Tailoring the structural and magnetic properties of Ni zigzag nanostructures using different deposition angles

Magneto-optic Kerr effect (MOKE) microscopy is a widely used technique for observation and characterization of microscopic magnetic structures. While being efficient and easy-to-use, current commercial MOKE microscopes are not superb in time resolution, limited by the frame rate of the camera. Here, we introduce a revolutionary sensor, namely, the event camera, as a convenient add-on to traditional MOKE microscopy and explore the potential applications of event-based vision in research areas using MOKE microscopy. We use the frame stacking method to improve visibility to human eyes in generated slow motion videos. We perform a proof-of-principle feedback control experiment using the event-based vision data and characterize the overall latency of the feedback loop as short as 25 ms with our current prototype. Finally, we discuss the limitations of current event cameras in MOKE microscopy as well.

This paper reports a thorough microstructural characterization of glancing angle deposited (GLAD) TiO2 thin films. Atomic force microscopy (afm), grazing-incidence small-angle x-ray scattering (GISAXS) and water adsorption isotherms have been used to determine the evolution of porosity and the existence of some correlation distances between the nanocolumns constituting the basic elements of the film’s nanostructure. It is found that the deposition angle and, to a lesser extent, the film thickness are the most important parameters controlling properties of the thin film. The importance of porosity and some critical dimensions encountered in the investigated GLAD thin films is highlighted in relation to the analysis of their optical properties when utilized as antireflective coatings or as hosts and templates for the development of new composite materials.

Magnetization reversal of exchange-coupled and exchange-decoupled Nd-Fe-B magnets observed by magneto-optical Kerr effect microscopy

The freeze–thaw action of water inside rocks’ pores, cracks, and joints plays a dominant role in physical rock weathering where the temperature fluctuates across 0 °C. To understand this process in cold regions, artificial weathering was simulated in the laboratory. Diorite, basalt, and tuff were used as specimen, and were maintained in saturated conditions to accelerate the effect of freeze–thaw weathering. X-ray computed tomography (CT) images and scanning electron microscope (SEM) photographs were obtained to investigate changes in the inner microstructure along with repeated freeze–thaw cycles. In addition, physical properties were measured during the cycles. Particle detachment, crack initiation, and propagation and porosity increase due to volumetric expansion of water inside rocks were detected using X-ray CT and SEM. The decrease in P-wave and S-wave velocities, and in weight loss were also observed. Tuff specimens, which have low tensile strength, high porosity, and loose structure, were deteriorated rapidly, while diorite specimens on the other hand, which have high tensile strength, low porosity, and compact structure, showed relatively slight changes. The frost susceptibility of basalt specimens was found to be intermediate between tuff and diorite. The developed process for cycling and freezing set up can be useful to test the various stones in terms of frost susceptibility.

Pure TiO₂ thin films and Al doped TiO₂ thin films have been prepared by spin coating method. This work is carried out to determine the effect of Al on TiO₂ thin film. Because of Al doping thickness, optical properties, band gap, surface morphology, and structural properties of TiO₂ thin film changes. X-ray diffraction (XRD), Atomic Force Microscopy (AFM), Gravimetric Analysis, and UV-vis. Spectroscopy were carried out to find out the micro-structure, surface morphology, surface roughness, thickness and optical properties of the thin films. 0.5 M TiO₂ thin film shows 473 nm thicknesses where it changes with Al doping. Al also changes the crystal structure and the surface roughness of the film and both of them are carried out by using XRD analysis and AFM analysis. The surface roughness of the films was 12.239 nm for undoped TiO₂ thin film and for 6% Al doped the roughness increases to 85 nm which were calculated by using AFM analysis. The grain size of Al doped TiO₂ thin film was 19.51 nm and 26.95 nm were measured by XRD analysis.<div><br></div>

