Surface Topography Of Films Research Articles

Photophysical and optical properties of 4-(4'-(diphenylamino)benzylidene)-2-phenyloxazol-5(4H)-ones induced by the peripheral substituent

Photophysical and optical properties of 4-(4'-(diphenylamino)benzylidene)-2-phenyloxazol-5(4H)-ones differing in the peripheral substituent have been investigated in chloroform, solvent mixture, polymer matrix and solid state. These properties are influenced by the nature of the substituent on the phenyl ring and the environment. The dye bearing phenyl group or without substituent in para position of the phenyl group in 2-phenyloxazol-5(4H)-one moiety has the brightest emission in a solid state, whereas the dye with cyano functional group possesses the strongest emission in chloroform. The spectral behavior of the tested dyes is dependent on the solvent mixture. The fluorescence of the oxazolone dye in CHCl3/MeOH was reduced due to hydrogen bond formation, whereas addition of water to the THF or DMSO indicate the enhancement in emission caused by aggregation induced emission (AIE). The absorption and fluorescence spectra of the oxazolone polymer thin film are shifted to blue compared to the dyes dissolved in chloroform.The surface topography of the oxazolone thin films was examined using atomic force microscopy (AFM). The optical properties of the dye layers and dyes immobilized in PMMA matrix were determined by spectroscopic ellipsometry (SE). The absorption coefficient, refractive index, extinction coefficient and the energy bandgap can be effectively manipulated by changing substituent in the dye structure.

Influence of Ar gas pressure on the structural and optical properties and surface topography of Al-doped ZnO thin films sputtered by DC-Magnetron sputtering method

In this work, Aluminum doped Zinc oxide thin films were sputtered on glass substrate by the direct current (DC) magnetron sputtering method. The influence of Ar gas pressure on the structural and optical properties was measured. The optical parameters were calculated by UV–Visible spectroscopy, the nature of transition reveals direct allowed transition for the prepared films. Also, some physical quantities such as the strength of electron–phonon interaction, dissipation factor (tanδ) in the visible region and the lattice dielectric constant were presented for these thin films. The AFM analysis extracts surface parameters of the AZO thin films that help us to quantitively investigate the surface analysis. The band gap energy and transition index without any presumption about transition natural were calculated from Derivation Ineffective Thickness Method (DITM) and it was found that the reaction of Ar gas pressure plays an essential part in controlling the physical quantities of AZO thin films.

Hybrid Nanofillers Creating the Stable PVDF Nanocomposite Films and Their Effect on the Friction and Mechanical Properties.

The solvent casting method was used for five types of polyvinylidene difluoride (PVDF) nanocomposite film preparation. The effect of nanofillers in PVDF nanocomposite films on the structural, phase, and friction and mechanical properties was examined and compared with that of the natural PVDF film. The surface topography of PVDF nanocomposite films was investigated using a scanning electron microscope (SEM) and correlative imaging (CPEM, combinate AFM and SEM). A selection of 2D CPEM images was used for a detailed study of the spherulitic morphologies (grains size around 6–10 μm) and surface roughness (value of 50–68 nm). The chemical interactions were evaluated by Fourier transform infrared spectroscopy (FTIR). Dominant polar γ-phase in the original PVDF, PVDF_ZnO and PVDF_ZnO/V, the most stable non-polar α-phase in the PVDF_V_CH nanocomposite film and mixture of γ and α phases in the PVDF_V and PVDF_ZnO/V_CH nanocomposite films were confirmed. Moderately hydrophilic PVDF nanocomposite films with water contact angle values (WCA) in the range of 58°–69° showed surface stability with respect to the Zeta potential values. The effect of positive or negative Zeta-potential values of nanofillers (ζn) on the resulting negative Zeta-potential values (ζ) of PVDF nanocomposite films was demonstrated. Interaction of PVDF chains with hydroxy groups of vermiculite and amino and imino groups of CH caused transformation of γ-phase to α. The friction properties were evaluated based on the wear testing and mechanical properties were evaluated from the tensile tests based on Young’s modulus (E) and tensile strength (Rm) values. Used nanofillers caused decreasing of friction and mechanical properties of PVDF nanocomposite material films.

