Thin Films In Presence Research Articles

Tuning properties of CTAB-HSA-AuNR nanocomposite antibacterial thin films

Protein-based biomaterials such as thin films have an edge over synthetic and bio-based polymers, due to their biodegradability in addition to other interesting properties. Proteins can be utilized to create such materials with specific functional characteristics. We report the preparation of transparent human serum albumin thin films in presence of CTAB-capped gold nanorods with different compositions of protein as well as the plasticizer i.e., sorbitol. The mechanical properties, surface topology, morphology, molecular structure, moisture content, total soluble material, biodegradability, antibacterial activity and optical properties have been investigated. Gold nanorods act as crosslinkers and sorbitol as a plasticizer increases plasticity and hardness of the films. The films deposited are biodegradable, water soluble and flexible in nature. AFM images reveal a pattern on the surface with different average heights with an increase in surface roughness with the addition of sorbitol. NINT studies show increased hardness and elastic modulus with the same amount of sorbitol but higher amounts of protein. Fourier Transform Infrared spectroscopy studies indicate the change in molecular structure of the films, in terms of a change in the hydrogen bonding network that impacts the water content and hardness of the films. Most importantly the films show antibacterial property, modulated by the composition used. The interesting features and the enhanced mechanical properties pave the path for potential applications of the films. The study shows that the optimization of the composition is crucial to achieve the desired film material with required properties.

Roundabout-like defect as a guide of phase-slip lines in a superconducting thin film at low temperature

AbstractIn this work, we examined the kinematic vortex state in a low-temperature, mesoscopic superconducting thin film in presence of an external applied current $$\varvec{J}$$ J , at zero magnetic field. We analyzed the voltage-current ($$\varvec{V-I}$$ V - I ), resistivity-current ($$\varvec{R-I}$$ R - I ) curves, as well as the vortex-anti-vortex velocity $$\varvec{V_m}$$ V m and the superconducting-electron density (norm of the superconduting order parameter $$\varvec{\psi }$$ ψ ) as an applied current function. Additionally, we have calculated the voltage as a function of characteristic time ($$\varvec{V-t}$$ V - t ). The sample presents a roundabout shaped pinning center fabricated with a lower low-temperature superconducting material, which allows for control over the vortex dynamics within the sample. To study this system, we have solved the generalized time-dependent Ginzburg-Landau equations for a single-condensate system. Our results demonstrate that the kinematic vortices enter the sample through regions where the superconductivity is depleted, revealing an intriguing and novel behavior of the phase-slip lines in the defect. We found that when a higher $$\varvec{J}$$ J is applied and the defect is not centered, the point where the vortex anti-vortex pairs enter the film moves away from the defect and are located in a point tangent to the outer circle of the defect. Besides, our results show a way to control the dynamics of the vortices, critical currents, and points of annihilation or creation of the cinematic vortices by including defects in the sample, important in the design and development of devices applied in industry and engineering.

Structural and electrical behaviours of PEDOT:PSS thin films in presence of negatively charged gold and silver nanoparticles: A green synthesis approach

Negatively charged gold and silver nanoparticles are prepared using the dry leaf of Annona reticulata and are used to prepare thin films of PEDOT:PSS nanocomposites. Significant changes in structure, morphology and electrical behaviours of nanocomposite thin films are observed depending upon the type and concentration of nanoparticles. The composite nature of the films are evidenced from the X-ray diffraction, Fourier transform infrared and Raman spectroscopy, while the surface morphology and film thickness are obtained from the analysis of atomic force microscopy. The in-plane DC conductivity of the composite films is enhanced by a moderate value with increase in nanoparticle concentration. Electrical responses obtained from the impedance spectroscopy over a broad frequency range show that both the real and imaginary parts of the impedance vary as a function of nanoparticles concentration and applied frequency. Structural changes after composite formation and the corresponding modifications in electrical behaviors are explained.

