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Experimental realization of colossal permittivity associated with intrinsic dielectric polarization of defect-engineered (Nb, In) co-doped rutile TiO2 appears to be most suitable for microelectronics and solid-state device applications. Combining resonant photoemission spectroscopy, X-ray absorption spectroscopy, and density functional theory calculations, we here present a coherent understanding of electronic structure, in-gap defect states, doped electron localization, and their connection with macroscopic polarization for various doping configurations. Most often, conventional sample preparation conditions introduce in-gap states of Ti3+δ character, limiting the maximum achievable intrinsic polarization value. Our understanding provides a pathway to enhance intrinsic polarization and minimize dielectric loss through suitable defect-engineering.

Growth and coverage dependent electronic structure of MgO films on Ag(001) have been studied using low energy electron diffraction (LEED), X-ray photoelectron spectroscopy (XPS) and angle-resolved photoemission spectroscopic (ARPES) techniques. The appearance of mosaic structure in the LEED pattern has been observed around 10 ML coverage due to misfit dislocations in the metal-oxide interface. The XPS core level spectra show a substantial amount of binding energy shift relative to their bulk values, indicating the reduction of the on-site Coulomb (U) and change transfer (Δ) energies in oxide layers. This binding energy shift is mainly associated with the image charge screening effect of the highly polarizable metallic substrate. The effect of image charge screening is also reflected in the valence band electronic structure as the bands are shifted to lower binding energies with decreasing film coverage maintaining the bulk MgO band gap till 5 ML. However, for the film coverages below 5 ML, the band gap is reduced substantially in presence of O 2p-Ag 5sp hybridized bands with the finite size effects in proximity to the Ag(001) substrate. Furthermore, our measured valence band electronic structure has been compared with the theoretical calculations and a good agreement has been observed between them for the bulk MgO, however, a more detailed calculation is necessary to explain the monolayer MgO band structure properly.

The surface antiferromagnetic ordering of MnO(001) ultrathin films has been probed using Low-energy Electron Diffraction (LEED) and Angle-Resolved Photoemission spectroscopy (ARPES) techniques. We observe coherent exchange scattered half-order spot in LEED which is only visible at low electron beam energy ( 40 eV) and arises below a certain temperature with a periodicity of the magnetic unit cell of MnO(001) surface, confirms its magnetic origin. A thickness dependent evolution of surface antiferromagnetic (AFM) Neel temperature has been observed for the MnO films. Interestingly, we found the Neel temperature of the MnO films exceed its bulk Neel temperature even in the ultrathin limit ( ∼ 2 ML). Detailed LEED analysis reveals that the increase of the Neel temperature is due to the presence of strain and the image charge screening effect in the film while, the competition between the finite size effects, surface strain, and substrate polarizability ultimately determine the observed Neel temperature. The surface magnetic critical exponent ( β 1 ) varies from 0.16 ± .03 to 0.81 ± .03, upon changing film thickness from 3 to 10 ML, indicates the transition from nearly 2D Ising system to 3D Ising/Heisenberg system. Furthermore, upon paramagnetic (PM)-AFM transition, ARPES energy distribution curves (EDCs) show, opening an energy gap of 150 meV with an increased occupation in the e g levels is good agreement with the theoretical prediction of the presence of AFM-II type ordering in the film.

The growth mode, structural and electronic properties of vanadium films on Ag(0 0 1) were investigated using low energy electron diffraction (LEED), X-ray photoelectron spectroscopy (XPS) and angle-resolved photoemission spectroscopy (ARPES) techniques. Previously, it was believed that the layer-by-layer growth of vanadium films is possible (for the first 3–4 layers) at the substrate temperature range of 373–428 K, while our results suggest, vanadium prefers to grow in a three-dimensional (3D) island form and Ag segregates on top of vanadium islands. Detailed band dispersion mapping along the high symmetry directions of V(0 0 1) surface Brillouin zone (SBZ) clearly shows the presence of quantum-well states (QWS) along with the desired bands of V(0 0 1) surface, due to the formation of Ag/V/Ag(0 0 1)-like structure. At different growth temperatures, a substantial change in the valence band electronic structures are also observed due to the appearance of sp and d derived Ag QWS, spreading all over the valence band, originating from the different island height of the segregated Ag layers. QWS are absent for the low temperature (∼108 K) grown films, indicating the absence of Ag-segregation. Furthermore, we compare our band dispersion data with the available theoretical calculations and good agreement between them is observed. Moreover, our results can be a valuable resource for some future research of noble metal-transition metal interfaces in particular in understanding a complexity of the valence band spectra. These results will also help to explain why contradictory results are reported in the literature on monolayer magnetism of V/Ag(0 0 1) system.

Surface termination is known to play an important role in determining the physical properties of materials. It is crucial to know how surface termination affects the metal-insulator transition (MIT) of V$_2$O$_3$ films for both fundamental understanding and its applications. By changing growth parameters, we achieved a variety of surface terminations in V$_2$O$_3$ films that are characterized by low energy electron diffraction (LEED) and photoemission spectroscopy techniques. Depending upon the terminations, our results show MIT can be partially or fully suppressed near the surface region due to the different filling of the electrons at the surface and sub-surface layers and change of screening length compared to the bulk. Across MIT, a strong redistribution of spectral weight and its transfer from high-to-low binding energy regime is observed in a wide-energy-scale. Our results show total spectral weight in the low-energy regime is not conserved across MIT, indicating a breakdown of `sum rules of spectral weight', a signature of a strongly correlated system. Such change in spectral weight is possibly linked to the change in hybridization, lattice volume ({\it i.e.,} effective carrier density), and spin degree of freedom in the system that happens across MIT. We find that MIT in this system is strongly correlation-driven where the electron-electron interactions play a pivotal role. Moreover, our results provide a better insight in understanding the electronic structure of strongly correlated systems and highlight the importance of accounting surface effects during interpretation of the physical property data mainly using surface sensitive probes, such as surface resistivity., Comment: 10 pages, 5 figures

Antiferromagnetic (AFM) CoO/NiO thin films are grown epitaxially on MgO(001) substrate and investigated by x-ray linear dichroism (XLD). Temperature-dependent measurement confirms that the observed XLD effect in this system originates entirely from the magnetic ordering. The temperature-dependent XMLD measurement indicates that the exchange coupling at the CoO/NiO interface can greatly enhance the Neeltemperature of the CoO layer. The XASof NiL2 edge shows the spin of the NiO in the system is in-plane.

