Wan Haliza Abd Majid

Electrical Characterization of Gold-DNA-Gold Structures in Presence of an External Magnetic Field by Means of I–V Curve Analysis

This work presents an experimental study of gold-DNA-gold structures in the presence and absence of external magnetic fields with strengths less than 1,200.00 mT. The DNA strands, extracted by standard method were used to fabricate a Metal-DNA-Metal (MDM) structure. Its electric behavior when subjected to a magnetic field was studied through its current-voltage (I–V) curve. Acquisition of the I–V curve demonstrated that DNA as a semiconductor exhibits diode behavior in the MDM structure. The current versus magnetic field strength followed a decreasing trend because of a diminished mobility in the presence of a low magnetic field. This made clear that an externally imposed magnetic field would boost resistance of the MDM structure up to 1,000.00 mT and for higher magnetic field strengths we can observe an increase in potential barrier in MDM junction. The magnetic sensitivity indicates the promise of using MDM structures as potential magnetic sensors.

Degradation of Single Layer MEH-PPV Organic Light Emitting Diode (OLED)

The degradation process of a single layer electroluminescence (EL) polymer MEH-PPV organic light emitting diode (OLED) with the MEH-PPV thickness of 57plusmn3 nm is discussed. Typical structure of OLED fabrication is Al/MEH-PPV/ITO (indium tin oxide). Electroluminescence (EL) spectrum indicates that the emission of MEH-PPV device is the yellow orange color. The device degrades by days as demonstrated by the increased in the turn on voltage obtained from I/V curves. The scanning electron microscope (SEM) images show some bubbles emerge on the surface of the device after an electric field was applied to it.

DNA Strand Patterns on Aluminium Thin Films

A new patterning method using Deoxyribose Nucleic Acid (DNA) strands capable of producing nanogaps of less than 100 nm is proposed and investigated in this work. DNA strands from Bosenbergia rotunda were used as the fundamental element in patterning DNA on thin films of aluminium (Al) metal without the need for any lithographic techniques. The DNA strands were applied in buffer solutions onto thin films of Al on silicon (Si) and the chemical interactions between the DNA strands and Al creates nanometer scale arbitrary patterning by direct transfer of the DNA strands onto the substrate. This simple and cost-effective method can be utilized in the fabrication of various components in electronic chips for microelectronics and Nano Electronic Mechanical System (NEMS) applications in general.

Current-Voltage Characterization on Au-DNA-Au Junctions under the Influence of Magnetic Field

We utilized Deoxyribonucleic acid (DNA) strands immobilized between a metal gap and its behavior was investigated. The DNA strands were initially prepared using the PCR method while gaps of 10.00 μm lengths were created on gold layer deposited onto silicon substrate. Once immobilized, current-voltage characterization was carried out on the Au-DNA-Au structure fabricated under the presence and absence of magnetic field. Experimental results clearly highlight the behavior of the DNA strands similar to semiconductor materials. An exponential decrease observed in the current in presence of external magnetic field suggests possible future application as a magnetic sensor.

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.

Ligand-Stabilized ZnO Quantum Dots: Molecular Dynamics and Experimental Study

Different aminoalcohol ligands, monoethanolamine (MEA), diethanolamine (DEA) and triethanolamine (TEA) were employed to passivate the surface of ZnO quantum dots (ZnO QDs). High-resolution transmission electron microscopy (HRTEM) imaging revealed that the higher branched aminoalcohols produced smaller sized ZnO QDs. The average size for ZnO/MEA, ZnO/DEA, and ZnO/TEA were found to be 3.2, 2.9, and 2.4 nm. TEA ligands were effective in producing stable, monodisperse ZnO QDs compared with DEA and MEA ligands. Molecular dynamics and semi-empirical calculations suggested that TEA and DEA ligands interact strongly with the partial charge of ZnO dangling bonds and have a large molar volume to hinder the diffusion of precursors through the ligands to the surface of ZnO resulting in a smaller particle size as compared with MEA ligands. As the size of ZnO QDs decreases from ZnO/MEA to ZnO/TEA, the absorption edge and emission peak maximum blue-shifts to a shorter wavelength due to the quantum size effect. The bandgap of ZnO/MEA, ZnO/DEA, and ZnO/TEA was determined to be 3.97, 4.07, and 4.23 eV, and the emission peak was found to be 472, 464, and 458 nm when excited using a 325 nm excitation wavelength, respectively.

Structural and Optical Properties of Nickel-Doped and Undoped Zinc Oxide Thin Films Deposited by Sol-Gel Method

ZnO thin films with and without Ni-doping were successfully deposited by sol-gel method with zinc acetate dihydrate as inorganic precursor, and nickel (II) acetate tetrahydrate as dopant. The solutions were prepared by dissolving zinc acetate and nickel (II) acetate in ethanol and diethanolamine (DEA) as its chelating agent. Thin films were fabricated by using spin-coating method on glass substrates. ZnO films were obtained by pre-heating and post-heating at 300 °C for 10 minutes and 500 °C for 1 h respectively. The films were analyzed by X-ray diffraction (XRD), UV-Vis transmittance and photoluminescence (PL). All samples exhibit high transparency in visible. Ni dopant does not alter so much ZnO structure, which due to the ion substitution between Ni and Zn. However, the Ni tends to create a dopant energy interlayer in ZnO energy band gap which cause significant change in PL intensity.

Pyroelectric Properties of Polyvinylidene Fluoride (PVDF) by Quasi Static Method

Our main objective is to investigate the behavior of polyvinylidene fluoride (PVDF) polymers when they are subjected to electric field in different temperature range. Initially, the PVDF powders were dissolved in acetone with different concentration and the PVDF films were then prepared by spin coating technique. The pyroelectric coefficients, p was calculated by using the quasi static method with different heating rates. The PVDF thin films prepared from different solution concentrations exhibit different pyroelectric coefficients. The results show that the difference solution concentrations of the sample and temperature heating rates will influence the value of pyroelectric coefficient.

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.

Investigations on Fractal Nanostructure of Zinc Oxide by Small Angle Neutron Scattering (SANS)

The zinc oxide nanoparticles were synthesized by solvothermal method for 18 h at150 ̊ C with presence of DEA. The molar ratio of Zn2+ solution and DEA was fixed at 1:1. The nanostructure was studied using Small Angle Neutron Scattering (SANS) in BATAN, Indonesia. From calculation, it shows that the material has surface fractal with primary particle size of 25 nm and agglomerate size of ̴ 200 nm. X-ray diffraction (XRD) was done and the the crystallite size was calculated using Scherrer equation. Field emission electron microscopy (FESEM) was done to observe the morphological structure. It shows that the sphere-like agglomerates construct of primary nanoparticles of ZnO.