Enhancement of spin Seebeck effect of reverse spin crossover Fe (II) micellar charge transport using PMMA polymer electrolyte

The electrochemical thermoelectric effect is capable of generating Seebeck and conductivity from a temperature gradient through redox reaction at the electrode. Conventional spin Seebeck effect (SSE) is the generation of spin voltage by solid coupling magnetic thin film in presence of magnetic field and temperature gradient. In this study, we demonstrate an enhancement of a magnetic free SSE of Fe (II) reverse spin‐crossover in electrolyte using 1% PMMA polymer additive in form of polymer electrolyte. The reverse spin effect of Fe (II) complex, which is confirmed by SQUID magnetometer analysis and DFT simulation, is able to produce magnetic free SSE in solution. A unique electrochemical behavior is found in form of SSE Fe (II) polymer electrolyte that is elucidated using cyclic voltammetry, electrochemical impedance spectroscopy, and UV‐Vis analysis. The polymer electrolyte that possesses strong spin Seebeck produces a maximum Seebeck coefficient and conductivity of 124 % and 233 % higher than that weak SSE and conventional liquid electrolyte. The spin Seebeck produces a high number of carrier density through fast diffusion at high spin state, and the opposite charge properties trend at low spin state. Cryo‐TEM analysis had shown that the generation of spin Seeebeck effect of the Fe (II) complex in solution also involves reverse spherical micelles formation. Thus, this study highlights the finding of a rare magnetic free spin Seebeck generation in polymer electrolyte that having potential for waste heat recycles, heat sensors, and thermal switches applications upon development.

Effect of odd viscosity on the stability of a falling thin film in presence of electromagnetic field

In the presence of an electromagnetic field, we studied the stability of a conductive thin liquid film flowing on a non-conductive inclined plate taking the effect of odd viscosity into account. Using the lubrication theory, a new liquid–gas interface evolution equation involving odd viscosity effect is derived. By analyzing the linear and non-linear stability of the evolution equation, we find that the odd viscosity and the magnetic field stabilize the flow, while the electric field destabilizes the flow. Linear study shows that the larger odd viscosity leads to the higher critical Reynolds number. The weakly nonlinear study reveals that in the limited amplitude range, the supercritical stable region and the explosion region will decrease with the increase of the odd viscosity. Conversely, the unconditionally stable region increases and the subcritical unstable region keeps almost unchanged.

Studies on Surface Morphology and Electrical Conductivity of PS Thin Films in Presence of Divalent Complexes

Optical properties and surface morphology of pure and doped Polystyrene films with different divalent metals of Zn, Cu and Sn and one concentration percentage have been studied. Measurements of UV-Vis spectrophotometer and AFM spectroscopy were determined. The absorbance, transmittance and reflectance spectrums were used to study different optical parameters such as absorption coefficient, refractive index, extinction coefficient and energy gap in the wavelengths rang 200-800nm. These parameters have increased in the presence of the metals. The change in the calculated values of energy gaps with doping metals content has been investigated in terms of PS matrix structural modification. The value of optical energy gap was found decreasing from 4.5eV of pure PS to reach 4.45, 4.38 and 4.32eV for Zn, Cu and Sn respectively. Measurement by AFM spectroscopy was done for two and three dimensional topographic images. From figures, the data of roughness average were 7.29, 7.31, 3.37 and 6.73nm for samples (Blank, Zn, Cu and Sn) respectively.

Rapid growth of zinc oxide nanobars in presence of electric field by physical vapor deposition