The phase transition of Si(111) surface from the reconstructed low-temperature (7x7) phase to the high-temperature (1x1) phase has been studied by using Low Energy Electron Microscopy (LEEM) and Low Energy Electron Diffraction (LEED) technique. Our experimental results confirm that the phase transition is of first order. Further, our results also show these phase transitions to be reversible. In the LEEM, we observe thattriangular (7x7) domains nucleate from the terrace edges and cover almost total surface when the temperature is reduced from the transition temperature. Surfaces that are quenched from very high temperature does not transform to (7x7) structure completely because of the destruction of mechanical stress on the surface.

The adsorption of oxygen on Mo(110) surface is studied by a combination of Low Energy Electron Diffraction (LEED) and Angle-Resolved Photoemission Spectroscopy (ARPES) measurements with fine coverage dependence. Oxygen adsorption at Mo(110) surface corresponds to ordering in a single-phase region p(2×2) and in a two-phase coexistence region p(2×1) structure at low and medium coverage respectively. Energy degeneracy of adsorption sites plays a significant role in the occurrence of two-domain structure. For moderately higher coverage, we observe the occurrence of a single-phase p(2×6) structure. Higher temperature oxygen annealing forms Molybdenum oxide (MoO2 ) on top of Mo(110) substrate surface. Band structure of clean Mo(110) surface exhibits the presence of d-derived surface states in the mid-region of the Γ¯ to N¯ symmetry line. We also observe dispersive bands, including both positive and negative curvature due to adsorption of oxygen on Mo(110) surface. Curvature of the Oxygen induced surface band gets reversed along Γ¯ to N¯ symmetry direction. Dispersive nature of oxygen-induced band increases at Γ¯ point with increasing oxygen coverage on the Mo(110) surface.

A passive balanced sub-harmonic mixer at Ku band from 12.6-14.4 GHz required for realization of miniaturized RF front-end of Command Receivers is designed and developed. The mixer is realized on 10mil Alumina subtrate using microstrip technology. GaAs Based Beam Lead Schottky antiparallel diode is used for the frequency mixing purpose. The design eliminates the need of high frequency LO requirement and frequency generation chain required in case of fundamental mixer. The designed mixer has conversion loss better than 10 dB with LO-RF isolation better than 60dB.

Growth and structure of Sn on W(110) from submonolayer to thick film (up to 8 monolayers) coverages at room temperature (RT) and as-well-as for higher temperatures (HT) (up to 673 K) have been studied using low energy electron diffraction (LEED), x-ray photoemission spectroscopy (XPS) and angle-resolved photoemission spectroscopy (ARPES) techniques. Surface structural evolution was studied where (3 × 1), (1 × 3) and (1 × 4) LEED patterns were observed for RT whereas (3 × 1) and (1 × 4) LEED patterns were observed for growth at 673 K due to the energetically available adsorption sites for Sn atoms on W(110) surface. The absence of alloy formation between Sn and W was confirmed by the XPS data where surface core level shift of Sn 3d was observed whereas no shift was observed for W 4f levels. Detailed electronic structures were studied along Γ ¯ - H ¯ and Γ ¯ - N ¯ directions for Sn deposited on W(110) with the help of ARPES. ARPES data for RT and HT case is mostly similar. A pair of splitted bands was observed due to the deposition of Sn near the surface projected band gap.

We present here a detailed growth optimization of CoO thin film on Ag(001) involving the effects of different growth parameters on the electronic structure. A well-ordered stoichiometric growth of 5 ML CoO film has been observed at 473 K substrate temperature and 1 × 10−6 mbar oxygen partial pressure. The growth at lower substrate temperature and oxygen partial pressure show non-stoichiometric impurity phases which have been investigated further to correlate the growth parameters with surface electronic structure. The coverage dependent valence band electronic structure of the films grown at optimized condition reveals the presence of interfacial states near the Fermi edge (EF) for lower film coverages. Presence of interfacial states in the stoichiometric films rules out their defect-induced origin. We argue that this is an intrinsic feature of transition metal monoxides like NiO, CoO, MnO in the low coverage regime.

Fractional order (1/2, 0) spots appear in the electron diffraction from NiO/Ag(0 0 1) films due to exchange scattering of low energy electrons by the antiferromagnetically ordered surface Ni moments. Utilizing these beams, imaging of the nanosized surface magnetic domains were carried out employing the high spatial resolution ( ∼ 10 nm) of the Low Energy Electron Microscopy (LEEM) in the dark-field (DF) mode. While selected through a contrast aperture, the four magnetic reflections produced by the p ( 2 × 2 ) antiferromagnetic sub-lattice lead to the visualization of the different magnetic twin domains. The intensity variations of different twin domains were measured as a function of electron beam energies via domain resolved LEEM I-V plots. The surface N e el temperatures ( T N ) of the films were measured using the temperature dependence of these half-order spot intensities. Detailed morphological studies of the size and shape of these nanodomains and their evolution as a function of the film thickness have been carried out with the help of pair-correlation function and fractal analysis. The size, shape and distribution of these magnetic domains are modified significantly by the strain relaxation mechanism beyond the critical film thickness. A method to estimate the relative domain sizes from a quantitative measure of the half-order spot intensities is manifested well below T N .

