Mohamad Hafiz Mohd Wahid

Effect of Annealing Temperature on the Crystallinity, Morphology and Ferroelectric of Polyvinylidenefluoride- Trifluoroethylene (PVDF-TrFE) Thin Film

The annealing temperature for 250 nm PVDF-TrFE (70:30 mol %) spin coated thin films were varied at solvent evaporation (Ts = 79 °C), Curies transition (Tc= 113 °C), till melting temperature (Tm = 154 °C). XRD measurement showed that, there was an improvement in the crystallinity of the annealed films, consistent with the increased in the annealing temperatures. Morphological studies of the annealed PVDF-TrFE thin films as observed with Field Emission Scanning Electron Microscope (FESEM) (100k magnification), showed enhanced development of elongated crystallite structures known as ferroelectric crystal. However, thin film annealed at 160 °C (AN160) showed fibrous-like structure with appearance of nanoscale separations, which suggested high possibility of defects. Ferroelectric characterization indicated an improvement in the remnant polarization of annealed PVDF-TrFE thin films with the exception to AN160 in which leakage of current was inevitable due to the presence of cracks on the film surface.

Dielectric Properties of PVDF-TrFE/PMMA: TiO2 Multilayer Dielectric Thin Films

This paper reports on the dielectric properties of multilayer PVDF-TrFE/PMMA:TiO2 thin film. Two samples were fabricated on ITO substrates; one with PVDF-TrFE only and another PMMA:TiO2 on PVDF-TrFE on (PVDF-TrFE/PMMA:TiO2). Both samples were produced by spin coating method. Dielectric properties were characterized using impedance spectroscopic. Dielectric constant, k, capacitance and dielectric loss, tan δ values of PMMA:TiO2/PVDF-TrFE were measured in the frequency range 0 – 50 kHz. The result for dielectric loss did not show any significant different between the samples with and without nanocomposite PVDF-TrFE layer. However, the dielectric constant are affected when depositing a nanocomposite PVDF-TrFE layer on PMMA:TiO2. The dielectric constant is decreased by 0.3 from 7.9 to 7.6.

Different surface morphology of annealed PVDF-TrFE thin films and the effect on its ferroelectric properties

The different morphology of 250 nm PVDF-TrFE (70:30 mol%) thin films were observed in relation to its ferroelectricity. The annealing temperatures were varied from solvent evaporation (Ts), Curies transition (Tc), up to melting temperature (Tm). It was found that the annealing process promoted the development of elongated crystallite structure also known as ferroelectric crystal, which significantly improved the ferroelectric properties of PVDF-TrFE (70:30 mol%) thin films. However, the presence of nanoscale separations on the thin film annealed over Tm (AN160) suggested high possibility of defects, and hence a reduction in ferroelectric properties of thin films.

Surface Modification of Polyvinylidenefluoride-Trifluoroethylene Film Using Argon Gas Plasma

This study investigates the surface properties of plasma surface modified spin coated PVDF-TrFE (70/30) film using Atomic Force Microscopy (AFM), Water Contact Angle (WCA) and X-ray Photoelectron Spectroscopy (XPS). The surfaces of the spin coated PVDF-TrFE film were modified using 13.56 MHz rf Argon plasma. The exposure time of the charged particle PVDF-TrFE films were varied for 1, 3 and 5mins. Prior to modification, the average surface roughness obtained was 8.615nm, but upon modification, the surface roughness was found to increase to 12.466nm. The value of the contact angle of the modified film was reduced from 90o to 43o and the XPS analysis showed dehydrofluorination of PVDF-TrFE films surfaces. The improved in surface roughness and the increased in wettability of the modified film, resulted in good biocompatibility of the modified PVDF-TrFE thin films. This phenomenon has created interest in researchers for developing functional polymer used for applications in areas such are biomedical, bio-analytical assays, textile and even food industry.

The Study of the Surface Morphology of PVDF/MgO Nanocomposites Thin Films

This study investigates the effect of varying loading percentages of MgO on the topography and morphology of Poly (vinylideneflouride)/Magnesium Oxide (PVDF/MgO) nanocomposites thin films. PVDF/MgO nanocomposites spin coated thin films with thicknesses ranging from 200nm to 456nm were successfully characterized. The nanocomposite solutions were spin coated on Al-glass substrates at 1500rpm. The topography and surface roughness of PVDF/MgO nanocomposites were characterized by using AFM. FE-SEM was used to investigate the surface morphology of the nanocomposites thin films and ATR-FTIR was used to determine the chemical bonding of PVDF/MgO nanocomposites. MgO (7%) was found to be the optimum loading percentage for PVDF/MgO nanocomposite film with favorable distribution of MgO particles, minimum defects and high content of β-phase as evident by FESEM and FTIR.

