Advanced Materials Research Vol. 832

Abstract: In the present study, ITO nanocolumn was successfully deposited onto a glass substrate by RF magnetron sputtering. The effect of deposition pressure was investigated. X-ray diffraction analysis indicates that the intensity of the (400) peak orientation is highest at sputtering pressure of 5 mTorr. The results from UV-visible (UV-vis) spectroscopy revealed that the optical transmittance above 80 % was obtained from the all samples in the visible range of 400-800 nm. The larger grain size was observed from the top view of field emission scanning electron microscopy (FESEM) image as the sputtering pressure was increase. Dense nanocolumn arrays were obtained from the sample deposited at sputtering pressure of 5 mTorr. The surface roughness were decreased at high sputtering pressure of 10 mTorr was observed from atomic force microscopy (AFM) surface morphology. The electrical properties were obtained using standard two-point probe measurements. The lowest electrical resistivity was determined from the sample that prepared at sputtering pressure of 5 mTorr.

Abstract: Indium tin oxide was prepared using RF magnetron sputtering at different substrate temperature. The morphological and electrical properties were investigated. Morphological properties were observed by atomic force microscopy. Electrical properties were measured using standard two-point probe measurements. The result shows that the average roughness and peak to valley value are highest at high substrate temperature. The watershed analysis shows that the total grain boundaries are highest at the substrate temperature of 200°C. The lowest resistivity value of 9.57×10^-5 Ωcm is obtained from ITO nanocolumn deposited at substrate temperature of 200°C. The improvement of morphological and electrical properties as transparent conducting oxide was observed from ITO nanocolumn deposited at substrate temperature of 200°C.

Abstract: Carbon nanotube (CNT) has been synthesized using camphor oil as a starting material via two-stage catalytic chemical vapor deposition. The as-synthesized CNT was then incorporated into acrylate matrix by suspension polymerization method, using various loading of CNT (as a filler) varied from 0.2 to 1.0 g with 0.2 g weight interval in the nanocomposite thin film. The acrylate/CNT nanocomposite thin film was characterized using micro-Raman, ultraviolet-visible and impedance spectrometer. As confirmed, the various loading of CNT had a significant impact on structural, optical and impedance characteristics. The paper contributes the recent achievements in material progress of CNT/polymer nanocomposite.

Abstract: Intrinsic graphene is defined as a one-atomic-thick planar film of sp²-hybridized carbon atoms which are densely packed in a hexagonal crystal lattice structure. This material has opened up a host of possibilities with its extraordinary properties and is expected to be utilized in many practical applications. This article reviews the recent advances in growth techniques for the production of graphene. The main characterization techniques for graphene are highlighted. Finally, the critical issues relating to potential health risk, safety and toxicity of graphene have also been highlighted.

Abstract: In this research, we fabricated UV photoconductive sensor using aluminium (Al)-doped ZnO nanorod-nanoflake network thin film. These nanostructures were deposited on the seed-layer-coated glass substrate using sonicated sol-gel immersion method. By using Al contacts, it was found that the performance of the UV photoconductive sensor is very good. The responsivity of the device was 46.4 mA/W with sensitivity of 17.5 under 365-nm UV light (5 mW/cm²) at bias voltage of 10 V. Our study revealed that these nanostructures are very promising material for the UV photoconductive sensor applications.

Abstract: In this research, we prepared aluminium (Al)-doped ZnO nanorod arrays on the glass substrate using sonicated sol-gel method. These nanorod arrays were annealed at 500 °C in air and oxygen environment using thermal furnace. Field emission scanning electron microscopy (FESEM) image reveals that nanorod arrays were deposited vertically aligned on the substrate. The stress characteristics of air-annealed and oxygen-annealed Al-doped ZnO nanorod arrays were investigated using Raman spectroscopy and X-ray diffraction (XRD) measurement. The electrical properties of the samples were investigated using two-probe current-voltage (I-V) measurement system. The results show that annealing atmospheres greatly influenced the stress and electrical properties of the nanorod arrays.

