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The structural and electrical transport properties of Ge ion-implanted CoSb3 thin films were investigated. These thin films were deposited by pulsed laser deposition on the quartz substrates and 100 keV Ge ions were implanted with the ion fluences ranging from 5 × 1014, 1 × 1015 to 5 × 1015 ions/cm2. Scanning electron microscopy shows an enlargement in grains with the increase of ion fluence which is attributed to the contribution from local annealing and the creation of ion-induced defects. The electrical resistivity (ρ) measurements indicate that Ge implantation strongly influences the temperature-dependent resistivity and hence affect the charge carriers. The decrease in mobility and an increase in carrier concentration with the ion fluences lead to a decrease in electrical resistivity. The conduction mechanism study reveals that this system exhibits Mott type variable range hopping characteristics (ln ρ $$\propto$$ 1/T1/4) in the low-temperature regime for all the samples and follow the small polaron hopping conduction mechanism, ln (ρ/T) $$\propto$$ 1/T, at high temperature up to 400 K. The room temperature Hall effect measurement and the temperature-dependent Seebeck effect reveal that these films are of n-type.

In this work, pure and Zn ion doped SnO2 nanorods (Zn:SnO2) were prepared by hydrothermal method. Structural and microstructural properties of these nanorods were characterized by X-ray diffraction and high-resolution transmission electron microscopy analysis. Further, the Zn:SnO2 nanorods have been systematically investigated through optical studies such as UV–visible, Raman and photoluminescence spectroscopies. The stochiometric composition of the Zn:SnO2 had been confirmed by X-ray photoelectron spectroscopy studies. The samples revealed out that the dopant Zn ions creating the oxygen vacancies, which can enhance the gas sensing performance of SnO2. As a result, the Zn doped SnO2 nanorods are very suitable for gas sensing applications.

In the present report, systematic studies on nanoclustered Au catalyzed vapour-liquid–solid growth of silicon nanowires (SiNWs) by plasma enhanced chemical vapour deposition (PECVD) technique are described. The growth of SiNWs is performed on not so conventional sapphire substrate as well as commonly used Si substrate. SiNWs grown on different substrates are characterized for their morphologies and structures. Field emission scanning electron microscopy analysis of grown SiNWs, having an average diameter of ~ 800 nm and a typical length of ~ 10 µm, shows a slight increase in density of nanowires grown on Si substrate when compared to that for the samples grown on sapphire without any morphological changes. Structural studies using high resolution transmission electron microscopy confirm the crystalline nature of SiNWs where the crystalline core with polycrystalline shell is encapsulated in the amorphous phase. Confocal Raman analysis, unambiguously, confirms the presence of amorphous silicon oxide and amorphous Si (a-Si) in the SiNWs. Electron energy loss spectroscopy for the Si L2,3 shows the presence of a-Si and SiO2 at the surface of nanowire affirming the encapsulation of SiNWs in amorphous phase. Annealing of the samples conducted at 900 °C for 15 min restores the crystalline nature within the SiNWs which is confirmed further from Raman analysis.

Two series of samarium co-doped in 10 mol% Gd doped ceria Ce0.90Gd0.1O1.95(GDC10) formulated as Ce0.9-xSmxGd0.1O2-δ(CS) and Ce0.9Gd0.1-xSmxO2-δ(GS) (x = 0.0, 0.03, 0.05 0.10) were synthesized by glycine nitrate auto combustion method. The structural effects of Sm substitution in the GDC10 solid solution have been studied by X-ray diffraction (XRD) and Raman spectroscopy techniques. An increased lattice constant (5.407 A to 5.414 A) with decreasing crystallite size (28.6 nm 22.5 nm) was observed in both the Ce substituted by Sm (CS) and Gd substituted by Sm (GS) in GDC10 crystal system. The highest oxygen vacancy concentration ( V O ⋅ ⋅ = 2.65 × 1021 cm−3) was found for 10 mol % Sm and 10 mol % Gd doped ceria (Ce0.8 Sm0.1Gd0.1O1.90) composition (CS10) evaluated by spatial correlation model from Raman spectroscopy. The microhardness of the sintered pellets was investigated by Vickers hardness measurement. The highest fracture toughness was found to be 1.85 ± 0.27 MPa m1/2 for Ce substituted by 3 mol% Sm composition (CS3) among the overall compositions. The surface morphology and elemental composition of the CS and GS compositions were analyzed by FESEM. The morphology and composition of optimized electrolyte (CS10) was further analyzed by HRTEM and XPS respectively. AC impedance spectroscopy revealed that CS10 composition has an improved ionic conductivity (σ800 = 0.147 × 10−3 S‧cm−1) with significantly reduced activation energy (0.85 eV) in the temperature range of 673–1073 K under air atmosphere. A mechanism for conductivity enhancement by oxygen vacancy for CS compositions has been proposed. The effect of Sm as a secondary co-dopant in the GDC10 electrolyte was studied in detail to establish a candidate electrolyte material for operating solid oxide fuel cells in the intermediate temperature range (673–1073 K).

