Surface Roughness Of Thin Films Research Articles

Zirconium oxide thin films deposited via DC magnetron sputtering: corrosion and morphological investigation

Purpose The purpose of this study is to investigate the structural, surface roughness and corrosion properties of the zirconium oxide thin films deposited onto SS304 substrates using the direct current (DC) magnetron sputtering technique. Design/methodology/approach DC sputtering at different powers – 80, 100 and 120 W – was used to deposit ZrO2 thin films onto different substrates (Si/SS304) without annealing of the substrate. Atomic force microscope (AFM), energy-dispersive X-ray spectroscopy (EDS), Tafel extrapolation and contact angle techniques were applied to investigate the surface roughness, chemical compositions, corrosion behavior and hydrophobicity of these films. Findings Results showed that the thickness of the deposited film increased with power increase, while the corrosion current decreased with power increase. AFM images indicated that the surface roughness decreased with an increase in DC power. EDS analysis showed that the thin film has a stoichiometric ZrO2 (Zr:O 1:2) composition with basic uniformity. Water contact angle measurements indicated that the hydrophobicity of the synthesized films decreased with an increase in surface roughness. Originality/value DC magnetron sputtering technique is infrequently used to deposition thin films. The obtained thin films showed good hydrophobic and anticorrosion properties. Finally, results are compared with other deposition techniques.

A Hybrid Pulsed Laser Deposition Approach to Grow Thin Films of Chalcogenides.

Vapor-pressure mismatched materials such as transition metal chalcogenides have emerged as electronic, photonic, and quantum materials with scientific and technological importance. However, epitaxial growth of vapor-pressure mismatched materials are challenging due to differences in the reactivity, sticking coefficient, and surface adatom mobility of the mismatched species constituting the material, especially sulfur containing compounds. Here, a novel approach is reported to grow chalcogenides-hybrid pulsed laser deposition-wherein an organosulfur precursor is used as a sulfur source in conjunction with pulsed laser deposition to regulate the stoichiometry of the deposited films. Epitaxial or textured thin films of sulfides with variety of structure and chemistry such as alkaline metal chalcogenides, main group chalcogenides, transition metal chalcogenides, and chalcogenide perovskites are demonstrated, and structural characterization reveal improvement in thin film crystallinity, and surface and interface roughness compared to the state-of-the-art. The growth method can be broadened to other vapor-pressure mismatched chalcogenides such as selenides and tellurides. This work opens up opportunities for broader epitaxial growth of chalcogenides, especially sulfide-based thin film technological applications.

Sputter grown CuO thin films: Impact of growth pressure and annealing temperature on their microstructural architectures

High-quality copper oxide (CuO) thin films were deposited on the silicon (Si) substrate at the room temperature using the physical vapour deposition (PVD) technique named radio frequency (RF) sputtering. The copper-oxide thin-films were single crystalline and of uniform thickness. Subsequently, the influence of growth pressure (low gas pressure - 3 mTorr and high gas pressure - 100 mTorr) and post growth annealing at different temperatures (300 °C to 700 °C) were investigated to understand the microstructural and morphological changes of the thin film. With the influence of growth pressure and post thermal annealing temperature, significant changes in crystallinity, surface roughness, and surface oxidation rate of the CuO thin film were detected, which were adequately analyzed via several characterization techniques. X-ray diffraction (XRD) patterns revealed the phase formation with good crystallinity of the film, which is substantiated by Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) characterization. Atomic force microscopy (AFM) images disclosed that the surface roughness of the film and grain size. By gaining insights into the structural and surface properties of CuO/Si thin films, this research presents new prospects for tuning of CuO phases, structures, and compositions for multifunctional applications.

The Effect of Annealing Temperature on the Surface Roughness and Crystal Structure of ZnO Thin Films Prepared by Electron Beam Evaporation Method on Glass Substrate

The Effect of Annealing Temperature on the Surface Roughness and Crystal Structure of ZnO Thin Films Prepared by Electron Beam Evaporation Method on Glass Substrate

Topography hierarchy of biocompatible polyhydroxyalkanoate film.

