L. N. Ismail

Enhancement in Dielectric Constant and Structural Properties of Sol-Gel Derived MgO Thin Film using ZnO/MgO Multilayered Structure

High dielectric constant, low porosity and nano-dimension particle of single layer magnesium oxide, MgO and multilayer ZnO/MgO were synthesized at different MgO solution molar concentration by the simple chemical solution technique. The MgO molar concentration was found to alter the properties of both single and multilayer films. Observation reveals the surface morphology change form uniform to agglomerate and porous structure with corresponding increase in molar concentration. The increment in particle size and the formation of agglomerated particle were observed by FESEM (JEOL JSM-J600F). The best prepared dielectric film for both single and multilayer is the film that deposited using 0.4 molar concentration MgO solution due to its high dielectric constant, uniform film, and the particle is in nanometer dimension with nonorod like structure.

Influence of Doping Concentration on Dielectric, Optical, and Morphological Properties of PMMA Thin Films

PMMA thin films were deposited by sol gel spin coating method on ITO substrates. Toluene was used as the solvent to dissolve the PMMA powder. The PMMA concentration was varied from 30 ~ 120 mg. The dielectric properties were measured at frequency of 0 ~ 100 kHz. The dielectric permittivity was in the range of 7.3 to 7.5 which decreased as the PMMA concentration increased. The dielectric loss is in the range of 0.01 ~ –0.01. All samples show dielectric characteristics which have dielectric loss is less than 0.05. The optical properties for thin films were measured at room temperature across 200 ~ 1000 nm wavelength region. All samples are highly transparent. The energy band gaps are in the range of 3.6 eV to 3.9 eV when the PMMA concentration increased. The morphologies of the samples show that all samples are uniform and the surface roughness increased as the concentration increased. From this study, it is known that, the dielectric, optical, and morphology properties were influenced by the amount of PMMA concentration in the solution.

Effect of Solvent on the Dielectric Properties of Nanocomposite Poly(methyl methacrylate)-Doped Titanium Dioxide Dielectric Films

A poly(methyl methacrylate)-doped titanium dioxide (PMMA:TiO2) nanocomposite film was obtained by spin coating the nanocomposite solution onto a silicon substrate. The nanocomposite solutions were prepared by dissolving the PMMA and TiO2 nanopowder in three different types of organic solvent, namely, toluene, tetrahydrofuran (THF), and acetone. We found that the dielectric properties of the PMMA:TiO2 nanocomposite are dependent on the type of solvent used. The dielectric properties measured at a frequency of 1 kHz showed that acetone gives the highest dielectric constant and capacitance compared with toluene and THF. Toluene gives the lowest dielectric loss among the three. The topography and roughness of the PMMA:TiO2 nanocomposite indicate that a particular solvent results in a different kind of surface morphology.

Dielectric and physical properties of PMMA:TiO 2 thin films by varying TiO 2 concentration

This research is to investigate the dielectric properties of PMMA: TiO2 nanocomposite thin films. The experiments are conducted by varying the TiO2 concentration from 0wt%, 1wt%, 2wt%, 3wt%. The results indicate that dielectric properties of PMMA: TiO2 nanocomposite thin film is affected by the amount of TiO2 concentration added into PMMA solution. The thin film with 3wt% indicate the higher dielectric constant with value 8.04 compare to others concentration. The capacitance result shows that when TiO2 are added its capacitance value is above pure PMMA where pure PMMA is about 0.004nF. However, for dielectric loss, it shows that the 3wt% thin film with value of 0.06 is lower than other concentrations. The FESEM images show that all the nanocomposite thin films have a porous surface. High porosity is obtained when the amount TiO2 concentration is increased.

Polarization-field hysteresis loop characteristic of nanostructured ZnO/MgO bilayer film based-MFIM capacitor

This research work investigates the ferroelectric characteristic of nanostructured ZnO/MgO bilayer based MFIM capacitor. The low leakage current (10-8 A.cm-2) of nanostructured ZnO/MgO bilayer films were observed for all annealed bilayer films. Nanostructured ZnO/MgO bilayer film annealed at 475°C was then utilized as insulator (dielectric) layer in the fabrication of MFIM capacitor due to its high resistivity (7.15×104 Ω.cm) and low leakage current density (10-8 A.cm-2). The optimized nanostructured ZnO/MgO bilayer film was proven to act as a stable buffer layer for the PVDF-TrFE in where the P-E loop can withstand for the applied voltage up to 190V. The polarization-field (P-E) hysteresis revealed high electrical strength of ZnO/MgO/PVDF-TrFE MFIM capacitor.

Electrical properties of spin coated PMMA for OFETs applications

Poly (methy-methacrylate) (PMMA) thin films were deposited by sol-gel spin coating method on glass substrates. PMMA powder was dissolved in 60ml Toluene with the concentration of the PMMA in the solution was varied from 30 ∼ 120 mg. Besides the PMMA concentration, we also studied the effect of the thin films thickness on the electrical properties. The results for electrical properties showed that there is a difference of the I–V, resistivity, conductivity and the dielectric constant with different thickness. Conductivity of the PMMA thin film was found to ∼ 10−6 Ωcm and continue to decrease as the PMMA concentration increased. Pinholes were identified to be formed on the films with the higher density due to the increasing PMMA concentration.

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.

Electrical Characterization of Metal-Ferroelectric-Insulator- Semiconductor having Double Layered Insulator for Memory Applications

Metal-ferroelectric-insulator-semiconductor (MFIS) devices were successfully fabricated using poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) and poly (methyl methacrylate): titanium dioxide (PMMA:TiO2) nanocomposite as ferroelectric and insulator films, respectively on n-type silicon (n-Si) substrate. Both ferroelectric and insulator films were prepared by sol-gel spin coating method. The electrical behaviour of metal-ferroelectric-metal (MFM) structure with PVDF-TrFE film and metal-insulator- metal (MIM) structure PMMA:TiO2 film exhibited different current characteristics. The capacitance of the MFIS devices was found to be 0.42 and 0.29 nF at frequency of 1kHz and 1 MHz respectively. Meanwhile, the dielectric loss values are constant (~60 × 10−3) in the frequency range from 100 Hz to 100 kHz. I-V results for MFIS are much higher than MIM and MFM is due to there is a trapped holes/electron located at the semiconductor- insulator interface which contributes to high leakage current in the MFIS device. We conclude, although interposing the PMMA :TiO2 nanocomposite insulator layer between the semiconductor and Al electrodes degrades the MFIS performance, nevertheless, they remain sufficiently good for use in organic electronic devices.

Sol-Gel Derived Nano-Magnesium Oxide: Influence of Drying Temperature to the Dielectric Layer Properties

Nano-magnesium oxide (Nano-MgO) had successfully deposited on glass substrate using sol-gel spin coating technique at different drying temperature (100, 200 and 300°C). The dielectric layer properties of deposited nano-MgO films were investigated in terms of its resistivity, leakage current density, relative permittivity, topology and morphology respectively. Changing in drying temperature resulted in variation of nano-MgO films properties and film dried at 200°C has compact, uniform, less porous and in nano size that lead to the enhancement in relative permittivity value.

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.