Papers by Author: Mohamad Hafiz Mamat

Abstract: In this work, a thermally stable multilayered transparent conducting oxide (TCO) utilizing TiO2 antireflection thin film (arc-TiO2) encapsulated under indium tin oxide (ITO) glass has been prepared by RF magnetron sputtering. The novel tri-functional conducting substrate with blocking layer capabilities has been designed via step-down interference coating structure of double layer antireflection coating (DLAR). The mixed-oriented type between the strongest ITO peak at (222) and a weak TiO2 peaks at (101) orientations have been observed under XRD analysis. The antireflection properties of double-layer ITO/arc-TiO2 is evidence with the existence of two maximum peaks around 410 nm and 750 nm. While, the corresponding reduction in reflectance of about 8% and 2% compared to bare ITO was achieved. The ITO/arc-TiO2 blocking layers conserves the low resistivity of ITO at 2.05 x 10-4 Ω cm, even after oxidizing during air annealing process above 400 °C. These results demonstrate that the multilayered ITO/arc-TiO2 with tailored refractive index by means of annealing treatment is a promising approach to realize a substrate which (a): electrically and thermally stable against processing temperature, (b): sustains the higher transmittance of the substrate even there is increase in total substrate thickness and (c): prevents electron recombination process occurring at the interface between the redox electrolytes and the TCO surface. The stable properties are found to be beneficial for use as TCOs in DSSCs.

Abstract: Nanostructured Aluminum (Al) doped Zinc Oxide (ZnO) thin films based ultra-violet (UV) sensors were prepared on glass substrates using immersion technique at different immersion times. Surface morphology results as characterized by scanning electron microscope (SEM) show that all prepared nanostructured Al doped ZnO were in form of nanorod structures with the typical diameter in the range of 60-250nm and the length within several micrometers. Photocurrent measurement results of the fabricated UV photoconductive sensor from nanostructured Al doped ZnO thin film immersed at 1 hr gives the highest photocurrent intensity compared with other samples.

Abstract: Nanostructured ZnO thin film has been prepared by using sol-gel method. The influence of annealing temperature on the structural, surface morphology and the properties has been investigated. The morphology of the nanostructured ZnO was observed by scanning electron microscopy (SEM) and their properties were measured by using the I-V measurement. The annealing temperature of 500°C, 600°C and 700°C has been observed and the I-V measurements were measured at different relative humidity to studies on the sensitivity of the nanostructured ZnO. The SEM demonstrates that the glass substrate was deformed at 700°C of annealing temperature and I-V measurement studies shows that the resistance of nanostructured ZnO thin film is decreased with annealing temperature and relative humidity. Sensitivity also decreases with the increases of annealing temperature.

Abstract: This paper focus on nanostructured Zinc Oxide (ZnO) thin film based humidity sensor prepared using sol-gel method immersion technique at different immersion time. Scanning Electron Microscopy (SEM) investigations reveal nanorods ZnO were deposited on glass substrate with nanorods length increased with immersion time. All fabricated sensors show current intensity increment response when relative humidity is increased. Sensor fabricated at 16 hr immersion time shows the highest sensitivity in this study.

Abstract: The properties of zinc oxide thin films were prepared by sol-gel spin-coating method have been presented. This study based on optical and electrical properties of ZnO thin film. The effects of annealing temperatures that exposed with two environments properties have been investigated. Environments exposed in room (27°C) and hot (80°C) temperatures which are stored by various days. Solution preparation, thin film deposition and characterization process were involved in this project. The ZnO films were characterized using UV-Vis-NIR spectrophotometer for optical properties. From that equipment, the percentage of transmittance (%) and absorption coefficient spectra were obtained. With two environments showed have different absorption coefficient are reveal and all films have low absorbance in visible and near infrared (IR) region but have high UV absorption properties. From SEM investigations the surface morphology of ZnO thin film shows the particles size become smaller and denser in hot temperatures while in room temperatures have porosity between particles.

