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The Shahabad Limestone Formation of Bhima Basin from Gogi-Kanchankayi area occurs in heterogeneous forms like massive/blocky limestone, argillaceous/ siliceous limestone and laminated/ flaggy limestone. These limestones are primarily composed of micrite, which often alters into sparry calcite on diagenesis with associated impurities of quartz, feldspar, barite, chlorite, glauconite, sulphides and carbonaceous matter. Geochemically, these limestones comprises of variable CaO with low MgO and P2O5 content. Trace elements concentration shows elevated Ba, Rb and depleted Sr. The current study classified these limestones as non-dolomitic and non-phosphatic types deposited in shallow marine carbonate platform setting with low energy conditions. Post-sedimentation, basin tectonics has resulted in reactivation of the basin margin fault causing intense fracturing of limestone. Subsequent hydrothermal movement along those fractures has resulted in re-mobilisation and re-precipitation of sulphides and carbonaceous matter, and along with alteration has facilitated the precipitation of the uranium bearing minerals.

Kanchankayi is located in the central part of the 55 km long Kurlagere-Gogi-Gundanahalli (KG) fault of Meso-Neoproterozoic Bhima basin of Southern India. Intensive integrated exploration in Kanchankayi has established a concealed, fracture-controlled, low-grade uranium deposit. Uranium mineralisation is mostly confined within the fractured limestone of Shahabad Formation and partly within fractured basement granite. Tectonic movements along the KG fault in Kanchankayi area have resulted in the northward thrusting of basement granite over the Bhima sediments forming a reverse fault geometry. Structural mapping and subsurface exploration has established that the uranium mineralisation is mainly confined to the fault zone. In general, the fault zone is characterised by steep southerly dipping to vertical limestone beds. Iso-dip contouring was attempted on the beds having equal angle of dip, with the premise that steep southerly dipping and vertical beds will reveal the trend and location of the fault zone on the surface. The iso-dip contour map reveals that the contour depicting the fault zone initially follows the basement-sediment contact and further NE i.e. towards Kanchankayi and transgresses into the Bhima sediments. This suggests that the fault zone, instead of following the basement-sediment contact, moves within the basin in Kanchankayi. Recent sub-surface exploration in Kanchankayi has corroborated this interpretation. The innovative approach in utilizing structural mapping and iso-dip contouring has not only given a new dimension to the exploration programme at Kanchankayi but also provided a model technique for exploration of concealed, structure-controlled, hydrothermal, vein-type uranium mineralisation in parts of Bhima basin.

A highly sensitive biosensing platform comprised of CdSe-ZnO core–shell nanostructures for targeted applications in protein detection is demonstrated. This innovative technique uses a microwave-assisted thermal decomposition method to produce a rapid, less hazardous, and user-friendly procedure to synthesize a semiconductor core surrounded by nanometer-thick metal oxide shells. The benefit of using a metal oxide shell includes mitigating the toxicity of the CdSe core, thus increasing its biocompatibility and minimizing its photochemical corrosion and oxidation. We present a simple one-pot microwave-assisted protocol for the formation of CdSe-ZnO core–shell quantum dots (QDs). These QDs optimize the recognition limit of bovine serum albumin (BSA) protein through a spectral signal at a considerably low concentration (2.5 × 10−6 M), thus demonstrating its potential to become a highly effective surface-plasmon-enhanced Raman spectroscopy (SERS)-like sensing platform. We report a QD material that can mimic a strong SERS-like behavior due to charge transfer affecting the local electric field.

In this research, we demonstrate a cost-effective method of developing a high temperature transparent heater by creating mesoscale (1–5 μm diameter) silver (Ag) wire network on glass. A colloidal solution of ethanol and cerium oxide (CeO2) is used to create a sacrificial template onto which Ag (100 nm) was deposited using electron beam (EB) evaporation. EB deposition parameters are critically optimized so that Ag wires are annealed instantly having rigid adherence to the substrate surface. A highly interconnected and continuous Ag network is obtained exhibiting transmittance up to 70% and sheet resistance of 1.13 Ω/sq, making it suitable for optoelectronic applications. This transparent conductor serves as a transparent heater when a DC voltage is applied to it, generating temperatures more than 200 °C at an operating voltage of just 4 V. This unique electro-thermal property can be attributed to the triangular junctions of Ag wire network that act as a micro-welding centers which impede the transport current path, favoring resistive Joules heating.