Ferroelectric characteristics of ZnO/MgO-based organic capacitor

Magnesium oxide, MgO with nanometre dimension particles size (36 to 73 nm) was successfully deposited on cleaned glass substrate. The drying temperatures were varied from 100 to 300°C and the dielectrics behaviour was investigated. From the results, it was revealed that variation of nano-MgO films properties obtained by changing the drying temperature. Nano-MgO film dried at 200°C was found to be a good dielectric layer due to it structural properties that resulted in the enhancement of relative permittivity value. The electrical properties shows better in dielectric layer characteristic where the resistivity was found to be 12.8 × 104 Ω.cm with leakage current density of 10−9 A.cm−2. The ZnO/MgO-based organic capacitor was fabricated and the remnant polarisation obtained was in range of 59 to 69 mC/m2 with capacitance value of 40 pF.

Effect of various annealing temperature on the morphological and dielectric properties of Polyvinylidenefluoride-Trifluoroethylene thin film

The morphology of PVDF-TrFE (70/30) thin film at various annealing temperature were investigated using non-contact mode Atomic Force Microscopy (AFM). Differential Scanning Calorimetry (DSC) technique was used to obtain T_C, T_m, and T_Crys of PVDF-TrFE. The prepared spin coated PVDF-TrFE (70/30) thin films were annealed at T_C (113°C), T_m (154°C), T_Crys (135°C) and T_c at cooling (55°C) in accordance to the DSC thermogram observed. Impedance Spectroscopy were conducted to study the dielectric characteristic of the thin films in order to substantiate the electrical behavior of the thin films From the results obtained, the thin films exhibited different morphologies depending on the annealing temperatures utilized. Formation of needle-like crsytallite structure was observed film annealed at and over T_m. Thin film re-crystallized at T_C has an optimized dielectric constant of ~7.8 at 10⁴ hz.

Dielectric constant of PVDF/MgO nanocomposites thin films

This study investigates the effect of varying loading percentage of MgO on the dielectric constant of Poly (vinylideneflouride)/Magnesium Oxide (PVDF/MgO) nanocomposite thin films. PVDF/MgO nanocomposite spin coated thin films were successfully fabricated and characterized. PVDF and nanocomposites solutions with loading percentage of MgO at 3, 5, 7, 9, and 11% were spin coated on Al-glass substrates at 1500rpm. The optimum percentage of PVDF/MgO thin film obtained from the dielectric measurement was 7%. The dielectric constant of PVDF/Mg(7%) nanocomposite at frequency 103 Hz was 21, with low dielectric loss and absence of visible film defects, as evident by FE-SEM images. In FTIR, broad bonding peaks at 840 and 880 cm−1 can be observed. Both bonding represented the -CH 2 and -CF 2 groups of PVDF, which indicated high β-phase content that attributed to the increment in the dielectric constant of PVDF/MgO(7%) nanocomposite. The PVDF/MgO(7%) nanocomposite is favorable for low frequency electronic application such as capacitor.

High crystallinity property of bilayer composited PbTiO 3 /PVDF-TrFE nanodielectric film capacitor

Innovative advance dielectric materials were utilized to fabricate novel thin film capacitor device. This includes ceramic and polymeric material combination which is considered to enhance the dielectric polarization. The dielectric film presented in the study focused on PbTiO3/PVDF-TrFE which was prepared through layer-by-layer spin coating deposition method. The PVDF-TrFE coating was aimed to encapsulate the fragility and to improve the crystallinity property of PbTiO3 thin film surface. The preferential orientation of (1 0 1) tetragonal perovskite PbTiO3 was obtained in this and high crystallinity was found on bilayered PbTiO3/PVDF-TrFE film. The bilayered film produced good film surface in term of its uniformity and surface roughness. The εr and tan (δ) value of bilayered PbTiO3/ PVDF-TrFE film was taken at 1 kHz that approximately 220 and 0.09 respectively.

Preparation of PVDF-TrFE layer-based bilayer composite PbTiO3/PVDF-TrFE films for MIM capacitor

The capacitor device has evolved from a simple device to an innovative and complex device. The capability of a capacitor is very much dependent on capacitance performance. Currently, researchers have shown interest in hybrid composites, which are capable of improving performance and increase reliability of devices. Thus, there is a need to fabricate thin films of hybrid dielectric materials such as polymer (PVDF-TrFE) and ceramic (PbTiO3). This study presents the preparation of the PVDF-TrFE layer for bilayer composite PbTiO3/PVDF-TrFE configured as metal–insulator–metal films capacitor. The deposition process utilised two methods: solvent casting and spin coating. The ceramic layer (first layer), PbTiO3, has optimum dielectric permittivity and tangent loss of about 138 and 0.9 taken at 1 kHz. The polymeric spin-coated layer (second layer) PVDF-TrFE films produced good dielectric property as compared to solvent casting prepared films. This provides an opportunity for further investigation of the dielectric property for enhanced understanding of capacitor-based devices.