Polyhydroxyalkanoates (PHAs) are used for various biomedical applications due to their biocompatibility. Surface properties, such as surface roughness, are crucial for PHAs performance. Traditional parameters used for the characterization of surface roughness, such as R a, are often insufficient to capture the complex and hierarchical (multiscale) topography of PHA films. We measure the topography and surface roughness of thin PHA films with atomic force microscopy and analyze the topography data using several relatively novel data processing methods, including the calculation of autocorrelation functions, topological data analysis, and the distribution of minimum and maximum values of pixels over the topography data. The results provide details of multiscale and anisotropic surface properties that are crucial to PHAs biocompatibility but often overlooked by traditional topography analysis methods.

Impact of Cd/Sn molar ratio and annealing temperature on the properties of spin coated Cd2SnO4 thin films

We have synthesized and characterized spin coated Cd2SnO4 (CTO) thin films in the present work by varying the Cd/Sn = 2,3,4, and 5 M ratios, and 450 and 500 οC annealing temperatures. The structural studies were done using X-ray diffraction (XRD) and the results show that all the films exhibit a polycrystalline nature with (311) plane preferred orientation corresponding to Cd2SnO4 inverse spinel cubic phase. The morphological studies were done using an atomic force microscope (AFM) and field emission scanning electron microscope (FESEM). The thin films obtained with a roughness of 3–40 nm, and uniformly distributed grains without cracks are evident from the micrographs. The elemental analyses were carried out by employing EDAX and XPS techniques. The optical properties such as transmittance, bandgap, and refractive index are obtained using UV–Vis spectroscopy. The films were showing high transmittance (75–93 %) in the visible region. The band gaps of the investigated samples are found to be in the range of 3.4 eV–3.7 eV. The refractive index of CTO thin films in the 350–1000 nm wavelength range is around 1.7 to 1.9. The electrical properties show better results for the films annealed at 500 οC. The mobility values obtained are in the range of 0.6–4 cm2/Vs for different Cd/Sn ratio samples. The carrier concentration of CTO thin films is in the range of 4 × 1018 to 28 × 1018 cm−3. The presence of defects such as oxygen vacancy, Cd/Sn interstitial, and self-doping of Cd and Sn results in increased carrier concentration at higher Cd/Sn ratios. Besides, the wettability analysis was performed by contact angle measurements, which infer a hydrophobic to hydrophilic conversion in terms of the surface roughness of CTO thin films. From optoelectrical results, it is evident that the films exhibited better optical and electrical properties and are suitable for optoelectronic devices.

Studying the Crucial Physical Characteristics Related to Surface Roughness and Magnetic Domain Structure in CoFeSm Thin Films

This study investigated the effects of varying film thicknesses and annealing temperatures on the surface roughness and magnetic domain structure of CoFeSm thin films. The results revealed that as the film thickness increased, both the crystalline size and surface roughness decreased, leading to a reduction in coercivity (Hc) and improved magnetic contrast performance. Energy-dispersive X-ray spectroscopy (EDS) analysis confirmed the presence of cobalt (Co), iron (Fe), and samarium (Sm) within the thin films. Notably, the 40 nm Co40Fe40Sm20 thin film annealed at 200 °C exhibited lower sheet resistance (Rs) and resistivity (ρ), indicating higher conductivity and a relatively higher maximum magnetic susceptibility (χac) at 50 Hz. These findings suggest that these films are well suited for low-frequency magnetic components due to their increased spin sensitivity. The 40 nm Co40Fe40Sm20 thin film, subjected to annealing at 200 °C, displayed a distinct stripe domain structure characterized by prominently contrasting dark and bright patterns. It exhibited the lowest Hc and the highest saturation magnetization (Ms), leading to a significant improvement in their soft magnetic properties. It is proposed that the surface roughness of the CoFeSm thin films plays a crucial role in shaping the magnetic properties of these thin magnetic films.

