Thin Film Layer Research Articles

Selective Ablation and Laser-Induced Periodical Surface Structures (LIPSS) Produced on (Ni/Ti) Nano Layer Thin Film with Ultra-Short Laser Pulses

The interaction of ultra-short laser pulses (USLP) with Nickel/Titanium (Ni/Ti) thin film has been presented. The nano layer thin film (NLTF), composed of ten alternating Ni and Ti layers, was deposited on silicon (Si) substrate by ion-sputtering. A single and multi-pulse irradiation was performed in air with focused and linearly polarized laser pulses. For achieving selective ablation of one or more surface layers, without reaching the Si substrate, single pulse energy was gradually increased from near the ablation threshold value to an energy value that caused the complete removal of the NLTF. In addition to single-pulse selective ablation, the multi-pulse USLP irradiation and production of laser-induced periodic surface structures (LIPSSs) were also studied. In the presented experiment, we found the optimal combination of accumulated pulse number and pulse energy to achieve the LIPSS formation on the thin film. The laser-induced morphology was examined with optical microscopy, scanning electron microscopy, and optical profilometry. To interpret the experimental observations, a theoretical simulation has been performed to explore the thermal response of the NLTFs after irradiation with single laser pulses.

Space exposure test of hardwood specimens in the International Space Station

To design a wooden satellite and select the appropriate wood species, we conducted a space exposure test of wood on the International Space Station (ISS). The space exposure test used the Japanese Experiment Module “Kibo” on the Exposed Experiment Bracket Attached on i-SEEP (ExBAS), which is connected to the exposed facility of the ISS. Three wood species considered candidates for the structure of a wooden satellite were used in the exposure test: honoki (Magnolia obovata), yamazakura (Cerasus jamasakura), and dakekanba (Betula ermanii). In the outgassing test conducted in preparation for the space exposure test, the collected volatile condensable materials (CVCM) of the three wood species were below the critical value; however, the total mass loss (TML) exceeded the critical value. However, this was not a problem, because most of the mass loss was due to water evaporation. A space exposure test was conducted for 10 months in 2022. Consequently, no change was observed in the weight of the exposed specimen, and no erosion due to atomic oxygen (AO) was observed. The exposure test was scheduled to be carried out in the forward direction of the ISS travel; however, owing to equipment trouble, it was installed in the opposite direction. This is because an insufficient AO flux collided with the specimen. In terms of wood color, the brightness of the three species decreased owing to space exposure, and saturation increased in two wood species, except for yamazakura. A thin-film layer was observed on the surface of the aluminum cover to which the exposed specimen was fixed, which may have also formed on the surface of the wood specimen, reducing its brightness. However, because the hue angle did not change significantly, only a slight deterioration of the surface layer owing to vacuum ultraviolet was observed. The results confirmed that the wood had hardly deteriorated in space for approximately 10 months.

A Low-Dropout Regulator Integrated With E-mode IGZO and D-mode ITO/IGZO Dual Layer Thin Film Transistors With Superior Uniformity and Stability

A Low-Dropout Regulator Integrated With E-mode IGZO and D-mode ITO/IGZO Dual Layer Thin Film Transistors With Superior Uniformity and Stability

Method for Extracting Optical Element Information Using Optical Coherence Tomography.

This study examines the measurement of film thickness, curvature, and defects on the surface or inside of an optical element using a highly accurate and efficient method. This is essential to ensure their quality and performance. Existing methods are unable to simultaneously extract the three types of information: thickness, curvature, and defects. Spectral-domain optical coherence tomography (SD-OCT), a non-invasive imaging technique with imaging depths down to the millimeter scale, provides the possibility of detecting the optical element components' parameters. In this paper, we propose an error correction model for compensating delay differences in A-scan, field curvature, and aberration to improve the accuracy of system fitting measurements using SD-OCT. During data processing, we use the histogram-equalized gray stretching (IAH-GS) method to deal with strong reflections in the thin film layers inside the optics using individual A-scan averages. In addition, we propose a window threshold cutoff algorithm to accurately identify defects and boundaries in OCT images. Finally, the system is capable of rapidly detecting the thickness and curvature of film layers in optical elements with a maximum measurement depth of 4.508 mm, a diameter of 15 × 15 mm, a resolution of 5.69 microns, and a sampling rate of 70 kHz. Measurements were performed on different standard optical elements to verify the accuracy and reliability of the proposed method. To the best of our knowledge, this is the first time that thickness, curvature, and defects of an optical film have been measured simultaneously, with a thickness measurement accuracy of 1.924 µm, and with a difference between the calibrated and nominal curvature measurements consistently within 1%. We believe that this research will greatly advance the use of OCT technology in the testing of optical thin films, thereby improving productivity and product quality.

