Angle Deposition Research Articles

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

In this work we investigated the influence of different deposition angles on the structural and magnetic properties of nickel thin films obtained by Glancing Angle Deposition. The films were deposited onto glass substrates at the angles of 65° and 85°. The structure of the films was studied by scanning electron microscopy, atomic force microscopy and X-ray diffraction, while the magnetic properties were analyzed using magneto-optical Kerr effect microscopy (MOKE). It was found that the variation in the deposition angle has a great influence on the porosity, crystallinity and surface roughness of the Ni films. The obtained changes in microstructure were correlated with the variation in the magnetic properties. MOKE measurements revealed that the thinner films, deposited at the angle of 85°, have a 2.5 times higher coercivity in comparison with the films deposited at the lower angle, which can be ascribed to their higher porosity.

Geometry and dilution rate analysis and prediction of laser cladding

Dilution rate is an important factor affecting the properties of laser cladding. However, the exact estimate of dilution rate in direct laser fabrication is still not fully developed. In this study, high-strength and wear-resistant YCF102 alloy powder is used to laser clad on the steel substrate. The area of the cladding layer is replaced by a part of the circle, and the relationship among the deposition angle, the clad width, and the area of the cladding layer is established. The geometry of the fusion zone is replaced by polynomial function of the fourth degree, and the relationship among the thermal tension angle, the clad width, the melting pool depth, and the area of the fusion zone is established. The value of the dilution rate is obtained by the area of the cladding layer and the fusion zone. The correlation coefficient of the area of cladding layer, the area of the fusion zone, and the dilution rate is also obtained. The estimate results coincident with the measurement results very well. The proposed theoretical model offers a basis for estimate of dilution rate in laser cladding.

Influence of fabric anisotropy on seismic response of circular foundation

Earthquake induced foundation failure has occurred in a number of events worldwide, such as the 1964 Niigata earthquake and 1995 Kobe earthquake. Fabric anisotropy has been considered as one of the factors that affect liquefaction characteristics. In this study, dynamic centrifuge tests were conducted for studying the influence of sand fabric anisotropy on seismic response of circular foundations. For this purpose, sub-angular Toyoura sand was used as the most anisotropic material, while sub-rounded Nevada sand was used for the comparison tests. Each group of tests were carried out in both dry and saturated conditions.These tests are considered complementary to similar centrifuge tests that the authors performed using rectangular foundations. The tests show that sand fabric anisotropy has significant impact on the seismic response of circular foundations as well, especially in saturated conditions. Specifically, as the deposition angle of the sand layer increased, the data show a remarkable decrease in acceleration amplitude concurrently with a considerable decrease of pore pressure ratio and foundation settlement. These effects were more pronounced in the sub-angular Toyoura sand. These effects of increased deposition angle are consistent with the corresponding decrease of bearing capacity and increase of footing settlements in static centrifuge tests from the literature.

Thickness-dependent magnetic anisotropy in obliquely deposited Fe(001)/Pd thin film bilayers probed by VNA-FMR**Project supported by the National Basic Research Program of China (Grant Nos. 2015CB921403 and 2016YFA0300701), the National Natural Science Foundation of China (Grant Nos. 51427801, 11374350, and 51671212), and the Chinese Government Scholarship (Grant No. 2015GXYG37).

The thickness-dependent magnetic anisotropy of obliquely deposited Fe(001)/Pd thin films on Mg(001) is investigated by fitting the field-dependent resonant field curve using the Kittel equation. In this study, three Fe film samples with thicknesses of 50 monolayers (ML), 45 ML, and 32 ML deposited at 0°, 45°, and 55°, respectively, are used. The magnetic anisotropy constant obtained from ferromagnetic resonance (FMR) spectra exhibits a dominant fourfold magnetocrystalline anisotropy (MCA) at the normal deposition angle with larger Fe thickness. However, the in-plane uniaxial magnetic anisotropy (UMA) is induced by a higher oblique deposition angle and a smaller thickness. Its hard axis lies between the [100] and [010] directions. The FMR data-fitting analysis yields a precise measurement of smaller contributions to the magnetic anisotropy, such as in-plane UMA. Due to MCA, when the magnetic field is weaker than the saturated field, the magnetization direction does not always align with the external field. The squared frequency-dependent resonant field measurement gives an isotropic Landé g-factor of 2.07. Our results are consistent with previous experiments conducted on the magneto-optical Kerr effect (MOKE) and anisotropic magnetoresistance (AMR) systems. Thus, a vector network analyzer ferromagnetic resonance (VNA-FMR) test-method for finding UMA in obliquely deposited Fe(001)/Pd bilayer ferromagnetic thin films, and determining the magnetic anisotropy constants with respect to the film normal deposition, is proposed.

