Mohamed Zahidi Musa

Effect of Post-Deposition Annealing Process on the Resistive Switching Behaviour of TiO2 Thin Films by Sol-Gel Method

The paper presents the memristive behaviour of spin-coated titania thin films on ITO substrate. The sample was annealed in air ambient at different annealing temperature and duration of 250 and 450 °C for 20 and 60 min. The effect of post-annealing process to the physical thickness and crystallinity of the films towards switching behaviour was studied. It was found that the thickness and crystallinity of the films increases as the post annealing process increases. Sample annealed at 250 °C for 20 min with thinner film showed better switching behaviour even though the sample is still in amorphous form. Thus, in our work, we believed that the crystallinity of the films does not affect the switching behaviour of the sample. The reliability of device performance was studied by repeating the measurement for three times.

Effect of RF Power on the Formation and Morphology Evolution of ZnO Nanostructured Thin Films

The effect of RF power on the formation and morphology evolution of ZnO nanostructured thin films deposited by magnetron sputtering are presented. This project focused on electrical, optical and structural properties of ZnO thin films. The effect of variation of RF power at 50 watt-250 watt at 200 °C on glass substrate of the ZnO thin films was investigated. The thin films were examined for electrical properties and optical properties using two point probe current-voltage (I-V) measurement (Keithley 2400) and UV-Vis-NIR spectrophotometer (JASCO 670) respectively. The structural properties were characterized using field emission scanning electron microscope (FESEM) (JEOL JSM 7600F) and atomic force microscope (AFM) (Park System XE-100). The IV measurement indicated that at RF power 200 watt the conductivity of ZnO thin film show the highest. All films show high UV absorption properties using UV-VIS spectrophotometer (JASCO 670). The root means square (rms) roughness for ZnO thin film were about 4 nm measured using AFM. The image form FESEM observed that transformation of structure size started to change as the RF power increase.

Transmittance Enhanced Properties of Novel Encapsulated ITO/Arc-TiO2 Antireflective TCO Substrate Prepared by RF Magnetron Sputtering

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.

The Influence of TiO2 Photoanode Morphology for Scattering Enhanced Properties of Dye-Sensitized Solar Cell

Effect of PEG on the TiO2 electrode morphology for scattering enhanced properties of the modified paste containing TiO2 sol-gel mixed with Degussa P-25 were investigated. The high surface area of the scattering centres in this study were formed by using nano size particles ascribed from TiO2 sol-gel while the sub-micron size particles were utilized from the reaction of PEG on the Degussa P-25 particles. The pore size distributions were tailored by varying the PEG content in the fabricated electrodes. Higher surface area with adequate pore size of P30 electrode has contributed to higher JSC and efficiency (η) of 11.35450 mA/cm2 and 2.479624 %, respectively. Photocurrent action spectra of IPCE of the DSSC exhibit the maximum of 42 % at 550 nm correspond to the P30 TiO2 electrode. Overall results suggest that the incorporation of TiO2 sol-gel component mixed with TiO2 paste derived from commercially available nanopowder could enhance surface area as well as serves for better light scattering effect, while PEG addition creates adequate pore size distribution to maximize the dye adsorbed on the TiO2 electrode.

Optimization of processing parameters on the controlled growth of c -axis oriented ZnO nanorod arrays

Optimization of the growth time parameter was conducted to synthesize high-quality c-axis ZnO nanorod arrays. The effects of the parameter on the crystal growth and properties were systematically investigated. Our studies confirmed that the growth time influence the properties of ZnO nanorods where the crystallite size of the structures was increased at higher deposition time. Field emission scanning electron microsope analysis confirmed the morphologies structure of the ZnO nanorods. The ZnO nanostructures prepared under the optimized growth conditions showed an intense XRD peak which reveal a higher c-axis oriented ZnO nanorod arrays thus demonstrating the formation of defect free structure.

