Dielectric Properties Of Films Research Articles

The phase transition and enhanced dielectric properties in La0.7Ba0.3MnO3 /P(VDF-HFP) composited films

Polymer-based ferroelectric composites, particularly those containing Poly (vinylidene fluoride) (PVDF), have emerged as preferred materials for flexible electronics and sensors owing to their excellent electro-mechanical attributes and ease of fabrication. The efficacy of PVDF composites is significantly influenced by the fillers and the proportion of the β-phase present. This research details the synthesis of La0.7Ba0.3MnO3 (LBMO) particles via solid-state reaction, surface-functionalized with acetic acid, and subsequently introduced as nucleating agents into Poly (vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) to fabricate LBMO/P(VDF-HFP) composite membranes. The LBMO fillers before modification significantly increased the β-phase content from 32.7 % to 87.8 % in 5 wt% unmodified LBMO/P(VDF-HFP) membranes. After modification, the hydroxyl groups attached to acetic acid-modified LBMO form hydrogen bonds with -CF2 groups in P(VDF-HFP), inducing the formation of the β phase while enhancing macroscopic polarization and piezoelectricity. At a 7.5 wt% acetate-modified LBMO doping level, the composite membrane exhibits a β-phase content of 64.5 %, but concurrently enhancing the film's dielectric properties. At 103 Hz, the dielectric constant of 5 wt% modified LBMO/P(VDF-HFP) membrane increases to 24.8, with a minimal rise in dielectric loss from 0.0293 to 0.0314. Moreover, under a 10 N compressive load at 1 Hz, the 5 wt% modified LBMO/P(VDF-HFP) composite achieves an open-circuit voltage of 4.3 V. These improved dielectric and piezoelectric properties indicate the composite's suitability for energy harvesting applications.

High Electrical and Mechanical Properties Obtained in a Polyimide‐Based Nanocomposite with Sandwich Structure via Multidimensional Design

AbstractAs an excellent polymer material, polyimide (PI) plays an important role in practical applications. However, traditional filler doping modification is hard to simultaneously improve the dielectric properties and mechanical properties of the film. Here, PI–boron nitride (BN) nanosheets/PI–sodium titanate nanotubes (STNs)/PI–BN composite films with sandwich structure are prepared by in situ polymerization and multilayer coating processes, which significantly enhance the electrical and mechanical properties of dielectric films. With only 0.5 wt% fillers doping, the AC breakdown strength of the composite film can reach 183.7 kV mm−1, which is 16.41% higher than that of pure PI. When the filler doping is 1.5 wt%, the corona aging time of the composite film achieves 311.7% higher than that of pure PI film. In addition, the composite film exhibits outstanding elongation at break (58%) and tensile strength (138.92 MPa) performance. The 2D BN of the outer layer and 1D STNs of the middle layer effectively block the injection of charge carriers while improving the internal polarization response. A mechanism related to microstructure and interface is proposed to explain the improvement of electrical and mechanical properties in detail. This work provides a useful idea for the accurate design of high‐performance dielectric films.

A high κ, transparent, and stretchable Cu@TiO2 core@shell nanowire/poly(dimethylsiloxane) composite film for sensitive wearable touch sensor

Touch sensors are crucial for the development of advanced wearable devices and enhancement of the user experience through human-machine interaction. The properties of dielectric films, including their high dielectric constants (high-κ), low loss tangents (tan⁡δ), transparency, and stretchability are key factors that impact the accuracy, reliability, and display visibility of wearable touch sensors. Here, we present an approach for fabricating a Poly(dimethylsiloxane) (PDMS)-based dielectric film that can achieve a dielectric constant 6 times larger than that of pure PDMS film by loading a very low wt% (3%) of copper@titanium dioxide (Cu@TiO2) core-shell nanowires (NWs) to PDMS matrix. TiO2 was deposited on surfaces of Cu NWs by a hydrothermal reaction to form the covering shell, and it is experimentally and theoretically proved that the shell can suppress the scattering from metal surfaces, resulting in improving the transparency, and reducing the dielectric loss of the film (tan⁡δ=0.01–0.06). The nanocomposite film also exhibits outstanding mechanical property (standing up to a tensile strain of 200%). The demonstration of a transparent, highly sensitive and low noise multi-touch sensor using high-κ film suggests that this film has potential application in next-generation of wearable electronic devices for human-machine interaction.

