene) along with tyrosinase as the bio-receptor. Specifically, the role of carbon nanostructures (i.e. 0D, 1D and 2D) on charge transfer resistance is investigated by applying time-varying electric field at the nano-bioelectrode followed by calculating the heterogeneous electron transfer rate, double layer capacitor current and their effects on limits of detection and sensitivities towards tyrosine recognition. A theoretical model based on Randel’s equivalent circuit is proposed to account for the redox kinetics at various carbon nanostructure/enzyme hybrid surfaces. It was observed that, the 1D morphology (single walled CNTs) exhibited lowest charge transfer resistance ∼2.62 kΩ (lowest detection limit of 0.61 nM) and highest electron transfer rate ∼0.35 μm s−1 (highest sensitivity 0.37 kΩ nM−1 mm−2). Our results suggest that a suitable morphology of carbon nanostructure would be essential for efficient and sensitive detection of tyrosine.

Nickel mono-silicide (NiSi) is considered as a promising material for developing low resistance contacts in complementary metal-oxide-semiconductor technology. In the present work, we report the effect of Ni film thickness on orientation control of low resistive Nickel mono-silicide (NiSi) phase formation using low energy ion irradiation at room temperature. In order to study the effect of Ni film thickness on NiSi phase formation, the Ni films of thicknesses 30 nm and 60 nm were deposited on Si (111) substrate using thermal evaporation technique in a high vacuum chamber. The as prepared Ni/Si samples were then irradiated via 120 keV Si ions with different fluences of 7 × 1014, 1 × 1015, 3 × 1015 and 7 × 1015 ions-cm−2 at room temperature. The x-ray diffraction and transmission electron microscopy measurements clearly confirm the formation of mono-silicide phase. The composition of the NiSi phase is determined by Rutherford backscattering spectrometry measurements. The crystallinity of NiSi phase has been observed to be better for 60 nm Ni film as compared to the 30 nm Ni film on Si substrate. Most of the NiSi crystallites are found to be oriented in (103) lattice plane. The resistivity and sheet resistance of the NiSi/Si films are found to be very low. The role of composition of Ni and Si in NiSi phase on resistivity and sheet resistance of the films has been investigated carefully. The detailed mechanisms behind the above observations have been discussed in the paper.

A field experiment was conducted during rabi season 2002-03 at research farm of C.S. Azad University of Agriculture and Technology, Kanpur, U.P. with the objective to study the effect of irrigation and nitrogen levels on growth, yield and nitrogen uptake by barley. The experiment was laid out in split plot design with three replications with treatments, comprising four levels of irrigation viz., I1= no irrigation, I2= one irrigation at tillering stage, I3= one irrigation at flag leaf stage and I4= two irrigations each at tillering and flag leaf stage in main plots and four nitrogen levels viz., N1= Control, N2= 30 kg ha-1, N3= 60 kg ha-1 and N4= 90 kg ha-1 in sub-plots. Results revealed that application of two irrigations first at tillering and second at flag leaf stage along with 90 kg nitrogen per hectare gives highest grain yield, straw yield, nitrogen content and nitrogen uptake by grain, straw and protein content as compared to other irrigations (no irrigation, one irrigation at tillering stage, one irrigation at flag leaf stage) and nitrogen treatments (0, 30 and 60 kg ha-1). A field experiment was conducted during rabi season 2002-03 at research farm of C.S. Azad University of Agriculture and Technology, Kanpur, U.P. with the objective to study the effect of irrigation and nitrogen levels on growth, yield and nitrogen uptake by barley. The experiment was laid out in split plot design with three replications with treatments, comprising four levels of irrigation viz., I1= no irrigation, I2= one irrigation at tillering stage, I3= one irrigation at flag leaf stage and I4= two irrigations each at tillering and flag leaf stage in main plots and four nitrogen levels viz., N1= Control, N2= 30 kg ha-1, N3= 60 kg ha-1 and N4= 90 kg ha-1 in sub-plots. Results revealed that application of two irrigations first at tillering and second at flag leaf stage along with 90 kg nitrogen per hectare gives highest grain yield, straw yield, nitrogen content and nitrogen uptake by grain, straw and protein content as compared to other irrigations (no irrigation, one irrigation at tillering stage, one irrigation at flag leaf stage) and nitrogen treatments (0, 30 and 60 kg ha-1).