The effect of Mo doping on the structural and dielectric properties has been investigated in detail for Co-Zn spinel ferrite. Solid state reaction technique has been used to prepare the CZMO. The structural analysis is performed using HRXRD technique which confirms the inverse spinel structure of the material. The frequency and temperature dependence of dielectric constant are studied which reveals that the dielectric dispersion is due to Maxwell-Wagner type polarization in agreement with Koop's phenomenological theory. The contribution of grain and grain boundary at high and low frequency respectively are evident in the dielectric constant. The variation of dielectric loss tangent with both the temperature and frequency has been studied. The room temperature and high frequency dielectric loss is observed to be very small. Also it is revealed that the dielectric loss tangent decreases with Mo substitution.

We have optimized Gd ion substitution in BiFeO 3 (BFO) and observed prominently change in structural, electrical and magnetic behavior of Bi 1+2x Gd 2x/2 Fe 1−2x O 3 ceramics synthesized through slow step sintering schedule. It is observed that with the increase in concentration of Gd (x=0.1), original structure of BFO is transformed from rhombohedral R 3 c space group to orthorhombic Pn 21 a space group. Surprisingly, unit cell volume is drastically contracted (35% for x=0.2) and the sintered specimen showed enhanced room temperature ferromagnetic behavior although the original BFO is normally G-type antiferromagnetic in nature at 643 K. It is expected that intrinsic chemical pressure within the bulk body built by the substitution of Gd in presence of excess bismuth greatly supported through unidirectional movement of electrical dipole moment with in each individual domain as a result of which suppression of leakage current with enhanced dielectric and ferroelectric hysteresis is observed.

The presence of denatured proteins within a therapeutic drug product can create a series of serious adverse effects, such as mild irritation, immunogenicity, anaphylaxis, or instant death to a patient. The detection of protein degradation is complicated and expensive due to current methods associated with expensive instrumentation, reagents, and processing time. We have demonstrated here a platform for visual biosensing of denatured proteins that is fast, low cost, sensitive, and user friendly by exploiting the plasmonic properties of noble metal nanoparticles. In this study we have exposed artificially heat stressed ferritin and gold nanoparticles to 3-aminopropyl triethoxysilane, which degrades the protein by showing a systematic blue shift in the absorbance spectra of the gold nanoparticle/ferritin and aminosilane solution. This blue shift in absorbance produces a detectable visual color transition from a blue color to a purple hue. By studying the Raman spectroscopy of the gold nanoparticle/ferritin and aminosilane solution, the extent of ferritin degradation was quantified. The degradation of ferritin was again confirmed using dynamic light scattering and was attributed to the aggregation of the ferritin due to accelerated heat stress. We have successfully demonstrated a proof of concept for visually detecting ferritin from horse spleen that has experienced various levels of degradation, including due to heat stress.

The ability to control the growth of materials with nanosized precision as well as a complex hollow morphology provides rationale for the study of systems comprising both characteristics. This study explores the design of TiO2 hollow nanotube shells deposited by atomic layer deposition (ALD) on vertically aligned SnO2 nanorods grown using the vapor–liquid–solid technique. The sacrificial template approach in combination with highly conformal coating advantages of ALD resulted in a highly reproducible method to create a large surface area covered by TiO2-protected SnO2 nanorods, which are about 60–100 nm in diameter and approximately 1 μm in length. ZnO was used as a sacrificial layer to create a 30 nm gap between SnO2 nanorods and 10 nm of TiO2 shells. Chemical etching of the sacrificial layer was used to create the desired hollow nanocomposite. A coin half-cell battery has been assembled using the TiO2-protected SnO2 nanorods as an anode electrode and lithium foil as a counter electrode and tested for li...

In this work, a series of multi-constituent nonwovens possessing multi-modal fiber diameter distribution was prepared and the air permeability of such nonwoven structures was measured. This approac...