Study on electrostatic discharge (ESD) characteristics of ultra-thin dielectric film

Electrostatic discharge (ESD) event usually destroys the electrical properties of dielectric films, resulting in product failure. In this work, the breakdown characteristic of machine mode (MM) ESD on three different nano size films of head gimble assemble are obtained experimentally. The breakdown voltage and thickness parameters show a positive proportional relationship, but they are generally very low and have large discrete characteristics (∼30%). The maximum and minimum breakdown voltages of the tested samples are 1.08 V and 0.46 V, which are far lower than the requirement of the current standard (25 V). In addition, the judgment criterion of product damage is given, and the relationship between discharge voltage polarity, initial resistance and breakdown voltage is studied. Finally, the theoretical analysis of the breakdown characteristic law has been given.

Preparation, Characterization and Dielectric Properties of Alginate-Based Composite Films Containing Lithium Silver Oxide Nanoparticles.

Polymer composites have found applications in diverse areas, ranging from the manufacturing of portable electronic devices to the fabrication of bioactive agent carriers. This article reports the preparation of composite films consisting of sodium alginate (SA) and lithium silver oxide (LAO) nanoparticles. The films are generated by solution casting; whereas the nanoparticles are fabricated by using the hydrothermal method. The effects of the nanoparticles on the morphological, thermal, and dielectric properties of the films are examined by using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) analysis, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Electrical measurements are also performed to determine the dielectric constant (ε′), dielectric loss (ε″), AC conductivity (σac), electrical moduli (M′ and M″), and impedance (Z' and Z″). The composite films are shown to be crystalline in nature, with nanoparticles having a diameter of 30–45 nm effectively disseminated in the polymer matrix. They also display good dielectric properties. Our results suggest that the films warrant further exploration for possible use in microelectronic applications.

Influence of radiation exposure on the properties of dielectric layers based on anodic aluminum oxide

Devices that are used in the aerospace industry must operate in extreme conditions, so it is important to understand how the properties of materials change under the influence of radiation and low temperatures. Anodic aluminum oxide, due to its mechanical and dielectric properties, is widely used in electronic devices with a high degree of integration. Radiation exposure can lead to degradation of the electrophysical parameters of dielectric films and can also change their chemical composition. The methods for studying the effect of radiation exposure on the dielectric properties of films are shown in this article. The research has been carried out and the results of the influence of α-particles on the dielectric properties of a porous film of anodic aluminum oxide during the influence of low temperature are presented.

Influence of substrate temperature on optical, structural and dielectric properties of TiO2 thin films prepared by spray pyrolysis technique

Titanium dioxide (TiO2) thin films are prepared on various substrates like glass and silicon wafers by spray pyrolysis method. The spray solution is prepared by dissolving titanium-tetra isopropoxide (TTIP) in ethanol. Optical, structural and dielectric properties of these films are studied by the transmittance spectra, X-ray diffraction (XRD), atomic force microscopy (AFM), capacitance–voltage (C-V) characteristics, respectively. TiO2 metal oxide semiconductor (MOS) capacitors are fabricated using TiO2 as a dielectric medium. C-V plots are analyzed to determine the dielectric constant (εr) of TiO2 film. The dependance of εr of the TiO2 films with the substrate temperature has been investigated.

