Advanced Materials Research Vol. 667

Abstract: Abstract. The 30 nm wide quantum wells on a 4x4 mm2 piece of GaAs/AlGaAs are formed when the layers of GaAs are deposited on AlGaAs films. The two-dimensional density of electrons is 3x1011 cm-2 and the mobility is 32x106 cm2/Vs. In such a sample the Hall resistivity as a function of magnetic field is not a linear function. Hence a suitable theory to understand the Hall effect is formulated. We find that there are phase transitions as a function of temperature. There are lots of fractions of charge which are explained on the basis of spin and orbital angular momentum of the electron. The nano meter size films of graphite also show that the Hall resistivity is non-linear and shows steps as a function of magnetic field. We make an effort to understand the steps in the Hall effect resistivity of graphite with quantum wells formed on the surface. It is found that the fractions are in four categories, (i) the principal fractions which are determined by spin and orbital angular momenta, (ii) the resonances which occur at the difference between two values such as =1-2, (iii) two-particle states which occur at the sum of the two frequencies and (iv) there are clusters of electrons localized in some areas of the sample. The spin in the clusters is polarized so that it becomes NS which is not 1/2 but depends on the number N, of electrons in a cluster.

Abstract: Sea bed logging (SBL) is a new technique for detection of deep target hydrocarbon reservoir. Powerful electromagnetic (EM) transmitter is required for the transmission of EM signal underneath the seabed. New aluminum transmitter with yttrium iron garnet (Y₃Fe₅O₁₂) based magnetic feeders was used in a scale tank to increase the magnitude of the magnetic field. Yttrium iron garnet samples were prepared using self combustion technique at different sintering temperatures of 750°C, 950°C and 1150°C. Characterizations of Y₃Fe₅O₁₂ samples were done by using XRD, RAMAN, FESEM and Impedence network analyser. X-ray diffraction results revealed that yttrium iron garnet phase with good crystallinity appeared at sintering temperature of 1150°C. Nanoparticles size ranging from 60 to 110 nm was investigated. Raman results also confirmed garnet structure of yttrium iron garnet at sintering temperature of 1150°C. Field emission scanning electron microscopy (FESEM) was used to image the morphology of the Y₃Fe₅O₁₂ nanoparticles. Magnetic properties of Y3Fe5O12 magnetic feeders illustrates that Y₃Fe₅O₁₂ has high Initial permeability (58.054), high Q-factor (59.842) and low loss factor (0.0003) at sintering temperature of 1150°C. Y₃Fe₅O₁₂ magnetic feeders with high Q factor were chosen for new aluminum EM transmitter. Experiments with a scale factor of 2000 were carried out in scaled tank. It was found that Al transmitter with Y₃Fe₅O₁₂ magnetic feeders increased magnitude of magnetic field strength up to 180%.

Abstract: The effect of annealing temperatures on the Zinc Oxide (ZnO) thin films properties has been investigated. 1.0 M ZnO solution was prepared by sol-gel method as coating solution for ZnO thin films deposition process. The thin films deposition was conducted by spin-coating technique on the silicon and glass substrates. The scanning electron microscopy (SEM) images reveal the evolution of ZnO surface morphology with annealing temperatures. The crystallinity improvement occurred at higher annealing temperature as shown by x-ray diffraction (XRD) result. The optical properties found to be varied at different annealing temperatures. The current-voltage (I-V) measurement results suggested the improvement of ZnO thin film electrical properties with annealing temperatures.

Abstract: Carbon nanotubes (CNTs) are said to be among the most potential materials in applications of nanodevices, nanocomposites and nanostructure due to their excellent mechanical and physical attributes. CNTs were first discovered by S. Iijima in 1991 where he has reported in his article the synthesis of needle-like tubes by using an arc-discharge evaporation. After the immense discovery, the number of research on CNTs has increased significantly, focusing on their mechanical characteristics, dynamics properties and applications in nanotechnology. This paper attempts to present a review of a quite number of publications on CNTs and their dynamic properties. The main topics covered in this review are the applications of CNTs, their dynamic characteristics including the modeling and simulation of vibrating CNTs, and finally the vibration modes of CNTs.