In developing countries like India, adulteration in the milk consumed by the population presents stern implications as tarnishing of the same poses serious issues, such as health deterioration, corruption, and so on. There are many adulterants that are added to milk, including water, flour, starch, and even urea, in quantitative measures making it undetectable. There are many devices in the market to measure adulteration in milk but most of them are bulky, require large sample volume, and need a technical operator for working. In the recent decade, microfluidics has emerged as a huge market for biomedical research. It has paved the pathway for a quick, robust, and plug-and-play device for various applications. This paper describes a low-cost, durable, and simple optofluidic microviscometer fabricated by the stereolithography technique. The device operation is based on the linear relationship between dynamic viscosity and channel width derived from the flow of two immiscible fluids inside a channel. The principle of operation is based on the modified Hagen–Poiseuille flow equation. The working principle is the viscosity-dependent capture of the microchannel width by the fluids flowing inside the microchannel under the laminar flow based on the pressure gradient between the inlets and the outlet. In this paper, around 60 milk samples with various adulteration ratios of various adulterants ranging from 1% to 10% have been tested. A best fit curve for every adulterant was defined, and the device was found to be accurate enough to measure the entire range of adulteration ratios with a high accuracy of 0.95.

The Al-induced crystallization of amorphous (a)-Si under thermal annealing and swift heavy ion irradiation has been investigated. The c-Al (50 nm)/a-Si (150 nm) thin films have been prepared on thermally oxidized Si-substrates. A set of samples have been annealed at temperatures ranging from 100 °C to 500 °C to achieve crystallization. Another set of similar samples have been irradiated at an elevated temperature of 100 °C using 100 MeV Ni+7 ions at fluences of 1 × 1012 ions-cm−2, 5 × 1012 ions-cm−2, 1 × 1013 ions-cm−2, and 5 × 1013 ions-cm−2. The crystallization of a-Si is observed at annealing temperature of 200 °C. The crystallinity increases with increasing temperature. On the other hand, irradiation using swift heavy ion leads to crystallization of a-Si at significantly lower temperature of 100 °C. The irradiation induced crystallization is explained in terms of creation of vacancies, interstitials and mixing of Si and Al atoms at a-Si/c-metal interface due to energy deposited by swift Ni ions.

A defect-based model of radiation-induced segregation in binary solid solutions is presented. The model consists of a set of reaction–diffusion equations governing the space and time evolution of vacancies, dumbbell interstitials and lattice atoms under irradiation. Irradiation, the mechanism driving evolution, is represented by stochastic and spatially-resolved defect generation events. A key feature of the model presented here is that the role of boundaries as defect sinks is ensured by a set of defect–boundary reaction boundary conditions. Defining defect–boundary interactions in this way makes it possible to capture both segregation and boundary motion simultaneously. The model is tested with Cu–Au solid solution. Enrichment of Cu and depletion of Au has been observed near the boundaries, in agreement with experimental observations. For a particular dose rate, the amount of segregation after a given period of irradiation has been found to be highest at an intermediate temperature. At lower temperatures, maximum segregation is observed by lowering the dose rates, and vice versa. The activation barrier for the defect–surface reactions plays a significant role in segregation near the boundaries. A slight increase in the sample size is also noticed during the simulations due to rapid migration of interstitials to the surface.

The Ni0.6+xZn0.4SnxFe2-2xO4 (x=0.00 to 0.04) samples were prepared by solution route technique. These samples were characterized by XRD and EPR spectra at X-band frequency (~9.2 GHz). The XRD spectra of these ferrites confirm the formation of spinel structure. The average particle size calculated by using Scherrer’s formula was found to be of the order of 24.7 nm. The EPR spectra of these ferrites are mainly due to Fe3+ ions. Fe2+ ions have very short spin-lattice relaxation time and therefore EPR spectra of Fe2+ could be observed only at very low temperature. This fact is also supported by the isomer shift values of these ferrites obtained from Mössbauer spectroscopy. The variation of geff and ΔHPP with Sn4+ concentration is attributed to the variation of superexchange interaction. Moreover in this system the dominant process of relaxation is the spin lattice relaxation rather than the spin-spin interaction.

