Surface Morphology Of Films Research Articles

Millisecond X-ray reflectometry and neural network analysis: unveiling fast processes in spin coating.

X-ray reflectometry (XRR) is a powerful tool for probing the structural characteristics of nanoscale films and layered structures, which is an important field of nanotechnology and is often used in semiconductor and optics manufacturing. This study introduces a novel approach for conducting quantitative high-resolution millisecond monochromatic XRR measurements. This is an order of magnitude faster than in previously published work. Quick XRR (qXRR) enables real time and in situ monitoring of nanoscale processes such as thin film formation during spin coating. A record qXRR acquisition time of 1.4 ms is demonstrated for a static gold thin film on a silicon sample. As a second example of this novel approach, dynamic in situ measurements are performed during PMMA spin coating onto silicon wafers and fast fitting of XRR curves using machine learning is demonstrated. This investigation primarily focuses on the evolution of film structure and surface morphology, resolving for the first time with qXRR the initial film thinning via mass transport and also shedding light on later thinning via solvent evaporation. This innovative millisecond qXRR technique is of significance for in situ studies of thin film deposition. It addresses the challenge of following intrinsically fast processes, such as thin film growth of high deposition rate or spin coating. Beyond thin film growth processes, millisecond XRR has implications for resolving fast structural changes such as photostriction or diffusion processes.

Monolithic Two-Terminal Tandem Solar Cells Using Sb2S3 and Solution-Processed PbS Quantum Dots Achieving an Open-Circuit Potential beyond 1.1 V.

Multijunction solar cells have the prospect of a greater theoretical efficiency limit than single-junction solar cells by minimizing the transmissive and thermalization losses a single absorber material has. In solar cell applications, Sb2S3 is considered an attractive absorber due to its elemental abundance, stability, and high absorption coefficient in the visible range of the solar spectrum, yet with a band gap of 1.7 eV, it is transmissive for near-IR and IR photons. Using it as the top cell (the cell where light is first incident) in a two-terminal tandem architecture in combination with a bottom cell (the cell where light arrives second) of PbS quantum dots (QDs), which have an adjustable band gap suitable for absorbing longer wavelengths, is a promising approach to harvest the solar spectrum more effectively. In this work, these two subcells are monolithically fabricated and connected in series by a poly(3,4-ethylene-dioxythiophene) polystyrene sulfonate (PEDOT:PSS)-ZnO tunnel junction as the recombination layer. We explore the surface morphology of ZnO QD films with different spin-coating conditions, which serve as the PbS QD cell's electron transport material. Furthermore, we examine the differences in photogenerated current upon varying the PbS QD absorber layer thickness and the electrical and optical characteristics of the tandem with respect to the stand-alone reference cells. This tandem architecture demonstrates an extended spectral response into the IR with an open-circuit potential exceeding 1.1 V and a power conversion efficiency of 5.6%, which is greater than that of each single-junction cell.

Effect of Gas Flow Rate and Ratio on Structure and Properties of Nitrogen-Doped Diamond-like Carbon Films

Diamond-like carbon (DLC) has attracted much attention due to its unique properties such as high chemical inertness, optical transparency, and high biocompatibility. In this study, the total gas flow rate was kept constant, while the ratio of reactive gases was varied to deposit nitrogen-doped diamond-like carbon thin films on glass substrates using radiofrequency plasma-enhanced chemical vapor deposition. The effects of the gas flow ratio on the composition, microstructure, surface morphology, and optical properties of the thin films were investigated through extended deposition times. It was found that with an increase in the nitrogen-to-methane gas flow ratio, the film surface became smoother and more compact. The maximum transmittance in the visible range reached 90%, and the highest and lowest transmittance in the same ultraviolet wavelength region differed by up to 25.62% among several sample groups. The optical bandgap decreased from 3.58 eV to 3.46 eV, contrary to the trend of the sp2 fraction variation. Compared with other studies, this study considered the preparation of nitrogen-doped diamondoids using a chemical vapor deposition method with a lesser total gas flow rate passed into it, which provides practical data reference value for the preparation of N-DLC.