Large-scale high purity and brightness structural color generation in layered thin film structures via coupled cavity resonance

Abstract Structural colors, resulting from the interaction of light with nanostructured materials rather than pigments, present a promising avenue for diverse applications ranging from ink-free printing to optical anti-counterfeiting. Achieving structural colors with high purity and brightness over large areas and at low costs is beneficial for many practical applications, but still remains a challenge for current designs. Here, we introduce a novel approach to realizing large-scale structural colors in layered thin film structures that are characterized by both high brightness and purity. Unlike conventional designs relying on single Fabry–Pérot cavity resonance, our method leverages coupled resonance between adjacent cavities to achieve sharp and intense transmission peaks with significantly suppressed sideband intensity. We demonstrate this approach by designing and experimentally validating transmission-type red, green, and blue colors using an Ag/SiO2/Ag/SiO2/Ag configuration on fused silica substrate. The measured spectra exhibit narrow resonant linewidths (full width at half maximum ∼60 nm), high peak efficiencies (>40 %), and well-suppressed sideband intensities (∼0 %). In addition, the generated color can be easily tuned by adjusting the thickness of SiO2 layer, and the associated color gamut coverage shows a wider range than many existing standards. Moreover, the proposed design method is versatile and compatible with various choices of dielectric and metallic layers. For instance, we demonstrate the production of angle-robust structural colors by utilizing high-index Ta2O5 as the dielectric layer. Finally, we showcase a series of printed color images based on the proposed structures. The coupled-cavity-resonance architecture presented here successfully mitigates the trade-off between color brightness and purity in conventional layered thin film structures and provides a novel and cost-effective route towards the realization of large-scale and high-performance structural colors.

Thin-film electrodes of dielectric elastomer-based actuators for an active vibration control system

Precision research and technological equipment, as a rule, is not able to provide its specification characteristics without a high-quality vibration protection system. Active vibration control of an object is provided with the help of an additional source of movement, an actuator. The most promising high accuracy actuators are based on smart materials, such as materials with shape memory, piezoelectric and magnetostrictive materials, electro- and magnetic active fluids and elastomers. Dielectric elastomer is one of the types of electroactive polymers. Actuators based on a dielectric elastomer show high performance in terms of accuracy and speed and operate due to the controllable deformation of the elastomer under the action of a high voltage electric field. The paper provides a comparison of actuators based on sheet and thin film control electrodes. The influence of the quality of the polymer surface and the type of electrodes on the travel range of the actuator and maximum amplitude of vibrations the system can suppress on the basis of a dielectric elastomer is estimated. The formation of the electrode by magnetron sputtering in vacuum makes it possible to create a thin-film layer of copper that covers the elastomer, despite the developed surface. The effect of ion treatment of an elastomer before coating on the quality of the formed electrode is considered. After the ion treatment, the surface of the elastomer acquires a more uniform regular structure. A thin-film electrode layer is formed according to the topology of the elastomer to an accomplished standard.

Novel Al/CoFe/p-Si and Al/NiFe/p-Si MS-type photodiode for sensing

CoFe and NiFe are used in the construction of Si-based metal-semiconductor-type photodiodes. Thin film layers are sputtered onto thep-Si surface where Al metal contacts are deposited using the thermal evaporation technique. Film characteristics of the layers are investigated with respect to the crystalline structure and surface morphology. Their electrical and optical properties are investigated using dark and illuminated current-voltage measurements. When these two diodes are compared, Al/NiFe/p-Si exhibits better rectification properties than Al/CoFe/p-Si diode. There is also a high barrier height where these values for both diodes increase with illumination. According to the current-voltage analysis, the existence of an interlayer causes a deviation in diode ideality. In addition, the response to bias voltage, the derivation of electrical parameters, and the light sensitivity of diodes are evaluated using current-voltage measurements under different illumination intensities and also transient photosensitive characteristics.