FDTD-Based Study on Equivalent Medium Approximation Model of Surface Roughness for Thin Films Characterization Using Spectroscopic Ellipsometry

Spectroscopic ellipsometry (SE) is an effective method to measure the optical constants of thin film materials which is very sensitive to the surface topography of thin films. When performing ellipsometric measurements of the optical constants of solid materials with rough surfaces, the equivalent medium approximation (EMA) model is often used to characterize the surface topography. The EMA model is determined by two parameters of equivalent thickness dEMA and the void volume fraction f. In most applications, the void volume fraction parameter f is always set to an empirical 50% without any instructions, and then the thickness parameter dEMA is determined by fitting. In order to improve the accuracy of the fitting results, it is necessary to validate the construction law of the EMA model in the ellipsometry analysis considering characteristic parameters of the actual surface topography. In this paper, the influence of the surface topographical parameters on EMA model is analyzed. The method of FDTD (finite difference time domain) is employed to simulate the SiO2 films with different topographical parameters and EMA model are carried out on these samples. The analysis results show that the EMA model constructed with dEMA = σ + 0.80 h (σ: the root mean square height, h: the average height) can better fit the SE parameters. The proposed method can facilitate a better understanding and utilization of the EMA model in SE application.

Optimization of electrodeposition time on the properties of Cu2ZnSnS4 thin films for thin film solar cell applications

The Electrochemical deposition was used to create a quaternary CZTS (Cu2ZnSnS4) kesterite thin layer. An aqueous solution of CZTS was used to deposit a thin layer over Indium Tin Oxide. The effects of deposition time (variation) on CZTS thin films under ambient conditions were investigated in this study. Several available characterization systems were used to study the samples as they were produced. The polycrystalline description of the layer is investigated by X-ray diffraction. The SEM as well as AFM study show that the deposition time improved surface morphology and topography of CZTS thin films which increase several nm in grain size. Furthermore, depending upon the deposition duration that affect the thickness and crystallinity of the films prepared, the optical study reveals an acceptable band gap in a range of 1.71–1.42 eV. Characteristics of high-quality CZTS absorber layers for solar cell applications are determined by deposition time variation. To check the effect of this band gap variation (1.71–1.42 eV, depending upon the deposition time) on the performance of a CZTS based thin film solar cell, a simulation software SCAPS-1D is being used.

Advanced microstructure, morphology and CO gas sensor properties of Cu/Ni bilayers at nanoscale

In this study, we investigated the morphology of synthesized Cu/Ni nanoparticles in trace of carbon sources by the co-deposition process of RF sputtering and RF-PECVD methods and localized surface plasmon resonance of CO gas sensing of Cu/Ni nanoparticles. The surface morphology was studied by analyzing 3D micrographs of atomic force microscopy using image processing techniques and fractal/multifractal analyses. The MountainsMap® Premium software with the two-way ANOVA (Variance analysis) and least-significant differences tests were used for statistical analysis. The surface nano-patterns have a local and global particular distribution. Experimental and simulated Rutherford backscattering spectra confirm the quality of nanoparticles. Then, prepared samples were exposed to CO gas flue to study their gas sensor application using the localized surface plasmon resonance method. Increasing the Ni layer over Cu one shows an interesting result in both morphology and gas sensing sides. Advanced stereometric analyses for the surface topography of thin films in conjunction with Rutherford backscattering spectrometry and Spectroscopic analysis make a unique study in the field.