For low-dimensional systems, symmetry breaking and surface reconstruction are critical for the observation of special vibrational properties of technical significance such as surface optical (SO), ...

This paper presents an experimental investigation of irradiation-induced evolutions in three different oxide dispersion strengthening (ODS) alloys. High-dose, dual beam Ni–He ion irradiations are carried out up to 700 °C. The significant dose-dependent changes in the ODS particle size and number density are documented and interpreted in terms of specific point defect transport mechanisms, from small angle neutron scattering, TEM, and pulsed low-energy positron system measurements combined. The corresponding micro-mechanical changes in the alloys are evaluated based on the indentation response, which is, in turn, interpreted in terms of related, sub-grain plasticity mechanisms. The room temperature tests (without dwell time) reveal that the microscale work-hardening rate increases with decreasing the particle number density and pronounced strain localization effect. The elevated temperature tests (up to 600 °C, with dwell time) show that the indentation creep compliance is mostly temperature-independent after irradiation up to 25 dpa at Tirr = 500 °C and markedly temperature-dependent, after irradiation beyond 40 dpa at Tirr = 600 °C. This effect is ascribed to particular creep mechanisms associated with indent-induced plasticity, i.e., high stress and high dislocation density conditions.

Thermal annealing of Ag-Cu bi-layer thin films on silica-glass substrates either in air or in oxygen environment has led to the formation of novel composite materials (Ag nanoparticles in compound metal oxide semiconductors). Optical absorption and electron microscopy results have confirmed the presence of Ag nanoparticles in oxide semiconductor materials upon annealing. Drastic reductions of the optical absorption intensity in samples annealed at higher temperatures in different atmospheres are explained as a result of thermal growth of the compound metal oxide semiconductor phases. In particular, X-ray diffraction and photoelectron spectroscopy measurements reveal the phases of mixed oxides in the annealed samples. Various experimental measurements discussed here corroborate well with the observed optical results.

Nonhydrogenated Diamond-like Carbon-gold (DLC-Au) nanocomposite thin films with various Au contents and cluster size (

Polarized Raman spectroscopy is capable of confirming the crystalline phase as well as the crystallographic orientation of the sample. At the same time, tip-enhanced Raman spectroscopy (TERS) is ca...

Argon ion beam induced phase transformation (monoclinic to tetragonal) and bubble formation in monoclinic zirconia (ZrO2) has been studied using grazing incidence X-ray diffraction, electron microscopy, Raman scattering and photoluminescence spectroscopy. Monoclinic zirconia samples were irradiated with low energy (120 keV) Ar+ ions at temperatures 300 K and 143 K. The as-sintered and Ar+ ion irradiated zirconia samples were then irradiated using an excimer laser of wavelength 248 nm (energy 5 eV) to study the defect rich material (after ion irradiation) behavior at extreme condition (where ionization process is dominant). Zirconia was found to undergo a partial phase transformation from monoclinic to tetragonal (≈20%; ion fluence 2 × 1017 ions/cm2) upon Ar+ ion irradiation at 143 K. Further, Ar bubbles were formed and the size of the bubble is found to increase with the ion fluence, irrespective of sample temperature during ion irradiation. The oxygen vacancies (produced during ion irradiation) lead to strain field in the sample and this strain field is the prime cause for phase transformation. The rate of phase transformation was found to be faster in case of ion irradiation at 143 K. Further it was observed that Ar+ ion irradiation lead to creation of defects and laser irradiation on as-sintered zirconia leads to annihilation of defects. However, when laser irradiation was carried out on ion irradiated zirconia, there is a competition between production and annihilation of defects where the production of defects by the Ar+ ion irradiation is a dominant one. Further, the present work confirms the role of O vacancy in the monoclinic to tetragonal phase transformation and the results are consistent with the earlier report (Simeone et al., 2000).

