Smooth Film Surface Research Articles

Nanostructured Poly(Phenazine)/Fe2O3 nanoparticle film modified electrodes formed by electropolymerization in ethaline - Deep eutectic solvent. Microscopic and electrochemical characterization

Electropolymerization in ethaline deep eutectic solvent (DES) was carried out to prepare three different electroactive polymers on iron oxide nanoparticle modified glassy carbon electrode substrates: poly(neutral red), poly(methylene green), and poly(Nile blue). The electrochemical properties of the novel nanocomposites were studied by cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy, and their morphologies were examined using scanning electron microscopy. Electrochemical characterization of the polymer films demonstrated similar voltammetric current response and impedance properties. Analysis of the cyclic voltammograms showed that the electrochemical processes at the polymer film coated electrodes are limited by surface reactions. Scanning electron microscopy images confirmed the results obtained by cyclic voltammetry and electrochemical impedance and showed more uniform and smooth polymer film surfaces produced in ethaline than those prepared in aqueous media, which can give important benefits for sensor and biosensor applications. Catalase enzyme was immobilized on the nanocomposite films, and the resulting biosensors were successfully used for the detection of H2O2, presenting low limits of detection with high repeatability and stability.

Hydrolysis and Condensation of n-BuSnCl3: Enabling Deposition of Smooth Metal Oxide Photoresist Thin Films.

Herein, we report hydrolysis and condensation chemistries of C4H9SnCl3 to molecular clusters and gel films. Precursor speciation plays a key role in film formation and quality toward realization of atomically smooth surfaces. Density functional theory investigations of C4H9SnCl3 and its reactions show that hydrolysis of the dimer (C4H9Sn)2(OH)2Cl4(H2O)2 has a high energetic penalty in the gas phase and when using a polarizable continuum solvation model based on density. These computations support our observed stability of the dimeric cluster in air, in various solvents, and through initial film deposition. It hydrolyzes and condenses to the [(C4H9Sn)12O14(OH)6]2+ dodecamer on-chip after a post film-deposition bake at 80 °C. Consequently, film surface smoothness is uniquely retained through on-wafer condensation.

Thermal, mechanical and microstructural characterization and antioxidant potential of Rhinobatos cemiculus gelatin films supplemented by titanium dioxide doped silver nanoparticles

Hybrid composites films were prepared by the incorporation of titanium dioxide doped silver nanoparticles (TiO2–Ag NPs) at different concentrations (1, 2, 3 and 4 wt%) into Rhinobatos cemiculus gelatin (RCG) matrix. The microstructure analysis, realized by scanning electron microscopy and atomic force microscopy revealed a homogenous structure and a smooth surface of the composite films. The mechanical properties, light transmission and moisture content of composite films are greatly dependent on the amount of added TiO2–Ag NPs. A gradual decrease in elongation at break was observed with the increase in TiO2–Ag nanoparticles content (reaching 16.05% at an addition level of 4%). Moreover, the addition of TiO2–Ag NPs considerably enhanced the antioxidant activity of nanocomposite films evaluated by DPPH radical scavenging activity and ferrous chelating activity. It is, thus, concluded that the incorporation of TiO2–Ag NPs into the gelatin matrix promotes the improvement of gelatin films’ performance.

Limit of incorporating cesium cations into formamidinium-methylammonium based mixed halide perovskite solar cells

Incorporating formamidinium (FA) into methylammonium (MA) based perovskite has brought significant thermal and environmental stability including best device performance. It has been shown that addition of Cesium (Cs) makes perovskite robust in terms of thermodynamic stability as well. We explore the means of incorporating Cs into a base perovskite of mixed cation (FA/MA) and mixed halide (I/Br) that has a proven track record of high performance through an inter-diffusion approach. With this approach, it has been shown that perovskites form a smooth film without any residual PbI2 and exhibit higher absorbance. Though the residual PbI2 disappeared with the increase in added Cs, the film morphology became rough for Cs concentration higher than 15%. Addition of small amounts of PbCl2 allowed inclusion of more Cs content, which resulted in smooth film surface and further improved device performance.