Preparation and Characterization of Nanostructured ITO Thin Films by Spray Pyrolysis Technique: Dependence on Annealing Temperature

Transparent conducting oxides (TCOs) like Indium tin oxide (ITO) have wide attention from all scientists which have low resistance and high visible light transmittance, used as transparent electrodes in many optoelectronic devices such as liquid crystal displays, touch screens, light emitting diodes, and solar cells. In this research, the relationship between the crystallization, optical transmittance, and surface roughness of nanostructured ITO thin films and the change in annealing temperature was investigated. To enhance the efficiency of this material in optoelectronic applications, both the optical transmittance in the visible region and the crystallite size must be increased. These results can be obtained by the heat treatment of the films. Nanostructured ITO thin layer films have been successfully prepared at a substrate temperature equal to (350)℃ by chemical spray pyrolysis (CSP) technique. The physical characterizations of nanostructured ITO thin layer films were investigated at different annealing temperatures (400,450 and 500)℃. The presence of diffraction peaks indicates that the as-deposited and post annealed films are polycrystalline cubic structure and the peak (400) is a preferred growth orientation. For all samples the value of intensity of diffraction peaks increases with increasing substrate temperature. The crystallite size of nanostructured ITO thin films is strongly related to the annealing temperature. The crystallite size estimated from XRD was found to rise with rising annealing temperature. The surface roughness of nanostructured ITO thin layer films increases with rising annealing temperature. High values of transmittance have been measured in the visible region 550 nm equal to (70, 82, 84 and 88)% corresponding to annealing temperature (350,400,450 and 500)℃ respectively.

Physical Quality of Edible Film with the Addition of Isolate Whey Protein on Water Content, Solubility, Thickness and Transparency

Edible film is a thin layer used to coat food, which functions as a barrier against mass transfer, such as water, oxygen, and fat. Edible film is a packaging material formed first in the form of a thin layer (film) before being applied to food ingredients and products. Adding whey protein isolate (WPI) to edible film can improve its physical quality. This research aims to determine the effect of adding whey protein isolate to edible film on the physical quality of edible film. The method used in this research was a completely randomized laboratory experimental design with five treatments and four replications. The addition of WPI 0.3%, 0.6%, 0.9%, and 1.2% to Edible Film gave a high significant effect (P<0.01) on solubility, degree of swelling, thickness, and transparency, and gave no significant effect (P>0.05) on water content. The results of testing edible films made from chitosan with the addition of 0.3%, 0.6%, 0.9% and 1.2% isolate whey proteine produced a water content 16.60-20.64%, solubility of 17.44-23.08%, swelling degree 71.08-76.42%, thickness 0.0725-0.0975 mm, and transparency 0.20-1.69. The addition of whey protein isolate (WPI) to edible film is thought to improve the physical quality of edible film.

High-responsivity photoelectrochemical ultraviolet photodetector based on SnO2 nanosheets-Ga2O3

Abstract Tin oxide (SnO2) has garnered significant attention for its high spectral selectivity when used as an ultraviolet photodetector. In this study, SnO2 nanosheets (NSs) were synthesized via a hydrothermal method, followed by spin-coating a layer of Ga2O3 thin film to construct a heterojunction photoelectrochemical ultraviolet photodetector (PEC UV PD). Initially, we investigated the effect of precursor composition on the properties of the Ga2O3 thin films. It was observed that the thickness of the films increased with higher precursor concentrations, while the optical bandgap decreased. Based on these findings, we successfully fabricated the SnO2 NSs-Ga2O3 PEC UV PD. Electrochemical analysis revealed that as the precursor concentration used for spin-coating Ga2O3 increased, the device's responsivity and detectivity initially increased and then decreased. After optimization, the device prepared with a 0.2M Ga(NO3)3 solution spin-coated on SnO2 exhibited excellent spectral selectivity (R 265nm/R 420nm ~ 4472), a responsivity of 4.86 mA W-1, and a detectivity of 2.72×109 Jones. This study demonstrates that coating Ga2O3 is an effective approach to constructing high-performance SnO2-based UV PDs.