Effect of Annealing Process on the Dielectric and Tunable Properties of (Bi1.5Zn0.5)(Nb0.5Ti1.5)O7(BZNT) Thin Film

Bi1.5Zn0.5Nb0.5Ti1.5O7 (BZNT) thin films were deposited on Pt/Ti/SiO2/Si substrates by radio frequency (rf) magnetron sputtering. In this paper, by studying the phase structure, surface morphology, and dielectric properties of BZNT films, it is found that by increasing the initial temperature in the annealing process, the film formation quality, internal stress and dielectric properties of the film can be improved. and the best performance of the BZNT film is obtained under the annealing process at the initial temperature of 500°C. The tuning amount (Tu), Dielectric loss (Loss) and quality factor (FOM) are: 13.55 percent, 0.00298 and 45.46, respectively.

A review of surface roughness impact on dielectric film properties

The importance of surface roughness with respect to the bulk properties of dielectric materials is often overlooked. Surface roughness or interfaces between different material layers often significantly affects the external properties of thin films. Surface roughness holds its commonalty and critical impact among many materials properties. This review summarises the recent work on the effect of surface roughness on the mechanical, thermal, physical, and dielectric properties of dielectric films. Appropriate roughness favours adhesion, filtration, biological fouling, tribological properties, and magnetic properties. Nevertheless, lower roughness generally benefits the dielectric properties of dielectric materials, with thicknesses ranging from a few nanometres to up to 50 μm. This review discusses surface roughness control and the techniques of measurement as well. It emphasises the importance and characterisation of sample surface roughness for a better understanding of the dielectric phenomenon, mechanisms, and electrical stress test setup for various dielectric films.

Stress Engineering of Dielectric Films on Semiconductor Substrates

Dielectric thin films deposited by plasma enhanced chemical vapor deposition (PECVD) have been extensively studied over the last decades due to their interesting optical and electrical properties besides their many applications in microelectronic and optoelectronic devices. Recently published studies have shown the impact of the mechanical properties of amorphous dielectric films on semiconductor substrates [1]. In strain engineering, stressed films are used to control on demand the physical properties of semiconductors at the surface such as bandgap energy, dielectric constant, and refractive index. We aim to study in this work how to control the distribution of the strain field beneath a dielectric film and how the changing of the residual stress affects the physical properties of the dielectric film itself. We deposited hydrogenated amorphous silicon nitride a-SiN:H films on Si, InP, and GaAs substrates using a capacitively coupled plasma reactor CCP-PECVD with a radiofrequency (RF) power at 13.56 MHz.The a-SiN:H films were deposited at 280 °C, with a thickness of approximatively 500 nm, using a SiH4/NH3/N2/Ar precursor mixture. The RF power injected into the plasma allows a tunable residual stress and a wide range of built-in stress, from tensile (+ 300 MPa) to compressive (– 400 MPa). To evaluate the residual stress in our deposited thin films, we used the standard method of wafer curvature measurements. The thickness and the refractive index were characterized by variable angle spectroscopic ellipsometry (VASE). The determination of Young’s modulus and hardness of the a-SiN:H films was performed by nanoindentation. We noticed that the adjustment of the residual stress leads to the modification of the film in terms of optical and mechanical properties. In order to investigate the deformation induced in the semiconductor, an understanding of the semiconductor mechanical behavior on a microscopic scale is required. Thus, we performed a detailed investigation of the effect of strain on the degree of polarization (DOP) of the photoluminescence signal on direct bandgap substrates [2]. After examining the DOP profiles beneath the film, it is interesting to note that the anisotropic deformation extends to significant depths (~ 8 µm), as illustrated in figure 1, while the horizontal distribution of the stress can propagate beyond the edge of the sample by a few microns (see figure 2). The confinement of light in some photonic devices such as photoelastic planar waveguides can be achieved by a photo-elastic effect in semiconductor using stressed dielectric films [3].[1] S. Gérard et al., “Photoluminescence mapping of the strain induced in InP and GaAs substrates by SiNx stripes etched from thin films grown under controlled mechanical stress,” Thin Solid Films, vol. 706, p. 138079, Jul. 2020, doi: 10.1016/j.tsf.2020.138079.[2] D. T. Cassidy, C. K. Hall, O. Rehioui, and L. Bechou, “Strain estimation in III-V materials by analysis of the degree of polarization of luminescence,” Microelectron. Reliab., vol. 50, no. 4, pp. 462–466, Apr. 2010, doi: 10.1016/j.microrel.2009.11.003.[3] P. A. Kirkby, P. R. Selway, and L. D. Westbrook, “Photoelastic waveguides and their effect on stripe-geometry GaAs/Ga 1-xAlxAs lasers,” J. Appl. Phys., vol. 50, no. 7, pp. 4567–4579, Jul. 1979, doi: 10.1063/1.326563. Figure 1

