Wan Mohd Daud Wan Yusoff

Structural, morphology and electrical properties of layered copper selenide thin film

Thin films of copper selenide (CuSe) were physically deposited layer-by-layer up to 5 layers using thermal evaporation technique onto a glass substrate. Various film properties, including the thickness, structure, morphology, surface roughness, average grain size and electrical conductivity are studied and discussed. These properties are characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), ellipsometer and 4 point probe at room temperature. The dependence of electrical conductivity, surface roughness, and average grain size on number of layers deposited is discussed.

Influence of Erbium Doping on Dielectric Properties of Zinc Borotellurite Glass System

Glasses of the system {[ (TeO2)70 (B2O3)30]70 (ZnO)30}100-y (Er2O3)y containing different concentration of Er2O3 (ranging from 0 to 5 mol %) was prepared from melt-quenching technique. The structural changes were studied by XRD analysis and FTIR analysis. The XRD pattern shows the glasses are amorphous. The higher concentration of Er2O3, the more unit of TeO3 would transform to TeO4 and formation of B-O vibrational groups. The density and molar volume was obtained attribute to non-bridging oxygen (NBO) and are found the density and molar volume of the glass system are increasing. The densities range from 3630 kg/m3 to 3960 kg/m3. The dielectric constant ε’ and dielectric loss factor ε’’ which were characterized in the frequency range 10-2 – 106 Hz over temperature range 50°C – 200 °C, show a larger value at lower frequency and higher temperature (above 110°C ). The results of dielectric response measurement show that interfacial polarization at low frequency, and orientation polarization at intermediate and high frequency.Keywords: Dielectric properties; Activation Energy; Rare Earth; Polarization; Non-Bridging Oxygen;

Dielectric and Conduction Processes and Behaviours in Ni0.3Zn0.7Fe2O4

Dielectric relaxation and conductivity of Ni0.3Zn0.7Fe2O4 (NZF) were studied in the frequency range between 0.01 Hz to 3 MHz and temperature range within 313 K to 473 K. The sample was prepared by mixing Zinc Oxide, Nickel Oxide and Iron Oxide and sintered at 1573 K for 10 hours long. Dielectric properties were studied using Novo Control Dielectric Spectrometer. Dielectric relaxation and conductivity phenomena were discussed using an empirical model to key out the dielectric relaxation process. Analyze peak frequency relaxation process consist of four slopes to explain the dielectric relaxation process. The conductivity of the sample indicates an activated process and activation energy of dc conductivity is 0.44 ± 0.01 eV.

Magnetoresistance studies of metallic granular and ceramic thin films for microsensor applications

Thin films of granular metal and manganites ceramic were fabricated using RF magnetron sputtering and pulsed laser deposition techniques. The GMR effect is highly influenced by the shape, size and distribution of the magnetic entities. The highest GMR value of 7.6% for Ag/sub 87.0/Fe/sub 9.5/Co/sub 3.5/ granular film measured at 1 Tesla at room temperature had been obtained. In the polycrystalline manganites system, low-field magnetoresistance (LFMR) had been observed due to the grain boundaries. LFMR of 4.3% and 6.2% measured at 0.1 Tesla at room temperature have been observed for both La-Sr-Mn-O and La-Ba-Mn-O samples. For the La-Sr-Mn-O film, LFMR ratio of 4.5% has been observed. This value meets the requirement as sensor element and it is currently used in many applications such as head sensing in hard disk.

Effect of Pr substitution on magnetoresistance in La/sub 2/3/Ba/sub 1/3/MnO/sub 3/ perovskite

Polycrystalline of (La/sub 1-x/Pr/sub x/)/sub 0.67/Ba/sub 0.33/MnO/sub 3/ with x = 0, 0.167, 0.33, 0.5, 0.67, 0.833, 1 have been prepared using solid state reaction. The effect of substituting praseodymium at La-site on magnetoresistance (MR) effect has been investigated. The electrical property, was determined by using standard four-point probe resistivity measurement in a temperature range of 30 K to 300 K. Metal-insulator transition temperature (T/sub p/) shifted to lower temperatures with the increases of Pr doping with the value of >300, 270, 250, 226, 202, 186 and 158 K for x = 0, 0.167, 0.33, 0.5, 0.67, 0.833, 1, respectively. Overall, MR drops slowly when temperature rises. All doping concentration give small variation range (5% to 25%) except for x=1.0, where this sample show significantly higher MR value at all temperature as compared to other samples. The highest MR value of 38% is observed at 270K. In the semiconducting portion, activation energy (E/sub a/) has been investigated. The E/sub a/ increases as the doping concentration increases.