Iron phosphate glass (IPG) is considered as a suitable alternate matrix for the immobilization of high level nuclear waste from fast reactors. Ion irradiation on IPG, induces changes in the charge state of the atomic species in IPG. When the metal ions (the glass formers or the glass stabilizers) change their charge state, the glassy nature is disturbed extensively. The changes in the charge state of Fe atoms in IPG, were characterized using XAS and EEL spectroscopy, in the present work. The analysis of core level spectra (XAS and EELS) showed that the concentration of Fe2+, on the whole, has increased and Fe3+ has reduced in the specimen upon ion irradiation. Since the Fe atom with charge state +2 exists only in glass phase of Fe3(P2O7)2, the rise in the population of Fe2+ implies that the glass phase of Fe3(P2O7)2 has increased in the glass matrix. The rise in the population of Fe2+ increases the viscosity of IPG, which in turn increases the glass forming ability.

Au nanorods (AuNRs) with a variety of aspect ratios (ARs) are used in surface-enhanced Raman spectroscopy (SERS), thermal therapy, and similar applications. In this study, we report a seed-mediated synthesis of AuNRs to cover different ARs in a single step with diluted HCl. This process ensures the realization of longitudinal surface plasmon resonance (LSPR) from the visible to the near-infrared region (∼650–1150 nm), improved uniformity with negligible by-products, and a low amount of surfactant. With no extra organic component, a halide (Cl−) that allows for the unique control of the LSPR is highlighted along with other growth-defining reagents. A comparative SERS of rhodamine and photothermal examinations were performed for halide- and non-halide-grown AuNRs with an AR of ∼7. An excellent enhancement factor (3 × 108) was achieved for the halide-grown AuNRs and was verified by a finite-difference time-domain (FDTD) simulation. Halide-grown AuNRs with a width of ∼5 nm demonstrated a highly improved plasmonic photothermal temperature of 45 °C, compared with that of 35 °C obtained from non-halide-grown AuNRs at a laser power density of only 1.1 W/cm2. The superior efficiency and photothermal effects of halide-grown samples in SERS are among the best reported, and significantly expand the scope of their application.

100 nm thin NiO-films on oxidized Si-substrates were pre-structured into small platelets of 100–5000 nm side-lengths utilizing the focused ion beam technique. The development of the individual platelets under grazing angle swift heavy ion irradiation was monitored using our “High Resolution In Situ Scanning Electron Microscope” installed in the beam line of the UNILAC ion accelerator at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt/Germany. This instrument allows us to in situ investigate the structural and compositional development of individual objects in the μm- and nm-range under swift heavy ion bombardment, from the very first ion impact up to fluences of some 1015 ions/cm−2. The sample is irradiated in small fluence steps and in between SEM-images (and EDX-scans) of one-and-the-same surface area are taken. Swift heavy ion irradiation at grazing incidence (tilt angle ≥80°) and continuous azimuthal sample rotation results in lateral shrinking and vertical growth of the platelets. At intermediate fluences additional rounding of edges and corners can be observed. At high fluences the deformation finally saturates. The deformation of the platelets is accompanied by huge sputtering of the exposed SiO2-layer, which due to the retracting edges of the platelets results in a pyramidal-like base underneath of the NiO-structures. In our presentation we will illustrate and discuss the reshaping mechanisms and underlying driving forces.

Low energy krypton ion beam induced phase transformation and bubble formation in monoclinic zirconia (ZrO2) has been studied using electron microscopy, Raman scattering, grazing incidence X-ray diffraction and photoluminescence spectroscopy. The zirconia samples were synthesized by the thermal decomposition method and 60 keV Kr+ ion irradiation was carried out at 300 K and 143 K. The as-sintered ZrO2 particles were found to be monoclinic in structure, however, upon 60 keV Kr+ ion irradiation, a fraction of the sample (∼4.9% (300 K) and ∼8.3% (143 K) for the ion fluence of 1 × 1017 ions/cm2) was transformed from monoclinic to tetragonal phase along with the formation of krypton bubbles. The size of the bubbles is found to increase with the ion fluence, irrespective of the sample temperature during ion irradiation. The phase transformation from monoclinic to tetragonal structure was mainly due to radiation damage process where the driving force is strain field associated with the O-vacancies. The monoclinic to tetragonal transformation rate is faster when the ion irradiation was carried out at 143 K and this is attributed to the immobility of defects and production of large number of oxygen vacancies. The krypton bubble formation might be hindering the monoclinic to tetragonal phase transformation rate.