Cell Adhesion Behaviors on Spider Silk Fibers, Films, and Nanofibers

Silk-based materials have garnered attention for use as medical supplies due to their mechanical toughness and low cytotoxicity. Silkworm silk has been applied as surgical sutures for decades. In contrast, the utilization of spider silk is limited mainly because of its scarcity. Although the biomimicry of spider silk has been developed using recombinant protein expression systems with the use of genetic engineering, the product often results in lower molecular weight and a lack of the N- or C-terminal regions. The incomplete sequence of the spider silk-like protein prevents the objective evaluation of the native spider silk as a medical application and retards the development of spider silk-inspired materials. Here, we reeled the native spider silk directly from live spiders and investigated the cell adhesion behavior based on three kinds of surface topography of spider silk-based substrates, namely, fibers, films, and non-woven fabrics. The cell adhesion behavior was largely influenced by the surface micro/nanostructure rather than the wettability of the surface. This study will contribute to promote the utilization of spider silk in the medical field as a candidate for promising bio-based fibers in the context of sustainable development goals.

Synthesis of CZTS kesterite by pH adjustment in order to improve the performance of CZTS thin film for photovoltaic applications

Quaternary CZTS (Cu2ZnSnS4) kesterite thin layers were successfully made by electrochemical deposition method. CZTS thin layers were deposited on Indium Tin Oxide (ITO) from an aqueous solution. In this work, the effects of pH adjustment under ambient conditions of CZTS thin films were studied. The as grown samples were investigated by numerous existing characterization systems. The X-ray diffraction (XRD) proves the polycrystalline description of the layer. The average crystallite size is varying from 10 ​nm to 24 ​nm of the films is dependent on the pH of the solution. All the thin films are in the CZTS kesterite phase attributed to A1 mode at 334 ​cm−1 verified by Raman spectroscopy. The SEM and AFM study show that the pH variation of the solution improved the surface morphology and topography of the CZTS thin films which increase several nm in grain size. Moreover, the optical analysis indicates a suitable band gap in the range of 1.5–1.8 ​eV depending upon the sulfurization temperature. It is found that the pH variation affects both the stability and the performance of the high-quality CZTS absorber layer applications. The CZTS layer with 4.80 pH was annealed at 450 ​°C and 500 ​°C, and at these temperatures the band gap was varied. At the end the band gap variations effect on the performance of CZTS based solar cell is being analyzed by using a simulation tool SCAPS-1D.

Fractal Analysis on Surface Topography of Thin Films: A Review

The topographies of various surfaces have been studied in many fields due to the significant influence that surfaces have on the practical performance of a given sample. A comprehensive evaluation requires the assistance of fractal analysis, which is of significant importance for modern science and technology. Due to the deep insights of fractal theory, fractal analysis on surface topographies has been widely applied and recommended. In this paper, the remarkable uprising in recent decades of fractal analysis on the surfaces of thin films, an essential domain of surface engineering, is reviewed. By summarizing the methods used to calculate fractal dimension and the deposition techniques of thin films, the results and trends of fractal analysis are associated with the microstructure, deposition parameters, etc. and this contributes profoundly to exploring the mechanism of film growth under different conditions. Choosing appropriate methods of surface characterization and calculation methods to study diverse surfaces is the main challenge of current research on thin film surface topography by using fractal theory. Prospective developing trends are proposed based on the data extraction and statistics of the published literature in this field.

Surface topography and tribological behavior of anodic oxidation films on an Al–Li alloy in flooded and starved ionic liquids

Anodic oxidation films (AOF) are prepared by a chromic acid process on a rolled surface (AOF-r) and a polished surface (AOF-p) of an Al–Li alloy. Surface topographies are featured as valleys and plateaus with dimples on AOF-r while plain with dimples and scratch marks on AOF-p. In flooded ionic liquid, AOF-r has better tribological property than AOF-p under heavy loads, which is determined by the bearing characteristic (Rpk, Rk, Rvk, and MR1). In addition, dimple on plateau of AOF-r is effective surface texture for increasing load-carrying capacity. In starved ionic liquid, AOF-p has better tribological property than AOF-r because the amount of lubricant engaged in sliding on AOF-p is higher than that on AOF-r.