Electrochemical anodization of cast titanium alloys in oxalic acid for biomedical applications

Titanium and its alloys have numerous biomedical applications thanks to the composition and morphology of their oxide film. In this study, the colorful oxide films were formed by anodizing cast Ti-6Al-4V and Ti-6Al-7Nb alloys in a 10% oxalic acid solution for 30 s at different voltages (20–80 V) of a direct current power supply. Atomic force microscopy was used as an accurate tool to measure the surface roughness of thin films on the nanometer scale. Scanning electron microscopy and X-ray diffraction were performed to analyze surface morphology and phase structure. According to the results, the produced titanium oxide layer showed high surface roughness, which increased with increasing anodizing voltage. The impact of anodizing voltages on the color and roughness of anodized layers was surveyed. The corrosion resistance of the anodized samples was studied in simulated body fluid at pH 7.4 and a temperature of 37 °C utilizing electrochemical impedance spectroscopy and the potentiodynamic polarization method. The anodized samples for both alloys at 40 V were at the optimal voltage, leading to a TiO2 layer formation with the best compromise between oxide thickness and corrosion resistance. Also, findings showed that TiO2 films produced on Ti-6Al-7Nb alloys had superior surface roughness properties compared to those of Ti-6Al-4V alloys, making them more appropriate for orthopedic applications. From the obtained data and the fruitful discussion, it was found that the utilized procedure is simple, low-cost, and repeatable. Therefore, anodization in 10% oxalic acid proved a viable alternative for the surface finishing of titanium alloys for biomedical applications.

Investigation of the hydrophilic nature and surface energy changes of HfO2 thin films prepared by atomic layer deposition

The wettability of metal oxides, which is directly related to the surface free energy (SFE), is used in a wide range of robust functional coatings, from hydrophilic to hydrophobic. Because wettability is significantly affected by solid surface properties, several studies on the determinant factors and their correlations have been conducted through the thin-film coating of metal oxides. Herein, we found that HfO2 thin films deposited via atomic layer deposition (ALD) are intrinsically hydrophilic. Simultaneously, a thickness-dependent wettability change is observed. These observations were investigated by measuring water contact angles (WCAs), film surface compositions, roughness, morphologies, and microcrystalline structures of the ALD-grown HfO2 thin films. It was deduced that the surface oxygen species significantly affected the intrinsic hydrophilicity of HfO2 thin films. In addition, the crystalline orientations evolved with film thickness, and thermal annealing was used to determine the thickness-dependent WCA trend. In particular, the transformation of the preferred m(-111) crystal orientation with a low SFE had a dominant impact on the SFE change in the HfO2 thin films. Considering the lack of fundamental studies on the SFE of ALD-grown HfO2 thin films, we believe that this study will help understand the wettability of HfO2 and its overall surface science.

Investigation on the influence of Zn content on the structural, optical, morphological and electrical properties of ternary compound Cd1−xZnxS window layer for CdTe solar cell

Ternary compound Cd[Formula: see text]Zn[Formula: see text]S thin films with different zinc compositions were deposited by the chemical bath deposition method, as a window layer for CdTe solar cells. The influence of Zn content on the structural, optical, morphological and electrical properties of Cd[Formula: see text]Zn[Formula: see text]S was studied from X-ray diffraction (XRD), SEM and UV-vis spectroscopy. We have considered the transformation of the crystal phase, change in the crystallite size and lattice parameters of Cd[Formula: see text]Zn[Formula: see text]S thin film with the change of Zn content through XRD studies. SEM measurement revealed that the size of Cd[Formula: see text]Zn[Formula: see text]S particles and surface roughness of thin film decreases with the increase of Zn composition. It was found that the band gap value obtained from transmittance spectrum became wider with the increase of Zn contents, which indicates the increase of film transmittance. The electrical resistivity of Cd[Formula: see text]Zn[Formula: see text]S thin films increased as Zn content [Formula: see text] increases. Finally, we measured the performances of CdTe solar cells using Cd[Formula: see text]Zn[Formula: see text]S thin films as a window layer and confirmed that desirable Zn content was in the range [Formula: see text] = 0.5-0.6.

On the Microcrystal Structure of Sputtered Cu Films Deposited on Si(100) Surfaces: Experiment and Integrated Multiscale Simulation.

