Solid State Phenomena Vol. 290

Abstract: Studies and production of anodic exfoliated graphene have been blossoming exponentially to meet the high demand for next generation optoelectronics devices. In this study, the effect of sulfate concentration on the graphene film is presented. The electrochemical exfoliation was conducted using a simple two-electrode system to study on the morphological and optical properties of graphene films using Atomic Force Microscope (AFM), Raman Spectroscopy and Ultraviolet–Visible (UV-Vis) spectrophotometer. Preliminary results show the presence of few layers graphene with nanometer-scale lateral dimension. The study suggests an alternative solution for the large-scale manufacturing capabilities of graphene is feasible

Abstract: In this study, aluminum nitride (AlN) thin films were grown on p-type silicon (100) substrate by sol-gel spin coating method. Two types of ethanol-based precursors were prepared, namely, precursors with and without the aid of diethanolamine (DEA). The objective of this work is to investigate the effects of the DEA on the surface morphology, structural and optical properties of the deposited thin films. The coating films were undergone nitridation process under ammonia ambient at 1100 °C for 60 min. The surface morphology and structural properties of the deposited AlN thin films were investigated by X-ray diffraction (XRD) and atomic force microscopy (AFM). XRD results revealed that both samples have AlN (100) preferred orientation. In addition, the crystallinity of sample without the aid of DEA is higher compared to the sample prepared with DEA. While, the AFM results showed that both samples have uniform and smooth surface. The optical properties of AlN thin films was investigated by Raman spectroscopy. For sample without DEA, Raman results showed the present of wurtzite AlN characteristics phonon modes of E₂(high) and A₁(LO) at 660 cm^-1 and 892 cm^-1, respectively. Whereas only E₂(high) is observed for sample with the aid of DEA. Finally, all the results revealed that the present of DEA has a strong influence on the properties of deposited AlN thin films and film prepared without DEA have better quality.

Abstract: In this report, indium nitride (InN) thin films were deposited on kapton polyimide flexible substrate by reactive radio frequency (RF) sputtering method using an indium target in a mixture of Ar and N₂ gases. The effects of the Ar:N₂ gas ratio on the properties of the deposited InN thin films were investigated by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), and energy dispersive (EDX) spectroscopy. The XRD revealed that the deposited films composed of polycrystalline wurtzite InN. The FESEM and AFM surface morphologies showed smooth and uniform surface of gas ratio at 60:40 compare to others gas ratio. Overall, the characteristics of the InN thin films were effectively improved with combination the N₂:Ar gas ration at 60:40. The results showed that the gas ratio plays an important role in improving the properties of the InN thin films.

Abstract: Abstract. In an effort to successfully fabricate InGaN-based for green emitting devices on patterned sapphire substrate, the indium composition in In_xGa_1-xN/GaN multi-quantum well structure is crucial because lower indium composition will shift the wavelength towards ultraviolet region. In this study, 5 micrometre of undoped GaN epilayer was deposited as a buffer layer prior to the growth structure. 6 pairs of InGaN/GaN multi-quantum well structure grown by metal organic chemical vapour deposition (MOCVD). In this research, the indium to gallium composition ratio was 9:1. The crystal and optical properties of the samples were characterized using field effect atomic force microscopy, high resolution x-ray diffraction, and photoluminescence spectroscopy.

Abstract: The study highlights the effects of growth temperatures ranging from 500 to 650 °C on the properties of indium nitride (InN) thin films prepared by sol-gel spin coating method followed by nitridation, also, the growth mechanism was studied in depth. The findings revealed that the InN crystal growth was promoted at the growth temperature of 600 °C, by which the crystalline quality of the deposited thin films was improved and the densely packed InN grains were formed. However, thermal decomposition of InN was observed at increasing temperature to 650 °C. Apart from that, the infrared (IR) reflectance measurement shows the presence of transverse and longitudinal-optical phonon modes of wurtzite structure InN. These vibrational modes were found to be slightly shifted from the theoretical values as a result of the incorporation of oxygen contamination in the deposited thin films.