In this contribution, electric field has some effects to increase growth for specific time duration on zinc oxide (ZnO) nanobars. First, the zinc (Zn) thin film has been prepared by 235,000 V/m electric field assisted physical vapor deposition (PVD) at vacuum of 1.33 × 10−5 mbar. Second, strong electric field of 134,000 V/m has been used in ambient for growing ZnO nanobars in term of the time include 2.5 and 10 h. The performances of the ZnO nanostructure in absence and presence of electric field have been determined by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results of XRD analysis showed that ZnO has a hexagonal bars structure and a strongly preferred (101) orientation which is strongest than without applying electric field. SEM analysis revealed that physical vapored ZnO thin film in presence of electric field are densely packed with uniform morphological, thinner and denser in distribution. Electric field effect for ZnO growth in 2.5 h is better than it in the 2.5 h without electric field but by passing the time the media influence has good power almost as same as electric field. Through this electric field in PVD, the compact and uniform Zn film has been achieved which is less diameter than ordinary PVD method. Finally, we carry out a series of experiments to grow different-orientation ZnO nanobars with less than 100 nm in diameter, which are the time saving process in base of PVD ever reported. Therefore, the significant conclusion in usage electric field is reducing time of growth.

Plasmon-assisted aggregation and spectral modification of the layered rhodamine 6G molecules

Rhodamine, a wide-used laser dye, is well-studied in the form of solution. Contrary to that, information on the properties of rhodamine in the thin film form is limited. Even less is known about modification of structural and optical properties of the rhodamine thin films in presence of the plasmonic nanoparticles. In this contribution we report on the results of experimental investigation of the rhodamine thin films doped with silver and gold nanoparticles supporting localized surface plasmon resonances. The nanoparticles were obtained on the quartz surfaces via physical vapor deposition. Then, part of the samples was covered up by the thin polymer film doped by rhodamine molecules using spin-coating technique. At the surfaces of other part of the samples the rhodamine thin films of different thicknesses were fabricated. In the near field of plasmonic nanoparticles, absorption and fluorescence spectra of the samples were enhanced and red-shifted. This enhancement was rationalized by the near fields effect and slight reduction of the decay time of the molecules. A new absorption and fluorescent band of rhodamine molecules which was red-shifted, is associated to J-aggregates formation and their fluorescence enhancement.

NO2 sensing properties of nanostructured tungsten oxide thin films

Tungsten oxide (WO3) nanoparticles have been successfully synthesized by sol–gel method for detection of NO2 gas in the low concentration range (5–100ppm). The sensor based on WO3 was fabricated on glass substrate using simple and cost effective drop casting method. The structure and morphology of WO3 nanoparticles were studied using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) techniques. X-ray photoelectron spectroscopy (XPS) confirms formation of WO3. The chemiresistive gas sensing performance of WO3 films were studied towards various reducing (NH3, H2S, CH3OH & C2H5OH) and oxidizing (NO2 & Cl2) gases in the 100–300°C temperature range. The experimental results demonstrate that, WO3 films were highly sensitive and selective towards NO2 gas than other test gases. The relationship between sensor response and various concentrations of NO2 gas was systematically studied and explored. WO3 thin films exhibit maximum response of 34% (towards 100ppm NO2) with very fast response time of 24s and are able to detect low concentration of 5ppm NO2 gas with response of 16%. The proposed sensing mechanism of WO3 thin films in presence of air and NO2 gas was discussed. Furthermore, the interaction of NO2 gas with WO3 film was also investigated using impedance spectroscopy.

Magnetoelectric coupling of multiferroic chromium doped barium titanate thin film probed by magneto-impedance spectroscopy

Thin film of BaTiO3 doped with 0.1 at. % Cr (Cr:BTO) has been prepared by pulsed laser deposition technique. Film was deposited on Pt/SrTiO3 substrate at 500 °C in 50 mTorr Oxygen gas pressure using KrF (298 nm) laser. Polycrystalline growth of single phase Cr:BTO thin film has been confirmed by grazing angle X-ray diffraction. Cr:BTO film exhibited remnant polarization 6.4 μC/cm2 and 0.79 MV/cm coercivity. Magnetization measurement of Cr:BTO film showed magnetic moment 12 emu/cc. Formation of weakly magnetic domains has been captured by magnetic force microscopy. Theoretical impedance equation fitted to experimental data in Cole-Cole plot for thin film in presence of transverse magnetic field resolved the increase in grain capacitance from 4.58 × 10−12 to 5.4 × 10−11 F. Film exhibited high value 137 mV/cm-Oe magneto-electric (ME) coupling coefficient at room temperature. The high value of ME coupling obtained can reduce the typical processing steps involved in multilayer deposition to obtain multiferrocity in thin film. Barium titanate being best ferroelectric material has been tailored to be multiferroic by non ferromagnetic element, Cr, doping in thin film form opens an avenue for more stable and reliable spintronic material for low power magnetoelectric random excess memory applications.

