Advanced Materials Research Vols. 93-94

Abstract: In this report, we present sputtered zinc oxide (ZnO) thin films grown with different argon (Ar) and oxygen (O2) gas-timing sequence. Metallic zinc (Zn) with 5N-purity was used as a sputtering target, while Ar and O2 of 6N-purity were used as the bombard and reactive gases, respectively. The crystalline orientation, surface morphology, chemical composition, optical and electrical properties of deposited ZnO thin films were determined by XRD,AFM and UV-VIS measurement, respectively. The XRD result implied that deposition ZnO thin films at different O2 gas-timing control corresponded to the (002) plane of hexagonal ZnO structure at 2Ө = 34.4◦. Furthermore, when the reactive time of O2 was increased, the transmittance of ZnO thin films exhibited the energy gap increase from ~2.95 to ~3.18 eV, whereas the surface roughness was found to decrease. Finally, ZnO thin films were oxidized after the deposition.

Abstract: The fabricated photonic crystal biosensor device consists of SOG material and titanium dioxide (TiO2) thin films as low and high refractive indexes dielectric layers, respectively. Nano-Imprinting Lithography (NIL) process was used to duplicate periodic line as grating structure from Ni-master mold onto SOG/glass. High refractive index dielectric thin film layer was deposited by using electron beam evaporation system. The surface morphology and thickness of thin film are characterized by atomic force microscope (AFM) and field emission scanning electron microscope (FE-SEM), respectively. The optical measurement system is set up to observed the sensitivity of fabricated device. A shift of reflected peak wavelength observed from DI-water and IPA was tested. The morphology and the thickness of the prepared dielectric thin films are affected to the efficiency of fabricated device.

Abstract: The Ruddlesden-Popper (RP) compounds, Sr3Fe2O7-δ, RP n = 2, were synthesized by citrate gel method. Co was selected as dopant and substituted on Fe-site. Thermal decomposition behaviour and phase analysis of Sr3Fe2-xCoxO7-δ (x = 0 - 1.0) were characterized using Simultaneous TGA-DTA analyzer (STA) and X-ray diffractometer (XRD), respectively. The result showed a single phase obtained from the doped compositions after calcination at 1200°C. The microstructure of sintered compositions characterized using Scanning Electron Microscope (SEM) showed the porous structure as a requirement for anode material. The highest electrical conductivity in this work was obtained from Sr3FeCoO7-δ. The oxidation states of Co in Sr3Fe2-xCoxO7-δ compositions investigated by X-ray absorption near edge structure (XANES) technique were found to be +2 and +3 due to the Co K-edge energies existing between these of Co2+ and Co3+.

Abstract: American foulbrood, European foulbrood, Chalkbrood diseases and the varroa mite are all serious problems for beekeepers. These problem have led to the death of bee larvae and adults and ultimately in many cases severe economic loss. The most common method to treat these problems is through chemical treatments, however, such treatments are not generally acceptable due to the harmful chemical residues for the consumers. Here we pursue an alternative approach using essential oils studied in vitro. Lemon grass oil has been found to be the most effective agent against some microbial diseases and the parasitic mite. In this study we pursue an effective means to deliver the volatile oils by using porous ceramic materials as supporting media. In field trials, we used porous ceramics prepared using diatomaceous earth and activated charcoal as the main starting materials. The amount of activated charcoal was varied at 10, 20, 25, and 42.1 g. to determine optimal adsorption and control emission of the volatile lemongrass oil.

Abstract: Compositions of lanthanum chromite substituted with Sr on the La site and Ni on the Cr site were synthesized by Citrate gel. The suitable calcination temperature of these compositions was 1100°C for 4 hrs to obtain a perovskite phase. The sample bars were formed by cold isostatic press and sintered at 1400°C for 5 hrs in air. The phase, microstructure, electrical conductivity were determined by XRD, dc four-probe as a function of temperature and their chemical compositions were identified by ICP analysis. The result of La0.9Sr0.1Cr0.5Ni0.5O3-δ shows the maximum conductivity of 72.76 Scm-1at 800°C in air. With further addition of Sr dopant, the conductivity of La0.8Sr0.2Cr0.5Ni0.5O3-δ decreases to a value of 54.98 Scm-1. In addition, the structure tends to change from orthorhombic to rhombohedral.