This work reports on the influence of grain boundary modification on the tribological properties of nanocrystalline titanium carbide (nC-TiC) - amorphous carbon (a-C) nanocomposite films. TiC thin films were deposited by magnetron sputtering using TiC target in optimized hydrogen containing atmosphere. Nano/ultrananocrystalline TiC phase and short ranged ordered graphite phase were found to be dispersed in the a-C matrix in thin films. Chemical composition and also the chemical structure of the graphitized phase and a-C in the grain boundary were modified by controlling the substrate temperature. Raman spectroscopy showed that at room temperature, the films were dominated by a-C phase occupying the grain boundary. However, at moderate deposition temperature, graphitization of the film was observed and such modification was associated to the formation of short ranged crystalline graphite phase within a-C matrix. The friction coefficient was found to decreased with increase in the I(D)/I(G) ratio of Raman shift in the films. A sustainable ultralow value of friction coefficient was observed in the films with TiC nano/ultrananocrystalline phase surrounded by nanographitized domains. This could be associated to the layered lattice structure of short ranged graphite phase which readily shears and produces negligible frictional resistance. Sustainability of ultralow value of friction coefficient and high wear resistance are attributed to the formation of graphitized transfer film.

We report the synthesis of polycrystalline (poly)-SiGe alloy thin films through solid state reaction of Si/Ge multilayer thin films on Si and glass substrates at low temperature of 500 °C. The pristine thin film was deposited using electron beam evaporation with optimized in-situ substrate heating. Our results show the co-existence of amorphous Si (a-Si) phase along with the poly-SiGe phase in the pristine thin film. The a-Si phase was found to subsume into the SiGe phase upon post deposition annealing in the temperature range from 600° to 800 °C. Additionally, dual energy band gaps could be observed in the optical properties of the annealed poly-SiGe thin films. The stoichiometric evolution of the pristine thin film and its subsequent effect on the band gap upon annealing are discussed on the basis of diffusion characteristics of Si in poly-SiGe.

Bulk quantities of nanocrystalline yttria stabilized hafnia (YSH) powders with crystallite size ranging from 8 to 15 nm were successfully prepared for the first time through nitrate fusion synthesis at a temperature as low as 673 K. The yttrium content was varied from 6 to 30 mol%. The dependence of the properties of the final product on the quantity of the dopant was investigated. Microstructural investigations were carried out with scanning electron microscopy and transmission electron microscopy. A maximum relative sintered density of 98.2 ± 0.3% T.D (theoretical density) was obtained for YSH containing 10 mol% yttrium by using “two-step sintering” at a final temperature of 1773 K. Anisotropic shrinkage factor (0.70–0.95) was found to vary linearly with the compaction pressure. SEM investigations reaffirmed that the sintered pellets comprised uniform distribution of faceted grains and elemental mapping revealed that yttrium is distributed uniformly in these sintered YSH monoliths.

Nanocrystalline powders of (U0.5Ce0.5)O2±x solid solutions were synthesized in bulk (100–200 g) through the citrate gel combustion. The fuel (citric acid) to oxidant (nitrate) mole ratio (R) was varied from 0.1 to 1.0. Two independent lots of the products obtained through the gel-combustion were calcined at 973 K in air and in a mixture of argon containing 8% H2 respectively. All these powders were characterized for their bulk density, X-ray crystallite size, specific surface area, size distribution of the particles, porosity as well as residual carbon. The morphology and microstructures of these powders were studied by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) respectively. Nanocrystalline single phase fluorite solid solutions having a typical crystallite size of about (7–15 nm) were obtained. These powders were highly porous comprising cuboidal flaky agglomerates. The combustion mixture with an ‘R’ value of 0.25 was found to undergo volume combustion and was found to yield a product that was distinctly different. The systematic investigation on synthesis and characterization of nanocrystalline UCeO2 is reported for the first time.

Electrochemical measurements combined with high resolution transmission electron microscopy studies have been used to follow the microstructure changes in nanoporous Au subjected to electro-oxidation and oxygen reduction reactions. The microscopy results reveal that different types of lattice defects such as stacking fault tetrahedra present in as-dealloyed and oxide formed nanoporous Au. It is shown that Au inter-planar spacing in the defect concentrated regions in as-dealloyed nanoporous Au has increased by 8%. This anomalous change may be attributed to the binding of oxygen containing ads-species in the electrolyte on Au atoms, albeit weakly, in the presence of defects.