Structural Properties and Wettability of TiO2 Nanorods

The structural and wetting properties of as‐deposited, annealed, and UV‐exposed TiO2‐slanted nanorods grown on different substrates have been studied. The slanted nanorods of 250 nm thickness are deposited on silicon, fluorine‐doped tin oxide, and glass at 80° using glancing angle deposition (GLAD) by employing e‐beam evaporation. The structural evolution shows that the prior seeding on the substrate affects the morphology dramatically, while a different angle of deposition can tune a plane substrate for exciting morphologies by GLAD technique. Annealing and UV exposure redefine the grown material and change the structural and wetting behavior of the TiO2 films. Notably, annealing the sample at 500 °C for 1 h has decreased the contact angle, and all the annealed samples become hydrophilic. Further, the UV radiation exposure makes all the samples super‐hydrophilic. It is demonstrated that by choosing an appropriate substrate, controlled properties of our interest with or without external stimuli can be achieved. Nevertheless, these samples will find interesting applications in self‐cleaning, photocatalysis, gas sensing, antireflection coating, etc.

SiOx by magnetron sputtered revisited: Tailoring the photonic properties of multilayers

Abstract Traditionally porous silicon based photonic structures have been prepared by electrochemically etching of silicon. In this work, porous multilayers of nanocolumnar SiOx and SiO2 thin films acting as near infrared (NIR) 1D-photonic nanostructures are prepared by magnetron sputtering deposition at oblique angles (MS-OA). Simultaneous control of porosity and stoichiometry of the stacked films is achieved by adjusting the deposition angle and oxygen partial pressure according to a parametric formula. This new methodologoy is proved for the synthesis of SiOx thin films with x close to 0.4, 0.8, 1.2, 1.6 and nanostructures varying from compact (at 0° deposition angle) to highly porous and nanocolumnar (at 70° and 85° deposition angles). The strict control of composition, structure and nanostructure provided by this technique permits a fine tuning of the absorption edge and refraction index at 1500 nm of the porous films and their manufacturing in the form of SiOx-SiO2 porous multilayers acting as near infrared (NIR) 1D-photonic structures with well-defined optofluidic responses. Liquid tunable NIR Bragg mirrors and Bragg microcavities for liquid sensing applications are presented as proof of concept of the possibilities of this MS-OA manufacturing method as an alternative to the conventional electrochemical fabrication of silicon based photonic structures.

Interference suppression of light backscattering through oblique deposition of a layered reflecting coating: bi-layer on a substrate.

We theoretically demonstrate the possibility of entirely suppressing light backscattering towards the incident beam from a rough bilayer fabricated by deposition at an oblique angle, such that the substrate relief is replicated at a certain angle to the substrate surface. The necessary conditions of the scattering suppression were formulated. Interference suppression was observed experimentally (633 nm wavelength, 45° incidence angle, -35° scattering angle) with a set of SiO2-on-Ta2O5 bi-layers fabricated at different deposition angles. We detected a suppression of the scattering from the bi-layer fabricated at the deposition angle of 7.7° by a factor of about 30 compared with that from the sample deposited at normal incidence. The observed value of the scattering suppression was limited by the background noise of the measurements.

Hexagonal arrays of gold triangles as plasmonic tweezers.

We present theoretical and experimental studies of the plasmonic properties of hexagonal arrays of gold triangles, fabricated by angle-resolved nanosphere lithography method. Our numerical and experimental results both show that a change in the angle of gold deposition affects the size and the distance between the triangles, leading to a controlled shift in their absorption and scattering spectra. We calculate the force exerted on the polystyrene particles of 650 nm radii numerically while passing above the hexagonal arrays. Simulation results show that the presented hexagonal arrays of gold triangles can operate as efficient plasmonic tweezers with a controllable operating wavelength and high trap strength, owing to the additive interaction of the neighboring triangles. Moreover, we apply the realized plasmonic nanostructures in a conventional optical tweezers configuration and show that the optical tweezers stiffness can be effectively modulated by the plasmonic forces, at the IR wavelength of 1064 nm.