Abstract: Recently, a piezoelectric method using piezoelectric characteristics of epoxy adhesives has been successfully developed for the adhesive joints, which can monitor continuously the damage of adhesively bonded structures without producing any defect induced by inserting a sensor. However, due to low piezoelectric properties of epoxy adhesives, the detection of micro crack was impossible. At the cryogenic temperature, the detection of micro crack is important to estimate the fatigue life because the polymeric adhesives become very brittle. Therefore, in this work, the epoxy adhesive was modified by quartz nano-particles which have much higher piezoelectric properties than the epoxy adhesives. To investigate the effects of quartz nano-particles, the static and dynamic tests of the tubular adhesive joints were performed to compare the joint strength and sensitivity of damage monitoring performance. From the experiment result, it was found that the quartz nano-particles not only improved the joint strength but also increased the sensitivity of damage monitoring performance at cryogenic temperature.

Abstract: La3Ni2O7±δ and La2.9Sr0.1Ni2O7±δ Ruddlesden-Popper nickelate were synthesized via citrate gel method. The electrical property of Mn and Co dopants on Ni site in these systems was investigated as possible cathode for solid oxide fuel cells. The result of X-ray diffraction shows the presence of La2NiO4 in La3Ni2-xMxO7±δ and La2.9Sr0.1Ni2-xMxO7±δ (M = Mn or Co) as M content increases from x = 0.1 for Mn and x = 0.2 for Co. With further increase of Mn dopant (x ≥ 0.4), LaMnO3 and La2O3 appear with La2NiO4. The grain size of sintered sample decreases as Mn content increases. However, it slightly decreases with increasing Co content. The TEC value increases with Co content. The DC four-point measurement shows a decrease in the conductivity as Co content increases for both La3Ni2-xCoxO7±δ and La2.9Sr0.1Ni2-xCoxO7±δ systems.

Abstract: The organic-inorganic hybrid photovoltaic (PV) cells based on cadmium sulphide (CdS) and cobalt phthalocyanine (CoPc) films have been fabricated and characterized their PV performance. This investigated the effects of the organic and inorganic layer thickness on the photovoltaic properties, these thickness was controlled at various values such as 10, 30 and 50 nm. However, the performance of the hybrid photovoltaic cells was depending on the organic layer thickness. The optimize results of PV cell with CoPc 10 nm and CdS 30 nm showed an open-circuit voltage (Voc) = 0.536 V, a short-circuit current density (Jsc) = 0.1020 mA/cm2, a fill factor FF = 0.281 and a power conversion efficiency (η) = 0.01536 % under the AM1.5 conditions. Efficiency is enhanced by 22 times with the addition of a buffer layer, bathocuproine (BCP) 5 nm, the power conversion efficiency (η) value from 0.01536 to 0.34571%.

Abstract: Modified poly(3-hexylthiophene) (P3HT) with molecule of 1,4-dithienyl-2,3,5,6-tetrafluorobenzene in the main chain was developed as a new class of conjugated polymer with high stability. The structural and optical characteristics of modified polymer were investigated by x-ray diffraction (XRD) and optical absorption spectroscopy. By comparing to characteristic of P3HT, the XRD pattern of modified polymer showed the diffraction peak shifted from theta of 5.4o to 5.9o with decrease intensity. This indicates that the modified polymer chain has a reducing in structural coplanarity and crystallinity. Since the electrical property can be related to the morphology and structure of thin film, the electrical conduction of modified polymer was studied with the structure of ITO/modified P3HT/Al. The result of I-V characteristic measurement of modified polymer as a function of temperatures showed that the conductance decreased with decreasing temperature. The mobility of copolymer was also evaluated by using time of flight measurement and mobility value of 5x10-4 cm2/Vs was obtained at room temperature.

Abstract: Titanium nitride (TiN) film has been widely used as a diffusion barrier layer for VLSI contact metallization because TiN is an excellent barrier against inter-diffusion between Al and Si substrate or silicide. In this work, we studied the properties of TiN films deposited by DC magnetron sputtering with varying N2:Ar flow rate ratio in order to optimize growth conditions and film properties provided for Al diffusion barrier purpose. The TiN films were deposited at the constant pressure level and sputtering time. The crystalline orientation, composition and electrical properties of deposited TiN films were characterized by XRD, AES-depth profile and Four Point Probe measurement, respectively. The XRD results show that the deposited TiN film has two preferred orientations of TiN(111) and TiN(200) planes. The highest intensity of the TiN(111) plane was obtained when the N2:Ar flow rate ratio was 3:1. The electrical resistivity was increased when the N2:Ar flow rate ratio was decreased. The minimum electrical resistivity is 127.8 μΩ-cm when the N2:Ar flow rate ratio is 3:1.