Multiferroic materials have attracted considerable attention as possible candidates for a wide variety of future microelectronic and memory devices, although robust magnetoelectric (ME) coupling between electric and magnetic orders at room temperature still remains difficult to achieve. In order to obtain robust ME coupling at room temperature, we studied the Pb(Fe0.5Nb0.5)O3/Ni0.65Zn0.35Fe2O4/Pb(Fe0.5Nb0.5)O3 (PFN/NZFO/PFN) trilayer structure as a representative FE/FM/FE system. We report the ferroelectric, magnetic and ME properties of PFN/NZFO/PFN trilayer nanoscale heterostructure having dimensions 70/20/70 nm, at room temperature. The presence of only (00l) reflection of PFN and NZFO in the X-ray diffraction (XRD) patterns and electron diffraction patterns in Transmission Electron Microscopy (TEM) confirm the epitaxial growth of multilayer heterostructure. The distribution of the ferroelectric loop area in a wide area has been studied, suggesting that spatial variability of ferroelectric switching behavior is low, and film growth is of high quality. The ferroelectric and magnetic phase transitions of these heterostructures have been found at ~575 K and ~650 K, respectively which are well above room temperature. These nanostructures exhibit low loss tangent, large saturation polarization (Ps ~ 38 µC/cm2) and magnetization (Ms ~ 48 emu/cm3) with strong ME coupling at room temperature revealing them as potential candidates for nanoscale multifunctional and spintronics device applications.

High quality ultrathin transition-metal dichalcogenide films and their Vander Waals heterostructures are very promising for fabrication of optoelectronic devices for their superior photovoltaic performance, extreme flexibility and long lifetime due to suitable band gap and excellent light absorption capability. Designing the appropriate and suitable band structures of these materials is crucial for its promising applications. Especially, thin molybdenum disulfide (MoS 2 ) film is further attractive as compare to its monolayer counterpart for broad-spectral photo-detectors and photovoltaic application. However, very little understanding regarding the underlying physics behind the photo-response behavior of thin MoS 2 films is known. Here, we demonstrate a large photovoltaic response in thin MoS 2 films which produces an enormous photo-generated carrier and enhance the photocurrent by forming a heterojunction with p-type Si substrate. MoS 2 based photovoltaic devices efficiently produce high short-circuit photocurrent values of 18 mA/cm 2 and reasonably high power-conversion efficiency up to 4.5%. The present work will provide valuable scientific input of layered MoS 2 films for other emerging optoelectronic applications.

We report on the study of the low-temperature fabrication of ZnO thin film transistors on high-k gate dielectrics: Al 2 O 3 , HfO 2 and ZrO 2 . All gate dielectrics were grown by atomic layer deposition at 150 °C and the ZnO semiconductors were grown by rf magnetron sputtering at room temperature. The electrical characteristics and device performance have been investigated systematically, along with the thin film structural properties by X-ray diffraction and atomic force microscopy. Highly (0 0 0 2)-oriented ZnO thin films were observed and their surface morphology revealed similar microstructures regardless of the bottom gate oxides. The fabricated thin film transistors showed high on/off ratio larger than 10 5 and low subthreshold voltage swing. The discrepancy of the device performance in these combinations indicated a significant gate dielectrics and interface dependence.

Sensor related research has greatly increased over the last two decades due to the need for technology and devices for health and environmental monitoring as well as for biological warfare detection. New developments in biosensor design are crucial as these devices are in increasing demand in daily life. This paper presents a device based on electrochemical sensing using a working electrode with zinc oxide (ZnO) nanorods functionalized with glucose oxidase (GOx). Among all metal oxide nanostructures, ZnO nano-materials play a significant role as a sensing element in biosensors due to their properties such as high isoelectric point (IEP), fast electron transfer, non-toxicity, biocompatibility, and chemical stability. The glucose sensor was designed and fabricated on a silicon substrate. The ZnO nanorods were grown by the hydrothermal technique. The sensor has a linear range of 0.1mM-10.6mM, sensitivity of 18.15μA cm-1 mM-1 and a limit of detection of 0.1mM.