Zinc-cobalt oxide (Zn1−xCoxO) thin films refer to a semiconductor material based on zinc oxide (ZnO) doped with cobalt (Co). This material is studied mainly for its modified magnetic, electronic and optical properties, particularly in the context of diluted magnetic semiconductors (DMS). This study analyzes the effect of cobalt doping on the structural optical, and magnetic properties of ZnO thin films, fabricated using alow-cost, scalable ultrasonic spray technique. Zinc-cobalt oxide (Zn1−xCoxO) thin films were successfully deposited on glass substrates using the ultrasonic spray pyrolysis technique at a substrate tem- perature of 450 ◦C, with cobalt doping concentrations of x = 0%, 1%, 3%, and 5%. X-ray diffraction (XRD) analysis revealed a hexagonal wurtzite structure for all samples, with no secondary phases, indicating effective incorporation of Co2+ ions into the ZnO lattice. Raman spectroscopy indicated the emergence of structural disorder and defect-related modes, consistent with the increase in Urbach energy. Scanning electron microscopy (SEM) showed granular surface morphologies, and a non-homogeneous surface pattern is visible on all samples. Atomic Force Microscopy (AFM) showed an increase in surface roughness and grain size with increasing doping concentration. Optical measurements confirmed high transmittance in the visible range and a gradual de- crease in optical band gap from 3.21 eV to 2.95 eV with increasing Co content. The spectroscopy, and vibrating sample magnetometer (VSM) revealed that all films are intrinsically ferromagnetic. The origin of the ferromagnetism was found to be an intrinsic property of the Co-doped ZnO thin films.

Co-sputtering is a simple yet effective technique for fabricating a thin film of composite materials and different compositions by adjusting the electrical power of each sputtering target. However, practical issues arise when depositing cermet materials such as Ni-YSZ and Ni-GDC because of the contrasting characteristics of metal and ceramic sputtering targets. For example, the surface binding energy of GDC is significantly higher than that of Ni, resulting in a considerably lower sputtering yield of GDC. The difference in sputtering yield is further exacerbated by the low power density limit of the GDC target, which is set by its unfavorable material properties such as brittleness and low thermal conductivity. In contrast, due to its magnetic property, Ni requires sufficiently high sputtering power during magnetron sputtering.This work combines co-sputtering with advanced sputtering techniques such as glancing angle deposition (GLAD) and oblique angle deposition (OAD) to fabricate otherwise unobtainable Ni-GDC anode microstructure with various compositions. Reduced flux capture area of Ni caused by the high incident angle of GLAD allowed control of thin-film compositions, and optimal composition was determined based on fuel cell performance and electrochemical impedance spectroscopy (EIS) analysis. A sufficient amount of GDC was necessary to expand the triple-phase boundary (TPB) and suppress the thermal agglomeration of highly mobile Ni.The effect of electrode nanostructure on fuel cell performance was also investigated. The ballistic shadowing effect during OAD was utilized to produce thin-film electrodes with various porosities. With the increase of the deposition angle, the porosity increased, whereas the in-plane electrical conductivity decreased due to the reduced density. The columnar structure was also manipulated by managing the substrate position through azimuthal rotation. As a result, various columnar structures such as vertical posts, slanted posts, and zig-zag were fabricated, and the optimal microstructure was determined via electrochemical examinations.

The classic challenge faced by researchers dealing with liquid crystals is to control the LC molecular orientation and hence optimise the optical properties. Well known techniques for influencing LC texture include the use of surfactants or thin film alignment layers. The underlying limitation common to such techniques is that while excellent control of LC anchoring at the substrate surface is achieved, molecular alignment in the bulk of the LC is reliant entirely upon the cooperative effects and resulting elastic properties of the LC material. Generally, this has worked sufficiently well in practice, but unfortunately, the complete dependence on the intermolecular forces of the LC means that unencumbered, reversible switching is not always possible. Our group has taken a unique approach to influence LC orientation. Using glancing angle deposition (GLAD), highly porous thin films can be grown possessing isolated columnar microstructure whose shape can be tailored via substrate motion during film deposition. In particular, we can grow films of helical columns with controlled pitch and handedness. These films exhibit circular dichroism and optical activity similar to that seen in chiral LCs. The high porosity of GLAD films permits fluids such as LCs to be introduced into the pores, leading to a new type of hybrid optical material. Most significantly, initial work showed that when achiral LCs were embedded in chiral GLAD media, there was an enhancement of the circular dichroism and optical activity as the chiral GLAD film served to induce a chiral orientation in the LC. In this report, we start with a brief overview of the GLAD process and some relevant optical studies, leading to a review of GLAD/LC hybrid materials, switchable devices, and finally, a discussion of recent research optical characterisation and some ideas for future avenues of investigation.