Spontaneously formed cellulose-based random micro-textured film for light extraction in organic light-emitting diodes

This study utilized cellulose-based external light extraction films to enhance the outcoupling efficiency of organic light-emitting diodes (OLEDs). These films were created through a straightforward fabrication employing the biopolymers hydroxyethyl cellulose (HEC) and tannic acid (TA). We observed that the hydrogen bonding between HEC and TA could spontaneously generate a random microtextured surface on the HEC: TA films. Furthermore, the surface morphology of the HECTA film can be adjusted by varying the TA content. When applying the HECTA films as an external light-extraction layer for OLEDs, we noticed a remarkable improvement in the external quantum efficiency and current efficiency of the OLEDs up to 54% compared to those without the HECTA film. Additionally, the HECTA film displayed an outstanding ability to absorb ultraviolet light. Therefore, it is anticipated that the HECTA film can significantly contribute to prolonging the stability of OLEDs.

Molecular dynamics simulations and experimental studies on low-temperature growth of GaN

Growth mechanisms of (0001) wurtzite GaN films at low temperature are investigated by molecular dynamics simulations and experiments. The crystallization properties of GaN films deteriorate dramatically at low temperature due to the limited energy available for atomic surface migration and incorporation into the perfect lattice sites. In our simulation, growth interruption stage is periodically introduced and the as-deposited GaN films are treated with energy-carrying argon ions at this stage. The surface atoms located at the weak binding sites can acquire energy from the argon ions for secondary migration and incorporation into the perfect lattice sites. As a result, the crystallization properties of GaN films are significantly improved. GaN films are experimentally grown on sputtered AlN/sapphire substrates at 600 °C via inductively coupled plasma metal organic chemical vapor deposition along with periodic argon plasma treatment. The as-deposited film acquires energy from the plasma, leading to significant improvement of the crystalline properties. The surface morphology of the GaN film demonstrates a noticeable smoothing effect, with an evident increase in grain size from submicron to micron level. Additionally, GaN film with the optimized surface morphology exhibits high c-axis and in-plane orientations, and the full width half maximums of (002) and (102) x-ray diffraction rocking curves are 0.25° and 0.32°, respectively. These results provide effective guidance for the growth of GaN films at low temperature.

Surface Morphology of Thin Films of (Y0.06Ga0.94)2O3 Activated by Cr3+

Surface Morphology of Thin Films of (Y0.06Ga0.94)2O3 Activated by Cr3+

Deposition of ZnO thin films with different powers using RF magnetron sputtering method: Structural, electrical and optical study

Zinc Oxide thin films at room temperature with good crystallinity quality have been deposited at different Radio Frequency powers. Magnetron sputtering technique has been carried out on glass and oriented Si(100) substrates. The film structure has been characterized by X-ray Diffraction (XRD) and MicroRaman spectroscopy, which possesses a wurtzite structure with (002) preferential orientation selecting suitable conditions. Scanning electron microscope (SEM) and atomic force microscopy (AFM) have been utilized to determine the films surface morphology. The stoichiometry has been verified by Energy dispersive X-ray spectroscopy (EDX) analysis. The optical behaviors of the deposited films have been characterized by Ultraviolet Visible (UV-Vis) (optical transmittance measurements) as well as by Photoluminance characterization. Electrical properties, Current-Voltage (I-V) and Capacitance-Voltage (C-V) have been studied in details for Zinc Oxide on Silicon film that deposited at different Radio Frequency power. The high transparency, electrical behavior and smooth surface allow to use these Zinc Oxide films in photovoltaic cells and optoelectronics application.