Furan-2,5- and Furan-2,3-dicarboxylate Esters Derived from Marine Biomass as Plasticizers for Poly(vinyl chloride).

Esters of furan dicarboxylic acids (DAFs) were synthesized by a one-pot reaction between marine biomass-derived galactaric acid and bioalcohol under solvent-free conditions and were fully characterized. The catalyst amount could be reduced without loss of reaction yields using p-xylene as the material separation agent. Also, a possible mechanism was proposed for the first time. Then the properties of four DAFs as plasticizers on the poly(vinyl chloride) (PVC) matrix were investigated. The experimental results showed that DAFs exhibit competitive efficiencies of plasticization when compared to the most commercialized plasticizer, DOP. It was found that the combination of DAFs and PVC produced homogeneous smooth-surface films, indicating miscibility between them. ATR-FTIR depicted the upshift of carbonyl absorption bands after mixing with the PVC matrix, with a magnitude of at most 18–21 cm–1. TGA, DSC, and UTM data illustrated equivalent plasticization efficiencies. Due to their small molecular weights, the investigated DAFs are more volatile. However, due to bearing an oxygen atom in the aromatic furan ring, the degree of polarization of DAFs was boosted and helped inhibit leaching into the surrounding media. In brief, these synthetic compounds have promising feasibility as biobased plasticizers. Moreover, another interesting point is that the properties of furan-2,3-dicarboxylic acid derivatives were studied for the first time and herein reported.

Low-field electron emission from carbon cluster films: combined thermoelectric/hot-electron model of the phenomenon

Thin carbon films consisting of separate nanometer-scale sp2 carbon islands with smooth vacuum boundary deposited on Si wafers were found to be capable of low-field electron emission – starting from macroscopic field magnitudes as low as ∼1 V/µm. For such films, we suggest a novel model of emission facilitation by thermoelectric field associated with heat generation concentrated in nanosized areas. Quantitative estimates performed on the basis of this hypothesis for typical experimental conditions gave estimates for local thermoelectric field magnitude and lateral non-uniformity of surface potential as high as ∼100 V/μm and a few Volts, respectively. Thus, the suggested model explains the low-field emission capability of smooth-surface nanocarbon films observed in many previous experiments.

Engineering surface roughness of nanocellulose film via spraying to produce smooth substrates

Due to the requirements of smooth cellulose substrates for printing electronic circuits to have proper conductance, nanocellulose (NC) have been used as a substrate for electronic material such as solar panels, supercapacitors and flexible electronics etc. Recently we developed a process to produce smooth NC films by spraying onto an impermeable substrate. The spray coated NC film has a shiny and glossy smooth surface where it was in contact with the substrate. In this study, we investigated the effect of i) substrate surface chemistry, ii) substrate roughness, iii) NC fibre diameter and iv) addition of carboxymethyl cellulose (CMC) in NC suspension on the roughness of the smooth surface of NC film. The three parameters controlling the roughness of the resultant NC films were the roughness of the substrate surface, the fibril diameter of the NC and CMC addition.Adding 1.5 wt. % CMC had only a small effect with very smooth substrates but had a larger effect with rougher substrates. The best roughness obtained is 336 ± 117 nm at a 259.1 μm × 259.9 μm inspection area when spraying of 1.5 wt. % CMC – 1.75 wt.% NC suspension on the super polished stainless steel (SSS). The controlling order of roughness of NC films was found to be 1.5 wt. % CMC addition in 1.75 wt.% NC suspension>base substrate > fibril diameter. The addition of CMC in the film decreases the surface roughness by reducing the friction experienced between the fibres. This reduction in friction allows the fibril network to form a smoother film when compared to a film without the presence of CMC.This study has shown that spraying of NC on base surfaces produce a smooth NC film in a rapid single step, with a smoothness that can be tailored across fibrils.