Accretion and photodesorption of CO ice as a function of the incident angle of deposition

Non-thermal desorption of interstellar and circumstellar ice mantles on dust grains, in particular ultraviolet photon-induced desorption, has gained importance in recent years. These processes may account for the observed gas phase abundances of molecules like CO toward cold interstellar clouds. Ice mantle growth results from gas molecules impinging on the dust from all directions and incidence angles. Nevertheless, the effect of the incident angle for deposition on ice photodesorption rate has not been studied. This work explores the impact on the accretion and photodesorption rates of the incidence angle of CO gas molecules with the cold surface during deposition of a CO ice layer. Infrared spectroscopy monitored CO ice upon deposition at different angles, ultraviolet irradiation, and subsequent warm-up. Vacuum ultraviolet spectroscopy and a Ni-mesh measured the emission of the ultraviolet lamp. Molecules ejected from the ice to the gas during irradiation or warm-up were characterized by a quadrupole mass spectrometer. The photodesorption rate of CO ice deposited at 11 K and different incident angles were rather stable between 0° and 45°. A maximum in the CO photodesorption rate appeared around 70° incidence deposition angle. The same deposition angle leads to the maximum surface area of water ice. Although this study of the surface area could not be performed for CO ice, the similar angle dependence in the photodesorption and the ice surface area suggests that they are closely related. Further evidence for a dependence of CO ice morphology on deposition angle is provided by thermal desorption of CO ice experiments.

Crystallographically oriented porous ZnO nanostructures with visible-blind photoresponse: Controlling the growth and optical properties

We have grown catalyst-free crystallographically oriented porous ZnO nanostructures by pulsed laser deposition (PLD) method. The deposition was performed in two stages for each sample. In the first stage, self-seeding of ZnO was performed on the quartz substrate, and the angle of deposition (seeding-angle) was varied. Thus, the growth of seeds is different here. In the second stage, the deposition was performed at a glancing angle (at 85°) for the fixed duration of time to grow the nanostructures. These PLD-grown nanostructures acquire highly oriented wurtzite structure. We find that the seeding-angle during the first stage is the determining deposition parameter which influences the growth and other properties of these nanostructures in a controllable manner. The variation in seeding-angle systematically tunes the crystallographic orientation and porosity, which in turn influences the visible-blindness and ultraviolet (UV) photoresponse of these nanonetworks. Here we report the growth of completely defect-free crystallographically oriented nanostructures with necessary porosity for application in visible-blind UV photodetection.

Silica-based antireflection coating by glancing angle deposition

ABSTRACTIn this study, silica-based multilayer graded-index antireflection coatings have been developed by RF magnetron sputtering exploiting the mechanism of glancing angle deposition (GLAD). GLAD is an extension of oblique angle deposition (OAD) where substrate rotation is also applied along with OAD. The optical properties of the films have been tailored by varying the oblique angle of deposition. Each subsequent layer of the multilayer coating has been deposited at a different oblique angle and has different thickness and refractive index. The refractive index of the films reduces successively as we move from the bottom to the top layer achieved by an increase in porosity with a subsequent increase in the flux incidence angle. These multilayer coatings when applied on glass substrates, exhibit a reduction in the average reflectance of glass from 8.75% to 1.6% in a wavelength range of 400–800 nm.

Atomistic simulation of the glancing angle deposition of SiO2 thin films

The classical molecular dynamics simulation of the glancing angle deposition of silicon dioxide films with practically meaningful dimensions is performed. The formation of separated slanted columnar structures is investigated for different deposition angles and different energies of sputtered silicon atoms. It is shown that a decrease in the angle between the flux of deposited atoms and the normal to the substrate leads to the decrease of column thicknesses and distances between the columns. The high-energy deposition with small deposition angles results in the formation of dense films without separate columnar structures. The increase of substrate temperature leads to partial merging of nearby columns. The glancing angle deposition with low energies of sputtered silicon atoms results in the growth of disordered columns with different dimensions, shapes, and tilt angles. Annealing of high-energy glancing angle deposited films results in partial merging of slanted columns. The obtained simulation results are in a good agreement with existing experimental data.