The impact of ester groups on 1,8-naphthalimide electron transport material in organic solar cells

Recently, 1,8-naphthalimide (NI) molecules have emerged as a new category of organic electron transport materials (ETMs) employed in organic solar cells (OSCs). Among them, NI molecules with a "NI-π-NI" molecular structure commonly exhibit over aggregation in films owing to their planar molecular structures, which is unfavorable for solution-processed film fabrication in OSC devices. In this work, we successfully synthesized a new NI molecule named NDT-2, employing a strategy that incorporates a solubilizing ester group modification to induce twisted molecular planarity, thereby reducing intermolecular over-aggregation and optimizing quality of the film. Interestingly, the NDT-2 modified by ester groups as a π bridge exhibits an enlarged molecular dihedral angle, enhanced alcohol solubility, a smoother film surface morphology, and improved film forming quality. Ultimately, OSCs incorporating NDT-2 as the ETM achieved a notable power conversion efficiency (PCE) of 17.1%. This study introduces a design strategy that utilizes ester functional groups to improve film forming quality of ETM, offering valuable insights for the development of advanced, alcohol-soluble NI molecules as efficient ETMs in OSCs.

The role of extracted Patchouli residue microparticle on the mechanical and microbial properties macroalgae biopolymer

AbstractMacroalgae is extensively being used to develop eco‐friendly biopolymer or biodegradable films, but have inferior mechanical strength. This study aims to enhance the mechanical properties of seaweed films by incorporating Patchouli microparticles (PMP) derived from dried Patchouli plants (DP‐PMP) and extracted residue (ER‐PMP) from Patchouli extraction process widely use in the perfume and cosmetic industry. The PMPs, were incorporated into films forming solution at varying concentrations (1%, 3%, 5%, and 7% wt/wt) respectively. Despite similar thermal properties, the inclusion of ER‐PMP resulted in an increasing ash residue content with an increase in concentration. The optimal tensile strength was achieved with a 3% PMP loading, while higher concentrations resulted in a decline in strength. Notably, the sample containing 1% PMP demonstrated superior elasticity. Moreover, with increasing concentrations of PMPs, all samples displayed elevated surface roughness and enhanced hydrophobicity. All samples display significant antimicrobial activity against E‐coli and Salmonella sp.; however, the sample incorporating ER‐PMP showed less effect. In summary, the study suggests that DP‐PMP and ER‐PMP can serve as effective fillers to enhance the mechanical properties of seaweed biofilms, with an optimal loading of 3%. Their antimicrobial activity renders them suitable biopolymers for active packaging in food applications and other purposes.Highlights Patchouli microparticle (PMP) enhance the properties of seaweed film. Film's surface morphology and hydrophobicity changed with increase in PMP. Introduction of either PMPs increase antimicrobial properties of the film. PMP from extracted residue (ER) provide lower antimicrobial activity. 3% DP‐PMP gave the optimum properties of the film for overall attributes.

Solution processable benzo[b]thiophene derivatives as small molecular organic semiconductors for organic field effect transistors

In this study, four new organic semiconductors based on benzo[b]thiophene derivatives were synthesized and characterized as the active layer of organic field-effect transistors (OFETs) to investigate the effect of different isomers and end-group moieties on the electrical performance. The top-contact/bottom-gate OFETs were fabricated via solution-shearing methods and exhibited p-channel activity. In particular, the thin film with a single BT moiety attached via the 6-position showed the highest mobility up to 0.055 cm2/Vs and current on/off ratio of 2.5 × 107. The microstructure and surface morphology of the thin films were analyzed by X-ray diffraction (XRD) and atomic force microscopy (AFM) to investigate the factors contributing to the difference in electrical performance of the devices.

Effect of acrylic acid on water‐whitening resistance of polyacrylate latex films and its mechanism

AbstractTwo groups of polyacrylate latexes with higher (21 ~ 35 °C) or lower (−33 ~ −43 °C) glass transition temperatures (Tg) were prepared by adjusting the monomer ratio of butyl acrylate (BA) and styrene (St), and the effect of acrylic acid (AA) on water‐whitening resistance of these latex films was investigated. It was found that the water‐whitening resistance of the two groups of latex films was different. With the increase of AA content, the water whitening resistance of the latex films with higher Tg continued to improve, while that of the latex films with lower Tg increased first and then decreased. A series of characterizations, such as light transmittance, water whitening, water absorption, static water contact angle, surface morphology, and optical microscope test of the latex film, and so forth, showed that the reason for this difference was that under higher AA content (≥5%), compared with the polyacrylate latex films with lower Tg, the latex films with higher Tg could reach the saturation state of water absorption quickly, and water in these latex films exhibited continuous and large area distribution, rather than formation of many so‐called micro‐ or nano‐scale water sacs that can scatter light as found in the latex films with lower Tg.