Cobalt–Zinc ferrites are an important material for designing multiferroic composite. The Mo (4d-transition metal) doped Cobalt–Zinc ferrites are synthesized using ceramic (solid-state reaction) method. Investigation of detailed ac and dc electrical conductivity, dielectric and magnetic properties of Co0.65Zn0.35Fe2−x Mo x O4 (x = 0.0, 0.1 and 0.2) spinel ferrites have been reported here. The recorded XRD pattern confirms the formation of inverse spinel structure of the material. The dielectric dispersion has been studied in detail and the existence of non-Debye type relaxation behavior has been confirmed. The dielectric tangent loss is found to be very small at high frequency. The ac conductivity follows the correlated barrier hopping like model. Also the conduction process can be best explained on the basis of Verwey-de Boer mechanism. Magnetic phase transition of the material is estimated from magnetization vs. temperature plots.

In this work, we have studied photo-electronic current transport in a back-gated graphene field-effect transistor. Under the light illumination, band bending at the metal/graphene interface develops a built-in potential which generates photonic current at varying back-gate biases. A typical MOSFET type back-gated transistor structure uses a monolayer graphene as the channel layer formed over the silicon dioxide/silicon substrate. It is shown that the photo-electronic current consists of current contributions from photovoltaic, photo-thermoelectric and photo-bolometric effects. A maximum external responsivity close to 0.0009A/W is achieved at 30μW laser power source and 633nm wavelength.

We have demonstrated the attachment of aligned ZnO nanorod arrays on to the electron beam lithographically patterned oxide surface at lower beam energy. At higher beam energy (~ 20 KeV), the accumulated negative charges that already built on the surface in due course of irradiation restricts the growth of nanorod arrays. This causes a negative shielding potential close to the surface at micron level, and completely unfavorable for the attachment of the negative ZnO carriers. However, at comparatively lower beam energy (~ 5 KeV or less), the secondary electrons are responsible for the pattern with the irradiation zone centered by the local positive field. This allows negatively charged ZnO nanorod arrays to grow at lower beam voltages, which initiate site selective attachments. This protocol of site selection is very useful for various sensor fabrications.

Compound III-V semiconductors such as GaAs have the potential to replace Si as the channel material in metal-oxide-semiconductor-field-effect-transistors (MOSFET) due to their high electron mobility. However, it is extremely important to remove native oxide from the surface of GaAs. GaAs surfaces were self-cleaned through fast pulsing of the Trimethylaluminum (TMA) precursor by reducing and restraining the regrowth of native oxides using the atomic layer deposition (ALD). The thermal conversion of As-O in to Ga-O reduction was evaluated by the x-ray photoelectron spectroscopy. Metal oxide semiconductor (MOS) capacitor was using ZrO2 as high-k gate dielectric on n-GaAs substrates, and their superior performance in electrical properties has been demonstrated. ZrO2/GaAs capacitor exhibits superior capacitance-voltage characteristics reduced leakage current due to reduced interfacial trap density. These studies have remarkable significance for the development of high-throughput innovative electronics, using ZrO2 as high-k dielectric. The interfacial characteristics and band alignments of high-k ZrO2 on n-GaAs have been investigated by experimentally and density functional theory. We have demonstrated that the frequency dispersion due to interface traps in capacitance-voltage characteristics of ZrO2/GaAs interface was significantly reduced through self-cleaning by trimethylalumina. The experimental valence band offset of 2.10 eV from X-ray photoelectron spectroscopy is found to be lower than that of the calculated value of 3.02 eV. The calculated conduction band offset is 1.21 eV compared to the experimental value of 1.38 eV confirms significant reduction of interface traps due to the Fermi-level pinning minimizing band misalignment.

