Film Coefficient Research Articles

The Piezoresistive Performance of CuMnNi Alloy Thin-Film Pressure Sensors Prepared by Magnetron Sputtering

Effects of varying Mn and Ni concentrations on the structure and piezoresistive properties of CuMnNi films deposited by magnetron sputtering with a segmented target were investigated. An increase in the Ni content refines the CuNi film grains, inducing an increase in defects such as internal micropores and a decrease in film density. At the same time, the positive piezoresistive coefficient of the film changes to negative. When 17.5 at.% Ni was added, the negative piezoresistive coefficient of the CuNi film was −2.0 × 10−4 GPa−1. The doping of Ni has a weakening effect on the positive piezoresistive effect of the film. Adding Mn into Cu refines the film grains while increasing the film density. The surface roughness of the film decreases with the increase in Mn content. When the Mn content was 16.7 at.%, the piezoresistive coefficient reached the largest recorded value of 23.81 × 10−4 GPa−1, and the film exhibited excellent repeatability in multiple piezoresistive tests. After the CuMn film with 16.7 at.% Mn was annealed at 400 °C for 2 h, the film grains grew slightly and the film residual stress decreased. The optimization of the film structure can reduce the scattering of electrons during transportation. The piezoresistive coefficient of the film was further improved to 35.78 × 10−4 GPa−1.

Facile Z-scan determination of nonlinear refractive index and absorption coefficient of dye-doped polymer film

Facile Z-scan determination of nonlinear refractive index and absorption coefficient of dye-doped polymer film

Simultaneously realizing reversal of piezoelectric coefficient and enhancement of piezoresponse by chromium-doping in aluminum nitride films

Polarity inversion is an interesting phenomenon in non-centrosymmetric wurtzite-structured aluminum nitride (AlN), which offers an important platform to establish acoustic devices with heteropolar junctions. However, previous studies showed that switching polarity generally resulted in only reversing the piezoelectric coefficient (d33) in AlN films. Here, we discovered that appropriate Cr-doping would not only allow to reverse d33 but also improve piezoelectric response in the c-axis oriented AlN films by co-sputtering dual targets of Cr and Al. Specifically, the d33 was reversed from +2.6 pC/N for the undoped AlN to −2.6 pC/N for the 6.2 at. % Cr-doped CrxAl(1−x)N films. As the Cr-doping ratio increased to 9.3 at. %, d33 was −7.0 pC/N, which was 1.7 times higher than that of the undoped AlN films. Independent PFM phase image measurement offered further evidence of the polarity inversion by comparing the undoped and 9.3 at. % Cr-doped CrxAl(1−x)N films. This work offers a simple doping strategy that allows for simultaneous reversal of piezoelectric coefficient and enhancement of piezoresponse. As a result, it establishes a promising foundation for the design and development of acoustic wave devices featuring heteropolar junctions.

Efficient statistical approach for thermo-electrical properties of gadolinia-doped ceria thin films

The thermo-electrical properties of gadolinia-doped ceria (GDC) thin films play a vital role in solid oxide fuel cell (SOFC) applications. Nonetheless, the effects of temperature, dopant concentration, and thickness on thermal expansion, and ionic conduction remain ambiguous. In the present study, we propose an efficient theoretical approach to emphasize the roles of surface layers and surface vicinity (called next-surface layers) on the thermo-electrical properties of GDC thin films. Using statistical moment method, thermal expansion coefficient, and ionic conductivity are calculated as functions of temperature, dopant concentration, and thickness. The lattice strain and ionic disorder in the surface and next-surface layers cause an increase in thermal expansion coefficient and ionic conductivity of thin films. Compared with bulk GDC, the thermal expansion coefficient is slightly larger while the ionic conductivity is more than one to two orders of magnitude enhancement and exhibits the maximum value at the higher concentration. The ionic conductivity depends non-linearly on the dopant concentration and the maximum conductivity is shifted toward a higher value as the temperature increases. The enhancement in thermal expansion coefficient and ionic conductivity offers new opportunities for SOFC electrolytes whose efficiency can be effectively controlled by tailoring the thickness. The theoretical calculations are compared to measured results from experiments.