Abstract: MgZnO thin films are proposed as a new dielectric material for 1 GHz monolithic microwave integrated circuit (MMIC) applications. The high permittivity of this material enables size reduction; furthermore this can be fabricated using a low cost processing method. In this work, MgZnO/Pt/Si thin films were synthesized using a sol-gel spin coating method. The samples were annealed at various temperatures with the effects on physical and electrical properties investigated at direct current (DC) and high frequencies. The physical properties of MgZnO thin film were analyzed using X-Ray diffraction, with the improvements shown in crystalline structure and grain size with increasing temperature up to 700 °C. DC resistivity of 77 Ωcm at higher annealing temperature obtained using a four point probe station. In order to prove the feasibility at high frequencies, a test structure consisting of a 50 Ω transmission line and capacitors with 50 × 50 μm electrode area were patterned on the films using electron beam lithography. The radio frequency (RF) properties were measured using a Wiltron 37269A vector network analyzer and Cascade Microtech on-wafer probes measured over a frequency range of 0.5 to 3 GHz. The dielectric constant, loss tangent and return loss, S₁₁ improve with the increment annealing temperature. The dielectric constant was found to be 18.8, with loss tangent of 0.02 at 1 GHz. These give a corresponding size reduction of ten times compared to conventional dielectrics, silicon nitride (Si₃N₄). These indicate that the material is suitable to be implemented as a new dielectric material for 1GHz MMIC applications.

Abstract: New market trend for organic solar cell (OSC) require lightweight, cost effective, environmentally friendly and flexible. Transparent conductive electrode (TCE) is a main building block in organic solar cell in determining the device performance. Indium tin oxide (ITO) is widely used as transparent conductive material however it has major drawbacks due to relatively expensive, brittle and it limited to use on flexible substrate. This paper provides a short review of the transparent conductive electrode material which required for OSC applications. Issues related with existing TCE material such as ITO is also highlighted. Thus, alternative green material resources which offer low cost, environmentally friendly, mechanically robust and low sheet resistances are strongly required. Graphene is suitable candidate due to their outstanding properties such as good electrical, green material, chemical and thermally stable as well as remarkable mechanical strength and flexibility. The performance of transparent graphene electrode using low cost fabrication method which related with electrical, optical and power conversion efficiency was reviewed. We believed this work will provide beneficial input toward the improvement of OSC device performance.

Abstract: Single-walled carbon nanotubes (SWCNT) were synthesized by using a simple evaporating method and a double furnace system. Ethanol was chosen as a carbon precursor because it has an evaporating temperature of 78 °C and was reported to produce a high purity of CNTs. Evaporated ethanol can be used as a precursor for carbon nanotubes (CNTs) synthesis. Ethanol was evaporated at 80 °C and channeled directly into a double furnace system. Furnace 1 was maintained at 180 °C and furnace 2 was set at 700 °C, 800 °C and 900 °C. The CNTs were then characterized by thermogravimetric analysis (TGA), field emission scanning electron microscopy (FESEM) and Raman spectroscopy. Helical CNTs were observed at 700°C, webs of hollow tubes at 800 °C, and long tube structures at 900 °C based on FESEM. The diameter of CNTs that were synthesized ranged between 54 - 200 nm. Raman spectrum revealed that the G-band was 1590 cm^-1 and the D-band was about 1350 cm^-1. SWCNT was determined by RBM (radial breathing mode) to be between 200 - 300 raman shifts (cm^-1). The modified CVD (chemical vapor deposition) system set up in the present study is successfully used for large scale synthesis of CNTs from an aqueous precursor such as ethanol.

Abstract: Water pollution is a serious, persistent and emerging problem not only in Malaysia but all over the world. It has negative impacts on the sustainability of water resources, aquatic flora and fauna and community health. It significantly reduces total water availability because of the lack of suitable and cost-effective pollutant treatment facilities. Current facilities for water purification are time consuming, expensive and have low affinity and efficiency to newly emerging micro pollutants in water. Carbon nanotube (CNT) based nanocomposites and hybrids have attracted huge attention for their potential in the treatment of newly emerging micropollutants in water bodies. Addition of various molecules and binders such as magnetic nanoparticles, pollutant binding and degrading receptors and enzymes has added new dimensions in the fibrous shape, high aspect ratio, large surfaces, and accessible mesopores of CNTs. In this review, we have outlined the recent progress and future prospects of multifunctional CNT-hybrids for the treatment of both conventional priority and newly emerging micropollutants in water environment. The review also has highlighted the future strategies for overcoming the shortcomings of existing techniques and materials for water purification applications.