Sputtered Cu/Si thin films were experimentally prepared at different sputtering pressures and characterized using X-ray diffraction (XRD) and an atomic force microscope (AFM). Simultaneously, an application-oriented simulation approach for magnetron sputtering deposition was proposed in this work. In this integrated multiscale simulation, the sputtered atom transport was modeled using the Monte Carlo (MC) and molecular dynamics (MD) coupling method, and the deposition of sputtered atoms was simulated using the MD method. This application-oriented simulation approach was used to simulate the growth of Cu/Si(100) thin films at different sputtering pressures. The experimental results unveiled that, as the sputtering pressure decreased from 2 to 0.15 Pa, the surface roughness of Cu thin films gradually decreased; (111)-oriented grains were dominant in Cu thin films and the crystal quality of the Cu thin film was gradually improved. The simulation results were consistent with the experimental characterization results. The simulation results revealed that the transformation of the film growth mode from the Volmer-Weber growth mode to the two-dimensional layered growth mode resulted in a decrease in the surface roughness of Cu thin films; the increase in the amorphous compound CuSix and the hcp copper silicide with the decrease in the sputtering pressure was responsible for the improvement of the crystal quality of the Cu thin film. This work proposed a more realistic, integrated simulation scheme for magnetron sputtering deposition, providing theoretical guidance for the efficient preparation of high-quality sputtered films.

High Optical Contrast of Quartet Dual-Band Electrochromic Device for Energy-Efficient Smart Window.

A quartet dual-band electrochromic device (ECD) was developed to selectively control the transmittance from the visible to near-infrared wavelengths for the application of an energy-efficient smart window. The new AgNO3+TBABr+LiClO4 (ATL)-based electrolyte was developed to independently control the redox reaction of lithium and silver ions to demonstrate the quartet mode of an ECD. A dual-band ECD with a sandwich structure was assembled using an ATL-based electrolyte, WO3 electrochromic layer, and antimony-doped tin oxide (ATO) ion storage layer. The employed WO3 and ATO films were fabricated using a nanoparticle deposition system (NPDS), a novel ecofriendly dry deposition method. Four modes, namely, transparent, warm, cool, and all-block modes, were demonstrated via an independent redox reaction of both lithium and silver ions through the simple control of the applied voltage. In the warm mode, the localized surface plasmon resonance effect was exploited by producing silver nanoparticles upon two-step voltage application. Furthermore, since the high surface roughness of the WO3 thin film fabricated by NPDS maximized the light scattering effect, 0% transmittance at all wavelengths was observed in the all-block mode. Dual-band ECD showed high optical contrasts of 73% and long-term durability over 1000 cycles with no degradation. Therefore, the possibility of controlling transmittance at the target wavelength was confirmed using a simple device with a simple process, suggesting a new strategy for the design of dual-band smart windows to reduce the energy consumption of buildings.

A sight of view on electrical impacts, structural properties and surface roughness of tungsten trioxide thin film: effect of substrate temperatures in WO3/Si device fabrication

Monoclinic WO3 thin films have been effectively deposited by a simple spray pyrolysis technique at a molar concentration of 0.01 M on a glass substrate in the temperature range of 473 to 673 K. These WO3 films were used as an interlayer between the metal and the semiconductor, which formed the basic structure of the photodetector. Effect of substrate temperature on WO3 films during the process of the deposition was systematically interpreted with respect to the structural, morphological, optical and electrical properties of the WO3 films. The x-ray diffraction pattern revealed the polycrystalline nature of the prepared films with monoclinic phases. At the substrate temperature of 623 K, the nano-thin films were strongly bonded to each other as observed from the FE-SEM images. Visible and ultraviolet spectroscopies indicated the band gap (Eg) of the WO3 thin film is 3.30 eV. The dc electrical study recorded a sharp increase in the electrical conductivity of the prepared film at substrate temperature of 623 K for tungsten trioxide. It is worth noting that all diodes showed a positive photoresponse under illumination. In particular, the photodetector with the thickness of 300 nm showed higher responsivity 0.02 A/W and detection specificity 8.29 × 1010 Jones.

Heteroacene-Based Polymer with Fast-Switching Visible-Near Infrared Electrochromic Behavior.