A unified approach for the calculation of in-plane dielectric constant of films with interdigitated electrodes

Interdigitated electrodes (IDEs) on dielectric films is an important electrode design in electrical components such as transducers and sensors. Further development and use of IDEs for characterization of the in-plane properties of dielectric films requires models for the capacitance, particularly when used in a multilayer stack. Previous models for the capacitance have permitted erroneous boundary conditions between layers with associated limitations to accuracy. In this work we present a new model based on fulfilling the boundary conditions between layers with different dielectric constant. We further demonstrate how the model can be used to calculate the in-plane dielectric constant and polarization of BaTiO3 films. The model is shown to outperform previous models using both the experimental data from BaTiO3 films on SrTiO3 substrates and finite element method simulations of the corresponding case. One important advantage compared to previous work is that the new model provides good results regardless of film thickness.

Dielectric Properties of PMMA Films Reinforced with Ag/rGO Hybrid Composites

Nanocomposite materials consisting of polymer matrices and nano-sized fillers have fascinated scientists with their superior functional properties, attained at relatively low filler loading. In this work, nanocomposite films of poly(methyl methacrylate) (PMMA)-reinforced with different concentrations of partially reduced graphene oxide/silver (rGO/Ag) hybrid were prepared in two different solvents following an ex situ chemical method. By employing solvent casting, all the samples were prepared as free-standing films. The structural and morphological characterisations of a GO/Ag hybrid and the as-prepared film samples were done with different tools such as x-ray diffraction (XRD), UV–Vis absorption spectroscopy, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and electron microscopy (SEM and TEM). Chemical microanalysis of the nanohybrid was carried out by energy-dispersive x-ray (EDX) spectroscopy. Dielectric properties of these films have been carried out at room temperature in the frequency range of 100 Hz–2 MHz using an LCR meter, and these films show considerable changes in their properties when loaded with GO/Ag hybrid nanocomposites. The filler and solvent-dependent properties shown by the free-standing films make them a promising candidate for the fabrication of flexible energy storage devices.

Effect of Thermal Cycling on the Thermal and Mechanical Properties of Dielectric Materials

Photosensitive polymers or dielectric materials such as polyimides (PIs) have been used in fan-out wafer-level packaging process (FOWLP) as a redistribution layer for quite some time. In the condensed 2-D and 3-D packaging processes, the dielectric materials are applied multiple times to create as many as four or five redistribution layers. At the end of the process, the first layer may experience up to four times of heat cycles in which the polymer properties may change. However, the effect of heat cycles on properties of dielectric film as well as their contributions to the wafer-level warpage is still unclear. To understand the changes of materials’ properties after several heat cycles, the thermal and thermo-mechanical properties of negative-tone and positive-tone types of dielectric films are characterized by using the thermomechanical analysis (TMA), dynamic mechanical analysis (DMA), and thermogravimetric analysis (TGA). The glass transition temperature ( ${T}_{g}$ ), coefficient of linear thermal expansion (CTE), and modulus (storage, ${E}'$ , and loss, ${E}''$ ) are analyzed and compared. In addition, the morphology of the films before and after heat cycles is also analyzed.