Memristor devices have been rapidly emerging as a promising candidate in the field of non-volatile memory devices. There are a wide range of applications such as non-volatile random access memory, dynamic random access memory, image processing, flash memory, neural networks, and artificial intelligence. In recent years, many new materials for memristors have been investigated including metal-oxides due to their potential for high-density integration, high endurance, fast switching behavior, low power consumption and simple structure. Among the promising binary transition metal oxide materials, such as nickel oxide, zirconium oxide, zinc oxide, hafnium oxide, and Ta2O5, TiO2 films are extensively used to fabricate nonvolatile memristor devices due to its simple structure and compatibility with CMOS integration processes. Recently, ZnO has been widely used for various applications due to its good electrical conductivity, wide band gape (3.37 eV), high exciton binding energy (~60 meV), low cost, nontoxicity, high mechanical and thermal stability. When doped with Aluminum ZnO grown via atomic layer deposition (ALD) has been reported to show resistivity values ranging from insulating to on the order of 10−3 Ω·cm, which is suitable for memory device electrodes. Many methods are available for synthesis of thin films such as magnetron sputtering, pulsed laser deposition, thermal oxidation, electrodeposition, chemical vapor deposition, sol gel chemical reaction, and atomic layer deposition. ALD technique is considered promising for potential application in the preparation of memristors based on active TiO2 layers. The ALD is a self-limiting technique that allows one atomic layer growth for each growth cycle. ALD can precisely control the film layer thickness, stoichiometry, composition, uniformity, and sharp interfaces. ALD also shows perfect conformal coverage when it deposits thin film on complex surface structures. Therefore, ALD is considered as a novel and competitive method to deposit MIM memory structures. To create such MIM devices, first a transparent Al:ZnO film was grown on a Si wafer as a transparent bottom electrode followed by an active layer of TiO2 film. Then the top contact layer consisting of Al:ZnO was deposited in-situ on the TiO2 layer to complete the memristor structure. All the thin films in the memristor structure were synthesized sequentially by ALD technology. Several physical characterization techniques have been utilized to analyze the ALD TiO2 thin films of memory devices. The crystal structure was determined by X-ray diffraction (XRD). The film morphology was studied by field emission scanning electron microscopy (FE-SEM). The surface roughness was measured by atomic force microscopy (AFM). The electric properties were tested by a semiconductor parametric analyzer. The results demonstrate promising memristive properties of synthesized ALD TiO2-Based Memristors sandwhiched between Al:ZnO electrical contacts.

Different grades of magnetic cobalt ferrite (CoFe2O4) nanoparticles were synthesized with various molar ratios of Fe+2 to Co+2 ions in the initial salt solutions by the co-precipitation method. The crystal structure and morphology of the nanoparticles are obtained from X-ray diffraction and transmission electron microscopy studies. Fourier transform infrared spectroscopy analysis exhibited the Fe–O stretching vibration ~540 cm−1, confirming the formation of metal oxide. The magnetic studies demonstrate that all of the nanoparticles are superparamagnetic at 300 K. The saturation magnetization and coercivity of the CoFe2O4 nanoparticles are affected by the molar ratios of Fe+2 to Co+2 ions. Among all the synthesized nanoparticles, the system with 75:25 molar ratio of Fe+2 to Co+2 ions with a particle size of 13 nm showed a high magnetization of 90 emu/g.

GaAs surfaces were self-cleaned through fast pulsing of the Trimethylaluminum (TMA) precursor by reducing and restraining the regrowth of native oxides using the atomic layer deposition (ALD). The thermal conversion of As–O in to Ga–O reduction was evaluated by the X-ray photoelectron spectroscopy. Metal oxide semiconductor (MOS) capacitor was using ZrO2 as high-k gate dielectric on n-GaAs substrates, and their superior performance in electrical properties has been demonstrated. ZrO2/GaAs capacitor exhibits superior capacitance–voltage characteristics reduced leakage current due to reduced interfacial trap density. These studies have remarkable significance for the development of high-throughput innovative electronics, using ZrO2 as high-k dielectric.

The reduction of native oxides on GaAs substrates is studied by short time pulsing of the metal precursor for self-cleaning mechanism using atomic layer deposition (ALD) of Trimethyl aluminum (TMA). The short time pulsing of the TMA is effective for self-cleaning mechanism to reduce the GaAs native oxides. X-ray photoelectron studies demonstrated that the pulsed deposition of TMA in the range of 2 to 4s is the most effective way of cleaning the GaAs native oxides. Microscopic studies clearly demonstrate the sharp interface between dielectric/GaAs. GaAs based metal oxide semiconductor (MOS) capacitors were fabricated with ZrO2 and HfO2 gate dielectrics using ALD. The effect of growth temperature of dielectric films on GaAs was studied. The as deposited samples have a significant amount of fixed charge in the bulk of the gate dielectric and at dielectric/semiconductor (ZrO2 or HfO2/GaAs) interface, which causes the flat band shift and frequency dispersion.