SnO2 and Mn-doped SnO2 single-phase tetragonal crystal structure quantum dots (QDs) of uniform size with control over dopant composition and microstructure were synthesized using the high pressure microwave synthesis technique. On a broader vision, we systematically investigated the influence of dilute Mn ions in SnO2 under the strong quantum confinement regime through various experimental techniques and density functional theoretical (DFT) calculations to disclose the physical mechanism governing the observed ferromagnetism. DFT calculations revealed that the formation of the stable (001) surface was much more energetically favorable than that of the (100) surface, and the formation energy of the oxygen vacancies in the stable (001) surface was comparatively higher in the undoped SnO2 QDs. X-ray photoelectron spectroscopy (XPS) and first-principles modeling of doped QDs revealed that the lower doping concentration of Mn favored the formation of MnO-like (Mn2+) structures in defect-rich areas and the higher doping concentration of Mn led to the formation of multiple configurations of Mn (Mn2+ and Mn3+) in the stable surfaces of SnO2 QDs. Electronic absorption spectra indicated the characteristic spin allowed ligand field transitions of Mn2+ and Mn3+ and the red shift in the band gap. DFT calculations clearly indicated that only the substitutional dopant antiferromagnetic configurations were more energetically favorable. The gradual increase of magnetization at a low level of Mn-doping could be explained by the prevalence of antiferromagnetic manganese-vacancy pairs. Higher concentrations of Mn led to the appearance of ferromagnetic interactions between manganese and oxygen vacancies. The increase in the concentration of metallic dopants caused not just an increase in the total magnetic moment of the system but also changed the magnetic interactions between the magnetic moments on the metal ions and oxygen. The present study provides new insight into the fundamental understanding of the origin of ferromagnetism in transition metal-doped QDs.

Bi2Te3 nanorods (NRs) have been successfully synthesized at different reaction temperatures via a surfactant-assisted hydrothermal method. The experimental observations revealed that the reaction temperature, SDBS surfactant (sodium dodecylbenzene sulphonate) and its concentration affect the morphology of Bi2Te3. It is identified that an imperfect oriented attachment mechanism is the dominant growth mechanism for the evolution of Bi2Te3 NRs. Moreover, a subsidiary growth mechanism namely the Oswald ripening process could also affect the Bi2Te3 NR growth process at higher reaction temperatures. Thermoelectric property measurements revealed that flake-decorated Bi2Te3 NRs achieved the maximum power factor value of ∼1.32 μW cm−1 K−2 at 410 K, which was higher than those of porous and smooth Bi2Te3 NRs. Such an enhancement in the power factor of flake-decorated Bi2Te3 NRs is primarily attributed to their outstanding electrical conductivity at 410 K.

The major structural material employed in the primary coolant system of pressurized heavy water reactors is carbon steel. The formation of corrosion products on the structural material surfaces, transportation to the core by the coolant and deposition of activated corrosion products on the out-of-core surfaces are controlled by several factors. Magnetite is the major corrosion product formed on carbon steel. The nickel released from other structural materials viz., nickel based steam generator tubes, partially converts the magnetite to nickel ferrite. These oxides, if modified to nano size, could improve the protectiveness of the interfacial film. Nickel ferrite synthesized by co-precipitation method was deposited on magnetite coated carbon steel by pulsed laser deposition technique and characterized by laser Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy. The results showed that the deposited nickel ferrite film was nanocrystalline and in single phase. The corrosion resistance and the electronic properties of the deposited film were evaluated by electrochemical techniques and the results are discussed in this paper.

The robust surface states of bismuth selenide (Bi2Se3) topological insulator (TI) that could potentially be harnessed for quantum computing and spintronics applications are often eclipsed by defect-induced bulk carriers. With the objective of suppressing the electronic transport in the bulk, we explore the effects of ion irradiation-driven isoelectronic doping in thin films of Bi2Se3 with 600 keV antimony (Sb+) ions at 45° oblique incidence. The distribution of Sb+ ions introduced into the system has been mapped using Rutherford backscattering spectroscopy. The heavy Sb+ ion irradiation has been observed to cause a change from parabolic magnetoresistance to linear magnetoresistance behavior in the irradiated films due to mobility fluctuations. Subsequent annealing in selenium environment has been found to reverse the damage produced by the irradiation, but with significant modifications in the quantum coherence signatures. Weak antilocalization behavior has been observed in the weak magnetic field limit and has been analyzed within the purview of the Hikami-Larkin-Nagaoka model. It has been found that the channel-separated Bi2Se3 film becomes completely channel-mixed due to the induced defects, yielding a system with a single coherent channel upon irradiation. In the as-deposited film, the temperature-dependent power law decay of the coherence length has been found to have two different exponents within the measured temperature range. On the other hand, the irradiated-annealed film has a single decay exponent which has been found to tend to − 0.5, indicating that electron-electron interaction is the only de-phasing mechanism involved. This work establishes the effectiveness of ion irradiation in tuning the quantum coherence phenomena in Bi-based TI systems.