Design and Optimization Methodology of Coplanar Waveguide Test Structures for Dielectric Characterization of Thin Films

This paper describes an accurate design method of coplanar waveguide (CPW) test structures on characterizing dielectric properties of thin films with arbitrary thickness. Current CPW measurement method has difficulty in providing accurate dielectric properties of films with extremely small thickness. To address this issue, an optimized algorithm is presented to generate proper geometric parameters of CPW test structures for films with different thickness. To validate the accuracy of the proposed design methodology, various test cases of CPW structures with different dimensions have been designed and implemented, the extracted dielectric properties (e.g., dielectric constant and loss tangent) from the S-parameters of the different test cases are compared to the benchmark results simulated by accurate electromagnetic tool Ansys HFSS. It demonstrates the efficacy of the proposed optimized method on quickly producing correct dimensions of CPW test lines for accurate properties characterization of thin films.

Formation of SnO and SnO2 phases during the annealing of SnO(x) films obtained by molecular beam epitaxy

SnO and SnO2 films were obtained on the SiO2 surface by the molecular-beam epitaxy method. The initial films are in the polycrystalline phase. The annealing of SnO(x) films at a temperature of 300 °C resulted in the formation of the tetragonal SnO phase. Three vibration modes Eg, A1g, and B1g with the frequencies of SnO bond vibrations of 113, 211 and ~360 cm−1, respectively, which correspond to the SnO phase, were first observed by the Raman spectroscopy method. The orthorhombic SnO2 films were obtained by increasing the annealing temperature to 500 °C. Based on the valence band XPS (X-ray photoelectron spectroscopy) spectrum, several features with the binding energy approximately 5 eV, 7.5 eV and 11 eV, which are the same with the valence band of SnO2, were identified. The refractive index and absorption coefficient were investigated by the spectral ellipsometry technique. The high absorption coefficients correspond to the high Sn content. The film dielectric properties were revealed at the temperature higher than 300 °C. The refractive index values lie in the range of 1.5–2.6 for the visible spectral region. The pronounced absorption edges at 2.85 eV and 3.6 eV corresponding to those of stannous oxide (SnO) and stannic oxide (SnO2) were observed. The photoluminescence (PL) from the SnO(x) films was observed at room temperature. The increase of the annealing temperature resulted in the increase of PL intensity. Such PL intensity behavior is likely due to the Sn nanoislands.

Hydrogenation in multicrystalline silicon: The impact of dielectric film properties and firing conditions

AbstractHydrogenation is a crucial step for improving the efficiency of multicrystalline silicon solar cells. In this work, we investigate the influence of different firing and annealing conditions on the efficacy of bulk hydrogenation in state‐of‐the‐art high‐performance multicrystalline silicon, for a range of hydrogen‐containing dielectric layers. All of the dielectric films studied, including aluminium oxide, amorphous silicon, and silicon nitride deposited with different tools, yield similar bulk lifetimes when annealed at optimal conditions. However, the optimal conditions vary between films, depending on the film properties. The overall hydrogenation effect does not appear to be affected by the cooling rate used during firing or by the application of illuminated annealing, performed at 250 ° C under 8 sun illumination. Moreover, we monitor in situ changes in the recombination behaviour of grain boundaries during the hydrogenation process, using a micro‐photoluminescence spectroscopy system with a temperature controlled stage. It is found that the hydrogenation reaction occurs at the annealing temperature range between 400 ° C and 500 ° C.