Self-assembled nanostructures of CulnGaSe2 (CIGS) comprising of nanosheets with sheet thickness of 20 nm have been developed via one-step electrochemically alloying technique. These self-assembled nanoplates exhibit highly intersecting behavior and transform from CuSe to CIGS as the reduction potential was varied. The morphological analysis indicated that the process resulted in a progression of crystallites to a series of heavy dense intersecting nanoplates. Further analyses revealed that the nanostructures keep their integrity on heat treatment. The structure confirms the inclusion of Indium and Gallium at higher reduction potentials and its transition from pseudoamorphous to polycrystalline structure. A strong correlation between reduction potential, and the composition was established. The spectroscopic and optical spectra clearly prove that the direct band gap for the as-grown and annealed thin films, and appropriate for solar cell applications. These self-assembled dense interweaved nanoplates structure have not been observed previously in CIGS semiconductor system and have potential implications forenergy applications.

The ability to control the growth of materials with nanosized precision as well as a complex hollow morphology provides rationale for the study of systems comprising both characteristics. This study explores the design of TiO

Aluminum (Al) doped ZnO with very high Al concentration acts as metal regarding its electrical conductivity. ZnO offers many advantages over the commonly-known metals being used today as electrode materials for nuclear detector fabrication. Often, the common metals show poor adhesion to CdZnTe or CdTe surfaces and have a tendency to peel off. In addition, there is a large mismatch of the coefficients of thermal expansion (CTE) between the metals and underlying CdZnTe, which is one of the reasons for mechanical degradation of the contact. In contrast ZnO has a close match of the CTE with CdZnTe and possesses 8-20 times higher hardness than the commonly-used metals. In this presentation, we will explore and discuss the properties of CdZnTe detectors with ZnO:Al contacts.

Y 1 x Pr x )Ba 2 Cu 3 O 7- y is a unique superconductive material for the investigation of the interrelation between crystal structure, chemical composition and physical properties. In order to grow large crystals of high quality, an extensive study has been made of the Y 2O 3 -Pr 6 O I1 -BaO-CuO growth system. The eutectic composition of the BaO-CuO flux is confirmed by the improved thermogravimetric method (ITGA) as occurring at the molar composition of 7:18. The pseudo-binary phase diagram of (Y, Pr)BCO-(7BaO+18CuO) has been determined by means of differential thermal analysis (DTA), by X-ray diffraction and by study of crystal growth. Using the phase diagram, suitable compositions and temperature programs have been established for the growth of large crystals and for the separation of the crystals from the flux. Single crystals with a wide range of Pr doping have been obtained from a eutectic BaO-CuO flux. The dependence of the Pr concentration in the crystals on the composition of the initial melt has been determined by electron probe microanalysis and X-ray microanalysis. The superconducting transition temperature is found to decrease monotonically with increasing Pr concentration.

Graphene Oxide (GO) based low cost flexible electronics and memory cell have recently attracted more attention for the fabrication of emerging electronic devices. As a suitable candidate for resistive random access memory technology, reduced graphene oxide (RGO) can be widely used for non-volatile switching memory applications because of its large surface area, excellent scalability, retention and endurance properties. We demonstrated that the fabricated metal/RGO/metal memory device exhibited excellent switching characteristics, with on/off ratio of two orders of magnitude and operated threshold switching voltage of less than 1 V. The studies on different cell diameter, thickness, scan voltages and period of time corroborate the reliability of the device as resistive random access memory. The microscopic origin of switching operation is governed by the establishment of conducting filaments due to the interface amorphous layer rupturing and the movement of oxygen in the GO layer. This interesting experimental finding indicates that device made up of thermally reduced GO shows more reliability for its use in next generation electronics devices.

CdZnTe (CZT) has made a significant impact as a material for room-temperature nuclear-radiation detectors due to its potential impact in applications related to nonproliferation, homeland security, medical imaging and gamma-ray telescopes. In all such applications, common metals, such as gold, platinum and indium, have been used as electrodes for fabricating the detectors. Because of the large mismatch in the thermal-expansion coefficient between the metal contacts and CZT, the contacts can undergo stress and mechanical degradation, which is the main cause for device instability over the long term. Here, we report for the first time on our use of Al-doped ZnO as the preferred electrode for such detectors. The material was selected because of its better contact properties compared to those of the metals commonly used today. Comparisons were conducted for the detector properties using different contacts and improvements in the performances of ZnO:Al-coated detectors are described in this paper. These studies show that Al:ZnO contacts to CZT radiation detectors offer the potential of becoming a transformative replacement for the common metallic contacts due to the dramatic improvements in the performance of detectors and improved long-term stability.