We investigate the magnetic coupling across the antiferromagnetic–antiferromagnetic (AFM–AFM) interface for the prototypical CoO-NiO bilayer system where the bulk Néel temperature (T N ) of NiO is higher than that of CoO. Using the temperature-dependent exchange-scattered electron intensities from the surface AFM lattice, the surface T N of CoO was estimated as a function of the CoO/NiO film thicknesses. Our results show that the surface T N of CoO layers is enhanced significantly from its bulk T N value and approaching the T N of the NiO layers, as the thickness of the CoO layers is reduced to the monolayer limit. Thus, thinner CoO layers are found to have higher T N than thicker layers on NiO, contrasting with the expected finite-size behavior. In addition to the short-range magnetic exchange coupling at the CoO-NiO interface, we observe the existence of a longer-range magnetic coupling across the interface, mediated by the magnetic correlations. Thus, the magnetic proximity effect is attributed to a combination of a short-range and a weaker long-range magnetic coupling, explaining the long AFM order propagation length in AFM–AFM superlattices and bilayers. Further, our results indicate a new approach to tune the AFM Néel temperature by varying the individual layer thickness of the bilayer system through the magnetic proximity effect.

Epitaxial hexagonal V2O3(0001) films were grown on cubic Ag(001) substrate for coverages ranging from 1-20 monolayers equivalent (MLE) and have studied their structure, electronic structure and the metal-insulator transition (MIT) using Low Energy Electron Diffraction (LEED), X-ray Photoelectron Spectroscopy (XPS) and Angle-Resolved Photoemission Spectroscopy (ARPES) techniques. Detailed LEED and XPS study reveal that, for the lower film coverages (∼1 MLE), a complex (coexisting phase of) vanadium oxide is formed while from 3 MLE coverage onwards, three-dimensional crystallites of V2O3 grows epitaxially. Our LEED results also show that the hexagonal surface of V2O3(0001) is stabilizing on top of square symmetry substrate by the formation of twin-domain structure, where each domain is rotated by 90o. Our photoemission results show that the surface of V2O3 is more insulating than its bulk, similar to the case of many strongly correlated oxide surfaces which is discussed based on the valence band electronic structure with varying probing depth. Evolution of the surface electronic structure was also studied as a function of the film thickness. Further, the effect of lattice strain, film thickness and the domain formation on the metal-insulator transition (MIT) are discussed. The change in the orbital occupancy of (a1 g, e g π ) and ( e g π , e g π ) orbitals of V 3 d , a vanishing of quasiparticle (QP) peak and opening an energy gap at the Fermi level is observed below a critical temperature as a consequence of the MIT.

Cure characteristics, Mooney viscosity and physico-mechanical properties of natural rubber (NR) containing CTAB modified kaolin have been studied. NR mix containing 6 phr (parts per hundred part rubber) of CTAB modified kaolin showed significant increases in cure rate and state of cure as compared to gum NR compound and a mix containing the same amount of unmodified kaolin. Lower Mooney viscosity of the NR mix containing CTAB modified kaolin suggested improved processability. Reinforcing effect of CTAB modified kaolin in NR was evident from higher chemical crosslink density index, tensile modulus, hardness, tensile strength and tear strength. Besides, the NR vulcanizate containing 6 phr of CTAB modified kaolin showed lower abrasion loss and heat build-up which could be beneficial for applications such as tire treads.

Magnetic properties of an antiferromagnetic film can be modified by the presence of another antiferromagnetic film. The surface antiferromagnetic ordering of CoO/10ML NiO bilayer on Ag(001) substrate have been probed by using Low-energy Electron Diffraction (LEED) technique. We observe coherent exchange scattered half-order spot in LEED which is only visible at low electron beam energy (

A new surface imaging facility has been established at Saha Institute of Nuclear Physics (SINP), Kolkata for the study of real-time growth dynamics and surface structure characterization of solid materials, which is a first in the country. Low Energy Electron Microscopy (LEEM) and Photoemission Electron Microscopy (PEEM) are surface science technique that can be used to image atomically clean surface, atom-surface interactions, phase transitions and thin films. Both LEEM and PEEM methods are based on the cathode lens principle and have proven to be very important in many applications. LEEM-PEEM system offers a unique ability to acquire real-time images over a wide temperature range while providing high lateral resolution of few nanometres. Here, we present details of the facility along with the experimental results on different samples to demonstrate the performance of the system.

CoO-NiO epitaxial bilayer system grown on MgO(001) substrate is investigated using x-ray magnetic linear dichroism (XMLD) spectroscopy with varying CoO overlayer thickness. An analysis of the Ni L 2 edge XMLD spectra using anisotropic XMLD formulation within a two-domain model reveals that the Ni moments undergo a spin reorientation with increasing CoO thickness. Such a spin reorientation is attributed to the competing magnetic interactions at both the NiO film interfaces, suggesting the existence of a sharp horizontal domain wall separating the in-plane and out-of-plane NiO domains. Our study also demonstrates a possible way to investigate the spin-structure along the thickness within the same chemical structure using a model-based approach, in a noninvasive manner.