The Impact of Substrate Temperature on the Adhesion Strength of Electroplated Copper on an Al-Doped ZnO/Si System.

This research, which involved a comprehensive methodology, including depositing electroplated copper on a copper seed layer and Al-doped ZnO (AZO) thin films on textured silicon substrates using DC magnetron sputtering with varying substrate heating, has yielded significant findings. The study thoroughly investigated the effects of substrate temperature (Ts) on copper adhesion strength and morphology using the peel force test and electron microscopy. The peel force test was conducted at angles of 90°, 135°, and 180°. The average adhesion strength was about 0.2 N/mm for the samples without substrate heating. For the samples with substrate heating at 100 °C, the average peeling force of the electroplated copper film was about 1 N/mm. The average peeling force increased to 1.5 N/mm as the substrate heating temperature increased to 200 °C. The surface roughness increases as the annealing temperature of the Cu/AZO/Si sample increases. These findings not only provide a reliable and robust method for applying AZO transparent conductive films onto silicon solar cells but also underscore its potential to significantly enhance the efficiency and durability of solar cells significantly, thereby instilling confidence in the field of solar cell technology.

Preparing a Phytosome for Promoting Delivery Efficiency and Biological Activities of Methyl Jasmonate-Treated Dendropanax morbifera Adventitious Root Extract (DMARE).

(1) Background: Methyl jasmonate-treated D. morbifera adventitious root extract (MeJA-DMARE), enriched with phenolics, has enhanced bioactivities. However, phenolics possess low stability and bioavailability. Substantial evidence indicates that plant extract-phospholipid complex assemblies, known as phytosomes, represent an innovative drug delivery system. (2) Methods: The phytosome complex was created by combining MeJA-DMARE with Soy-L-α-phosphatidylcholine (PC) using three different ratios through two distinct methods (co-solvency method: A1, A2, and A3; thin-layer film method: B1, B2, and B3). (3) Results: Initial evaluation based on UV-Vis, entrapment efficiency (EE%), and loading content (LC%) indicated that B2 exhibited the highest EE% (79.98 ± 1.45) and LC% (69.17 ± 0.14). The phytosome displayed a spherical morphology with a particle size of 210 nm, a notably low polydispersity index of 0.16, and a superior zeta potential value at -25.19 mV. The synthesized phytosome exhibited superior anti-inflammatory activities by inhibiting NO and ROS production (reduced to 8.9% and 55.1% at 250 μg/mL) in RAW cells and adjusting the expression of related inflammatory cytokines; they also slowed lung tumor cell migration (only 2.3% of A549 cells migrated after treatment with phytosomes at 250 μg/mL), promoting ROS generation in A549 cell lines (123.7% compared to control) and stimulating apoptosis of lung cancer-related genes. (4) Conclusions: In conclusion, the MeJA-DMARE phytosome offers stable, economically efficient, and environmentally friendly nanoparticles with superior inflammation and lung tumor inhibition properties. Thus, the MeJA-DMARE phytosome holds promise as an applicable and favorable creation for drug delivery and lung cancer treatment.

Microstructure Evolution Analysis of Ni/YSZ Cermet Electrode using Cross-Sectional Model Cells

Abstract Degradation of solid oxide cells can be partially attributed to the microstructural changes in Ni/YSZ fuel electrodes owing to Ni migration. This study aims to evaluate the microstructural evolution of Ni/YSZ fuel electrodes as a function of the oxygen potential along the thickness direction. To this end, comb-shaped Ni-patterned electrodes were designed on the top layer of a YSZ thin film using two different systems: (a) a symmetrical Ni-patterned electrode and (b) an asymmetrical Ni–Pt electrode with a reference electrode. In the symmetrical electrode, one side of the Ni-patterned electrode operated at the fuel cell (FC) mode, exhibiting expansion that led to an increase in triple-phase boundary (TPB) length and a decrease in electrolyte width. Conversely, the Ni-patterned electrodes that operated in electrolysis (EC) mode showed a slight migration away from the electrolyte. Detailed microstructural changes in the EC mode were examined using the asymmetrical electrode, revealing a correlation between water vapor content and Ni morphology. The results suggest that the amount of water vapor adsorbed on the electrode surface causes the decrease of oxygen potential at TPB. This causes the decrease in the wettability that led to significant change of Ni microstructure across the electrode length.