The electrochromic properties and application of electronically conducting polymers (ECPs) (PTRPZ-EDOT) consisting of a 3,4-ethylenedioxythiophene (EDOT) and the heteroacene-based molecular scaffold, 6H-pyrrolo[3,2-b:4,5-b'] bis [1,4] benzothiazine (TRPZ), are reported. Known for its high electron mobility and conducting properties, the novel TRPZ scaffold was synthesized to possess two EDOT molecules termini affording TRPZ-EDOT. Electropolymerization of TRPZ-EDOT resulted in remarkable spectroscopic and conductive properties suitable for electrochromic device fabrication. Using atomic force microscopy (AFM), the average surface roughness and surface topography of PTRPZ-EDOT polymer thin films were determined. Spectroelectrochemical data showed that the polymer achieved switching times of 4.07 (coloration) and 0.47 s (bleaching) at 539 nm. The PTRPZ-EDOT film exhibits an optical contrast of 36-44% at 539 nm between its neutral and colored states, respectively. The NIR region from 1000 to 1700 nm shows the appearance of charge carrier bands with a 0-1 V potential range. An electrochromic device was successfully fabricated from PTRPZ-EDOT, showcasing the potential and applicability of the polymer material for advanced technologies such as smart windows, flexible electrochromic screens, and energy storage devices.

Influence of Al and Cu Doping on the Structure, Morphology, and Optical Properties of ZnO Thin Film

In this study, ZnO thin films doped with Al (AZO) and Cu (CZO) were fabricated on a glass substrate via sol-gel spin coating. The influence of 1 atomic % Al and Cu doping on the structure, morphology, as well as optical properties of ZnO thin film was then analyzed with X-ray diffraction (XRD), atomic force microscopy (AFM), and UV-Vis spectroscopy. XRD analysis revealed that all samples possessed hexagonal wurtzite crystal structures with 3 to 4 preferred orientations. Al and Cu doping caused a decrease in crystal size, while the lattice strain (e) and dislocation density (ρ) were increased. AFM indicated that Al and Cu doping reduced the surface roughness of the ZnO thin film. Optical measurement showed that all samples exhibited high transmittance (> 80%) in the visible light region. Transmittance was reduced after doping, while the band gaps for ZnO, AZO, and CZO thin films are 3.26, 3.28, and 3.23 eV. This study showed that an addition of 1 atomic % transition metal (Al and Cu) greatly influences the structure, morphology, and optical properties of ZnO thin film.

Antibacterial efficiency of cadmium thin films deposited by the thermionic vacuum arc

In this study, thin films of the pure Cadmium (Cd) were deposited on glass and high-density polyethylene (HDPE) samples by the Thermionic Vacuum Arc (TVA) method. The structural and surface morphological properties of Cd thin-films were investigated using X-ray diffraction patterns (XRD), field emission scanning electron microscope (FE-SEM), and atomic force electron microscope (AFM). The water contact angle (WCA) was determined by a Krüss DSA100 model goniometer. The antibacterial activities of the Cd-coated and uncoated samples were investigated by direct-contact test and modified Kirby-Bauer test against Escherichia coli O157:H7 ATCC35150, Staphylococcus aureus ATCC6538P and Listeria innocua ATCC33090. Cd thin films deposited on both samples were found to be in crystalline form. The Crystallite size of the films deposited on glass and HDPE were calculated as 52.1 and 72.5 nm, respectively. The SEM and AFM depict the Cd films uniform distribution of grains. The root mean square (Rms) surface roughness of Cd thin film was found as 39.3 nm and 70.3 nm on glass and HDPE substrates, respectively. The WCA measurements showed the cadmium coatings increased the hydrophobicity of glass and HDPE samples. Direct-contact test showed both Cd-coated samples totally inhibited E. coli O157:H7 and L. innocua strains after 2-h of contact time. Modified Kirby-Bauer test indicated the Cd-coated HDPE samples showed the highest antibacterial activity against L. innocua however Cd films did not have any antibacterial activity for both samples against S. aureus.

