Papers by Author: Mohamad Rusop Mahmood

Abstract: The enhancement of ferroelectric and dielectric properties of PVDF-TrFE by incorporating various percentages of Magnesium Oxide (1 – 7%) for spin coated nanocomposite thin film was demonstrated. Observations showed uniform distribution and low agglomeration of MgO in the PVDF-TrFE nanocomposite thin film, especially for 3% MgO. Additionally, the 3% MgO incorporated into PVDF-TrFE had generated the highest P_r (88 mC/m²) and dielectric constant (13.6) in comparison other percentage compositions. However, the addition of more than 3% MgO filler loading caused a reduction in the ferroelectric and dielectric properties of the nanocomposite thin films.

Abstract: Pure amorphous Carbon (a-C) thin films had been deposited by Aerosol-Assisted CVD (AACVD) onto glass substrate in Argon atmosphere. The camphor oil was chosen as the carbon precursor to prepare the a-C thin films with the deposition time of 15 minutes, 30 minutes, 45 minutes, 60 minutes and 75 minutes. The electrical, optical and structural properties of the deposited a-C were discussed by using the current-voltage solar simulator system, UV-Vis-Nir spectrophotometer and Raman spectroscope respectively. For the electrical characterization, the samples showed the photoresponse performance when being illuminated under AM 1.5 illuminations: 100 mW/cm², 25°C. Transmittance value for the a-C thin films was also considered high ~80% and the structural analysis by using Raman spectroscope exhibit two main peaks known as the D-peak and G-peak which is typical for the a-C.

Abstract: The annealing temperature for 250 nm PVDF-TrFE (70:30 mol %) spin coated thin films were varied at solvent evaporation (T_s = 79 °C), Curies transition (T_c= 113 °C₎, till melting temperature (T_m = 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.

Abstract: The annealing temperature of 250nm PVDF-TrFE (70:30 mol%) spin coated thin films were optimized. The annealing temperature were varies starting from solvent evaporation (T_s), Curies transition (T_c), up to melting temperature (T_m). The result shows that the dielectric constant increases with the increasing of annealing temperature. Supported with the XRD observation indicating there were an improvement in crystallinity consistently with the increasing of the annealing temperature. Morphological properties of the annealed PVDF-TrFE thin films were observed by utilizing Field Emission Scanning Electron Microscope (FESEM) at 100k magnification. It can be found that, the annealing temperature promotes the development of elongated crystallite structure which known as ferroelectric crystal. However, the presence of nanoscale cracks on the thin film annealed at 160°C (AN160, over T_m) suggesting high possibility to posed defects while in device applications.

Abstract: 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.

Abstract: Multi-walled carbon nanotubes/natural rubber (MWCNTs/NR) nanocomposites is formed by incorporating nanotubes in a polymer solution and subsequently evaporating the solvent. Using this technique, nanotubes will be dispersed homogeneously in the NR matrix in an attempt to increase the mechanical properties of these nanocomposites. Mechanical test results show an increase in the tensile strength for up to 19 times in relation to pure NR. In addition to mechanical testing, the morphology of the MWNTs into NR was studied by Field Emission Scanning Electron Microscopy (FESEM) in order to understand the morphology of the resulting system. Slight shift noted from FTIR and Raman analyses from each different wt. % of MWCNTs with the NR due to the stress transfer that indicates reinforcement of the nanotubes.

Abstract: Nano-MgO thin films were grown on the cleaned glass substrate via sol-gel spin coating techniques using magnesium acetate tetrahydrate, ethanol and nitric acid. For the thin films deposition, the solutions were prepared at six different molar concentrations (0.1M, 0.2M, 0.4M, 0.6M, 0.8M and 1M). The thickness and roughness of nano-MgO films was found to be increased with an increase of molar concentration. The increment in particle size and agglomerated particles were observed from FESEM (JEOL JSM-J600F) images as the molar concentration increased from 0.1M to 1.0M. The results showed 0.4M nano-MgO films have the best properties for example it has a uniform film, non-porous structure and has nanometer dimension size which around 42.8nm.

Abstract: In this study, a novel approach of using two different methods was investigated to prepare the CuI thin films. The CuI thin films in this research were prepared by spin coating method and by mister atomizer. Both methods used CuI powder as a precursor and acetonitrile as a solvent. The thickness of CuI films in this research range from nm – um thickness depending on the deposition technique. The 2 point probe I-V measurement was used to measure the electrical properties. The resistivity of about 10⁶ Ω cm-10¹ Ω cm was observed with CuI thin films using spin coating technique. Then, the surface morphology shows all the films exhibit a microsturucture CuI particles in a case of mister atomizer method. For optical measurement, the ultraviolet-visible- near infrared (UV-VIS-NIR) measurement (Perkin Elmer Lambda 750) was used. The optical band gap of about ±3.1 eV and ±2.9 eV were observed in those CuI films. These properties of different technique are applicable for application in electronic devices such as in solar cells.

Abstract: Align Carbon Nanotubes (A-CNTs) is very promising materials and offer attractive applications especially in opto-emission devices and nanoelectronic. Normally CNTs prepared by catalytic chemical vapor deposition using various types of template such as alumina, quartz, silicon and glass template. In this paper, Novel method was introduced to prepare A-CNTs which is combination between immersion and evaporation method. The align CNTs were successfully growth on Porous Silicon template (PSiT) without catalyst. Camphor oil is used as precursor and evaporation temperature is at 800 °C. The PSiT was prepared by photo-electrochemical anodization method. The surface morphology of PSiT layer and A-CNTs were studied using Field Emission Scanning Electron Microscope (FESEM).While Raman spectroscopy will be carried out to study the degree of crystallinity or graphitization of A-CNTs. The growth mechanism will be discussed in this paper. Stubby A-CNTs was successfully growth with 30 nm diameter and 250 nm length on PSiT without metal catalytic process. Meanwhile, this novel technique was found that PSiT is an ideal template for growing A-CNTs without metal catalyst assisted. This novel technique was capable to obtained carbon nanotubes without metal catalyst assisted and improves their purity of product with low cost.

Abstract: Finding on the one-dimensional purified aligned carbon nanotubes (ACNT) was prepared using botanical hydrocarbon: camphor powder in a two-stage catalytic chemical vapor deposition will be presented. For the first time, the hydrocarbon source and catalyst were patterned in different alumina boats in the system. The growth of ACNT has achieved free standing formation with higher aspect ratio. In contrast, unpurified carbon nanotubes have some drawbacks and require some treatments to fully utilize their capabilities in various applications. The results reveal that the crystallinity and purity of functionalized align carbon nanotubes was increased after wet-chemical technique and heat treatment process. In this paper, the results provide evidence showing that it was in good agreement with the field emission scanning electron microscopy, micro-Raman and thermogravimetric analysis.