Abstract: The properties of nanostructured aluminum (Al) doped zinc oxide (ZnO) thin film for thin film transistors (TFT) are presented. This research has been focused on optical and structural properties of Al doped ZnO thin film. The influence of Al doping concentration at 0~5 at.% on the Al doped ZnO thin film properties have been investigated. The thin films were characterized using UV-Vis-NIR spectrophotometer for optical properties. The surface morphology has been characterized using field emission scanning electron microscope (FESEM). The absorption coefficient spectra obtained from UV-Vis-NIR spectrophotometer measurement show all films have low absorbance in visible and near infrared (IR) region but have high UV absorption properties. The calculated Urbach energy indicated the defects concentrations in the thin films increase with doping concentrations The FESEM investigations shows that the nanoparticles size becomes smaller and denser as the doping concentration increase.

Abstract: Aluminum (Al) doped Zinc Oxide (ZnO) thin films were prepared using sol-gel spin-coating method at different doping concentrations. The effects of Al doping concentration at 0~5 at.% on the Al doped ZnO thin film properties have been investigated. The thin films were characterized using Current-Voltage (I-V) measurement and field emission scanning electron microscope (FESEM) for electrical properties and surface morphology, respectively. The I-V measurement result indicated electrical properties of Al doped ZnO thin film improved with Al doping. The FESEM investigations show that the nanoparticles size becomes smaller and denser as the doping concentration increase.

Abstract: In this work, ZnO thin films were deposited by RF Magnetron sputtering at different substrate temperatures in the range of 100-400oC on glass substrate. The thin films were characterized using field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), and I-V measurement, for morphology and electrical properties study. Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) were used to study the structural and morphology of the thin films. The particle size varied from 41nm to 146nm showing that the nucleation of ZnO thin films as the substrate temperatures increased. Higher particle size was observed as the substrate temperatures increased up to 400oC as well as high conductivity of thin films at 400oC.

Abstract: Solid state dye-sensitized solar cells (DSSCs) were first reported in 1991 without employing p-type as hole conductor. The p-type as hole conductor was first introduced in 1995 and CuI is preferred among others p-type semiconductors. However, in 2003 utilizing of CuI based DSSC was found unstable by the excessive iodine strongly decreased the photocurrent of the cell. Later then, the stability of CuI based DSSCs was reported can be improved by added small amount of triethylamine hydrothiocyanate (THT) in the CuI coating solution. Following to that, in this work new chemical is introduce as an option to present situation which can give equally or better effective for fabrication of solid-state DSSCs. The chemical is called tetramethylethylenediamine (TMED), is employed to CuI in sol-gel process and their characterizations have been studied. The CuI coating solution was prepared by dissolved CuI powder with acetonitrile and added in 0.5mL TMED. Using spin coating technique the sol then deposited onto glass and silicon substrate at room temperature. The film were analyzed by their particles conductivity using pH meter, surface morphology using Field Emission Scanning Electron Microscope (FE-SEM) and optical properties using ultraviolet visible spectroscopy (UV-Vis) and photoluminescence (PL) measurement. The results of this sol-gel were compared with other CuI sol-gel which prepared by dissolved CuI powder with acetonitrile only. The optical transmittance within ultra-violet range exhibited that thin film is transparent and it optical band gap have been studied. Further clarification and measurements need to be done in order to prove that the proposed chemical can be used as an option.

Abstract: Titanium dioxide nanowires have successfully prepared by hydrothermal method. The effect of hydrothermal growth temperature on the morphology and structural properties of TiO2 nanowires have been investigated. It was observed that at low temperature of 100 °C, the formation of nanowires was at early stage, while hydrothermal treatment at 130 °C showed the TiO2 precursor acquired enough energy for formation of the nanowires. Increased the temperature to 200 °C was formed the bundle of nanowires in microsize. The diameter of nanowires increased as the temperature increased. The TiO2 nanowires produced at temperature of 150 °C and annealed at 500 °C showed highest crystallinity with anatase phase.