Papers by Author: N.A.M. Asib

Abstract: Mist-atomization deposition method was applied in order to grow ZnO nanoparticles on Au-seeded glass substrates acting as seeded template. Ag doped ZnO thin films were deposited on ZnO seeded templates by solution-immersion method. The influence of Ag doping content on the optical and Raman scattering properties of ZnO films were systematically investigated by UV-Vis transmittance measurement measured by ultra-violet visible spectroscopy (UV-Vis) and Raman scattering spectrum measured by Raman spectroscopy under room temperature. From UV-Vis transmittance measurement, the incorporation of Ag dopant to the ZnO makes the transmittance wavelength shifted to the shorter wavelength as compared to the pure ZnO. From Raman spectra, 4 cm^-1 downshift is observed in Ag-doped thin films as compared to pure ZnO thin films. This Raman peak shift shows that a tensile stress existed in the Ag-doped ZnO film.

Abstract: In this work, seeded porous silicon (PSi) was used as a substrate in the growth of ZnO nanostructures. PSi was prepared by electrochemical etching method. ZnO thin films as seeded were deposited via sol-gel spin coating method. ZnO nanostructures were grown on seeded PSi using hydrothermal immersion method. In order to study the effect of post-heat treatment on the substrate, post annealing temperature were varied in the range of 300 to 700 °C. The FESEM results shows ZnO thin film composed of nanoparticles were distributed over the PSi surface. Based on AFM characterization, the smoothest surface was produced at post annealing temperature of 500 °C. There are two different peaks appeared in PL characterization. The peak in near-UV range is belonging to ZnO thin films while a broad peak in visible range can be attributed to ZnO defects and PSi surface. In addition, FESEM, XRD and PL were used to characterize the ZnO nanostructures. The FESEM results revealed ZnO nano-flower were successfully grown on seeded PSi. Hexagonal wurtzite of ZnO with dominated by the plane (100), (002), and (101) was found by XRD characterization. Two different peaks in UV range and visible range can be attributed to ZnO nano-flower and various defects of ZnO, respectively.

Abstract: Different layers of PMMA spin coated onto substrate were successful prepared by sol-gel spin-coating method. PMMA was dissolved in toluene solvent and was aged for 24 hours to produce the homogeneous solution. The films were then characterized by Raman Spectroscopy and Ultraviolet-Visible (UV-Vis) spectroscopy. Raman spectroscopy studied reveals the 7 layers of PMMA film exhibit the strong and sharp intense peak at observed band around 810 cm^-1 that is due to the symmetric CC₄ stretching. The UV-Vis measurement present 7 layers of PMMA film have good absorption due to the small size of particles and uniform surface of the film.

Abstract: In this studies, we present different layers of PMMA films spin coated onto glass substrate by using sol-gel spin-coating method. Atomic Force Microscope (AFM) reveals the surface morphology of the samples uniformly distribute on the substrate. 1 layer sample show white particles of PMMA clearly spread on the substrate and become closely-packed after the layer of PMMA increase to 3, 5 and 7 layers. 7 layers completely dense surface morphology due to the excessive number of the particles of PMMA in the sample. The approximate roughness was recorded between ranges 0.10 – 0.25 nm. Raman spectra shown 7 layers of PMMA films as the lowest Raman intensity with strong and intense peak at band about 1024 cm^-1 which is probably due to the excessive number of particles and rougher surface present in the sample.

Abstract: Mist-atomization deposition method was applied in order to grow ZnO nanostructures with various surface morphologies. ZnO was deposited from the mixture of zinc nitrate hexahydrate (Zn (NO₃)₂.6H₂O) and stabilizer, hexamethylenetetramine (HMTA, C₆H₁₂N₄) aqueous solutions onto Au-seeded glass substrate. The mixture was sprayed onto the surface of Au-seeded glass substrate at various growth temperatures of room temperature (RT), 100, 200, and 300 °C. The obtained structures were characterised by room-temperature photoluminescence (PL), field emission scanning electron microscopy (FESEM), and UV-VIS-NIR spectrophotometer. It is found that ZnO growth on 300 °C substrate temperature shows the best absorbance properties and highest UV emission peak with denser distribution amongst all. The optical and morphological properties of sprayed ZnO nanostructures largely depend on the substrates temperature during spraying the zinc nitrate solution and on the Au-seeded glass substrates.