Effect of different substrates on Si and Ta co-doped Ga2O3 films prepared by pulsed laser deposition

In this study, the structure, morphology, electrical and optical properties of Si and Ta co-doped gallium oxide (Ga2O3) films deposited on (1 0 0) Ga2O3, (0 0 0 1) sapphire and quartz substrates by pulsed laser deposition are analyzed. The Si and Ta co-doped Ga2O3 film on Ga2O3 substrate possessed the best crystal quality with a high carrier concentration of 1.12 × 1020 cm−3 and a conductivity of 2.13 S·cm−1 compared to the sapphire and quartz substrates. The Si and Ta co-doped Ga2O3 films on different substrates exhibited high transmittance (>73%) above 300 nm and smooth film surface. The optical gap of Si and Ta co-doped Ga2O3 films on Ga2O3, sapphire and quartz substrates decreases from 4.89 to 4.85 eV, and the corresponding Urbach energy increases from 0.396 to 0.704 eV, so the homoepitaxial Si and Ta co-doped Ga2O3 film possess the best quality.

Orodispersible films containing ball milled aripiprazole-poloxamer®407 solid dispersions.

This research aimed at developing ODFs containing an antipsychotic drug - aripiprazole (ARP). ARP, as a BCS II class molecule, requires enhancing its water solubility prior to formulating. Therefore, a solid dispersion of ARP - Poloxamer® 407 was prepared by ball milling, then incorporated into the films. It was found that co-processing led to an over 100-fold increase in drug solubility in comparison with pure drug. Moreover, ODFs with solid dispersion showed faster drug release (>95% below 15min) and disintegration (<30s), compared with raw ARP films. These results are believed to be due to the solubilization effect of poloxamer and enhanced wettability of the film. Films containing solid dispersions were found to possess smoother film surfaces and favorable mechanical properties - flexibility and strength. The ODF formulations, prepared by a casting method, were based on three different polymers (Kollicoat® IR, Kollicoat® Protect or PVA). It was found that not only the form of the incorporated drug, but also the type of film-forming polymer had an impact on the analyzed parameters. The use of PVA was beneficial in the film formulation with aripiprazole in comparison to other tested film-forming polymers.

Promising molybdenum trioxide films for optically detectable gas sensor and solar cell applications

Sub-stoichiometric molybdenum trioxide (MoO3−x) thin films were grown by thermal evaporation techniques on glass, single crystal silicon Si and Fluorine doped Tin Oxide (FTO) glass substrates with different thicknesses. It was found that, Oxygen vacancies play an important role on properties of MoO3−x films. The structural properties of these films were analyzed by means of x-ray diffraction, energy dispersive analysis of x-ray, scanning electron microscopy. The film surface uniformity and smoothness with thickness was tested using the surface roughness measurement for MoO3−x films grown on glass and FTO. The optical properties of all presented films were investigated using UV–vis–near-infrared (NIR) spectrophotometer Optical transmittance and reflection of MoO3−x film were measured in the wavelength range from 200 to 2500 nm. MoO3−x film with 500 nm thick was tested optically for gas sensor applications. The effect of chlorine exposure on the optical transmittance of MoO3−x film with 500 nm thick deposited on glass was studied. Transmittance degradation as increasing the period of exposure was observed, indicating to the high sensitivity of MoO3−x to chlorine gas. The electrical resistivity and Seebeck coefficient of MoO3−x film with 500 nm thick were measured. Low resistivity (∼10−3 Ω.cm) and high transmittance (∼78%) in the visible spectrum of the film of 100 nm thick deposited on FTO coated glass substrate recommended it to be promising as transparent conductive electrode for solar cell.