Design and fabrication of highly efficient antireflective coating in MWIR on germanium using ion-assisted e-beam deposition

We present the design, fabrication, and characterization of a multilayer anti-reflective (AR) coating on a Germanium (Ge) substrate for mid-wavelength infrared (MWIR) applications using the ion-assisted electron-beam evaporation (IAPVD) technique. The AR coating structure comprises five layers of thin films, alternating between low (nL) and high (nH) refractive index materials, specifically silicon dioxide (SiO2) and Ge. The total thickness of the multilayer structure is maintained below 2 μm. The design was meticulously optimized for the 3.6–4.9 μm MWIR range using OptiLayer software, achieving an impressive average transmission of 99.492 % and an average reflectance of merely 0.508 % over a broadband spectral width of 1300 nm. Following the fabrication process using the IAPVD technique, the empirical results demonstrated an average transmission of 98.56 % and a reflectance value of 0.177 % within the 3.6–4.9 μm range. A strong correlation was observed between the simulated and the fabricated results, with a deviation of only 0.331 % on the reflectance value, proving the accuracy and reliability of the design and fabrication process. This work introduces a highly efficient solution for AR coatings on Ge surfaces, enhancing the performance of electro-optical applications in the MWIR region. To the best of our knowledge, the newly designed Ge/SiO2 multilayer structure and the results achieved have not been previously documented in the literature, and offer substantial improvements in transmission efficiency and reflectance reduction for Ge-based optical systems.

Fabrication with magnetic-spin coating: Influence of magnetic-inertia energy ratio on gold-pickering ferrofluid droplet assembly morphology

Magnetic self-assembly of nanoparticles is a well-known technique for creating thin-film array-patterned functional microstructures. However, an uncontrollable hierarchical assembly formation of magnetically stimulated particles has hindered the desired formation of free-standing two-dimensional (2D) array patterns in thin-film layers. In this study, we proposed a fluidic shearing effect from spin coating to reduce magnetically stimulated particles’ disarrayed and complex chain formations, thus promoting linear array formations, even as the film becomes thinner. A series of tests were conducted on a gold-Pickering ferrofluid emulsion (GPFE) dispersed in 15.2 mPas aqueous polyvinyl alcohol (PVAh), which was subjected to varying spin speeds under magnetic setups such as single (SI), compound (CC), and concentric (CR). These setups were chosen to observe the influence of magnetic field strength and distribution on the generated pattern profile from microscopic binary images of the resulting thin films. The aim was to quantify the formed chain thickness (ChT), chain gaps (ChG), and chain lengths (ChL) to capture the morphology and geometrical features of the formed patterns. Our results showed that the quantified values of these profiles and their dimensionless relationships were significantly influenced by the ratio between the applied magnetic packing energy and the centrifugally controlled fluidic energy, QPD. This investigation showed that ChT/ChG for a corresponding QPD value is 98.6% the same for all configurations, and CR was the best setup going forward, as it yielded the lowest array quality defectivity of 14%. Therefore, we assert that this fabrication method offers flexibility, cost-effectiveness, and expandability in generating linear array patterns that contain graduating variability in grating order dimensions within a single cast that can serve efficiently as a substrate for biomolecules under enhanced Raman and Infrared spectroscopies.