In the present study, (Cu2S) thin films were deposited by using chemical bath deposition (CBD) technique. The effect of the preparation conditions on film properties was studied by varying the molar concentration (M) of thiourea [CS(NH2)2] (0.6, 1, 1.3, 1.6 M). The optical properties data revealed that the optical Energy gap was in the range (2.68-2.75eV). The structural properties of the films were investigated by X-ray diffraction (XRD). The results indicate that they have a nanocrystalline structure with chalcocite phase and crystalline structure at the diffraction angle 32.7° corresponds to the crystalline level (431) which belongs to the monoclinic crystal structure. The results of the scanning electron microscopy (SEM) showed the formation of nanostructured Cu2S with grain size in the range of (90-140nm). Atomic Force Microscope (AFM) was used to study the surface topography and grain distribution on the film surface. Energy dispersive X-ray (EDX) was used to investigate the elemental analysis of the film. Raman peaks were observed at (265-474cm-1). Hall Effect showed that all (Cu2S) films have p-type conductivity due to the copper, and the electrical conductivity increases with increase the molecular concentration of thiourea. .

In this work, WS2 thin films approximately 200 nm thick were successfully synthesized on glass substrates using RF sputtering, applying deposition rates of 1 and 2 Å/s. The impact of these rates on the films’ structure, surface morphology, optical properties, and electrical characteristics was thoroughly investigated. Field emission scanning electron microscope analysis revealed a morphology transition from nanoparticles to nanosheets as the rate increased. Atomic force microscope (AFM) analysis revealed that higher deposition rates increased grain size, nanosheet formation, and surface roughness in WS2 films. X-ray diffraction and Raman results showed enhanced crystallinity and the emergence of multiple growth orientations at higher deposition rates. Optical measurements indicated reduced transmittance and bandgap in the higher-rate film, attributed to morphological and structural improvements. Hall effect results showed significantly enhanced electrical conductivity in the nanosheet-based film due to increased carrier concentration and mobility. The Urbach energy values were also extracted, showing lower disorder in the high-rate film (79 meV) compared to the low-rate sample (106 meV). These findings underscore the key role of deposition rate in tailoring WS2 thin film properties for optoelectronic applications.

In this work, different thicknesses of silver (Ag) thin films were prepared on flexible polyethylene terephthalate (PET) plastic substrates by screen printing technology. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to characterize morphology and surface roughness of the Ag thin films. Crystallinity and crystallites sizes of the films were verified on High resolution X-ray diffraction (HR-XRD) system. From the AFM, rough surfaces were revealed with root mean square surface roughness (RMS) ranging from 20 to 40 nm for different thicknesses of the films and were found to be strongly dependent on the film thickness. The HR-XRD spectra showed different crystalline orientations of Ag thin films (with various thicknesses) produced by the screen printing technique. All the experimental findings were subsequently discussed.

Magnetization reversal and domains structures in (Co/Ni/Co/Pt) multilayers

Energy product enhancement in sufficiently exchange-coupled nanocomposite ferrites

It is known that glancing angle deposition (GLAD) utilizing extreme self-shadowing during film growth can produce periodic microstructures on a predefined seed layer using electron-beam evaporation. This deposition process has been applied to the fabrication of periodic arrays of magnetic pillars and has possible applications in optical devices. Critical to the production of these microstructures is adherence to a narrow angular flux distribution centered at an oblique incidence angle, and optimizing the seed pattern for the desired film characteristics. In this article, a low-pressure, long-throw collimated GLAD sputter deposition has been used to fabricate submicrometer scale periodic pillar and quasihelical microstructures over a range of seed separations (e.g., 150, 300, 600, 900, and 1200 nm) and deposition angles (82.5° and 86° with respect to the substrate normal). We have found that for fixed deposition parameters, periodic quasihelical growth degenerates into pillars as the seed separation increases, and that the transitional region over which this degeneration occurs shifts to high seed separations with increasing flux incidence angles. This and other growth trends are also observed and described using the three-dimensional (3D) ballistic simulator, 3D-FILMS, which has proven to be successful in simulating the growth of aperiodic and periodic GLAD films. The use of sputtering for periodic GLAD simplifies the process control, and should enable deposition of a broader range of materials for diverse applications including magnetics, optics, and sensors.

The growth dynamics of 1D nanorods (NRs) composed of noble metals is ambiguous during glancing angle deposition (GLAD). The continuum equation (CE) model describes ballistic deposition limited by adatom diffusion, not verified in GLAD of noble metal NRs. In this work, GLAD is operated at Ts (substrate temperature) below room temperature to create inclined Ag NRs, and the CE fits the growth orientation of NRs with deposition angles at fixed Ts well. The CE fitting evaluates the diffusion activation energy (Ed) as 0.23 eV, showing that Ag NRs are poly-crystalline with dominant (111), as confirmed by XRD. This work introduces an effective approach to study the growth thermodynamics of 1D nanostructures and evaluate the Ed of adatoms with relatively low melting points.