ZnO has intrinsic semiconductor conductivity because of an unintentional doping mechanism resulting from the growth process that is mainly attributable to oxygen vacancies (VO) positioned in the bandgap. ZnO has multiple electronic states that depend on the number of vacancies and the charge state of each vacancy. In addition to the individual electron states, the vacancies have different vibrational states. We developed a high-temperature precursor vapor mask technique using Al2O3 to pattern the atomic layer deposition of ZnO and Al:ZnO layers on ZnO-based substrates. This technique was used to create a memristor device based on Al:ZnO thin films having metallic and semiconducting and insulating transport properties ZnO. We demonstrated that adding combination of Al2O3 and TiO2 barrier layers improved the resistive switching behavior. The change in the resistance between the high- and low-resistivity states of the memristor with a combination of Al2O3 and TiO2 was approximately 157%. The devices were exposed to laser light from three different laser diodes. The 450 nm laser diode noticeably affected the combined Al2O3 and TiO2 barrier, creating a high-resistivity state with a 2.9% shift under illumination. The high-resistivity state shift under laser illumination indicates defect shifts and the thermodynamic transition of ZnO defects.

We demonstrate that a nanostructured metal thin film can achieve enhanced transmission efficiency and sharp resonances and use a large-scale and high-throughput nanofabrication technique for the plasmonic structures. The fabrication technique combines the features of nanoimprint and soft lithography to topographically construct metal thin films with nanoscale patterns. Metal nanogratings developed using this method show significantly enhanced optical transmission (up to a one-order-of-magnitude enhancement) and sharp resonances with full width at half maximum (FWHM) of ~15nm in the zero-order transmission using an incoherent white light source. These nanostructures are sensitive to the surrounding environment and the resonance can shift as the refractive index changes. We derive an analytical method using a spatial Fourier transformation to understand the enhancement phenomenon and the sensing mechanism. The use of real-time monitoring of protein-protein interactions in microfluidic cells integrated with these nanostructures is demonstrated to be effective for biosensing. The perpendicular transmission configuration and large-scale structures provide a feasible platform without sophisticated optical instrumentation to realize label-free surface plasmon resonance (SPR) sensing.

We demonstrate the electro-thermal control of aluminum-doped zinc oxide (Al:ZnO) /vanadium dioxide (VO2) multilayered thin films, where the application of a small electric field enables precise control of the applied heat to the VO2 thin film to induce its semiconductor-metal transition (SMT). The transparent conducting oxide nature of the top Al:ZnO film can be tuned to facilitate the fine control of the SMT of the VO2 thin film and its associated properties. In addition, the Al:ZnO film provides a capping layer to the VO2 thin film, which inhibits oxidation to a more energetically favorable and stable V2O5 phase. It also decreases the SMT of the VO2 thin film by approximately 5–10 °C because of an additional stress induced on the VO2 thin film and/or an alteration of the oxygen vacancy concentration in the VO2 thin film. These results have significant impacts on technological applications for both passive and active devices by exploiting this near-room-temperature SMT.