Dielectric and optical properties of zirconium titanate thin films by reactive DC magnetron co-sputtering

Zirconium titanate thin films were deposited on alumina substrates by DC magnetron reactive co-sputtering by varying substrate temperature and the effects of substrate temperature on optical and dielectric properties of the films have been studied intensively by available characterization techniques. The optical parameters were determined by Swanepoel's method. The films exhibited high transmittance in the visible region and the optical band gap of the films varied from 3.1 to 2.8 eV as the temperature varied from 33 to 400°C. The film deposited at room temperature exhibit a high transmittance of 71%. Dielectric constant measurements have been carried out at 10 GHz of frequency. The dielectric constant increased with increase in temperature and the film deposited at 400oC exhibited a high dielectric constant (40) and a low dielectric loss (0.026).

ANNEALED In2S3 THIN FILMS PREPARED BY SPRAY TECHNIQUE: REPORT ON THE STRUCTURAL, OPTICAL AND DISPERSION ENERGY PARAMETERS

In2S3 thin films with different S/In molar ratios (from 1.5 to 3.5) were deposited via a spray pyrolysis technique on glass substrates at 340∘C. Then, the obtained films were annealed at the same temperature 400∘C for 2[Formula: see text]h. X-ray diffraction study reveals the formation of cubic [Formula: see text]-In2S3 phase with (400) as preferred orientation. The crystallite size varies in the range 64–97[Formula: see text]nm. Optical analysis exhibits that transmittance in visible and near infrared regions is higher than 65% for all films. The optical band gap varied from 2.58[Formula: see text]eV to 2.67[Formula: see text]eV. The optical parameters (refractive index, extinction coefficient, dielectric constants) were calculated through the transmittance ([Formula: see text]) and reflectance ([Formula: see text]). Dispersion parameters ([Formula: see text], [Formula: see text]), high frequency dielectric constant ([Formula: see text]), refractive index ([Formula: see text]), oscillator length strength ([Formula: see text]), average oscillator wavelength ([Formula: see text]) and optical moments ([Formula: see text]) were determined by Wemple–DiDomenico model. The surface and volume energy losses with photon energy were also calculated. The optical and electrical conductivities were estimated. These properties of In2S3 films are important for photovoltaic applications.

Anomalous dielectric constant value of graphene oxide/Polyvinyl alcohol thin film

Graphene oxide/polyvinyl alcohol (GO/PVA) composites have been developed using facile colloidal processing technique to form a super dielectric spacer of 106 order. The dielectric characteristics of GO/PVA composite were investigated at a frequency range from 20 Hz to 1 M Hz. The electrical analysis showed a complex interaction that is quite different than Debye but could be explained using Bruggeman and Maxwell-Garnett assumptions in the high-frequency range and Percolation theory in the low range. Due to the ageing effect and the observed high imaginary part, an investigation of GO film dielectric properties were investigated. The results incorporate a crucial role of water contents on corresponding GO and GO/PVA electromagnetic interaction besides the well-established functional group's theory. Transmission electron microscopy, X-ray diffraction, dispersive Raman, potentiostat/galvanostat and LCR meter were utilized to perform microscopic, structure and electrical characterizations.

Effects of oxygen pressure during deposition on the dielectric properties of amorphous titanium dioxide thin films

Thin films of TiO2−δ on Si substrates were prepared by pulsed laser deposition for the study of the influence of the O2 growth pressure on their properties, especially the dielectric ones for the integration into MOS capacitances, and the identification of the nature of any excess charges induced by oxygen vacancies. In order to achieve an amorphous growth, low deposition temperatures of 100 °C and 300 °C were chosen. The structure of the films depends on the growth pressure, showing a window of anatase crystalline growth at 300 °C and intermediary growth pressures. The electric and dielectric properties of the films were investigated, and a clear relation between the excess charges produced by oxygen vacancies and the dielectric properties is established. Interestingly, the excess charges do not form small polarons, but are delocalized in the material, leading to high losses for low growth pressures. The optimal growth conditions for the use in capacitances seem to be a growth temperature of 100 °C and a growth pressure of 0.01 mbar, resulting in a dielectric constant of 60 with dielectric losses between 0.2 and 0.002.