Research on pyroelectric enhancement mechanism of PZT thin films and optimization design of infrared detectors

In this paper, the PZT10/90 thin film was successfully deposited on the Pt/TiO2/SiO2/Si substrate using RF magnetron sputtering, and the dielectric and pyroelectric properties of the thin film were measured and characterized. The measurements show that the dielectric constant of the PZT10/90 thin film is further reduced compared to the previously reported PZT30/70 thin films, which is beneficial for improving the figure of merit of the PZT. The dielectric constant and loss tangent of the PZT10/90 thin film are 173 and 0.016 at 1kHz and the pyroelectric coefficient of the thin film is 20 nC·cm-2·K-1 at room temperature. In addition, a pyroelectric infrared detector based on the PZT thin film was designed, a feasible detector fabrication process was proposed, and the structure of the pyroelectric infrared detector was optimized using simulation software based on the finite element method. The developed infrared detector has promising applications in the fields of spectroscopic instruments and smart seekers.

Enhanced antifungal properties of poly(butylene succinate) film with lignin nanoparticles and trans-cinnamaldehyde for mango packaging

Sustainable poly(butylene succinate) (PBS) films incorporating lignin nanoparticles (LN) and trans-cinnamaldehyde (CN) have been developed to preserve mango freshness and provide food safety. PBS/LN, PBS/CN, and PBS/LN/CN composite films were produced by blown film melt extrusion. This study investigated the effect of CN-LN on the CN remaining content, thermal, mechanical, and barrier properties, diffusion coefficient, and antifungal activity of PBS films both in vitro and in vivo. Results showed that LN in the PBS/LN/CN composite film contained more CN than in the PBS/CN film. The compatibility of CN-LN with PBS produced homogeneous surfaces with enhanced barrier properties. PBS/LN/CN composite films demonstrated superior antifungal efficacy, inhibiting the growth of Colletotrichum gloeosporioides and preserving mango quality during storage. Results suggested that incorporating LN into PBS composite films prolonged the sustained release of antifungal agents, thereby inhibiting microbial growth and extending the shelf life of mangoes. Development of PBS/LN/CN composite films is a beneficial step toward reducing food waste and enhancing food safety.

Modeling and analysis of elastohydrodynamic lubrication of orthogonal face gear with installation errors

Installation error is one of the most prominent factors affecting the lubrication of face gear. To analyze the lubrication performance of the face gear with installation errors, the installation error model of the orthogonal face gear transmission system is established. Then, the contact path, equivalent curvature radius, load distribution and entrainment velocity are studied using the face gear loaded tooth contact analysis (LTCA). On this basis, the lubrication governing equations of the face gear are established according to the elastohydrodynamic lubrication (EHL) theory. In addition, the oil film thickness, oil film pressure and coefficient of friction in the process of face gear drives are calculated using the method of progressive mesh densification (PMD). Finally, the effects of axis intersection angle error, axis intersection error and axial displacement error on lubrication characteristics are analyzed. The results reveal that when the axial intersection angle error and axial displacement error are negative and the axial intersection error is positive, the minimum oil film thickness of the face gear tooth surface is less than that without error. When the error values are the same, the minimum oil film thickness and coefficient of friction have larger changes with the axial displacement error than with the axis intersection error, and the contact path has a bigger movement range.

Investigation of Alkane-Assisted dodecylamine on flotation desilication of magnesite Tailings: Molecular dynamics simulations and model optimization

Investigating the reverse flotation desilication process of magnesite tailings (MT) holds substantial merit in the context of magnesium metal recovery from solid waste. However, scant attention has been devoted to exploring the influence of the carbon chain length of diverse alkanes on the reverse flocfloatation desilication of MT. This research systematically delved into the selective adsorption behavior exhibited by dodecylamine (DDA) and its compound collectors on the surfaces of quartz and magnesite. As the carbon chain length of alkanes increases, the efficacy of reverse flotation desilication of MT diminishes. Under optimized conditions, the concentration of MgO in the concentrate registers a 0.93% increment, accompanied by a 2.05% reduction in SiO2 content. The optimal MgO grade attains 42.68%. The augmenting carbon chain length of alkanes leads to a decline in the dispersibility of the compound collector and a reduction in the diffusion coefficient of the monolayer film at the alkane/water interface. The compound collector, comprising n-heptane and DDA, manifests a noteworthy synergistic promotion effect on the flotation desilication of MT. This effect reduces the multilayer adsorption of DDA, promotes more hydrogen bonding formation, and favors DDA adsorption on the quartz surface over magnesite. Consequently, issues related to froth entrapment and poor selectivity are alleviated. Longer alkane chains in the compound collectors result in a stronger van der Waals force effect between the carbon chains. This effect causes DDDA to slide more easily on the quartz surface, which is not conducive to enhancing the hydrophobicity of the surface. Furthermore, alkane-induced hydrophobic flocculation increases the floccules size of quartz, enhancing the likelihood of bubble-particle adhesion. This investigation elucidates the molecular-level mechanism underlying alkane hydrophobic flocculation with varying chain lengths, contributing a theoretical foundation and technical support for the large-scale MT management and the sustainable production of magnesium metal.