The granite in Samingiri — Dilsekgiri area occurs as discordant, isolated pluton within the migmatitic terrain of West Garo Hills district, Meghalaya. The pluton is exposed over 140 sq km (18 km × 8 km). It exhibits structures of solid state and piecemeal stoping effect proximal to the contact and enveloped by a contact metamorphic aureole of albite-epidote-hornfels facies. Modally, it is biotite-monzogranite and biotite-syenogranite with minor biotite, chlorite, epidote and sericite and accessories like zircon, apatite, allanite, pyrite, magnetite and sphene. Geochemically, it is marked by restricted composition (69–76 wt% SiO2), high alkalies, low Ca, metaluminous to strongly peraluminous (Molar Al2O3/CaO+Na2O+K2O = 0.95 − 1.54), high FeO/MgO, high Ga/Al, high contents of Rb, Sr, Ba, Y, Zr and Ce and depleted in Ti and P. The field observation, mineralogical and geochemical aspects indicate the post-tectonic nature of West Garo pluton more like as A-type granite formed by partial melting of lower crustal blocks followed by low to moderate degree of fractional differentiation. Low Ca, alkaline nature and peraluminous character point to A-type nature of West Garo granite significantly different from other granites of Meghalaya Plateau. Rb-Sr age (616±86 Ma) of granite, however, corresponds to widespread Middle to Upper Pan African activity, a thermal event prevailed during Late Proterozoic — Early Palaeozoic (500–800 Ma) period, manifested in the form of several granitic intrusions in the basement gneissic complex and the overlying Proterozoic metasediments of the Shillong Group in Meghalaya Plateau.

The fabrication of condensed silica and mesoporous silica coated spinel CoFe 2 O 4 and FeCo alloy magnetic nanocomposites are reported. The encapsulation of well-defined 5 nm thick uniform silica layer on CoFe 2 O 4 magnetic nanoparticles was performed. The formation of mesopores in the shell was a consequence of removal of organic group of the precursor through annealing. The NiO nanoparticles were loaded into the mesoporous silica. The mesoporous silica shells leads to a larger coercivity than that of pure CoFe 2 O 4 magnetic nanoparticles due to the decrease of interparticle interactions and magneto-elastic anisotropy. In addition, the FeCo nanoparticles were coated by condensed and mesoporous silica. The condensed silica can protect the reactive FeCo alloy from oxidation up to 300 °C. However, saturation magnetization of FeCo nanoparticles coated by silica after 400 °C annealing is dramatically decreased due to the oxidation of the FeCo core. The mesoporous silica coated magnetic nanostructure loaded with NiO as a final product could be used in the field of biomedical applications.

We report almost perfectly vertically aligned ZnO nanorod arrays synthesized by the hydrothermal route at considerably lower temperature on a sputtered Al:ZnO seed layer using different growth strategies. The nanorod arrays demonstrate remarkable alignment along the c-axis over a large area. Several barrier layers, such as ZnO, Al2O3, BaTiO3 and SiO2, were introduced to form the p-i-n junction to reduce the leakage current. The photocurrent is significantly reduced in nanorod arrays on AZO/SiO2/p-Si heterojunction due to multiple scattering phenomena from ZnO hexagonal facets associated with the nanorod arrays. This research may open up venues for various optical and opto-electronic applications where highly aligned nanostructures are desired.

Here, we have synthesized Zinc Oxide (ZnO) nanorods at room temperature using zinc acetate and hexamethylenetetramine as precursors followed by characterization using X-ray diffraction (XRD), fourier transform infra red spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy. The growth of the synthesized ZnO was found to be very close to its hexagonal nature, which is confirmed by XRD. The nanorods were grown perpendicular to the long-axis and grew along the [001] direction, which is the nature of ZnO growth. The morphology of the synthesized ZnO nanorods was also confirmed by SEM. The size of the nanorod was estimated to be around 20-25 nm in diameter and approximately 50-60 nm in length. Our biocompatibility studies using synthesized ZnO showed no significant dose- or time-dependent increase in the formation of free radicals, accumulation of peroxidative products, antioxidant depletion or loss of cell viability on lung epithelial cells.

Magnetic nanoparticles of CoFe 2 O 4 have been synthesized under an applied magnetic field through a co-precipitation method followed by thermal treatments at different temperatures, producing nanoparticles of varying size. The magnetic behavior of these nanoparticles was investigated. As-grown nanoparticles demonstrate superparamagnetism above the blocking temperature, which is dependent on the particle size. One of the nanoparticles demonstrated a constricted magnetic hysteresis loop with no or small coercivity and remanence at low magnetic field. However, the loop opens up at high magnetic field. This magnetic behavior is attributed to the preferred Co ions and vacancies arrangements when the CoFe 2 O 4 nanoparticles were synthesized under an applied magnetic field. Furthermore, this magnetic property is strongly dependent on the high temperature heat treatments that produce Co ions and vacancies disorder.