The stability of a binary solid solution under irradiation has been studied. This has been done by performing linear stability analysis of a set of nonlinear reaction-diffusion equations under uniform irradiation. Owing to the complexity of the resulting system of eigenvalue equations, a numerical solution has been attempted to calculate the dispersion relations. The set of reaction-diffusion equations represent the coupled dynamics of vacancies, dumbbell-type interstitials, and lattice atoms. For a miscible system (Cu-Au) under uniform irradiation, the initiation and growth of the instability have been studied as a function of various control parameters.

Using multicanonical Metropolis simulations we estimate phase transition properties of 3D Potts models for q=4 to 10: The transition temperatures, latent heats, entropy gaps, normalized entropies at the disordered and ordered endpoints, interfacial tensions, and spinodal endpoints., Comment: 18 pages, 7 figures. Correction of minor typos, one reference added

A model to study the formation of compositional patterns in concentrated binary alloys under irradiation is presented. In this model, six atomic and defect species are considered: regular lattice atoms (A and B), dumbbell interstitials (AA, BB and AB) and vacancies. In addition to long range diffusion of these species, local defect-defect (vacancy-interstitial recombination) and defect-atom (dumbbell-atom) reactions have also been considered. The model tracks simultaneous evolution of all the species in reaction-diffusion formalism. Irradiation events are modeled as a stochastic point process which changes the concentration of all the species instantaneously in a random fashion. In each irradiation event, a spatial distribution of point defects (core-shell distribution: core dominated by vacancies and shell by interstitials) has been introduced in the system which drives the kinetics of diffusion and reaction. The model has been non-dimensionalized with respect to intrinsic length and time scales of the material system and solved numerically using finite difference technique. Applying this model to CuAu solid solution, we have shown that the alloy exhibits spinodal-like decomposition with specific steady state wavelengths that depend on the irradiation conditions.

We study Kolmogorov-Johnson-Mehl-Avrami (KJMA) theory of phase conversion in finite volumes. For the conversion time we find the relationship $\tau_{\rm con} = \tau_{\rm nu} [1+f_d(q)]$. Here $d$ is the space dimension, $\tau_{\rm nu}$ the nucleation time in the volume $V$, and $f_d(q)$ a scaling function. Its dimensionless argument is $q=\tau_{\rm ex}/ \tau_{\rm nu}$, where $\tau_{\rm ex}$ is an expansion time, defined to be proportional to the diameter of the volume divided by expansion speed. We calculate $f_d(q)$ in one, two and three dimensions. The often considered limits of phase conversion via either nucleation or spinodal decomposition are found to be volume-size dependent concepts, governed by simple power laws for $f_d(q)$., Comment: 4 pages, 4 figures. Additions after referee reports: Scaling of the variable q is proven. Additional references are added

A theoretical/computational model for the irradiation-driven compositional instabilities in binary solid solutions has been developed. The model is suitable for investigating the behavior of structural alloys and metallic nuclear fuels in a reactor environment as well as the response of alloy thin films to ion beam irradiation. The model is based on a set of reaction-diffusion equations for the dynamics of vacancies, interstitials, and lattice atoms under irradiation. The dynamics of these species includes the stochastic generation of defects by collision cascades as well as the defect reactions and diffusion. The atomic fluxes in this model are derived based on the transitions of lattice defects. The set of reaction-diffusion equations are stiff, hence a stiffly stable method, also known as the Gear method, has been used to numerically approximate the equations. For the Cu-Au alloy in the solid solution regime, the model results demonstrate the formation of compositional patterns under high-temperature particle irradiation, with Fourier space properties (Fourier spectrum, average wavelength, and wavevector) depending on the cascade damage characteristics, average composition, and irradiation temperature.