Optical analyses of annealed copper films by a method based on Bruggeman homogenization formalism: Influence of deposition angle and annealing temperature

Normal and oblique angle depositions were used to produce copper thin films which were subsequently annealed with flow of nitrogen gas at different temperatures (100, 180 and 350 °C). Optical responses of these samples obtained at near normal incidence angle using both s- and p-polarized lights. Field emission scanning electron microscope (FESEM) analyses of the samples provided the physical structure and morphology of the samples. Bruggeman homogenization formalism calculations were used to propose a method for prediction of the reflection spectra which were compared and fitted to the experimental results. The most effective factors in this type of work were found to be the film thickness, the material inclusion (void fraction) and the thickness ratio of copper nitride layer formed on top of copper layer to the thickness of copper layer which was estimated from comparison of theoretical optical spectra with those of experimental results. Results showed that the latter ratio increases with annealing temperature and the highest temperature of 350 °C caused a drastic change in the optical spectra of the samples.

Structure evolution and stress transition in diamond-like carbon films by glancing angle deposition

In this article the diamond-like carbon films have been prepared by the strategy of the glancing angle deposition using unbalanced magnetron sputtering technique. It is found that the structure and the residual stress of the films are strongly dependent on the deposition angle. Of particular interest is that the stress of the films significantly transforms from compressive to tensile state as a function of the deposition angle, which is attributed to the result of the competition and mediation between compressive stress due to surface capillary forces of the island surface and tensile stress due to the coalescence of the islands during Volmer-Weber growth of the films. Based on this mechanism, the nearly stress-free film with desirable performance can be prepared at the proper deposition angle. The correlation between the residual stress and the atomic-bond structure also reveals that the stress transition is not only related to the sp2-bonded carbon content, but also closely to the changes of the heptatomic and pentatonic rings in the carbon network. This work demonstrated herein will provide a promising route to prepare the stress-free diamond-like carbon films with desirable performance.

Influence of inherent anisotropy on the seismic behavior of liquefiable sandy level ground

Inherent anisotropy is a crucial aspect to consider for an improved understanding of the strength and deformation characteristics of granular materials. It has been the focus of intense investigation since the mid-1960s. However, inherent anisotropy’s influence on ground seismic responses, such as liquefaction, has not been extensively studied. In this paper, inherent anisotropy’s influence on ground seismic responses is examined through a series of dynamic centrifuge model tests on liquefiable level sand deposits. During the model setup, five different deposition angles (0, 30, 45, 60, and 90 degrees) were achieved using a specially designed rigid container. The models were exposed to tapered sinusoidal input accelerations and the recorded results were fully investigated. It was found that deposition angle-caused inherent anisotropy significantly influenced the excess pore pressure responses during the shaking and dissipation phases. The amount of excess pore pressure build-up and the high excess pore pressure duration increased with the deposition angle, while the dissipation rate decreased as the deposition angle increased. The inherent anisotropy also influenced liquefaction-induced ground settlement, with volumetric strain increasing along with the deposition angle. With respect to response acceleration, inherent anisotropy’s effects depended on the amount of excess pore pressure build-up (i.e., degree of liquefaction). In view of these results, it was concluded that a sandy ground, deposited at a higher angle (i.e., closer to 90 degrees), is more susceptible to liquefaction and that inherent anisotropy’s influence should be considered when evaluating the liquefaction potential and performing effective stress analyses.

Electrical resistivity and elastic wave propagation anisotropy in glancing angle deposited tungsten and gold thin films

We report on experimental investigations of electrical resistivity and surface elastic wave propagation in W and Au thin films sputter-deposited by glancing angle deposition. For both metals, the angle of deposition α is systematically changed from 0 to 85°. Dense and compact films are produced with a normal incident angle α = 0°, whereas inclined and porous columnar architectures are clearly obtained for the highest angles. Group velocities and DC electrical resistivities of W and Au films are significantly changed in x and y directions as α increases from 0 to 85°. Isotropic behaviors are always observed for Au films, whereas anisotropic velocity and resistivity are clearly measured in W films prepared with incident angles higher than 60°. The anisotropic coefficient reaches 1.8 for velocity and 2.0 for resistivity in W films, while it remains in-between 1.0 and 1.2 in Au films whatever the incident angle. This directional dependence of electrical resistivity and elastic wave propagation is connected to the anisotropic structural characteristics of W inclined columns (fanning of their cross-section), while Au columns exhibit a more symmetric growth as a function of the incident angle.