Synthesis of Nanostructured Al-Doped Nb<sub>2</sub>O<sub>5</sub> Thin Films Using DC Sputtering Plasma for the Gas Sensors Applications

Nb2O5 is one of the most favorable transparent conducting oxide materials, which is efficiently used in thin film gas sensors especially for reducing gases. In this research, Al-doped Nb2O5 thin films on glass substrates with the DC plasma sputtering method for sensing NH3 and NO2 gases. The effect of thermal oxidation time on morphological, structural properties, and gas sensing properties of Nb2O5: Al thin films are investigated. Annealing was performed at 450 ° C for two hours. The results of X-ray diffraction (XRD) revealed that the structures are amorphous. Surface topography and growth behavior of Al-doped Nb2O5 thin films have an essential role in the optimization of gas sensing properties of these films. Also, atomic force microscopy (AFM) has been used to investigate the surface topography of the obtained films. Obtained results from these analyzes revealed that the films have monoclinic phase and surface topography of Nb2O5:Al thin films affected by Al-doped, the roughness and grain size of the surface increased with the increase in the Al content. Also, the effect of Al-doped on the performance of Nb2O5 thin films gas sensors is investigated. The results indicated that the best response was Nb2O5 film of NH3 gas and Nb2O5:1%Al of NO2 gas.

Effects of tensile stress on electrochemical characteristics and structural morphology of P110SS steels in carbon dioxide-saturated solution

A high-temperature autoclave was used to grow CO2 corrosion-product films on P110SS steel specimens while the surface of the specimens was continuously subjected to tensile stress in a four-point bending jig; the autoclaving times were 6, 18, 36, and 72 h. A scanning electron microscope was used to observe the surface topography of the corrosion-product films formed on the P110SS steels. An x-ray diffraction was used to analyze the phase compositions of the corrosion products. The electrochemical performance of the films was investigated using electrochemical impedance spectroscopy and potentiodynamic polarization curves. The results showed that tensile stress could hinder the formation of corrosion-product films; the integrity and compactness of the films worsened, but the phase compositions of the films did not change. The applied tensile stress resulted in a smaller grain size of the corrosion-product films, and the grain boundaries increased. In addition, owing to the induced tensile stress, the charge transfer resistances decreased, and the corrosion current densities increased for the P110SS steels with corrosion-product films in a 3.5 wt% NaCl solution saturated with CO2.

Use of the reflective background oriented schlieren technique to measure free surface deformations in a thin liquid layer non-uniformly heated from below

To measure liquid film surface deformations, we use the Background Oriented Schlieren (BOS) technique with a reflective optical scheme, which includes a random dot pattern located above the liquid surface, and a camera that captures its reflection from the liquid interface. The substrate was covered with a special black coating to minimize stray light reflection, which allowed to provide clear visualization of the dot pattern reflected from the free surface even for very thin liquid films. Local slopes of the film surface cause the dot displacement on the pattern image relative to the pattern image captured in the absence of any free-surface deformations. Hence, the topography of the liquid film surface is encoded by the apparent displacement of the dot pattern. Using the cross correlation image processing, the displacement vector field was determined, which was then substituted in Poisson equation to reconstruct the free-surface profile of the liquid film. The main advantages of this technique are: applicability for liquids with surface temperature inhomogeneities, experimental simplicity, sensitivity and applicability for both transparent and opaque liquids. Using the reflective BOS technique and using substrate with black coating we measure the free-surface deformation field of a thin layer of silicone oil non-uniformly heated from below. Despite the fact that thermocapillary shear stresses tend to decrease the thickness of the liquid layer in hotter regions, in the experiment, a convex deformation of the liquid film surface was observed above the heater for a few seconds immediately after the start of heating. This phenomenon is explained by the expansion of the liquid induced by the heating, due to the dependence of the liquid density on temperature. The measurement results are compared with those obtained in a single point using the confocal sensor. A good agreement is achieved.

