Characterization of nanocrystalline indium tin oxide thin films prepared by ion beam sputter deposition method

Indium tin oxide (ITO) thin films were deposited on glass substrates by ion beam sputter deposition method in three different deposition conditions [(i) oxygen (O₂) flow rate varied from 0.05 to 0.20 sccm at a fixed argon (1.65 sccm) flow rate, (ii) Ar flow rate changed from 1.00 to 1.65 sccm at a fixed O₂ (0.05 sccm) flow rate, and (iii) the variable parameter was the deposition time at fixed Ar (1.65 sccm) and O₂ (0.05 sccm) flow rates]. (i) The X-ray diffraction (XRD) patterns show that the ITO films have a preferred orientation along (400) plane; the orientation of ITO film changes from (400) to (222) direction as the O₂ flow rate is increased from 0.05 to 0.20 sccm. The optical transmittance in the visible region increases with increasing O₂ flow rate. The sheet resistance (R_s) of ITO films also increases with increasing O₂ flow rate; it is attributed to the decrease of oxygen vacancies in the ITO film. (ii) The XRD patterns show that the ITO film has a strong preferred orientation along (222) direction. The optical transmittance in the visible spectral region increases with an increase in Ar flow rate. The R_s of ITO films increases with increasing Ar flow rate; it is attributed to the decrease of grain size in the films. (iii) A change in the preferred orientations of ITO films from (400) to (222) was observed with increasing film thickness from 314 to 661 nm. The optical transmittance in the visible spectral region increases after annealing at 200 °C. The R_s of ITO film decreases with the increase of film thickness.     

Characterization on pulsed laser deposited nanocrystalline ZnO thin films

Nanocrystalline zinc oxide thin films were deposited on glass and silicon substrates by using pulsed laser deposition at different laser energy densities (1.5, 2, and 3 J/cm²). The film thickness, surface roughness, composition, optical and structural properties of the deposited films were studied using an α-step surface profilometer, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), optical transmittance, and X-ray diffraction (XRD), respectively. The film thickness was calculated as 244 nm. AFM analysis shows that the root-mean-square roughness increases with increasing laser energy density. XPS analysis shows that the interaction of zinc with oxygen atoms is greatly increased at high laser energy density. In the optical transmittance spectra, a shift of the absorption edge towards higher wavelength region confirms that the optical band gap increases with an increase in laser energy density. The particle size of the deposited films was measured by XRD, it is found to be in the range from 7.87 to 11.81 nm. It reveals that the particle size increases with an increase in laser energy density.     

Electrothermal analysis of AlGaN/GaN high electron mobility transistors

Efficiency of AlGaN/GaN HEMTs used in high power, high frequency applications is thought to be limited by parasitic thermal effects. In this study, we investigate coupled electrical and thermal transport in AlGaN/GaN HEMTs using an ensemble Monte Carlo model. Calculation of the non-equilibrium phonon population reveals a hot spot in the channel that is localized at low drain-source bias, but expands towards the drain at higher bias, significantly degrading channel mobility.     

Synthesis,characterization, and magneto‐electric properties of (1−x)BCZT‐xCFO ceramic particulate composites

Synthesis of a new magnetoelectric [(1?x)(Ba_0.85Ca_0.15)(Zr_0.1Ti_0.9)O₃‐xCoFe₂O₄] (weight fraction x=0, 0.1, 0.2, 0.3, 0.4, 0.5 and 1) ceramic particulate composites with its structural characterization and magneto‐electric properties have been reported here in this study. Lead free piezoelectric (Ba_0.85Ca_0.15)(Zr_0.1Ti_0.9)O₃ (BCZT) and ferrimagnetic CoFe₂O₄ (CFO) were synthesized using sol‐gel and combustion methods respectively. (1?x)BCZT‐xCFO magnetoelectric composites were then synthesized by mixing of the calcined individual ferroic phases with required weight fractions. Powder X‐ray diffraction studies indicate the coexistence of BCZT and CFO phases in the composites sintered at 1300°C. 0.5BCZT‐0.5CFO composite showed high strain sensitivity (dλ/dH) of 52×10^?9 Oe^?1, which is comparable to that of pure CFO (50×10^?9 Oe^?1). A high piezoelectric voltage constant (g₃₃) of 8×10^?3 V m/N was measured for 0.8BCZT‐0.2CFO sample. All the composites showed magnetoelectric effect and a high magnetoelectric coupling coefficient (α_ME) of 6.85 mV/cm Oe was measured for 0.5BCZT‐0.5CFO composite at 1 kHz and a large ME coefficient of 115 mV/cm Oe at its resonance frequency. The effect of microstructure on the magnetoelectric properties of [(1?x)BCZT‐(x)CFO] composites has been studied and reported here as a function of its piezoelectric (BCZT)/ferrite (CoFe₂O₄) content.     