Structural Changes of UHV Deposited Titanium Thin Films in Presence of Oxygen Flow and Temperature

Ti films of same thickness, and near normal deposition angle, and same deposition rate were deposited on glass substrates, at room temperature, under UHV conditions. Different annealing temperatures as 393K, 493K and 593K with uniform 8 cm3/sec, oxygen flow, were used for producing titanium oxide layers. Their nanostructures were determined by AFM and XRD methods. Roughness of the films changed due to annealing process. The gettering property of Ti and annealing temperature can play an important role in the nanostructure of the films.

Crystallization of ion amorphized Ge2Sb2Te5 thin films in presence of cubic or hexagonal phase

The crystallization kinetics of amorphous Ge2Sb2Te5 (GST) thin films, generated by ion implantation, on top of crystalline GST, either in the cubic or hexagonal phase, was investigated by means of time resolved reflectivity measurements, x-ray diffraction, in situ transmission electron microscopy, and Raman analyses. The crystallization occurred at a lower temperature with respect to a fully amorphous film and in both cases the crystalline phase started growing at the underlying amorphous-crystalline (a-c) interface. However, it was not a solid phase epitaxial growth since cubic GST was always obtained, independent of the phase of the underlying crystal. We speculate that the a-c interface behaves as a continuous region of potential nucleation sites in the crystallization making the crystallization process more efficient.

Applicability of the Meyer–Neldel rule in a-Se 90Ge 10− xIn x thin films in presence of light

Temperature dependence of conductivity is measured in dark as well as in presence of light in amorphous thin films of Se 90Ge 10− x In x in the temperature range 285–365 K and in the intensity range 6400–10 750 lx. It is observed that pre-exponential factor ( σ 0) depends on activation energy (Δ E). A straight line between ln σ 0 and Δ E indicates the presence of MN rule in dark as well as in presence of light. A strong correlation between MN conductivity pre-factor σ 00 and characteristic energy kT 0 has also been observed. The origin of this correlation and the MN rule can be attributed to the effect of the exponential energy distribution of defect traps.

Role of Ag in the Epitaxial Growth of Oxide Thin Films

ABSTRACTIn this paper, we have reported our investigations related to the growth of high temperature superconducting YBa2Cu3O7-δ (YBCO) and colossal magnetoresistive La0.7MnxO3-δ (LMO) thin films in presence of silver. The films were grown using pulsed laser deposition (PLD) techniques and characterized using x-ray diffraction, scanning electron microscopy, Squid magnetometer. The focus of our work is on the realization of significant improvement in microstructural and physical properties of these films by the addition of a common material (silver) to the films during their in-situ formation. Optical emission studies of plumes emanating from Ag target have been carried out to find the role of Ag acting as additional source of oxygen-supply to oxide lattices during film-growth.

Micromagnetics of soft magnetic thin films in presence of defects

We solve numerically the Landau-Lifshitz-Gilbert equation and calculate the magnetization in a magnetic film including a nonmagnetic defect for two initial magnetization states consisting of circular structure with 4 domains and 7 domains. The defect at the vortex wall restrains the magnetization temporarily but the vortex wall comes out of the defect beyond a critical applied field. This critical field increases as the defect size becomes large. The defect at the film side fixes the magnetization at the film edge. The edge defect leads to a reproducible magnetization state inside the film, though a locally stable structure appears for the magnetic thin film without defects. It seems that the defect may improve the stability of the magnetic thin film head.