The surface antiferromagnetic (AFM) ordering of ultrathin CoO(0 0 1) films grown on Ag(0 0 1) has been investigated using low energy electron diffraction (LEED) and valence band photoemission spectroscopy. We have observed coherent exchange scattered half-order spots in LEED with a periodicity of the magnetic unit cell of the CoO(0 0 1) surface. These spots show very low intensities (2–3% of the integer-order spots) and are visible only below a critical temperature for low electron beam energies ( T N ) of CoO(0 0 1) for different film coverages has been observed and it is exceeding the bulk T N even in the ultrathin limit. The enhancement of surface T N has been explained by the combined effects of finite size, surface strain, and polarizability of the underlying substrate. The critical behaviour near T N shows a coverage dependent evolution as the magnetic critical exponent ( β ) varies from 0.16 to 0.48 upon increasing film coverage from 0.5 ML to 10 ML, suggesting crossovers in the critical behaviour. Furthermore, upon transition from paramagnetic (PM) to AFM phase, minor modifications of the valence band electronic structure have been observed such as enhancement of spectral weight in the Co 3d band as well as widening of an energy gap relative to E F by ~ 150 meV, in agreement with the theoretical predictions.

We present here a comprehensive growth procedure to obtain a well-ordered MnO(001) ultrathin film on Ag(001) substrate. Depending upon the oxygen partial pressure during the growth, different phases of manganese oxide have been detected by Low Energy Electron Diffraction (LEED) and X-ray Photoelectron Spectroscopic (XPS) studies. A modified growth scheme has been adopted to get well-ordered and stoichiometric MnO(001) ultrathin film. The detailed growth mechanism of epitaxial MnO film on Ag(001) has been studied step by step, using LEED and XPS techniques. Observation of sharp ( 1 × 1 ) LEED pattern with a low inelastic background, corresponds to a long-range atomic order with low defect densities indicating the high structural quality of the film. The Mn 2p and Mn 3s core-level spectra confirm the oxidation state as well as the stoichiometry of the grown MnO films. Apart from the growth optimization, the evolution of strain relaxation of the MnO(001) film with film thickness has been explored.

Natural Rubber/Organo-kaolin composites with mechanical properties tailored to meet specific structural requirements were developed from Natural Rubber and Kaolin intercalates obtained from derivatives of rubber seed oils (Hevea brasiliensis) and tea seed oils (Camellia sinensis). The kaolin intercalation process was achieved in the presence of hydrazine hydrate. Performance characteristics and analysis of the composites were conducted using tensile test, tear resistance test, De-Mattia flex fatigue test and scanning electron microscopy. Modulus of resilience and modulus of toughness were the major performance criteria evaluated in the study. The modulus of toughness were obtained as follows for the composites: Natural Rubber/Tea Seed Oil modified kaolin composites at 6 phr filler loading as 174.54 MPa; Natural Rubber/Rubber seed oil modified kaolin composites at 10 phr filler loading as 107.64 MPa; Natural Rubber/Unmodified kaolin composites at 2 phr filler loading as 67.27 MPa. The most resilient of the composites investigated was found to be Natural Rubber/Unmodified kaolin composites at 10 phr filler loading with a value 54.63 MPa and the least resilient was found to be Natural Rubber/Tea seed oil modified kaolin composites at 10 phr filler loading with a value 0.27 MPa.

Growth of tin (Sn) on Ag(001) substrate has been studied at elevated temperatures using low energy electron diffraction (LEED), x-ray photoemission spectroscopy (XPS) and angle-resolved photoemission spectroscopy (ARPES) measurements. A c (2 × 2) ordered surface is observed for very low coverages (0.1 ML) of Sn which subsequently transforms into a p (2 × 2) ordered surface for 0.25 ML Sn coverage, suggesting formation of a substitutionally ordered surface alloy. For higher coverages of Sn beyond 0.5 ML, no further structural evolution was observed with a constant p (1 × 1) LEED pattern. Our XPS results indicate diffusion of Ag atoms into Sn layers and forming Ag–Sn alloy film. Along with LEED and XPS, our ARPES results confirm the presence of an ordered Ag overlayer on the alloy film, suggesting a sandwich structure. Our studies are important in understanding the growth mechanism and electronic properties of Sn films on noble metal substrates.

Surface structure and electronic structure of ultra thin NiO flms grown on Ag(0 0 1) substrate have been investigated in detail by means of low energy electron diffraction and photoemission spectroscopic studies under systematic modifications of surface Ni to O stoichiometry. Mild Ar+ bombardments (300 eV) were applied to the oxide films to produce predominant surface oxygen vacancies. These vacancy defects, which are mostly localized to the near surface region of the film, produce ‘defect states’ within the forbidden energy gap which pin the Fermi level (EF) away from valence band maxima. Angle-dependent X-ray photoemission spectroscopic studies have been undertaken to characterize the core level as well as the valence band electronic structures of the film which confirm the existence of metallic nickel clusters at the sputtered surface. The depletion of oxygen at the NiO surface produced by annealing in ultra high vacuum at sufficient temperature and its enhanced effect on the monolayer NiO film have been elucidated.

We have investigated the electronic structure of monolayer Cr deposited on Ag(001), using angle-resolved photoemission spectroscopy (ARPES) measurements and density functional theory (DFT) calculations. It is favorable for the Cr layer to be buried one layer deep, resulting in a 1 Ag/1 Cr/Ag(001) sandwich structure with the moments on the Cr atoms aligned antiferromagnetically in a c(2 × 2) arrangement. Both experiment and theory agree well on the measured/calculated band dispersions and their intensities. Two relatively flat bands arise from antiferromagnetic Cr 3d states; in addition, quantum well states with strong curvatures are prominent near both the X and M points of the surface Brillouin zone. Our results suggest that the buried Cr monolayer in Ag(001) could serve as a prototypical system to study two-dimensional antiferromagnetism in the presence of weak electronic correlation effects

Growth of tin (Sn) on Ag(001), Ag(111) and W(110) substrate has been studied at elevated temperatures (473 K) using x-ray photoemission spectroscopy (XPS) and low energy electron diffraction (LEED). For Sn growth on silver substrates, it is noticed that both Sn 3d and Ag 3d core-level spectra shift in the higher binding energy direction due to the formation of surface alloy with the substrate. In both cases, surface alloy finally transforms into bulk alloy finally reaching bulk Sn value. For Sn growth on W(110) only Sn 3d core-level spectra shift in the higher binding energy direction due to surface core-level effect whereas no shift for tungsten core-level was noticed confirming no alloy formation. Sn is incorporated into the surface of substrate silver layer by removing every alternate or every third silver atoms to relieve the surface tensile stress as confirmed by LEED. On the other hand, tungsten being hard, Sn forms an overlayer structure by sitting in different energetically available positions rather than forming an alloy as energetically also it is not possible. Sn forms alloy with soft substrate silver and form overlayer films with tungsten. These studies are important in understanding the growth mechanism of Sn films on metal substrates.