Irganox separation in spin coated polyurethane thin films

For medical polymers, their surface condition is an important factor for their biocompatibility in potential applications. The occurrence of antioxidant separation, in form of additive blooming onto the material surface causes changes in the chemical composition, topography, stability and could influence the bioactivity of the medical devices. In this study, the separation of Irganox antioxidant occurring after the spin coating of polyurethane into thin films under 1 µm thickness was examined. The phenomenon was observed with different polymers from the Pellethane series. The extent of the blooming and its aftereffects were evaluated using scanning electron microscopy (SEM), atomic force microscopy (AFM), x-ray photoelectron spectroscopy (XPS) and Raman microscopy. The compatibility of Irganox with the polymers was compared on the basis of the Hansen solubility parameter (HSP) concept. Additionally, Raman imaging in combination with basis analysis was established as a viable and fast method for polymer-additive distinction. The surface coverage of the bloomed areas increased with film thickness, and with it, its impact onto the surface chemistry and topography of the thin films. Simple protein coating tests indicated that the bloomed areas slightly impact the ability of fibronectin to form protein netting structures on the surface.

Facile fabrication of silk fibroin/graphene oxide composite films and real‐time morphological observation in stretching

AbstractLayer‐structured regenerated silk fibroin (SF)/graphene oxide (GO) composite films were fabricated by a facile solution casting method. Fourier transform infrared spectroscopy, X‐ray diffraction, and thermal gravity analysis confirmed the successful incorporation and uniform dispersion of graphene oxides in the SF matrix. To visualize GO's effect on the morphological evolution, atomic force microscopic images were recorded in real‐time during the composite elongation to establish a correlation between microscopic structural characters and macroscopic mechanical properties. The result showed that the incorporation of graphene oxide into the SF matrix resulted in chain conformational transition, film surface flattening, and mechanical reinforcement. Surface roughness dramatically decreased from 65 to 10 nm, while tensile modulus increased substantially from 8.61 to 22.37 MPa by adding well‐dispersed graphene oxide up to 1 wt% into the SF matrix. Through the real‐time AFM observation under the horizontal stretching mode, the surface topography of original SF films varied from tori‐spherical aggregations to rod‐like ones resulting from GO's incorporation. In the meantime, SF's hydrophobicity was also increased, as manifested by contact angle increase from 30.81° to 45.09°.

Structure and Oligonucleotide Binding Efficiency of Differently Prepared Click Chemistry-Type DNA Microarray Slides Based on 3-Azidopropyltrimethoxysilane.

The structural characterization of glass slides surface-modified with 3-azidopropyltrimethoxysilane and used for anchoring nucleic acids, resulting in the so-called DNA microarrays, is presented. Depending on the silanization conditions, the slides were found to show different oligonucleotide binding efficiency, thus, an attempt was made to correlate this efficiency with the structural characteristics of the silane layers. Atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and X-ray reflectometry (XRR) measurements provided information on the surface topography, chemical composition and thickness of the silane films, respectively. The surface for which the best oligonucleotides binding efficiency is observed, has been found to consist of a densely-packed silane layer, decorated with a high-number of additional clusters that are believed to host exposed azide groups.

Effects of thickness on the wettability and electrical properties of Sn thin films

Sn films of four thicknesses, 50, 200, 500, and 1000 nm, were deposited on Si (111) substrates by a thermal evaporation technique, and the effects of thickness on the structural, surface morphology, electrical, and wettability properties were investigated. X-ray diffraction studies revealed the coexistence of predominantly β-Sn (metallic phase) and small concentration of α-Sn (semiconducting phase) in all samples except the 1000 nm thickness sample which is entirely β-Sn. The crystallite size and surface roughness enhance with thickness, and the 1000 nm film shows secondary nucleation growth which lowers the average crystallite size and the surface roughness of the sample. The 50 nm film shows semiconducting electrical properties while all other samples are metallic. The wettability studies found that Sn films are hydrophobic with a maximum water contact angle of 128° for the 1000 nm sample. It is concluded that the thickness critically determines the phase formation, surface topography, electrical properties, and hydrophobic properties of Sn films.