A systematic study of the influence of citric acid to nitrate mole (R) ratio (R = 0 to 0.50) on the citrate gel-combustion synthesis of nanocrystalline (nc) ThO 2 in bulk quantities (30 g) by using citrate gel-combustion was carried out. The nc-ThO 2 powders were characterized for their bulk density, size distribution of particles, specific surface area, carbon residue and X-ray crystallite size. All these powders were compacted at pressures varying from 60 to 353 MPa and sintered by using the “two-step sintering” method. Powders prepared from a mixture with an “R” value of 0.125 compacted at 243 MPa yielded a maximum sintered density of 98.8 ± 0.3% T.D. For nc-ThO 2 , this is the highest sintered density reported so far. The microstructural investigations on nc-ThO 2 powders were carried out by using both scanning electron microscopy (SEM) and transmission electron microscopy (TEM). SEM images of the sintered thoria monoliths revealed faceted grains with well defined grain boundaries. Shrinkage anisotropy factor (α) revealed that the compacts prepared from the powders obtained from starting mixtures with R values of 0.125–0.50 had undergone uniform sintering (near isotropic shrinkage).

The cubic polytype of SiC (3C-SiC) epilayer grown on Si has been irradiated with 200 keV Si+ ions for various ion doses (0.025 dpa- 0.6 dpa) followed by 14 MeV Si+ ion irradiation (ion fluences: 1 × 1014 –1 × 1015 ions/cm2) at room temperature to study the recovery of damage caused by low energy ions. The disorder was estimated using Raman Scattering results and it is explained by direct impact model. From the total disorder and chemical disorder values, the three stages of damage evolution is clearly observed upon 200 keV Si+ ion irradiation. Upon 14 MeV Si+ ion irradiation on 3C-SiC, the sample has not amorphized even upto the ion fluence of 1 × 1015 ions/cm2. The present experimental results show that when the damage(caused by low energy ion) is less (

Nano-crystalline oxides of manganese prepared from the radiolysis of aqueous permanganic acid solution at ambient conditions showed structural and compositional changes with variation in absorbed gamma dose. The radiolytically formed nano-oxide was transformed into different micro-structures, phases, shapes and sizes with radiation. This variation was probed using X-ray powder diffraction (XRD), laser Raman spectroscopy (LRS) and transmission electron microscopy (TEM). At lower doses formation of a mixture of nano-oxides of Mn(OH)2, λ-MnO2 was detected from XRD analysis. This nano-oxide mixture changed to stable Mn3O4 at higher doses. The maximum crystallite size was observed to be ~15 nm. LRS results also supported this inference. This paper presents the detailed study on the phase transitions of the radiolytically formed nano-manganese oxides and the possibility of its use as radiation marker for predicting radiation response.

Present study investigates the contribution of defects in the thermoelectric transport properties of Bi2Te3 thin films using 120 keV He+ and Ar+ ion irradiation. Charge carrier type is converted from n-type to p-type with He+ ion irradiation. Upon Ar+ ion irradiation, thin film exhibited p-type conductivity at lower ion fluence and n-type conductivity at higher ion fluences. In case of He+ ion irradiation, bismuth vacancies were suggested to increase hole density and responsible for p-type conductivity whereas in the case of Ar+ ion irradiation, Ar+ ion induce grain melting that suppresses defect density and consequently increases electron concentration. Bi2Te3 films irradiated with the He+ ion fluence of 1 × 1015ions/cm2 exhibited highest power factor value of ~6.3 μW/mK2 at room temperature.

Mesalazine (MZ) is a significant anti-inflammatory non-steroid drug prescribed for the prevention of inflammatory bowel diseases (IBD). However, it is very essential for sensitive and selective detection of MZ. The transition metal dichalcogenides (TMDs) have gained much interest due to their excellent electro-catalytic activity and highly conducting properties for these applications. The present research proposes the hydrothermally prepared WS2/rGO nanocomposite towards the selective detection of MZ. The physicochemical properties reveal the formation of a hexagonal phase of WS2 hierarchical flowers with stacked thin nanosheets of rGO. The developed WS2/rGO modified GC electrode exhibits a noteworthy lower limit of detection about 0.003 μΜ with good sensitivity ranging 20.71 μAμM−1cm2 which were all achieved within the linear range of 0–300 μM L−1. WS2/rGO/GC electrode exhibits subsequent negligible current responses ( ± 0.1μA) towards the anti-interference capability. The fabricated electrode shows remarkable repeatability, reproducibility, and stability towards MZ. Correspondingly, our electrode exhibits tremendous recovery of MZ in real analytical samples like hemoglobin, bovine serum albumin, human urine, and water which reveals the outstanding potential towards real-time practical application of the developed sensor.

The effect of thickness on structural and magnetic properties of Co-rich Bi10Co16O38 (BCO) sillenite thin films is investigated systematically. BCO thin films are deposited using a simultaneous evaporation of Bi2O3, Co targets with RF-DC magnetron sputtering along with post-annealing procedure. The magnetic studies reveal an ordered magnetic nature below film thicknesses of 100 nm. Further, the temperature-dependent and field-dependent magnetic data is evaluated to comprehend the microstructure impact on to the magnetic nature of Co-rich sillenite thin films.