Considering the importance of photo catalytic oxidation of organic pollutants by semiconductors using sunlight, in the present study, we prepared and studied CdS-TiO2 nanocomposite. The commonly used photocatalyst TiO2 as such has the drawback that it uses only the UV portion of sunlight. The CdS-TiO2 composite was prepared by a modified sol-gel method. The structure and optical properties were studied by means of XRD, TEM and UV-visible spectroscopy. The composite was tested for their photocatalytic efficiency by the time taken for the degradation of the dye methyl orange under illumination of by absorption spectroscopy of samples extracted at different time intervals. It is found that CdS-TiO2 is more efficient as a photocatalyst than pure TiO2.This is due to better absorption of light in the visible range.

Concrete is susceptible to cracking owing to drying shrinkage, freeze-thaw cycles, delayed ettringite formation, reinforcement corrosion, creep and fatigue, etc. Continuous inspection and maintenance of concrete infrastructure require onerous labor and high costs. If the damaging cracks can heal by themselves without any human interference or intervention, that could be of great attraction. In this study, a novel self-healing approach is investigated, in which fungi are applied to heal cracks in concrete by promoting calcium carbonate precipitation. The goal of this investigation is to discover the most appropriate species of fungi for the application of biogenic crack repair. Our results showed that, despite the significant pH increase owing to the leaching of calcium hydroxide from concrete, Aspergillus nidulans (MAD1445), a pH regulatory mutant, could grow on concrete plates and promote calcium carbonate precipitation.

We investigate the influence of film thickness and magnetism on the electronic structure of a strongly correlated prototypical system, MnO(001) films epitaxially grown on Ag(001), using angle-resolved photoemission spectroscopy (ARPES) and x-ray photoelectron spectroscopy (XPS) techniques. XPS measurements have confirmed the MnO stoichiometry as well as the layer-by-layer growth mode of the films, while the ARPES measurements have confirmed the high structural quality of the films by the observation of clear band dispersions devoid of any sample charging effects. For lower coverage films, finite-size effects/reduced correlation effects are observed, while from 3 ML coverages, bulklike band structures are formed. Detailed band mapping along $\overline{\mathrm{\ensuremath{\Gamma}}}\text{\ensuremath{-}}\overline{X}$ and $\overline{\mathrm{\ensuremath{\Gamma}}}\text{\ensuremath{-}}\overline{M}$ directions reveal a relative dispersion between Mn-derived ${e}_{g}$ and ${t}_{2g}$ states up to 1.2 eV, in contrast to previous ARPES results where maximum relative dispersions of $\ifmmode\pm\else\textpm\fi{}0.1$ eV were reported, while our results excellently match with the theoretically predicted dispersions. By comparing with theoretical results we show the hybridization between O $2p$ with the Mn ${e}_{g}$ states giving rise to the observed dispersions resulting from the highly dispersive nature of the O $2p$ bands. Furthermore, we show that during the paramagnetic (PM) to antiferromagnetic (AFM) transition, the valence band gets narrower with an enhancement of the $^{5}e_{g}$ peak intensity, along with the widening of the energy gap by 200 meV. Theoretically, Terakura et al. had predicted the possibility of a similar outcome due to the decrease of the effective $dd$ hopping between the oppositely magnetized cations during the PM to AFM-II transition because of the $dd\ensuremath{\sigma}$ type interaction, yet the experimental verification was absent in the literature. We believe that the exact same mechanism as predicted by Terakura et al. is responsible for the changes seen in the electronic structure during magnetic phase transition and argue that a similar trend can be seen for the prototype materials such as CoO and NiO.

LEED and photoemission measurements have been performed on ultrathin NiO films to reinvestigate its surface quality and valence electronic structures, respectively. On Ag(0 0 1) substrate, the best epitaxial order was observed for high temperature deposition with sufficient oxygen flux associated with a post-deposition oxygen annealing. The effect of the substrate vicinity on valence band electronic structure, in case of interfacial NiO layers, has been explained. The variation of Ni 3d to O 2p photoemission cross-section with photon energy ( hν ) has been demonstrated in this work.

Growth of Cu, Ag and Au thin films on graphite(0 0 0 1) surface and possible formation of quantum well (QW) states originating due to the confinement of thin film sp electrons within the band gap of graphite along ΓM symmetry direction are investigated using low-energy electron diffraction (LEED) and angle-resolved photoemission spectroscopy (ARPES). Higher surface diffusivity and surface energy of Cu on graphite surface led to cluster growth and does not reveal any quantum size effect, while Ag and Au films grow epitaxially in spite of large lattice mismatch. However, better surface ordering has been achieved by growing Ag and Au at low temperature (LT), followed by room-temperature (RT) annealing which are evident from LEED and the presence of sharp Shockley-type surface state (SS) at Fermi level (E F). ARPES study of Ag films on graphite does not show any QW states, whereas Au films demonstrate a very sharp SS, Au bulk bands and well-resolved QW states or resonances. The observed low in-plane dispersions of these Au QW states or resonances are compared with the dispersions obtained in the previous Au QW state studies as well as for free-standing Au films.