Fabrication and characterization of ITO/CuS thin films-based thermoelectric generators

In this study, thin films-based thermoelectric generators (TEG) were fabricated using the flash evaporated copper sulfide films and radio frequency (RF) sputtered ITO films, deposited on 26 × 76 mm2 glass substrates. After careful study of the Seebeck coefficient of both films, without and with annealing at 350 °C, the open-circuit voltage for the eight junctions was studied as a function of the temperature gradient. Applying a temperature gradient of 40 K, the obtained maximum voltage is shown to be 10.9 mV, which increases to 15.6 mV by annealing. The internal resistance of the TEG remains unchanged, possibly due to the inverse evolution of resistivity during the annealing process of the CuS and ITO films. The obtained outputpower is 13 nW for the as-deposited films and increases to 26.2 nW by annealing.

Large room temperature magnetoelectric response in quasi 1–2 nanocomposite films on mica substrate

AbstractA novel quasi 1–2 type magnetoelectric (ME) nanocomposite films composted of one‐dimensional CoFe2O4 nanofibers and two‐dimensional PbZr0.2Ti0.8O3 films on flexible mica substrate have been designed and fabricated. The ME coupling effects have been greatly enhanced due to the release of the clamping effect and the high strain transfer efficiency between the large aspect ratio of the nanofibers and ferroelectric thin films. The release of the clamping effect was confirmed by reducing the thickness of the mica substrate, in which the piezoelectric coefficient and ME coupling coefficient of the nanocomposite films have been greatly boosted by the decrease in the mica thickness. A large direct ME coupling coefficient of 630 mV/(cm Oe) and a converse ME coupling coefficient of 1.43 × 10−8 s/m have been achieved in the quasi 1–2 nanocomposite film with a substrate thickness of 25 µm. Furthermore, the stain‐mediated ME coupling was revealed by magnetic field/electric field‐induced local ferroelectric/magnetic domain switching dynamics.

Structure-Piezoelectric Property Relationships of Thin Films Composed of Electrospun Aligned Poly(vinylidene fluoride) Nanofibers.

In the past two decades, many studies on piezoelectric nanofibers (NFs) prepared from poly(vinylidene fluoride) (PVDF) and its copolymers, including single NFs, randomly oriented nonwoven mats, and aligned NFs, have been reported. However, studies on the relationships between the PVDF NF diameter, the orientation of the β-phase crystals inside NFs, and the piezoelectric properties of the NFs are still limited. In this study, the effect of the fiber diameter on the internal molecular packing/orientation and piezoelectric properties of aligned PVDF NF thin films was investigated. Herein, piezoelectric thin films composed of densely packed, uniaxially aligned, PVDF NFs with diameters ranging from 228 to 1315 nm were prepared by means of electrospinning with a rotating collector and successive hot-pressing and poling. The effect of the diameters of PVDF NFs on their internal structures, as well as the piezoelectric properties of the thin films, was investigated. All prepared NFs mainly contained β-phase crystals with a similar total crystallinity. The orientation of the β-phase crystals inside the NFs increased with an increase in the fiber diameter, resulting in an improved transverse piezoelectric coefficient (d31) for the thin films. The output voltage of the prepared thin films reached a maximum of 2.7 V at 104 Hz.

PbS QDs and rGO-decorated PbS QDs induced optical properties variations on P3HT:PC61BM composite thin films

PbS QDs and PbS QDs decorated with reduced graphene (rGO) are prepared by hot-injection method using PbO and hexamethyldisilathiane (HMDS) as Pb and S sources, respectively. PbS QDs and PbS QDs:rGO are used as an addition to poly(3-hexylthiophene-2,5-diyl):phenyl-C61-butyric acid methyl ester (P3HT:PC61BM) composite. The effect of their addition on the morphological, topographical and optical properties of spin-coated P3HT:PC61BM thin films are investigated. These additions tune the films to be more homogenous and more flatness as investigated in terms of field scanning electron microscope. The topographical properties of the films are explored by atomic force microscope. The results show decreasing in the grain size and the surface roughness in P3HT:PbSQDs:PC61BM film compared to other composites films. The optical properties of the films are studied over the spectral range 200–2500 nm. On one hand, the absorption coefficient of different films is computed and the optical band gap of the films is found to decrease after addition of PbS QDs and PbS QDs:rGO. On the other hand, the refractive index of the films is explained according to the single-oscillator model to get the dispersion parameters. In addition, the lattice dielectric constant and the ratio of the free-carriers concertation to their effective mass are evaluated.