For the first time it was demonstrated that nanocrystalline hafnia powders i.e. both the thermodynamically stable monoclinic phase and the metastable cubic phase could be synthesized by tailoring the nitrite to nitrate mole ratio (Φ) of the eutectic mixtures containing KNO 3 , NaNO 3 and NaNO 2 . All these nanocrystalline HfO 2 powders were characterized for their bulk density, size distribution of particles, specific surface area, carbon residue and X-ray crystallite size. All powders exhibited unimodal size distribution of particles. Transmission electron microscopy and Raman spectroscopy reaffirmed the values of crystallite size estimated through XRD investigations and the identity of the constituent phases. Grain coarsening was observed when the powders were heat treated at 1473 K.

A perovskite LaMnO 3 micro/nanostructure is a promising high-efficiency photocatalytic materials for the removal of various organic pollutants. This study presents the preparation of sub-micron LaMnO 3 particles with polyvinyl pyrrolidone (PVP) as a structure directing agent to control the primary morphology and aggregations. Furthermore, the sample was annealed at different temperatures to improve the crystallinity and perovskite phase formations. The possible formation mechanism was explained based on the annealing temperatures. An attempt has been made to study the effect of different morphologies of LaMnO 3 particles for the degradation of RB dye under visible light irradiation. The removal efficiency of 95% for RB dye in 60 min evidences the superior degradation capability of highly porous LaMnO 3 particles. The photocatalytic activity not only depends on porous structure, but also strongly based on crystallinity, and specific surface area of LaMnO 3 particles. Hence, the porous morphology displays a superior photocatalytic activity than other LaMnO 3 microstructures.

Applications of plasma-produced vertically oriented graphene nanosheets (VGNs) rely on their unique structure and morphology, which can be tuned by the process parameters to understand the growth mechanism. Here, we report on the effect of the key process parameters such as deposition temperature, discharge power and distance from plasma source to substrate on the catalyst-free growth of VGNs in microwave plasmas. A direct evidence for the initiation of vertical growth through nanoscale graphitic islands is obtained from the temperature-dependent growth rates where the activation energy is found to be as low as 0.57 eV. It is shown that the growth rate and the structural quality of the films could be enhanced by (a) increasing the substrate temperature, (b) decreasing the distance between the microwave plasma source and the substrate, and (c) increasing the discharge power. The correlation between the wetting characteristics, morphology and structural quality is established. It is also demonstrated that morphology, crystallinity, wettability and sheet resistance of the VGNs can be varied while maintaining the same sp3 content in the film. The effects of the substrate temperature and the electric field in vertical alignment of the graphene sheets are reported. These findings help to develop and optimize the process conditions to produce VGNs tailored for applications including sensing, field emission, catalysis and energy storage.

Ion-beam sputtering technique has been utilized for controlled synthesis of metal alloy nanoparticles of compositions that can be tuned. Analysis of various experimental results reveals the formation of Ag-Cu alloy nanoparticles on a silica substrate. Surface-plasmon optical resonance positions and observed shifts of Ag Bragg angles in X-ray diffraction pattern particularly confirm formation of alloy nanoparticles on glass samples. Sputtering induced nano-alloying mechanism has been discussed and compared with thermal mixing of Ag and Cu thin films on glass substrates. Compositions and sizes of alloy nanoparticles formed during ion-beam induced sputtering are found to exceed far from the values of thermal mixing.

Stannous oxide (SnO), an exclusive p-type oxide semiconductor in the oxide family, is a source of renewed interest because of its ability to be an excellent anode material. So far, there are very few reports on the vibrational properties of SnO and controversy remains in the assignment of vibrational modes. Textured single crystals of SnO were synthesized by a one-step solvothermal method. The as-synthesized SnO crystals have a wide (001) plane, as confirmed by high resolution transmission electron microscopy images. Raman spectroscopy is used for the identification of phase as well as crystalline orientation. Moreover, a unique assignment of phonon modes in SnO is also performed using polarized Raman spectroscopic studies for different orientations around c-axis of the crystal with the incident electric field vector. Thus, a novel methodology of phonon assignment is adopted with a minimum amount of data collection for a diatomic molecule having a tetragonal symmetry with a number of symmetry elements.