At least a partial substitution of carbon black/precipitated silica being used in the rubber industry with low cost reinforcing fillers based on china clay (kaolin) — a non-replenishable natural resource could lead to technical and economic viability. Low cost industrial byproducts/renewable natural resources such as Cashew Nut Shell Liquid (CNSL) or Rubber Seed Oil (RSO) or their derivatives may be used as organo-modifiers for kaolin to impart excellent compatibility with non-polar rubbers along with desired physico-mechanical properties for various applications. Results of the present study as obtained from XRD, TEM, SEM, TGA, CLD (chemical crosslink density) and tensile properties show that low dosages of kaolin modified with a solution of Phosphorylated Cashew Nut Shell Liquid prepolymer (PCNSL) in toluene could act as potential nano-reinforcing fillers for natural rubber (NR), as evidenced by improvements in filler dispersion, thermal stability and tensile properties of the vulcanizates.

$\mathrm{Ti}{\mathrm{O}}_{2}$ in the rutile phase is known to be an incipient ferroelectric. Considering Nb-Cr codoping we examine if ferroelectricity can be induced at the low doping limit in $\mathrm{T}{\mathrm{i}}_{(1\text{\ensuremath{-}}x)}{(\mathrm{N}{\mathrm{b}}_{0.5}\mathrm{C}{\mathrm{r}}_{0.5})}_{x}{\mathrm{O}}_{2}$ ($x=0.05%$, 1%, 5%, and 10%). A relaxor behavior is found in the temperature range 20--120 K which obeys the Vogel-Fulcher relation while pyrocurrent measurements confirm switching of the electric polarization. The spontaneous net polarization is doping dependent with a maximum at 1% and for doping concentrations above 5% is found to be paraelectric. Ab initio density functional theory based calculations suggest that the Nb-Cr pair behaves like a dipole and polarizes the neighboring $\mathrm{Ti}{\mathrm{O}}_{6}$ octahedra, stabilizing a ferroelectric ground state akin to magnetic impurities in dilute magnetic semiconductors. At larger doping concentrations one finds that Nb-Cr clusters result in a vanishing polarization.

Carrier density, substrate and synthesis temperature dependent impedance measurements have been performed on Poly(3,4-ethylenedioxythiophene) [PEDOT] based devices in metal/polymer/metal geometry at room temperature. The relaxation mechanism of carries in these devices can be varied as per the growth condition. It is observed that in stainless steel (SS)/PEDOT/Silver (Ag) devices, as the carrier density decreases the interface related mechanism takes control over bulk transport, but as the synthesis temperature is lowered the bulk transport dominates over interface related mechanism. The substrate dependent studies have shown that the electrode potential can alter the growth of polymer chains, which affects the relaxation mechanism of the carriers.

Present report details an analysis of X-ray reflectivity (XRR) for solution processed NiO thin films on Si (100) substrates. The films were annealed at 700–1,000 °C for 1 h in air. XRR data indicated growth of SiO2 layer from ~8 nm at 700 °C to ~66 nm at 1,000 °C along with significant variation of electron density profile. X-ray photoelectron spectroscopy and X-ray diffraction studies were used as supporting studies for phase purity and oxidation states of the NiO thin films as well as interfacial SiO2 layer.

The anti-clockwise bipolar resistive switching in Ag/NiO/ITO (Indium–Tin–Oxide) heterojunctional thin film assembly is investigated. A sequential voltage sweep in 0 → V max → 0 → −V min → 0 order shows intrinsic hysteresis behaviour and resistive switching in current density (J)–voltage (V) measurements at room temperature. Switching is induced by possible rupture and recovery of the conducting filaments in NiO layer mediated by oxygen ion migration and interfacial effects at NiO/ITO junction. In the high-resistance OFF-state space charge limited current passes through the filamentary path created by oxygen ion vacancies. In OFF-state, the resistive switching behaviour is attributed to trapping and detrapping processes in shallow trap states mostly consisting of oxygen vacancies. The slope of Log I vs Log V plots, in shallow trap region of space charge limited conduction is ~2 (I ∝ V 2) followed by trap-filled and trap-free conduction. In the low-resistance ON-state, the observed electrical features are governed by the ohmic conduction.

A label-free fiber-optic Fabry–Perot interferometric (FPI) immunosensor is proposed by layer-by-layer (LBL) self-assembly of a suspended chitosan and polystyrene sulfonate membrane at the tip of a hollow fiber. Immunoglobulin G (IgG) was immobilized on the polyelectrolyte substrate and the detection of target anti-immunoglobulin G (anti-IgG) was monitored through the measurement of substrate's effective optical thickness. The sensitivity and specificity of the sensor were studied using correlated and non-correlated anti-IgG/IgG pair. Sensitivity of 0.033 μm/(pg/mm2) and limit of detection of 0.005 nM was achieved with the sensor displaying minimal response toward non-correlated anti-IgG. The results demonstrate the feasibility of the sensor for immunosensing.