Study of the free carrier characteristics and surface morphology of AlGaAs/GaAs thin films deposited using MOCVD

Ultra-low loss optical thin films find broad applications in fields such as vertical-cavity surface-emitting lasers and optical atomic clocks. The main optical losses in AlGaAs/GaAs distributed Bragg reflectors (DBRs) prepared using metal-organic chemical vapor deposition (MOCVD) arise from absorption loss caused by free carriers within the layers and scattering loss caused by surface roughness. In this study, we fabricated AlGaAs and GaAs single-layer thin films with varying Al compositions on substrates of three crystal orientations and under different V/III ratios. The dependence of carrier concentration and surface morphology on different substrates and growth conditions was investigated. Thin films grown on substrates with three different crystal orientations exhibited three distinct growth modes (step-flow mode, SK mode, and FM mode). The impact of the V/III ratio on the growth mode was found to be complex. Higher V/III ratios resulted in poorer morphology for films grown on (100) substrates, while better morphology was observed on (211) B substrates. Furthermore, the surface morphology of films grown on (100) 15° off substrates showed less sensitivity to changes in the V/III ratio. With increasing Al composition, the carrier concentration of the films significantly increased. Elevating the V/III ratio proved effective in suppressing the incorporation of carbon, thereby reducing the carrier concentration of AlGaAs films. GaAs films exhibited a low carrier concentration at an appropriate V/III ratio. Additionally, the distinct abilities of different substrates to adsorb impurities exerted a significant impact on the carrier concentration of the films. This study demonstrates that, under optimal conditions, it is feasible to fabricate AlGaAs/GaAs Bragg mirrors with low carrier concentration and relatively small roughness on (100) 15° off substrates.

Poly(Vinylidene Fluoride‐CO‐Hexafluoropropylene) (PVDF‐HFP) Incorporated Acetylene Black: Electrical, Optical, and Structural Studies

AbstractThe primary goal of this study is to synthesize a high‐conducting polymer electrolyte film. The PVDF‐HFP and NaSCN film are prepared which showed the highest conductivity at 30 wt% dopant of NaSCN in the Polymer PVDF‐HFP which is 1.24× 10−4 S cm−1. Therefore, here the base polymer is taken as PVDF‐HFP and NaSCN (30 wt%) and further Acetylene Black is added to check the variation in the conductivity of the polymer film. Solution casting technique is used to create solid polymer electrolyte films using poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP) with salt sodium thiocyanate and Acetylene Black. Polarized optical microscopy (POM) is used to evaluate the morphology of the polymer film surface. Fourier transform infrared spectroscopy (FTIR) to check the presence of functional group is used, impedance spectroscopy is used for the measurement of the conductivity of the sample, linear sweep voltammetry for finding electrical stability window, and transference number measurements for concentration of charge carriers are done for the electrical studies of polymeric films. The 1 wt% Acetylene Black doped polymer electrolyte film is found to have the maximum ionic conductivity, which is 1.95 × 10−3 S cm−1. The solid polymer electrolyte film has an electrochemical stability window (ESW) of 4.8 V and tion value of 0.83.

산화아연 나노입자 유형이 카라기난 기반 복합 필름의 구조, 기계적 및 항균 특성에 미치는 영향

In this study, zinc oxide nanoparticles (ZnONPs) were synthesized using three distinct zinc salts: zinc acetate, zinc chloride, and zinc nitrate. These ZnONPs were subsequently utilized in the fabrication of carrageenan-ZnONPs (Car-ZnONPs) composite films. The study assessed influence of the various ZnONPs on the morphological, water vapor barrier, color, optical, and antimicrobial properties of the Car-ZnONPs composite films. The surface morphology and UV-blocking attributes of the composite films were affected by the type of ZnONPs used, but their surface color, transparency, and chemical structure remained unaltered. The composite film's thickness and elongation at break (EB) significantly increased, while the tensile strength significantly decreased. In contrast, film’s elastic modulus (EM) and water vapor permeability coefficient (WVP) showed no significant difference. All the composite films with added ZnONPs demonstrated potent antibacterial activity against Escherichia coli O157:H7 and Listeria monocytogenes. Among the carrageenan-based composite films, Car-ZnONPsZC showed the highest antibacterial and UV-blocking properties, and its elongation at break was significantly higher than that of the pure carrageenan films. This suggests that ZnONPs composite films have the potential to be used as an active packaging film, preserve the safety of the packaged food and extend shelf life.