End group tuning in small molecule donors for non-fullerene organic solar cells

Two novel small molecules, which consist of electron donating benzodithiophene core bridged through bithiophene π-spacer with terminal either dicyanovinyl (DCV-Me) or n-butyl cyanoester (CNAB) electron-withdrawing groups, were designed and used as donor materials for all-small molecule OSCs (all-SM-OSCs) with a non-fullerene acceptor (IDIC). The novel donor oligomers were firstly characterized by thermal gravimetric analysis, differential scanning calorimetry, UV–Vis spectroscopy, and cyclic voltammetry as well as studied by density functional theory calculations. The simple change of the DCV-Me to CNAB group leads to more pronounced crystallinity, higher solubility and higher energy levels in the donor BDT-2T-CNAB. The photovoltaic devices based on the BDT-2T-CNAB:IDIC blend exhibit higher short-circuit current (Jsc) and fill factor, and thus much higher power conversion efficiency (PCE) of 6.17% than those of BDT-2T-DCV-Me:IDIC devices (1.56%). Compared to the BDT-2T-DCV-Me system, the BDT-2T-CNAB based device shows smoother film surface morphology, and superior exciton dissociation, charge generation and charge carrier mobilities as well as lower non-geminate recombination losses. The results clearly demonstrate that the design of new small molecule donors for high-performance all-SM-OSCs should aim to choose suitable end acceptor units, among which the alkyl cyanoester groups are one of the most promising.

Epitaxial growth and multiferroic properties of artificial LCMO/BCZT heterostructure on (1 0 0) MgO substrate by pulsed laser deposition

Here, we reported the structure, morphology and multiferroic properties of the La0.67Ca0.33MnO3/Ba0.85Ca0.15Zr0.9Ti0.1O3 (LCMO/BCZT) magnetoelectric epitaxial heterostructure deposited on (1 0 0) MgO single crystal substrate using pulsed laser deposition. XRD RSM confirmed the epitaxial growth of the heterostructure with single oriented grains, and the smooth surface and uniform film growth of the heterostructure were revealed by the AFM analysis. The heterostructure exhibited multiferroic properties with a dielectric constant of 378, a remnant polarization of 10.26 µC cm−2, a maximum piezoelectric coefficient of 62.5 pm V−1 and a saturated magnetization 814.8 emu cm−3. The well-shaped ferroelectric and ferromagnetic hysteresis loops verified the multiferroic nature of the heterostructure with a maximum magnetoelectric coefficient αE31 of 36.9 mV (cm · Oe)−1.

Preparation and evaluation of orally disintegrating film containing donepezil for Alzheimer disease

The present study intended to prepare orally disintegrating film (ODF) containing donepezil (DP) for the treatment of mild to moderate alzheimer disease. HPMC and HPC, glycerine were used as film forming agents, plasticizer, respectively. The ODFs were prepared by solvent casting method. The method was optimized with full factorial design considering the amount of film forming agents, the proportion of HPMC: HPC, amount of plasticizer as independent variables and tensile strength, elongation, folding endurance and disintegration time as dependent variables. Furthermore the studies of mechanical, drug release and bioavailability of the optimized DP-loading ODF formulation were performed. The results indicated the prepared film hold uniform, smooth film surface, non-sticky and disintegrated within 30 s, and over 85% of the drug dissolved in the first 5 min. And there was no significant difference between the optimized ODF formulation and the marketed one in cmax, tmax and AUC0-t.Current study suggested the optimized ODF formulation will be an effective alternative for commercially available dosage forms for the treatment of Alzheimer's diseases.

Dopant solubility and charge compensation in La-doped SrSnO3 films

We investigate lanthanum (La) as an n-type dopant in the strain-stabilized tetragonal phase of SrSnO3 grown on GdScO3 (110) using a radical-based hybrid molecular beam epitaxy approach. Fully coherent, epitaxial films with an atomically smooth film surface were obtained irrespective of doping density. By combining secondary ion mass spectroscopy and Hall measurements, we demonstrate that each La atom contributes one free electron to the film, confirming that it occupies the Sr site in SrSnO3 and that it is completely activated. Carrier density exceeding 1 × 1020 cm−3 was achieved in La-doped SrSnO3 films, which is in excellent agreement with the dopant-solubility limit predicted by density functional theory calculations. A record-high room-temperature mobility of 70 cm2 V−1 s−1 at 1 × 1020 cm−3 was obtained in a 12 nm La-doped SrSnO3 film, making this the thinnest perovskite oxide semiconductor with electron mobility exceeding 25 cm2 V−1 s−1 at room temperature. We discuss the structure-dopant-transport property relationships, providing essential knowledge for the design of electronic devices using these materials.