Determination of damage evolution in CFRP subjected to cyclic loading using DIC

Damage evolution in carbon fibre reinforced plastic subjected to fatigue loading (R = 0.5, ?1, 2) has been studied using digital image correlation to obtain full‐field surface strains. Damage initiation being a local phenomenon, its effect on global parameters is not significant. The local transverse strain is a better indicator of delamination which affects transverse strain more than the longitudinal strain. Variation of normalized local transverse strain (ratio of local transverse strain to applied stress) near the initiated delamination indicates that the damage evolution occurs over 2 to 3 stages. Each stage has a stable damage growth with a drastic increase between the stages. The stages correspond to different damage mechanisms (matrix cracking, fibre‐matrix debonding, delamination, and fibre breakage) dominating at different periods during the fatigue life. Scatter in normalized local transverse strain plots due to large relative displacements was eliminated using different reference images for DIC. Waviness due to shift in the time at which the images are captured during the loading cycles was avoided using a sine curve fit to obtain maximum transverse strain in a cycle. Normalized local transverse strain plots were found to qualitatively reflect the physical extent of damage, thereby providing confidence in the methodology. Fatigue life curves were generated and run‐out lives were determined.     

Sea urchin shaped ZnO coupled with MoS2 and polyaniline as highly efficient photocatalysts for organic pollutant decomposition and hydrogen evolution

In this work, an attempt has been made to fabricate multifunctional composite photocatalysts by coupling sea urchin shaped ZnO with MoS₂ and polyaniline (PANI) sheets, and a significant improvement in photocatalytic activity was perceived with composites in comparison to pristine components. It was found that the ternary ZnO–MoS₂-PANI photocatalyst showed excellent adsorptive decomposition of organic pollutants natural sunlight irradiation. In addition, enhanced photocatalytic hydrogen evolution was also evidenced, which revealed the multifunctional nature of the photocatalysts. In the case of organic pollutant decomposition, the presence of MoS₂ in ZnO–MoS₂-PANI offers abundant catalytic active sites which result in adsorption of the pollutants and boost the photocatalytic activity. While for the photocatalytic hydrogen evolution, the binary ZnO-PANI composite showed the utmost activity in comparison to the pristine components and ZnO–MoS₂-PANI, which is due to the fact that the higher loading of MoS₂ in the composite increases the number of S atoms on the basal planes, which are inactive for H₂ evolution, and hence results in decreased photocatalytic activity. The results discussed in this work may pave the approach for the design and development of ZnO based multifunctional materials for diverse photocatalytic applications.     

Ecological health assessment of the Ousteri wetland in India through synthesizing remote sensing and inventory data

Ousteri Lake is one of the important wetlands in India, harbouring many different types of flora and providing a suitable habitat for many different fauna, being declared as a sanctuary in October 2008. The National Wetland Conservation Program of Ministry of Environment and Forests identified Ousteri Lake as a nationally important wetland, and the Bombay Natural History Society (BNHS) named it an Important Bird Area (IBA). The International Union for Conservation of Nature and Natural Resources (IUCN) also has identified this lake as a heritage site. The present study examined the state of environment in and around the Ousteri wetland, assessing the probable threats to the lake and its ecological environs. Ousteri Lake supports diverse rich and rare flora and fauna. Because of its extreme hydrological fluctuations over the annual cycle, the lake exhibits interesting patterns of flora and fauna. The north‐east monsoons leave the lake flooded during the winter months, while the scorching summers leave it totally dry. Ousteri Lake had been primarily used as a tank for irrigation purposes, with ~2,000 acres being cultivated. The main crop is paddy, and the only subsidiary is sugar cane. The natural vegetation, significantly altered by human activities, consists of over 220 species belonging to 63 families. The vegetation study conducted earlier have reported a total of 472 plant species, with the herbs being 40% of this total, followed by trees (21%). Other life forms in the lake are represented by less than 100 species. Ousteri Lake and its environs also provide a wide variety of habitat for many floral species, with 190 species being listed as least concern, 23 species as near threatened and 24 species as vulnerable, according to the IUCN Red List. About 14 floral species are being categorized as endemic. Further, about 202 fauna are listed as least concern, 13 species as near threatened, two species as vulnerable, three species as endangered and one as critically endangered. Moreover, five species are in an endemic category.     

Poly(m‐phenylenediamine)‐coated 316L SS: A promising material for bipolar plates in PEMFC environment

The applicability of conducting polymer coatings to enhance corrosion resistance of bipolar plates in proton exchange membrane fuel cells (PEMFC) is gaining greater significance as electrical conductivity is as important as corrosion resistance. Metaphenylenediamine (mPD) monomer was electropolymerized to poly(m‐phenylenediamine) (PmPD) conducting polymer over 316L SS and characterized by attenuated total reflectance infrared spectroscopy to confirm the formation of P mPD polymer. Scanning electron microscopy was used to study the surface morphology of the polymer. Open‐circuit potential, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization studies were conducted to assess the corrosion protection performance of the PmPD polymer coating in PEMFC environment. The charge‐transfer resistance measured from EIS for the coated substrates was higher than the uncoated substrate. Potentiodynamic polarization studies showed lower corrosion current density for the PmPD‐coated substrates. All the results proved that the PmPD‐coated substrates could exhibit enhanced corrosion resistance in PEMFC environment.