Nonenzymatic Sensor Based on Polythiophene/Titanium Dioxide (PTh/TiO2) Composite for the Determination of Malathion in Water

This study presents a novel nonenzymatic pesticide sensor utilizing a polythiophene/TiO2 (PTh/TiO2) film deposited on a glassy carbon (GC) electrode as the working electrode. The thiophene monomer was polymerized onto TiO2 by cyclic voltammetric method in the range of 0.0-2.5 V with 15 cycles at room temperature. The prepared electrode was used for the sensitive and selective detection of malathion thus providing the basis for facile electrochemical quantification. The surface morphology and crystal structure of the (PTh/TiO2) film were studied by SEM and XRD. FTIR was used for the structural analysis of (PTh/TiO2) film. FTIR results indicated that the PTh/TiO2composite structure was formed. The smooth surface morphology of PTh/TiO2 was supported by SEM results. XRD analysis verified that PTh is covered on TiO2 particles. The crystal phase of TiO2 was changed to amorph state after PTh modification. Additionally, the electrochemical characterization of polymer film and its response to malathion was examined by the CV method. Under optimized operational conditions, the response of the pesticide sensor was measured by CV in the range of -1 to 2.3 V versus the Ag/AgCl reference electrode due to the electrooxidation of malathion. The analysis focused on current values at -0.73 V, where the reduction of the PTh/TiO2 system occurred upon the addition of known amounts of malathion. The PTh/TiO2 composite film was sensitive to malathion in a linear range from 9.9 ppm to 436 ppm. The sensitivity was calculated as 57.5 μA/ µM cm2 whereas the detection limit was calculated as 7.45 µM. The maximum reaction rate was estimated as 767 μA. The developed sensor also showed good selectivity and reproducibility. The nonenzymatic pesticide sensor was successfully applied to detect malathion in tap water with at least 90% recovery.

Microwave dielectric characterization studies of PVDF-TrFE-Nafion blended films

The solution-based casting method fabricates the free-standing pure PVDF-TrFE, PVDF-TrFE-Nafion blended films and tests them for structural, morphological, and microwave studies. The X-ray diffraction pattern and FTIR spectrum confirmed the formation of the ferroelectric β-phase of PVDF-TrFE. The surface morphology of blended films is studied by scanning electron microscope (SEM), and noticeable changes in the morphological features are observed in the blended films resulting from the differences in the nucleation process in these films. Then using the open-ended coaxial probe method, the complex permittivity measurements were carried out over a large frequency range, from 0.5 GHz to 50 GHz. These results were verified with the Transmission-Reflection method using a rectangular waveguide in the X-band and Ku-band frequency range. The microwave absorption properties of the blends are also studied in the same frequency range. The stability of the dielectric properties and low microwave absorption indicates that the blending of PVDF-TrFE with Nafion results in a new potential material for high frequency flexible capacitor applications.

Characteristics of tunable aluminum-doped Ga2O3 thin films and photodetectors

Aluminum-doped Ga2O3 (AGO) thin films were prepared by plasma-enhanced atomic layer deposition (PE-ALD). The growth mechanism, surface morphology, chemical composition, and optical properties of AGO films were systematically investigated. The bandgap of AGO films can be theoretically set between 4.65 and 6.8 eV. Based on typical AGO films, metal–semiconductor–metal photodetectors (PDs) were created, and their photoelectric response was examined. The preliminary results show that PE-ALD grown AGO films have high quality and tunable bandgap, and AGO PDs possess superior characterizations to undoped films. The AGO realized using PE-ALD is expected to be an important route for the development of a new generation of gallium oxide-based photodetectors into the deep-ultraviolet.