Investigations for mechanical properties of PLA-HAp-CS based functional prototypes

Abstract This paper reports the investigations on blend of biocompatible and biodegradable polymer, poly lactic acid (PLA) reinforced with another biocompatible and bioactive polymer chitosan (CS) and ceramic material; hydroxyapatite (HAp) from material processing view point. The blend has been selected based upon melt flow index (MFI), flowability, thermal stability and mechanical testing. After ascertaining proportion/composition of PLA-HAp-CS on twin-screw extruder (TSE) feedstock filaments for fused deposition modelling (FDM) have been prepared. The fabricated feedstock filaments were used on FDM for printing of biomedical scaffolds (with input parameters as: layer thickness, deposition angle and infill density). The tensile and flexural tests of functional prototypes were performed on the universal tensile tester (UTT). Finally combined optimization was performed on tensile and flexural samples to determine the best setting of open-source FDM for printing of biomedical scaffolds.

Blaze of Multilayer Diffraction Gratings in the Soft X-Ray Range: Growth Design Taking into Account the Deformation of Groove Profiles

It is shown that changing the angle of deposition of a coating onto a nanostructured substrate with an asymmetric profile (high-frequency blazed grating) has an effect both on smoothing of the groove profile of a multilayer grating (its symmetrization and/ or a decrease in its depth) and induces a significant displacement of the groove-profile maximum either to the left or to the right relative to the substrate profile. It is established that the displacement of interlayer boundaries is a linear function of the angle of deposition of the material and the change in the profile depth is a nonlinear function. By controlling the orientation of the source of the depositing material with respect to the groove’s working facet, controlled deformation of the profile can be attained in the nonlinear continuous growth equation. At a certain orientation of the source and taking into account realistic profile boundaries, the maximum diffraction efficiency of a grating at a given order of the spectrum is predicted to be higher than the similar efficiency of a grating with perfect triangular boundaries positioned strictly vertically one above the other. The optimal values of the boundary displacement, which are found from simulating the growth of a W/B4C 2500/mm grating with a blaze angle of 1.76° and an antiblaze angle of 20°, make it possible to achieve a diffraction efficiency of about 0.82−0.9 relative to the reflection of a multilayer mirror optimized for a wavelength of 1.3 nm. The maximum achievable efficiency for steeper angles of a non-working facet is somewhat higher.

Nanotube structures: material characterization and structural analysis of Ge–Se thin films

Nanotube structures, formed in thin films of chalcogenide glasses open avenues for new applications, since they offer directional options for many effects in these otherwise completely disordered systems. One way to grow nanotubes is through formation of nano-columnar structures by confining them. In this work nano-columnar growth of thermally evaporated GexSe100−x (x = 20, 30, 40) films is achieved through oblique films deposition. The columnar structural organization of the films and its dependence upon the deposition angle and films composition are established by imaging the cross-sectional areas of the films through scanning electron microscopy. Atomic force microscopy, energy dispersive X-ray spectroscopy and Raman Spectroscopy studies reveal respectively variation in the surface porosity, composition changes and structural reorganizations occurring in the films as a function of obliqueness angles and material’s composition. These results are discussed in respect to the structural organization of films deposited under normal flux incidence and deformations and other structural effects caused by films' deposition under variable angles. Based on the experimental results an empirical formula for the tangent rule is suggested which links the incident flux angle α, and the nanotube inclination angle β.

Effect of Printing Parameters on the Mechanical Properties of Parts Fabricated with Open-Source 3D Printers in PLA by Fused Deposition Modeling

Abstract 3D polymer-based printers have become easily accessible to the public. Usually, the technology used by these 3D printers is Fused Deposition Modelling (FDM). The majority of these 3D printers mainly use acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA) to fabricate 3D objects. In order for the printed parts to be useful for specific applications, the mechanical properties of the printed parts must be known. The aim of this study is to determine the tensile strength and elastic modulus of printed materials in polylactic acid (PLA) according to three important printing parameters such as deposition angle, extruder temperature and printing speed. The central composite design (CCD) was used to reduce the number of tensile test experiments. The obtained results show that the mechanical properties of printed parts depend on printing parameters. Empirical models relating response and process parameters are developed. The analysis of variance (ANOVA) was used to test the validity of models relating response and printing parameters. The optimal printing parameters are determined for the desired mechanical properties.