Abstract: In this study, Zinc oxide (ZnO) nanostructures have been fabricated on glass substrates coated with Titanium dioxide (TiO₂) of different layers, which act as seeded-template, by a solution-immersion method. The substrates were coated with TiO₂ by using sol-gel spin coating at five different layers of TiO₂: 1, 3, 5, 7 and 9. The effects of the layers to the growth of ZnO nanostructures were observed by using Ultraviolet-Visible (UV-Vis) spectroscopy, Raman spectroscopy and Photoluminescence (PL) spectroscopy. UV-vis spectra of films display the increasing of absorbance properties at visible region as the TiO₂ layers increase, as well as at UV region. Meanwhile, at visible region the transparency of TiO₂: ZnO films reduce as the layers of TiO₂ increase from 1 layer to 9 layers. Raman analysis shows the presence of ZnO in all the TiO₂ seeded-templates. From the result, it is confirmed the existence of mixed crystalline structure of both materials in these TiO₂: ZnO thin films and PL spectra of the films show seeded TiO₂ thin films has lower intensity of visible emission and high ratio of I_UV/I_VIS compared to the non-seeded TiO₂ This contributes to the lower structural defects, oxygen vacancies, impurities and has the most improved optical properties.

Abstract: ZnO nanostructures were obtained by mist-atomisation technique. Nanostructured ZnO can be grown in aqueous solution of zinc nitrate hexahydrate as precursor solution with the addition of stabilizer hexamethylenetetramine (HMTA). ZnO nanostructures deposited by mist-atomisation, with applied heat from the glass substrates’ downside. Firstly, the glass substrates were seeded by Au with different thickness of 0 (non-seeded), 6, and 12 nanometer (nm). The growth of ZnO on different Au-seeded thickness is studied. The optical properties of ZnO nanostructures were examined by Ultraviolet-Visible (UV-Vis) spectroscopy. The morphology of the ZnO thin films obtained was studied by FESEM. FESEM micrographs shows different nanostructures formed on different thickness of Au-seeded glass. UV-vis spectra of ZnO nanostructures display high absorption in the UV region and high transparency in the visible region. There is improvement in UV absorption for ZnO growth on 6nm Au-seeded compared to non-seeded and 12 nm Au-seeded glass due to imperfect alignment of ZnO nanostructures.

Abstract: Sol gel immersion method has been used to synthesize magnesium doped zinc oxide (Mg:ZnO) thin film on glass substrate. The morphological of annealed thin film was study using atomic force microscopy (AFM) while UV-Visible spectroscopy was used to examine the optical transmittance properties. The optical band gap was estimated by using Tauc’s method. From the results, the surface roughness was change as annealing temperature increases. The increasing of annealing temperature also affects the transmittance spectra which are shifted to lower wavelength. The optical band gaps of the thin film were varied due to different annealed temperature.

Abstract: In this study, ZnO nanostructures were synthesized on porous silicon (PSi) substrate using hydrothermal immersion method. Different post-annealing temperatures were varied from 300°C to 600°C. Surface morphology was studied by field emission scanning electron microscopy. It shows that a better shape was produce at annealing temperatures of 500°C. Structural studies of ZnO nanostructure were implemented using X-ray diffraction grating. The result shows post-annealing can influence the crystallinty of ZnO. Photoluminescence spectra were used to study the optical properties of ZnO nanostructure. The result shows that peak corresponds to ZnO nanostructures are appeared in UV range. Besides, broad peaks are also appeared in visible range which is attributed to structural defects and PSi substrate.

Abstract: We have successfully demonstrated ZnO/Mg thin films on Mg seeded-template by using sol-gel spin-coating and immersion technique. By increasing weight percentage of Mg, zinc particles become agglomerate and displayed flower formed as displayed in FESEM characterization. It was observed that the morphology of the zinc particles on Mg seeded-template change from inconsistently distribution for 1 and 3 % into cluster flower-like of zinc particles for 5 and 7 % weight percentage of Mg. The optical properties of the ZnO/Mg thin films were examined by UV-Vis spectroscopy and the Tauc plot methods was used to estimate the optical band gap. The study reveals that, 7 % weight percentage of Mg was recorded as the highest transmittance which is more than 60 % in visible wavelength compared to others. With the rise weight percentage of Mg, the transmittance of the thin films was increased except for 5 %. This gradually downgraded to below 60 % of transmission most probably due to the grain size that becomes bigger. The optical band gap can be tuned by using different Mg percentage to the ZnO/Mg thin films.