High Temperature Wear Behavior of Titanium Nitride Coating Deposited Using High Power Impulse Magnetron Sputtering

Titanium nitride (TiN) coating has been used in various application as it gives excellent performance in many aspects. It has been proven to prolong machining tool life since the mid-1960s. Industrial deposition processes of TiN, including magnetron sputtering, arc ion plating, and chemical vapor depositions, have their individual advantages and limitations. Due to the rising demands of the dry machining technique, the massive amount of heat generated from the friction of cutting tools against the surface of a work piece has become the main issue to overcome. Oxidation of TiN, which occurs around 400 °C, puts a limit on the applications of the coatings. Comparing TiN tool coatings deposited by arc evaporation, the novel high-power impulse magnetron sputtering (HiPIMS) technology provides smoother film surface, denser structure and subsequent corrosion resistance. Therefore, this research aims to investigate the wear behavior of TiN thin film deposited by HiPIMS at high temperature. The influences of the coating properties on the wear resistance of coatings at high temperature are also investigated. The results show that the HiPIMS technique enables a denser epitaxial-grown TiN coating with higher surface hardness and adhesion in contrast with TiN coating deposited using direct current (DC) magnetron sputtering techniques, which provides a higher wear resistance.

Few-Layers Graphene Film and Copper Surface Morphology for Improved Corrosion Protection of Copper

Graphene has shown excellent corrosion protection of copper (Cu). The corrosion protection of Cu is governed by the characteristics of the deposited graphene and Cu surface morphology underneath. In this work, graphene films (1-2, 4-5 layers) were deposited on Cu using a chemical vapor deposition by changing hydrogen (H2) concentration during the annealing stage. The chemical structure and surface microstructural features of graphene/Cu were inspected by Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. The electrochemical corrosion performance of graphene/Cu was studied in 0.5 M sodium chloride solution using potentiodynamic polarization and electrochemical impedance spectroscopic measurements. The 1-2 layers of graphene and rough Cu surface were obtained for low H2 concentrations (0 and 2.5%), whereas high H2 concentrations, 20 and 50%, resulted in a smooth Cu surface and 4-5 layers of graphene. Our results showed that Cu with a smooth surface and multilayer graphene film exhibited the best corrosion resistance against electrochemical degradation. Tafel analysis revealed that Cu with 4-5 layers of graphene coating corroded nearly three orders of magnitude slower than the annealed Cu, without graphene coating. The results of this study can be useful for several applications where Cu is in close contact with salt species.

Oxygen-assisted synthesis of hBN films for resistive random access memories

In this letter, we report an oxygen-assisted chemical vapor deposition method to synthesize uniform large-area high-quality multilayer hexagonal boron nitride (hBN) films (denoted by O-hBN). Nonvolatile bipolar resistive switching (RS) of resistive random access memories (RRAMs) based on O-hBN films is presented. These RRAMs exhibit enhanced RS performance with lower cycle-to-cycle variability, lower set voltage, and higher current on/off ratio. The enhancement is benefited from the clean and smooth surface of O-hBN films and the reduction of grain boundaries which serve as an energetically favored path for ion migration. This scalable approach to synthesize hBN films could facilitate practical applications of hBN-based RRAMs.