Hopping nature of the Hall effect in a samarium nickelate film

We analyzed the temperature dependencies of the DC resistivity and Hall coefficient in thin films of samarium nickelate SmNiO3. A dominating hopping conductivity was revealed in the insulating phase below 400 K, which defines an exponential drop in the Hall coefficient with temperature. The estimated dependencies of the hopping activation energy, Hall mobility, and charge carrier density suggest that small polarons are responsible for hopping. The hopping transport explains the observed sign anomaly of the Hall coefficient in rare-earth nickelates.

Terahertz characterization of nano-scale high-entropy alloy films and their high-contrast grating applications

We investigated the optical constants of thin films of the Nb25Mo25Ta25W25 alloy, which belongs to high-entropy alloys (HEAs), with a transmission terahertz (THz) measurement system and discovered that the refractive index, extinction coefficient, and conductivity of the HEA thin film measured in the range of 0.3–1.0 THz all increased as the thickness of the thin film increased (the thickness was maintained in the range between 10 and 40 nm). According to the experimental results, this alloy with a high refractive index is suitable for producing high-contrast gratings (HCGs). The principle behind achieving a high contrast with a high-reflection HEA grating is to harness the confined plasmonic energy within the grating, thereby enhancing the localized plasmonic energy within the grating. This work elucidates that we can not only fabricate THz components by controlling the thickness of the thin film but also utilize the high refractive index of this material to create HCGs.

Optical, conductive, and ferroelectric properties of the first layer of dip-coated BiFeO3 films from methoxyethanol and acetic acid-based chemical dissolvents

The overall performance of the multilayer resulting in a sol-gel bismuth ferrite (BiFeO3) film will be primarily determined by the properties of the first layer, but this has yet to receive much attention, even though chemical and morphological defects of this layer can accumulate as the number of layers increases. Here, we perform an optical, conductive, and ferroelectric study of first layer (L 1) dip-coating sol-gel BiFeO3 films using two routes that vary only in the dissolvent; the first one is based on 2-methoxyethanol (MOE), and the second one on acetic acid (AA) with some MOE (AA-MOE). Tauc plots reveal a band gap of 2.43 eV and 2.75 eV for MOE (30 ± 5 nm thick) and AA-MOE (35 ± 5 nm thick) films, respectively. MOE films showed a dielectric function with features at ∼2.5 eV, ∼3.1 eV, and ∼3.9 eV, which were associated with charge-transfer transitions, but such features are absent in AA-MOE films. Advanced atomic force microscopy techniques were used to identify the fine features or defects of the BiFeO3 films: The conductive maps show that the charge transport pathways in both film routes are controlled by nanometer defects rather than grain or grain boundary defects. Current-voltage curves reveal high conductive pathway at a lower voltage for the MOE films than for AA-MOE films. The piezoelectric coefficient for MOE films was ∼20% higher than AA-MOE films. Both deposition methods yield ferroelectric films with an electromechanical strain controlled by the piezoelectric effect and minimal contribution from electrostriction. An optimization for the AA-MOE-based route in the withdrawal speed results in a significant reduction of morphological defects and a more than twofold increase in the piezoelectric coefficient. Our results broaden the understanding of optical and ferroelectric BiFeO3 films based on a chemical solution by dip-coating.

Coupling effect of partial composite texture and thermal effect on the performance of hydrostatic bearing

AbstractThis work is focused on performance computation of high speed rotor bearing system with partial composite texture. Since its viscosity at varying speeds affects working performance in different partial composite texture, therefore at design and development stage, it is necessary to know the composite texture and thermal effect acting on rotor‐bearing system that causes variation of performance. The effects of partial composite texture size and position on the performance of the bearing are studied. After the optimal structural parameters are determined, the effects of the partial composite texture and fluid thermos structure coupling on the bearing capacity, stiffness, and friction coefficient of the oil film are analysed. The results show that after considering the influence of thermal effect, the performance enhancement of composite texture bearing is better than that of smooth bearing. Considering the temperature effect, the bearing capacity of the composite textured bearing is increased by 51.4% compared with that of the smooth bearing, and the friction coefficient is reduced to 22.4%, which is better than the value without considering the temperature effect, the accuracy of the results is verified by experiments. This study provides a theoretical basis for the design of hydrostatic bearing and improving its performance.

Synthesis and characterization of a julolidine-based electro-optic molecular glass.