Thermal and mechanical properties of graphene sheet are of significant importance in the areas of thermal and stress management, respectively. Here, we report the thermal conductivity and high-pressure behaviors of unsupported vertical graphene nanosheets (VGNs) grown by electron cyclotron resonance-plasma enhanced chemical vapor deposition method. Structural morphology of the as-grown VGNs on SiO2/Si substrate suggests a homogeneous, uniformly interconnected network of graphene sheets standing vertically on a basal nanographitic layer. On examination of edges of exfoliated sheets using transmission electron microscopy, seven layers of graphene is estimated. The frequency of the G-band (E2g-in plane mode) is found to vary linearly with temperature. The first-order temperature coefficient for G-band is found to be 1.47(1) × 10–2 cm–1 K–1. Using the G-band temperature coefficient and its position dependence on excitation laser power, the thermal conductivity of the VGNs at room temperature is estimated to b...

Volume combustion was observed in the auto-ignition of the citrate gels containing the nitrates of yttrium/thorium for the first time in mixture with a fuel (citric acid) to oxidant (Y 3+ or Th 4+ nitrate) ratio close to that demanded by the stoichiometry. These nanocrystalline powders were characterized for their bulk density, specific surface area, particle size distribution, carbon residue and X-ray crystallite size and were sintered by both the conventional and the two-step method. The maximum relative sintered density of Y 2 O 3 was 98.9% TD. The sintered density of thoria (97.8% TD) is the highest among the values reported so far, for nanocrystalline ThO 2 . Characterization of the pellets and powders by using scanning electron microscopy and transmission electron microscopy reaffirmed nanocrystallinity and that the sintered pellets comprised faceted sintered grains. The two-step sintering was found to restrict “runaway” sintering.

We report the investigation on exchange spring coupling behavior of BaFe 12 O 19 /Fe 3 O 4 nanocomposite synthesized by simple mixing followed by heat treatment of individual ferrites. Morphologically tuned, well crystalline hard and soft ferrites were synthesized by simple chemical method and the phase composition, crystallinity, surface morphology and magnetic properties of the as prepared ferrites as well as the nanocomposites were studied by using XRD, FESEM and VSM respectively. Exchange coupling behavior is observed in the nanocomposite samples heated at 600 °C with simultaneous enhancements of (BH) max and remanence.

SnO 2 thin films were obtained by ex-situ oxidation of Sn metal film deposited by thermal evaporation. The oxidation of the Sn film was carried out at 600, 700 and 900 °C for 2 h in a controlled oxygen atmosphere. GIXRD confirmed the tetragonal rutile phase of SnO 2 which was further confirmed by Raman spectroscopy. The RBS measurements provided the thickness and chemical information of the film. Thickness of the film was in the range of 6⿿12 nm and the presence of Sn and oxygen in the films are shown. Scanning electron microscopy revealed spherical particles of different sizes for films annealed at different temperatures. The SnO 2 thin film oxidized at 900 °C was tested for methane gas sensing. A sensing response of 78.46% for 100 ppm of methane at an operating temperature of 100 °C which is one of lowest reported was obtained.

Bulk quantities (60 g) of nanocrystalline (nc) free flowing urania powders with crystallite size ranging from 38 to 252 nm have been synthesized for the first time by the citrate gel combustion method. A systematic study of the influence of the fuel (citric acid) to oxidant (nitrate) ratio (R) on the characteristics of the urania powders has been carried out for the first time. Mixture with an “R” value of 0.25 exhibited a vigorous auto-ignition reaction. This reaction was investigated with Differential Scanning Calorimetry (DSC) and in-situ thermogravimetry coupled with differential thermal analysis and mass spectrometry (TG-DTA-MS). The bulk density, specific surface area, X-ray crystallite size, residual carbon and size distribution of particles of this powder were unique. Microscopic and microstructural investigation of selected samples revealed the presence of nanocrystals with irregular exfoliated morphology; their Electron Energy Loss Spectra testified the covalency of the U–O bond.

The sensitivity of Positron Annihilation Spectroscopy (PAS) for probing vacancy defects and their environment is well known. Its applicability in determination of swelling and the peak swelling temperature was put to test in our earlier work on ion irradiated D9 alloys [1] . Upon comparison with the peak swelling temperature determined by conventional step height measurements it was found that the peak swelling temperature determined using PAS was 50 K higher. It was conjectured that the positrons trapping in the irradiation induced TiC precipitation could have caused the shift. In the present work, D9 alloys have been implanted with 100 appm helium ions and subsequently implanted with 2.5 MeV Ni ions up to peak damage of 100 dpa. The nickel implantations have been carried out through a range of temperatures between 450 °C and 650 °C. The evolution of cavities and TiC precipitates at various temperatures has been followed by TEM and this report provides an experimental verification of the conjecture.