Corrosion behavior of titanium modified by direct laser interference lithography

This paper reports on the corrosion behavior of Titanium Grade 2 when subjected to non-contact laser functionalization. Direct Laser Interference Lithography (DLIL) was used to create periodic topography with two different surface patterns on pre-modified titanium. Corrosion resistance was measured in physiological saline at 37 °C. Electrochemical Impedance Spectroscopy data (EIS) and potentiodynamic polarization curves were correlated with the characteristics of the passive films through analysis of the topography, chemical composition, and thickness of oxides formed on the titanium after surface modifications. The corrosion tests showed that laser-textured surfaces have a beneficial impact on titanium corrosion resistance in a physiological saline solution 0.9% NaCl. Moreover, the passive layer on DLIL-modified samples is more stable and less susceptible to growth in the corrosive environment. The results highlight the local interaction of DLIL treatment of the titanium surface after it had been shot-peened and acid-etched. The improved corrosion resistance in DLIL samples derives mainly from changes in the surface topography, chemical composition, and thickness of oxide films obtained after laser processing.

Effect of Annealing Temperature on Microstructure and Resistivity of TiC Thin Films

Titanium carbide (TiC) thin films were prepared by non-reactive simultaneous double magnetron sputtering. After deposition, all samples were annealed at different temperatures under high-vacuum conditions. This paper mainly discusses the influence of deposition methods and annealing temperatures on microstructure, surface topography, bonding states and electrical resistivity of TiC films. XRD (X-ray diffraction) results show that TiC thin films can still form crystals without annealing, and the crystallinity of thin films is improved after annealing. The estimated grain size of the TiC films varies from 8.5 nm to 14.7 nm with annealing temperature. It can be seen from SEM (scanning electron microscope) images that surfaces of the films are composed of irregular particles, and when the temperature reaches to 800 °C, the shape of the particles becomes spherical. Growth rate of film is about 30.8 nm/min. Oxygen-related peaks were observed in XPS (X-ray photoelectron spectroscopy) spectra, which is due to the absorption of oxygen atoms on the surface of the film when exposed to air. Raman spectra confirm the formation of TiC crystals and amorphous states of carbon. Resistivity of TiC films decreases monotonically from 666.73 to 86.01 μΩ·cm with the increase in annealing temperature. In brief, the TiC thin films prepared in this study show good crystallinity, thermal stability and low resistivity, which can meet the requirements of metal gate applications.

Relationship between structure, surface topography and tribo-mechanical behavior of Ti-N thin films elaborated at different N2 flow rates

Titanium nitride films were deposited by reactive magnetron sputtering on Si (100) wafers, glass and Ti6Al4V substrates. The film deposition was carried out in a gas mixture of Ar and N2. The nitrogen content was varied between 0 and 30 % of the total gas mixture. This variation led to the formation of different films with different microstructures. The microstructure of the Ti-N coatings presented nanocomposites with a low tendency to surface oxidation. From a pure Ti to tetragonal Ti2N and cubic Ti-N microstructures, the films showed a (111) TiN plane growth that led to an increase in the lattice strain and a decrease in the grain size when increasing the nitrogen flow rate. The water-film contact angle measurements showed that the surface hydrophobicity increased with the increase of nitrogen content in the film. Mechanical properties were measured and a strong dependence between microstructure and hardness was found. The Ti-N deposited under 20 % of N2 exhibited the highest hardness, the best adhesion and wear resistance, and the lowest friction coefficient with the presence of (111) fiber texture.