Organic electro-optic (EO) materials have recently gained considerable attention owing to their advantages compared to inorganic EO materials. Among different kinds of organic EO materials, organic EO molecular glass exhibits desired prospect because of its high chromophore loading density and large macroscopic EO activity. The objective of this study is to design and synthesize a novel organic EO molecular glass JMG utilizing julolidine moiety as the electron donor, thiophene moiety as the conjugated bridge, trifluoromethyl substituted tricyanofuran derivate (Ph-CF3-TCF) as the electron acceptor. The JMG's structure was characterized through NMR and HRMS. The photophysical property, glass transition temperature, first hyperpolarizability (β) and dipole moment (μ) of JMG were determined through UV-vis spectra, DSC test and DFT calculation. JMG's Tg reached to 79 °C and it can form high-quality optical film. The theoretical calculation shows that the first hyperpolarizability (β) and dipole moment (μ) of JMG were calculated to 730×10-30 esu and 21.898 D. After connecting poling with the poling voltage of 49 V/μm at 90 ℃for 10 min, the highest EO coefficient (r33) of the poled JMG films reached to 147 pm/V. A novel julolidine-based NLO chromophore with two tert-butyldiphenylsilyl (TBDPS) groups was successfully prepared and characterized. TBDPS group is introduced as the film-forming group, and it also plays the role of isolation group, which can suppress the electrostatic interaction between chromophores, improve the poling efficiency and further enhance the EO activity. The excellent performances endow JMG with potential applications in device fabrication.

Numerical evaluation of grain boundary electron scattering in molybdenum thin films: A critical analysis for advanced interconnects

We present a methodology for numerically evaluating grain boundary scattering in polycrystalline molybdenum (Mo) thin films. Two types of Mo films (an epitaxially grown (110)-single-crystal film and a <110>-fiber-textured polycrystalline thin film) were sputter-deposited under identical conditions on a lattice-matched (112‾0)-Al2O3 substrate and an amorphous glass substrate, respectively. This indicates equal background scattering (phonon and impurity scattering) for the two types. Further, the selected film thickness (236 nm) significantly exceeds Mo's inherent electron mean free path (11.2 nm), rendering surface scattering contributions negligible. The resistivity difference is therefore attributed to the grain boundary scattering. Using the Mayadas–Shatzkes model and an average grain size of 80.9 ± 2.8 nm (measured from a statistically significant number of grains (747)), the grain-boundary reflection coefficient for Mo films was determined to be 0.48 nm. The presented methodology, not limited to Mo, is expected to serve as a reliable analytical approach for advanced interconnects.

Tuning optical and electrical characteristics through Cu doping in spray pyrolysis fabricated Cr2O3 thin films

This study focuses on the physical properties of thin films of Cr2O3 and Cu-doped Cr2O3 (1−4 % Cu), with a thickness of approximately ∼500 nm. These films were deposited on preheated soda-lime glass substrates using the spray pyrolysis technique. The characterization of the thin films was carried out through Raman spectroscopy, UV–visible spectroscopy, and the four-point probe technique. The Raman analysis revealed vibrational modes associated with Eg and A1g symmetries in Cr2O3. The optical band gap energy exhibited a decrease from 2.92 eV to 2.6 eV with an increase in Cu content. The study also involved the evaluation of extinction coefficient, refractive index, dielectric constants, and optical conductivity of the thin films. The dispersion of the refractive index was studied using the single oscillator model (Wemple-DiDomenico). The electrical resistivity values decreased from 1000 Ω-cm to 33 Ω-cm with increasing Cu content. Notably, Cr2O3 thin films with 4 % Cu content demonstrated the best figure of merit, recording a value of 4.66 M Ω−1.

Bayesian optimization-based prediction of the thermal properties from fatigue test IR imaging of composite coupons

The prediction of the prevailing self-heat transfer parameters of a glass/epoxy composite coupon during fatigue testing in general and the distinction between viscoelastic- and frictional crack growth-related energy dissipation in particular, are not trivial problems. This work investigates the feasibility of predicting the convective film coefficient, the total work loss as well as the ratio between viscoelastic and fracture-induced damping from thermal images using Bayesian optimization in conjunction with 3D FE thermal analysis. To this end, glass fiber/epoxy biax coupons are pre-damaged by means of a drop weight impact machine and subsequently tested under uniaxial tension-tension high cycle fatigue conditions. IR images are taken of the self-heating thermal profile at steady-state conditions. Synthetic surface thermal images are generated by numerical thermal analysis of the damage distribution obtained by μ-CT scanning prior to testing. Bayesian optimization of the aforementioned parameters is conducted by minimizing the loss function between the as-measured and the synthetic IR image. The predicted work-loss is consequently validated against the measured hysteretic response, from which a very good agreement is found.