Effect of growth time on ZnO nanorod arrays by a facile sonicated sol-gel immersion technique

A facile sonicated sol-gel immersion technique has been presented for synthesizing ZnO nanorod arrays with controllable diameter and lengths on glass substrates. A sol-gel dip-coating deposition was first used to grow a thin layer of ZAO nanocrystals on substrate serving as seeds for the subsequent growth of the nanorod arrays. The effect of growth time of the ZnO nanorod arrays on the ZAO seed layer were investigated. The optical transmission properties of the ZnO nanorods has been investigated. The thickness of the nanorods can be controlled by the growth time. These highly oriented ZnO nanorod arrays are potential for the creation of functional materials, such as the electrode of the solar cells, optoelectronic devices and etc.

Effect of Sputtering Pressure on Optimization of Titanium Dioxide Nanostructures Prepared by RF Magnetron Sputtering

Titanium dioxide (TiO2) nanostructures were deposited on glass substrate by Radio Frequency (RF) magnetron sputtering. The samples deposited at various sputtering pressures and annealed at 723 K, were characterized using Atomic Force Microscope (AFM) to observe the surface morphology and topology, roughness properties and cross-sectional of TiO2 nanostructures, Field Emission Scanning Electrons Microscope (FESEM) to observe the particle sizes of TiO2 nanostructures and UV-vis spectroscopy to record the UV-vis transmission spectra. The aim of this paper is to determine which parameter of sputtering pressures influence the optimization of TiO2 nanostructures. AFM images show that the surface roughness of the samples decreases as the working pressures of sputtering increases. From FESEM images, it can be deduced that the higher the sputtering pressure, the smaller the particle size is. All the samples are highly transmittance with an average transmittance higher than 80% in the visible region as recorded by UV-vis transmission spectra. The relatively high transmittance of the sample indicates its low surface roughness and good homogeneity. For optimum TiO2 nanostructures deposited at various RF pressures it has the lowest surface roughness and the smallest TiO2 size particles with the indirect optical band gap of 3.41 eV.

Dispersion of TiO2 Nanopowder in the PMMA Matrix Prepared by Sonication-Solution Casting Method

This paper discussed on the structural properties of the PMMA/TiO2 nanocomposite films prepared using sonication-solution casting method. The structural properties of the nanocomposite films were compared by mixing the self-prepared TiO2 (~12 nm) and the commercially available TiO2 (25 nm) in the PMMA. The well dispersion of self-prepared TiO2 nanopowder was observed in the FESEM micrograph. XRD results show that the self-prepared TiO2 nanopowder decrease the crystallinity of the nanocomposite. Further, FTIR reveals that the interaction between the PMMA and TiO2 nanoparticles were detected.

Zinc Oxide Buffer Layer Insertion for Sensitivity Improvement in Aluminium-Doped Zinc Oxide-Based Humidity Sensors

The improvement of sensitivity toward humidity by insertion of buffer layer has been investigated. The insertion of hetero- or homo-buffer layer of zinc oxide (ZnO) thin film before deposition of high quality ZnO had been reported for the growth on highly mismatched substrate. Three samples are characterized with different properties which are as deposited ZnO thin film without buffer layer (as deposited ZnO thin film) , anneal ZnO thin film without buffer layer (ZnO thin film) and anneal ZnO thin film with buffer layer (ZnO/ AZO thin film). The structural properties of ZnO thin film has been characterized field emission scanning electron microscopy (FESEM) JEOL JSM 6701F, atomic force microscope AFM (Park System XE-100) and XRD (Rigaku Ultima IV). The electrical and optical properties has been characterized using 2 point probe I-V measurement (Keithley 2400) and UV-Vis spectrophotometer (JASCO 670) respectively. In this work, we have focused on investigating the humidity sensitivity of ZnO thin film deposited using RF magnetron sputtering (SNTEK RSP 5004-PVD) with and without the buffer layer (Aluminum-doped ZnO (AZO)) for humidity sensor application.

Electrical Characteristic of UV Sensor Using Nanostructured Al Doped ZnO Thin Film

The electrical properties of nanostructured Aluminum (Al) doped Zinc Oxide (ZnO) thin films based ultraviolet (UV) sensor prepared by sol-gel spin-coating method have been investigated. Uniform nanoparticles Al doped ZnO have been deposited with high absorption coefficient at UV region and low absorption coefficient properties in visible and near-infrared (NIR) region. I-V spectra show high sensitivity characteristic of UV sensor with fast response after UV light exposure.