Tuning the crystalline orientation of quasi 1D anisotropic Sb2Se3 as a function of growth temperature for thin film photovoltaic applications

Antimony selenide (Sb2Se3) shows excellent photon absorption in the visible region and hence gaining tremendous attention from the last decade for thin film photovoltaics. Also, it has unique one-dimensional crystal structure and simple binary composition. However, the growth of Sb2Se3 thin films with its predominant orientation along [hk1] to make use of easy electrical charge transport seems challenging due to various governing growth parameters. In this work, we have studied the role of growth temperature (between 200 ℃ and 320 ℃) in the crystalline orientation of Sb2Se3 thin films on glass substrates via close-space thermal evaporation. In addition to growth orientation, we have investigated the effect of growth temperature on the surface morphology, elemental composition, film thickness, and optical properties of Sb2Se3 thin films. Electrical properties and photoresponse were measured on [hkl] and [hk0] oriented films to understand the effect of anisotropy and it is inferred that [hk1] oriented film as a favorable one for the charge transport. Also, the photoresponse results showed fair photoconductance under white light illumination and zero applied bias.

Room-Temperature O3 Detection: Zero-Bias Sensors Based on ZnO Thin Films

ZnO thin films with a thickness of 300 nm were deposited on Si and Al2O3 substrates using an electron beam evaporation technique with the aim of testing them as low cost and low power consumption gas sensors for ozone (O3). Scanning electron microscopy and atomic force microscopy were used to characterize the film surface morphology and quantify the roughness and grain size, recognized as the primary parameters influencing the gas sensitivity due to their direct impact on the effective sensing area. The crystalline structure and elemental composition were studied through Raman spectroscopy and X-ray photoelectron spectroscopy. Gas tests were conducted at room temperature and zero-bias voltage to assess the sensitivity and response as a function of time of the films to O3 pollutant. The results indicate that the films deposited on Al2O3 exhibit promising characteristics, such as high sensitivity and a very short response time (<2 s) to the gas concentration. Additionally, it was observed that the films display pronounced degradation effects after a significant exposure to O3.

Electrosynthesis of toluidine blue on Fe3O4 nanoparticles modified electrodes in a deep eutectic solvent for the electrochemical determination of neurotransmitter epinephrine

The electrochemical methodology is important and challenging for rapid, simple, low-cost, sensitive, selective and reliable determination of biomolecules to diagnose and treat diseases. Our work presents the combination of the catalytic ability of a toluidine blue (TB) redox polymer and the important physical and chemical properties of Fe3O4 nanoparticles (Fe3O4NPs) to develop a new disposable sensor with advanced analytical performancecharacteristics for the determination of EP. Fe3O4NPs combined with poly(toluidine blue) (PTB) redox polymer film on a PGE support have been developed involving electropolymerization of TB in deep eutectic solvents (DES), which is a green solvent. Scanning electron microscopy (SEM) was used to evaluate the effect of the electrode composition on the surface morphology of the nanostructured PTB films, being correlated with the electrochemical characteristics observed by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV). It has been shown that combining Fe3O4NPs with PTB synthesized in DES improves the analytical properties of the sensor more than using each modifier individually due to synergistic effects. The analytical performance of PTBethaline-HCl/Fe3O4/PGE was evaluated for epinephrine (EP) reduction in the presence of an excess dopamine (DA) by DPV. The proposed sensor was used to determine EP using the reduction peak as a voltammetric signal instead of the oxidation peak usually employed to minimize possible interfering effects in biological samples. The developed sensor showed good response with high sensitivity (9.26 µA µM−1 cm−2), low detection limit (0.05 µM), wide linear range (0.19–20 µM), and excellent reproducibility (RSD 1.7 %) and repeatability (RSD 2.9 %). The practical applicability of the proposed sensor has been successfully tested for the quantification of EP in human serum and injection ampoule samples. This is a very promising analytical method for monitoring the level of EP in real samples.