Abstract: Carbon nanotubes (CNTs) are said to be among the most potential materials in applications of nanodevices, nanocomposites and nanostructure due to their excellent mechanical and physical attributes. CNTs were first discovered by S. Iijima in 1991 where he has reported in his article the synthesis of needle-like tubes by using an arc-discharge evaporation. After the immense discovery, the number of research on CNTs has increased significantly, focusing on their mechanical characteristics, dynamics properties and applications in nanotechnology. This paper attempts to present a review of a quite number of publications on CNTs and their dynamic properties. The main topics covered in this review are the applications of CNTs, their dynamic characteristics including the modeling and simulation of vibrating CNTs, and finally the vibration modes of CNTs.

Abstract: This paper reports on the results of Yb substitution for Ca on the superconductivity and structural properties of Bi_1.6Pb_0.4Sr₂Ca_2-xYb_xCu₃O_y superconducting samples with x = 0.000, 0.025, 0.050, 0.100 and 0.200 which prepared by coprecipitation (COP) method. The samples were characterized by X-ray diffraction (XRD), field-emission scanning electron (FESEM), electrical and resistivity measurement by four-probe method. It was found that the substitution of Yb decreased the critical temperature (T_{c zero}), critical current density (J_c) and volume fraction of Bi-2223 phase. The samples have T_{c zero} in the range 77 to 100 K. T_{c zero} gradually decreased with an increase in Yb concentration, corresponding to small change of the carrier concentration. J_c was measured to be 5.7512 A/cm² for pure sample and decreased to 4.1910 A/cm² for x = 0.025 at 77 K. The crystallographic structure was found to change slightly from tetragonal to orthorhombic in Yb substituted samples. The lattice parameter c of Yb samples decreased due to the incorporation of Yb³⁺ (0.858 Å) with smaller ionic size compare to Ca²⁺ (0.99 Å). From the SEM observation, the grain connectivity became weak with smaller plate-like grain for x > 0.025 Yb concentration resulting in the decreased of J_c.

Abstract: The synthesis of Cadmium Selenide (CdSe) by using wet chemical synthesis replace organometallic method. The oleic acid using as the capping agent for CdSe nanocrystals. Paraffin liquid using as solvent for Se and Cd precursor. In this paper, the optical properties at different time was investigated. For optical properties, photoluminescence spectroscopy (PL) was used and for surface morphology field emission scanning electron microscope (FESEM). This paper describe the effect of CdSe properties at different certain time.

Abstract: There are continuous interests worldwide in zeolites and we can see it with increasing number of scientific publications of the zeolite. Zeolite is an inorganic material that has very special properties over it. They are characterized by framework structures with uniform pore and channel systems. The term zeolite can be defined as hydrated aluminosilicates belonging to the family of the tecto – silicates, whereas the SiO4 tetrahedral are from three – dimensional super cages. Therefore, the aim of this paper is to study about commercial synthetic zeolite that purchased from Fluka. The results cover by Field Emission Scanning Electron Microscopy (FESEM), Fourier Transform Infrared Spectroscopy (FTIR) and X-ray diffraction (XRD).

Abstract: Titanium dioxide, TiO₂ is one of the semiconductor materials that can be produced in many ways, such as magnetron sputtering, CVD, and sol-gel process. This paper studied on the production of TiO₂ by sol-gel method using titanium tetra (IV) isopropoxide, TTiP. The solution of TiO₂ then deposited as a thin films onto glass substrate by spin-coating method. The purpose of this paper is to investigate the effect of molarity on the morphology, optical and electrical properties of the thin films. The effect on the morphology was observed by AFM. The electrical properties then observed by IV characteristic and finally on the optical properties were investigated by UV-Vis. The transmission obtained from UV-Vis showed that TiO₂ thin films are decreased around 18% at higher molarity in a visible region. The bandgap also decrease at high molarity. Higher molarity of TiO₂ in current-voltage characteristic gave a value of current density for 1.03×10-4 A/m2 and resistivity 1.95×107 Ωm.