High-Density Capacitive Energy Storage in Low-Dielectric-Constant Polymer PMMA/2D Mica Nanofillers Heterostructure Composite

The ubiquitous, rising demand for energy storage devices with ultra-high storage capacity and efficiency has drawn tremendous research interest in developing energy storage devices. Dielectric polymers are one of the most suitable materials used to fabricate electrostatic capacitive energy storage devices with thin-film geometry with high power density. In this work, we studied the dielectric properties, electric polarization, and energy density of PMMA/2D Mica nanocomposite capacitors where stratified 2D nanofillers are interfaced between the multiple layers of PMMA thin films using two heterostructure designs of the capacitors, PMMA/2D Mica/PMMA (PMP) and PMMA/2D Mica/PMMA/2D Mica/PMMA (PMPMP). The incorporation of a 2D Mica nanofiller in the low-dielectric-constant PMMA leads to an enhancement in the dielectric constant, with ∆ε ~ 15% and 53% for PMP and PMPMP heterostructures at room temperature. Additionally, a significant improvement in discharged energy density was measured for the PMPMP capacitor (Ud ~ 38 J/cm3 at 825 MV/m) compared to the pristine PMMA (Ud ~ 9.5 J/cm3 at 522 MV/m) and PMP capacitors (Ud ~ 19 J/cm3 at 740 MV/m). This excellent capacitive and energy storage performance of the PMMA/2D Mica heterostructure nanocomposite may inform the fabrication of thin-film, high-density energy storage capacitor devices for potential applications in various platforms.

Photovoltaic performance in CIGS solar cells: effects of using Mg- and Al-doped ZnO thin-film layers as alternative TCO and front contact layer

Photovoltaic performance in CIGS solar cells: effects of using Mg- and Al-doped ZnO thin-film layers as alternative TCO and front contact layer

Improving TFT Device Performance by Changing the Thickness of the LZTO/ZTO Dual Active Layer.

The primary objective of this research paper is to explore strategies for enhancing the electrical performance of dual active layer thin film transistors (TFTs) utilizing LZTO/ZTO as the bilayer architecture. By systematically adjusting the thickness of the active layers, we achieved significant improvements in the performance of the LZTO/ZTO TFTs. An XPS analysis was performed to elucidate the impact of the varying O2 element distribution ratio within the LZTO/ZTO bilayer thin film on the TFTs performance, which was directly influenced by the modification in the active layer thickness. Furthermore, we utilized atomic force microscopy to analyze the effect of altering the active layer thickness on the surface roughness of the LZTO/ZTO bilayer film and the impact of this roughness on the TFTs electrical performance. Through the optimization of the ZTO active layer thickness, the LZTO/ZTO TFT exhibited an mobility of 10.26 cm2 V-1 s-1 and a switching current ratio of 5.7 × 107, thus highlighting the effectiveness of our approach in enhancing the electrical characteristics of the TFT device.

Effect of interlayer stacking arrangement on the dielectric properties of hexagonal boron nitride thin films

Electrostatic properties of hexagonal boron nitride (hBN) thin films with different stacking arrangements were investigated using density functional theory combined with the effective screening medium method. Our calculations showed that the dielectric properties across layers of hBN thin films are sensitive to both the interlayer stacking arrangement and the number of layers. The polarization of bilayer hBN gradually decreases with increasing lateral displacement from AB stacking, and polarity inversion occurs for particular stacking arrangements. The polarity of bilayer hBN is sensitive to twisting displacement. The polarity monotonically increases with increasing the number of layers in hBN films with rhombohedral stacking arrangement.

Tunable Plasmon Resonance in Silver Nanodisk-on-Mirror Structures and Scattering Enhancement by Annealing.

In this study, we evaluated the surface plasmon characteristics of periodic silver nanodisk structures fabricated on a dielectric thin-film spacer layer on a Ag mirror substrate (NanoDisk on Mirror: NDoM) through finite difference time domain (FDTD) simulations and experiments involving actual sample fabrication. Through FDTD simulations, it was confirmed that the NDoM structure exhibits two sharp peaks in the visible range, and by adjusting the thickness of the spacer layer and the size of the nanodisk structure, sharp peaks can be obtained across the entire visible range. Additionally, we fabricated the NDoM structure using electron beam lithography (EBL) and experimentally confirmed that the obtained peaks matched the simulation results. Furthermore, we discovered that applying annealing at an appropriate temperature to the fabricated structure enables the adjustment of the resonance peak wavelength and enhances the scattering intensity by approximately five times. This enhancement is believed to result from changes in the shape and size of the nanodisk structure, as well as a reduction in grain boundaries in the metal crystal due to annealing. These results have the potential to contribute to technological advancements in various application fields, such as optical sensing and emission enhancement.