Mathematical models were developed for the heat and mass transfer phenomena during deep-fat frying of gulab jamun, a dairy dessert popular throughout the Indian subcontinent. Size, shape, core temperature, moisture and fat contents of the product were monitored at regular intervals during 8 min of frying. The heat transfer was described using both lumped capacity model and transient heat conduction equation. As the calculated Biot number for lumped capacity model was greater than 0.1, the convective heat transfer coefficient was determined using the transient heat conduction equation as 122.34, 116.12 and 94.10 W/(m2 K) at 135, 145 and 155C, respectively. The moisture transport was described using a partial differentiation equation analogous to the transient heat conduction. The moisture transfer coefficient, ranging from 10.41 × 10−6 to 14.35 × 10−6m/s, increased linearly with frying temperature. The Lewis number declined from 0.96 to 0.54 with increasing temperature, indicating that at higher frying temperatures moisture diffusivity gained predominance over thermal diffusivity. Fat uptake of the product followed fractional conversion first-order kinetic model. Practical Applications Gulab jamun, a popular dairy sweet of the Indian subcontinent, is processed by deep-fat frying of milk solids–starch dough balls, followed by soaking them in sugar syrup. Its manufacture is currently dominated by small-scale unorganized enterprises, leading to non-optimized process conditions and widely varying product quality. The present study aims at describing the heat, moisture and fat transfer during the deep-fat frying process of this product using mathematical models. The effects of process parameters, such as temperature and time, on thermal and mass transfer properties and diffusivities were evaluated. Such mathematical models provide information to food processing professionals that help in predicting and optimizing the frying process parameters of gulab jamun in order to achieve maximum energy efficiency and desired product quality.

Label-free, all-fiber immunosensors based separately on Mach–Zehnder interferometry (MZI) and Michelson interferometery (MI) implemented using only single mode fiber (SMF) are proposed and experimentally demonstrated. The proposed SMF–MZI and SMF–MI sensors rely on intermodal interference between the core mode and cladding modes to detect ambient refractive index changes due to protein absorption on the cladding–ambient interface. The fiber surfaces were functionalized with self-assembled polyelectrolyte layers (chitosan (CS)/polysodium styrene sulfonate (PSS)). Immunoglobulin G (IgG) was immobilized on the polyelectrolyte layer and anti-immunoglobulin G (anti-IgG) molecular binding events were monitored through measurement of wavelength shifts. The proposed immunosensors exhibit anti-IgG detection sensitivities of 27.37 nm/(ng/mm 2 ) and 5.91 nm/(ng/mm 2 ) with concentration detection limits of 0.181 nM and 4.941 nM for MZI and MI sensor respectively. The specificities of the sensors were investigated using correlated/non-correlated anti-IgG–IgG pairs. These results demonstrate the feasibility of these sensors for various bio/chemical applications such as DNA hybridization detection and immunosensing.

Kaolin was modified using a chemical complex of hydrazine hydrate and oleochemical sodium salts derived from rubber seed oil (SRSO) and tea seed oil (STSO) respectively. Characterization of the pristine kaolin and the modified kaolins were performed using Scanning Electron Microscopy (SEM), Simultaneous Thermogravimetric/Differential Thermal Analysis (TG/DTA) and UV Spectrophotometry. TG/DTA revealed that the incorporation of the oleochemical salts enhanced thermal decomposition of kaolin into metakaolin. Ultraviolet spectrophotometric studies conducted on the modified kaolin show for the first time that the SRSO-modified kaolin and STSO-modified kaolin have a peak absorbance wavelengths of 312.72 nm and 314.26 nm respectively. This shows that the modified kaolin is a promising candidate for sunscreen applications.

Growth of ultrathin Co layers on close-packed Ag(111)were investigated by means of Low Energy Electron Diffraction (LEED), X-ray Photoelectron Spectroscopy (XPS) and Angle-resolved Photoemission Spectroscopy(ARPES) techniques. The close-packed hexagonal face of Co(0001), exhibits a lattice misfit about 13% with Ag(111) surface which manipulates the growth to be incommensurate up to a certain thickness. The strain field causes aperiodic height undulation in the sub-angstrom regime of the film which was confirmed by p(1 × 1) LEED pattern along with a 6-fold moire reconstruction pattern in the lower film thickness (up to ∼2ML). The evolution of the LEED pattern was studied with increasing film coverage. Lattice strain was measured with respect to the relative positions of these double spots as a functionof film thickness. Almost a constant strain (∼13%) in the full range of film thickness explains the moire pattern formation in order to stabilize the incommensurate growth. For higher film coverages, an epitaxial well-ordered commensurate growth was observed. Core level and valance band electronic structures of these films were studied by XPS and ARPES techniques.

Surface electronic structure of ultrathin polar MnO film was studied by Low-energy Electron Diffraction (LEED) and Photoemission Spectroscopic (PES) techniques. Epitaxial monolayer to facet formation with increasing film thickness has been observed by LEED. Our LEED result shows p(2x2) surface reconstruction along with facet formation, stabilize the polar MnO(111) surface. The core levels and the valence band electronic structure of MnO films have been studied as a function of film thickness using X-ray and ultraviolet photoelectron spectroscopy techniques.

V2O3 ultrathin films were grown on Ag(001) substrate by reactive evaporation of vanadium (V) metal in presence of oxygen and their structural and electronic properties were studied by Low Energy Electron Diffraction (LEED), X-ray Photo Electron Spectroscopy (XPS) and Angle Resolved Photoemission Spectroscopic (ARPES) techniques, respectively. On top of square symmetry substrate Ag(001), hexagonal surface of V2O3 (0001) is stabilized in the form of two domain structure, rotated by 30°(or 90°)to each other, has been observed by LEED. Rather than epitaxial flat monolayer, formation of well-ordered V2O3 (0001) island has been confirmed from the LEED and the Photoemission Spectroscopic (PES) study. Stoichiometry of the grown film was confirmed by the XPS study. Evolution of valance band electronic structure of V2O3 (0001) surface has been studied as a function of film thickness by ARPES.