Abstract: Pulsed laser deposition (PLD) method has the advantages of high quality mirror finish, good densification and uniform thickness. In this work, Al₂O₃ thin films with different thicknesses were fabricated via the PLD method. The characteristics of the thin film samples were investigated using Grazing Incidence Diffraction (GID) technique and Field Emission Scanning Electron Microscope (FESEM). For the band gap studies, measurements were done using a UV-Vis NIR spectrophotometer. The deposition was done in the presence of oxygen gas with partial pressure of 2.66 Pa. FESEM images showed high quality, smooth and dense films obtained using the PLD method. The Al₂O₃ thin films have thicknesses of between 71.2 nm to 176 nm. The band gap energies obtained were in the range of 6.29 eV to 6.49 eV. It was observed that the band gap of the thin films increases as the thickness decreases due to the defects in the films.

Abstract: A facile, rapid, and noninvasive method for reconstructing ZnAl layered double hydroxide (LDH) is reported. ZnAl LDH series were synthesized at different Zn²⁺/Al³⁺ atomic ratio (1.5-4) via an alkali-free method and reconstructed under hydrothermal route (HTM) for the first time. Fresh Zn/Al LDHs were activated at 300°C and reconstructed under hydrothermal process. A better insight and correlation study between the physiochemical properties of reconstructed ZnAl LDH in terms of their crystallinity, surface area and basicity also will be gained here. BET surface area of rehydrated samples increased up to 355 m²/g (Zn:Al ratio 3:1). CO₂-TPD probed high number of basic sites density (0.1 mmol/g).

Abstract: Chitosan-Starch blend biopolymer electrolyte system doped with different percentage of BMIMNO₃ was prepared via solution casting technique. The crystalinity of the system was calculated using data extracted from x-ray diffraction (XRD). The film was characterized by impedance spectroscopy HIOKI 3531-01 LCR Hi-Tester to measure its ionic conductivity over a wide range of frequency between 50Hz-5MHz and at temperatures between 298 K and 378 K. The result exhibit the advantages of ionic liquid as a charge carrier and also revealed that addition of 5% of BMIMNO₃ shows the highest conductivity of (2.26 +-0.96) x 10^-4 Scm^-1 .Conductivity-temperature relationship indicate that the system seems to obey the Vogel-Tamman-Fulcher (VTF) behaviour.

Abstract: In thus study, Turmeric phosphor dye was extracted from Curcuma Longa L. via a simple technique using silica gel. The phosphor was used for light down-conversion of UV light for the manufacture white light emitting diode (WLED). The UV-LED was analyzed over 395nm wavelengths. The characteristics of the white light chromaticity were controlled by tuning the current and phosphor concentration. An optimum color rendering index (CRI) value of 63.4 was obtained. The chromaticity coordinates (CIE) and correlated color temperature (CCT) were measured for various currents and phosphor concentrations. The white phosphor exhibited CIE value of 0.355,0.338 and CCT of 4567 K. The concentration of phosphor and amount of applied current were confirmed to be major factors that control the intensity of white light emitted from the sample, where CIE and CRI of the emitted light steadily increased with the concentration of phosphor and current. Thus, phosphor concentration has a critical effect on conversion efficiency. Key words: Turmeric, phosphor, WLED, curcumin

Abstract: Phosphate buffer saline (PBS) is commonly applied as an electrolyte for glucose sensor application because ion concentration and osmolality of PBS are similar to the human body. Therefore, it is important to study the effect of concentration and pH of PBS to the electrocatalytic performance of the modified electrode in glucose detection. In this study, the modification of indium tin oxide (ITO) glass electrode by utilizing iron oxide nanoparticles (IONP) coated with citric acid (CA), glucose oxidase (GOx) enzyme and Nafion layer (Nafion/Gox/IONP-CA/ITO) were performed. IONP was prepared by using the precipitation technique through formation of colloidal stable IONP in water at physiological pH. The size of IONP-CA precipitates was ~19 nm with maghemite (γ-Fe₂O₃) phase characterized using transmission electron microscopy (TEM) and X-ray diffraction (XRD), respectively. Increasing the PBS concentration increased the electrocatalytic performance of the bioelectrode whereas pH of PBS buffer solution affected the GOx bioactivity. The modified electrode Nafion/Gox/IONP-CA/ITO displayed good electrochemical and electrocatalytic performance in glucose detection.