Electrochemically Deposited CZTSSe Thin Films for Monolithic Perovskite Tandem Solar Cells with Efficiencies Over 17%

In spite of the high potential economic feasibility of the tandem solar cells consisting of the halide perovskite and the kesterite Cu2ZnSn(S,Se)4 (CZTSSe), they have rarely been demonstrated due to the difficulty in implementing solution‐processed perovskite top cell on the rough surface of the bottom cells. Here, we firstly demonstrate an efficient monolithic two‐terminal perovskite/CZTSSe tandem solar cell by significantly reducing the surface roughness of the electrochemically deposited CZTSSe bottom cell. The surface roughness (Rrms) of the CZTSSe thin film could be reduced from 424 to 86 nm by using the potentiostatic mode rather than using the conventional galvanostatic mode, which can be further reduced to 22 nm after the subsequent ion‐milling process. The perovskite top cell with a bandgap of 1.65 eV could be prepared using a solution process on the flattened CZTSSe bottom cell, resulting in the efficient perovskite/CZTSSe tandem solar cells. After the current matching between two subcells involving the thickness control of the perovskite layer, the best performing tandem device exhibited a high conversion efficiency of 17.5% without the hysteresis effect.

Colloidal Synthesis of Semiconductor Films for Efficient Photoelectrochemical Hydrogen Generation

The semiconductor-based photoanodes have shown great potential on photoelectrochemical (PEC) hydrogen generation. Compared to the pristine semiconductor, photoanodes fabricated with doped semiconductors exhibit modulated bandgap structure and enhanced charge separation efficiency, demonstrating improved optoelectronic properties. In this work, we develop a colloidal cation exchange (CE) strategy on versatile synthesis of heterovalent doped chalcogenide semiconductor thin films with high surface roughness. Using Ag-doped CdSe (CdSe:Ag) thin films as an example, the organized centimeter-scale CdSe:Ag films with nanometer-scale thickness (thickness around 80 nm, length × width around 1.5 cm × 1.2 cm) exhibit enhanced optical absorbance ability and charge carrier density by tuning the energy levels of conduction and valence bands as well as improved electrical conductivity by Ag dopants compared to the pristine CdSe film obtained by the vapor-phase vacuum deposition strategy. In the meantime, the surface roughness of the as-prepared semiconductor thin films is also increased with abundantly exposed active sites to facilitate accessibility to water for hydrogen generation and suppress photogenerated carrier recombination. The CdSe:Ag film photoanodes exhibit superb PEC hydrogen generation performance with a photocurrent density of 0.56 mA/cm 2 at 1.23 V versus reversible hydrogen electrode, which is nearly 3 times higher than the pristine CdSe film. This work provides a new strategy on colloidal synthesis of photoelectrodes with modulated heterovalent doping and surface roughness for PEC applications.

Characterization of Zinc Oxide Semiconductor Thin Film Treated with Cold Plasma

In this study, the photovoltaic properties of zinc oxides are investigated. Different stoichiometries of zinc oxide can be made using vacuum deposition. Thermally evaporated zinc produces thin films of ZnO composed of orthorhombic and tetragonal phases that define the material's characteristics and performance. On-thermal plasma has removed a very thin layer from the surface of the thin film, known as non-thermal plasma, and made a surface cleanup. Measurements of the Atomic Force Microscope (AFM) show that the value of the granular volume rate increases when the duration of exposure to non-heat plasma increases. Measurements of the Atomic Force Microscope (AFM) show that there is an increase in thin film surface roughness values (Roughness, Sq), as well as the square root of the average roughness of the thin film surface (RMS), and this increase in roughness appears as the duration of exposure to non-thermal plasma increases.

Influence of corona poling on ZnO properties as n-type layer for optoelectronic devices

Corona poling effects on optical and structural characteristics of zinc oxide (ZnO) thin films prepared by sol–gel spin coating technique were investigated. Atomic force microscope study showed the formation of pyramidal grains structure on the Corona-treated surface. The green–yellow photoluminescence peak centered at 2.36 eV and correlated to the antisite oxygen OZn defect, was found to decrease. X-ray diffraction patterns demonstrated that the Corona treatment enhanced the polycrystalline nature and increased the grain sizes of the ZnO thin films, which was also beneficial for electron transport. The role of the surface roughness of the ZnO thin film as electron transport layer in determining the photovoltaic effect of the inverted solar cells (ISCs) was examined by fabricating ISCs based on P3HT/PC61BM. The power conversion efficiency (PCE) obtained from these fabricated ISCs increased from 3.05 to 3.34%.