A novel yellow colony-forming bacterium, strain P3B162T was isolated from the pokkali rice rhizosphere from Kerala, India, as part of a project study aimed at isolating plant growth beneficial rhizobacteria from saline tolerant pokkali rice and functionally evaluate their abilities to promote plant growth under saline conditions. The novel strain P3B162T possesses plant growth beneficial traits such as positive growth on 1-aminocyclopropane-1-carboxylic acid (ACC), production of indole acetic acid (IAA) and siderophore. In addition, it also showed important phenotypic characters such as ability to form biofilm and utilization of various components of plant root exudates (sugars, amino acids and organic acids), clearly indicating its lifestyle as a plant rhizosphere associated bacterium. Taxonomically, the novel strain P3B162T was affiliated to the genus Arthrobacter based on the collective results of phenotypic, genotypic and chemotaxonomic analyses. Moreover, molecular analysis using 16S rRNA gene showed Arthrobacter globiformis NBRC 12137T, Arthrobacter pascens DSM 20545T and Arthrobacter liuii DSXY973T as the closely related phylogenetic neighbours, showing more than 98% 16S rRNA similarity values, whereas the recA gene analysis displayed Arthrobacter liuii JCM 19864T as the nearest neighbour with 94.7% sequence similarity and only 91.7% to Arthrobacter globiformis LMG 3813T and 88.7% to Arthrobacter pascens LMG 16255T. However, the DNA-DNA hybridization values between strain P3B162T, Arthrobacter globiformis LMG 3813T, Arthrobacter pascens LMG 16255T and Arthrobacter liuii JCM 19864T was below 50%. In addition, the novel strain P3B162T can be distinguished from its closely related type strains by several phenotypic characters such as colony pigment, tolerance to NaCl, motility, reduction of nitrate, hydrolysis of DNA, acid from sucrose, cell wall sugars and cell wall peptidoglycan structure. In conclusion, the combined results of this study support the classification of strain P3B162T as a novel Arthrobacter species and we propose Arthrobacter pokkalii sp.nov.as its name. The type strain is P3B162T (= KCTC 29498T = MTCC 12358T).

Sodium salt of tea seed oil (TSO-Na) was organomodified with kaolin (China clay). The organo-kaolin was characterized by determining the FTIR and XRD. Results indicated that TSO-Na was successfully intercalated onto the kaolin surface. Nanocomposite of rubber copolymer with tea seed oil organomodified kaolin was prepared by incorporating 5phr organo-kaolin. The mechanical testing of the rubber vulcanizate involved the determination of tensile and tear property. The performance characteristics showed that there was considerable improvement in the tensile strength, tear strength and elongation at break properties of the organoclay filled vulcanizate compared to the unmodified polymer. Scanning electron microscopy (SEM) studies revealed that the incorporation of 5phr organoclay has remarkable effect on the failure mechanism of the NR filled vulcanizate. This is an indication that the failure mechanism is strongly dependent on the reinforcement effect of the modified filler marked by a higher extent of rubber-filler matrix interaction. There is therefore indication that tea seed oil can be organomodified with kaolin to serve as nanofiller.

Kaolin modified with sodium salt of rubber seed oil (RSO-Na) was compounded with natural rubber (NR) by melt intercalation. The effect of modified kaolin loading on the physicomechanical properties of the vulcanizates was examined by varying its incorporation (2–10 phr). The RSO-Na modified kaolin was characterized using infrared spectroscopy (FTIR) and X-ray diffraction (XRD). XRD of the unmodified and modified kaolin revealed an increased d-spacing of kaolinite to 14 Ǻ. FTIR spectroscopy also indicated the intercalation of RSO-Na onto the kaolinite surface. The tensile and tear properties increased with increasing filler loading even though an optimum of tensile strength was achieved at 8 phr of modified kaolin. The swelling index was reduced by filling with modified kaolin. The storage modulus value for the modified samples was higher than the NR vulcanizates with unmodified kaolin. Furthermore, the chemical crosslink density (CLD) of 0.651 at 8 phr modified kaolin indicated better reinforcement of the rubber-filler matrix. The morphological studies by SEM revealed that incorporation of modified kaolin up to 8 phr resulted in the improvement of failure properties of the resulting NR vulcanizates.

Melt rheology and extrudate morphology of polystyrene (PS)/polybutadiene (PB) blends were studied with special reference to the effect of blend ratio and two different types of compatibilisers, the random copolymers and block copolymers. Uncompatibilized blends had viscosities approximately intermediate between those of the component polymers. In the case of uncompatibilized blends both positive and negative deviation was observed in the viscosity-composition curve at different shear rate range studied. The viscosity of the compatibilized blend was found to increase when a few percent of block copolymer was added. However, at high concentrations of the compatibiliser, the viscosity values leveled off. This is due to interfacial saturation. Morphological investigations indicated that the size of the dispersed phase initially decreased when a few percent of the block copolymer was added followed by a clear leveling off at higher concentration. However, the random copolymer was not an effective interface modifier in agreement with microscopy study. These experimental results supports the earlier investigations of solid state NMR studies on these blends (Polymer (2005) 46(22):9385).

The use of thermoplastic/liquid-crystalline polymer (LCP) blends is recognized as a good strategy for reducing viscosity and improving mechanical properties relative to pure thermoplastics. This improvement, however, is only noticeable if the LCP fibrillates, in situ, during processing and the fibrils are kept in the solid state. In this article, we report a morphological, rheological, and rheo-optics study performed with two blends of poly(ethylene terephthalate) with a LCP, Rodrun LC3000 (10 and 25 wt % LCP content), and we show that the obtained droplet-shape relaxation time (the time the deformed droplet took to regain its spherical form after the cessation of flow) allowed for the explanation of the morphological observations. In fact, the droplet-shape relaxation time was higher for the blend with higher LCP content, for the higher experimentally accessible shear rates, and still increased at the highest shear rate, which explained the fibrils of the LCP dispersed phase observed in this blend, whereas for the lower LCP content blend, the droplet-shape relaxation time reached a low-value plateau for higher shear rates, which explained the absence of fibrillation in this blend. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008