Epitaxial BaSnO3 and SrSnO3 perovskite growth on SrTiO3(001) via atomic layer deposition

The authors report epitaxial BaSnO3(001) and SrSnO3(001) growth on SrTiO3(001) (STO) substrates via atomic layer deposition (ALD) at 180 °C, where the BaSnO3 growth rate is 0.46 ± 0.03 Å and the SrSnO3 growth rate is 0.69 ± 0.04 Å per ALD unit cycle. Reflection high-energy electron diffraction, x-ray diffraction (XRD), and rocking curve analyses verify the single crystalline nature of BaSnO3(001) and SrSnO3(001) thin films on STO(001), while the atomic force microscopy analyses reveal the smooth surface of the stannate films with rms roughness values of ∼0.4 nm, which is only slightly higher than the STO substrate roughness of 0.32 nm. Out-of-plane XRD and reciprocal space mapping show that both BaSnO3(001) and SrSnO3(001) (∼10 nm) are fully relaxed on STO(001), owing to the large lattice mismatches (5.1% for BaSnO3/STO and 3.2% for SrSnO3/STO). The visible light transmittance spectra indicate that ALD-grown BaSnO3 and SrSnO3 thin films have high transparency at 400–800 nm that matches the transparency of STO(001) substrates.

The acoustic emission from asperity interactions in mixed lubrication.

Gears typically operate in mixed lubrication conditions, where the lubricant film is too thin to prevent opposing surface asperities from interacting with each other. The likelihood/intensity of interactions is indicated by the Λ ratio: the ratio of smooth surface film thickness to surface roughness. Researchers have asserted that asperity interactions are the predominant cause of acoustic emission (AE) in healthy gear contacts. However, direct experiments on gears have yet to yield a clear relationship between the Asperity AE (AAE) and Λ ratio, this is in part due to the complexity of gear tooth contacts. In this paper, a disc rig was used to simulate a simplified gear contact so that the fundamental relationship between AAE and Λ could be investigated more effectively. By varying oil temperature and entrainment speed, a wide spectrum of lubrication conditions was generated. In contrast to other published studies, an independent measurement technique, the contact voltage (CV), was used to verify the amount of interactions, and repeated roughness measurements were used to confirm minimal surface wear. A simple, consistent and precise relationship between AAE amplitude and Λ was identified and defined for changes from full-film to mixed lubrication. Within the mixed lubrication regime, the AAE amplitude increased exponentially as Λ decreased at all speeds tested. It was also observed that an increase in speed always resulted in an increase in AAE amplitude, independently of any changes in Λ. This direct effect of speed was modelled so that the AAE could be predicted for any combination of speed and Λ within the tested envelope. This paper links gear contact tribology and AE with new precision and clearly demonstrates the potential of using AAE as a sensitive monitoring technique for the lubrication condition of gears.

Hole-transporting material based on spirobifluorene unit with perfect amorphous and high stability for efficient OLEDs

Hole-transporting materials (HTMs) capable of forming thermally stable amorphous film and possessing high electrochemical stability play an important role in organic light-emitting diodes (OLEDs), which can enhance the device performance. Herein, spirobifluorene-based HTM N-([1,1′-biphenyl]-2-yl)-N-(9,9-dimethyl-9H-fluoren-2-yl)-9,9′-spirobifluoren-2-amine (SFAF), employing fluorene-contained arylamine as the hole transporting unit, was synthesized, and the comprehensive properties of material were systematically investigated. Owing to the highly twisted spiro conformation, the SFAF exhibited a high glass transition temperature of 140 °C and a high thermal decomposition temperature of 402 °C. Moreover, a stably and homogeneously amorphous SFAF film was formed by increasing the treatment temperature up to 140 °C for 12 h and a smooth surface film was characterized by the atomic force microscope. In addition, the compound presented excellent electrochemical stability with nearly identical cyclic voltammetry curves during the 100 cycles. Green fluorescent OLED based on SFAF as the hole-transporting layer showed a satisfactory device performance. The SFAF with high stability was also applied as HTM in phosphorescence device, which exhibited a turn-on voltage of 2.2 V, a maximum brightness of 191127 cd m−2 and the maximum current efficiency of 63.80 cd A−1. This results indicate that SFAF is a great promising and potential hole-transporting material for highly efficient optoelectronic devices.