A.N. Afaah

A Review on Zinc Oxide Nanostructures: Doping and Gas Sensing

This paper presents a review on synthesis, structure, and growth mechanisms of one-dimensional nanostructures of ZnO. Solution-based method is a potential deposition technique for large-scale production as its advantages; the low cost, the simplicity of experimental set-up, and the low operating temperature. Mist-atomiser technique is one of the solution-based methods in synthesizing optimized ZnO nanostructures. Doping will lead for better properties of ZnO, which result to wide application area. Nanostructured ZnO is important in promising areas of application which devices utilizing nanostructures such as gas sensors and solar cells, since it is fairly easy to fabricate such forms of ZnO nanostructures, which have good charge carrier transport properties and high crystalline quality.

Effect of annealing temperature of magnesium doped zinc oxide nanorods growth on silicon substrate

Magnesium (Mg)-doped zinc oxides (ZnO) have been prepared on a silicon substrate by using the solution-immersion method. The nanorods films were annealed at different temperature 0°C, 250°C, 500°C respectively for 1 hour. The XRD diffraction indicated that the Mg-doped ZnO nanorods have good crystallinity with a hexagonal wurzite structure preferentially oriented along the (002) direction. PL spectroscopy at room temperature shows strong UV peaks appearing at 383 nm when annealed at 250°C. The intensity of broad emission peaks increases with increasing annealing temperature to 500°C which is possibility attributed to intrinsic defects.

Electrically conductive nanostructured silver doped zinc oxide (Ag:ZnO) prepared by solution-immersion technique

p-type ZnO films have been fabricated on ZnO-seeded glass substrate, using AgNO3 as a source of silver dopant by facile solution-immersion. Cleaned glass substrate were seeded with ZnO by mist-atomisation, and next the seeded substrates were immersed in Ag:ZnO solution. The effects of Ag doping concentration on the Ag-doped ZnO have been investigated. The substrates were immersed in different concentrations of Ag dopant with variation of 0, 1, 3, 5 and 7 at. %. The surface morphology of the films was characterized by field emission scanning electron microscope (FESEM). In order to investigate the electrical properties, the films were characterized by Current-Voltage (I-V) measurement. FESEM micrographs showed uniform distribution of nanostructured ZnO and Ag:ZnO. Besides, the electrical properties of Ag-doped ZnO were also dependent on the doping concentration. The I-V measurement result indicated the electrical properties of 1 at. % Ag:ZnO thin film owned highest electrical conductivity.

Effect of annealing temperature on the morphology and optical properties of PMMA films by spin-coating method

Poly(methyl methacrylate) (PMMA) films were deposited on glass substrate by sol-gel spin-coating method. The films were annealed for 10 minutes in furnace at different annealing temperature of room temperature, 50, 100, 150 and 200 °C. The effect of annealing temperatures to the surface and optical properties of PMMA films spin-coated on the substrate were investigated by Atomic Force Microscope (AFM) and Ultraviolet-Visible (UV-Vis) Spectroscopy. It was observed in AFM analysis all the annealed films show excellent smooth surface with zero roughness. All the samples demonstrate a high transmittance of 80% in UV region as shown in UV-Vis measurement. Highly transparent films indicate the films are good optical properties and could be applied in various optical applications and also in non-linear optics.

The Influence of Immersion Time to the Optical properties of ZnO Growth on PMMA-coated Substrate by Solution- Immersion Method

We present the growth of ZnO on PMMA-coated substrate under influence of different immersion time by solution-immersion technique. PMMA polymer was coated on the substrate by spin-coating method. The PMMA-coated substrate was then prepared for non- immersed and immersed for four (4) and six (6) hours in zinc solution. The optical properties of the film obtained were characterized using Photoluminescence (PL), Raman Spectra and Ultraviolet-Vis (UV-Vis) spectroscopy. It was found that shorter time of immersion (4 hours) produced higher intensity of PL and Raman. However, the reverse was found for UV-Vis measurement. The low absorption that was shown from the film immersed for 4 hours may correspond to the random distribution and orientation of ZnOparticle growth on PMMA-coated substrate.

Low Temperature Growth and Optical Properties of Zinc Oxide Nanostructure Prepared by Two-Step Solution-Based Deposition Method

ZnO thin films with typical c-axis (0 0 2) orientation were successfully deposited on glass substrates by two-step deposition method; mist-atomization and solution-immersion. The samples were annealed at selected temperature range of 350-500 ᵒC. The prepared samples then analyzed by Raman spectroscopy and photoluminescence (PL) spectroscopy. The optical properties of the samples were studied. The results of different annealing temperatures are also compared to investigate the optical and physical properties of each sample. Photoluminescence (PL) spectra showed low intensity in UV emission and high intensity in the visible emission, which indicates a good surface morphology of the ZnO nanorod. The Raman intensity changes in all sample were also tested.

Influence of Annealing Temperature to Surface Morphology of Flowerlike ZnO Deposited on Seeded Glass

Flower-shaped ZnO nanocrystals have been synthesized by a two-step solution based deposition method; mist-atomizer and solution-immersion on seeded glass substrate. The samples are annealed at different temperature in the range of 350 to 500 ᵒC. The structural properties of the samples were studied. Field emission scanning electron microscopy (FESEM) micrograph and atomic force microscopy (AFM) images for the ZnO thin films were obtained. Morphological changes due to various annealing temperature are discussed as changes observed in the ZnO crystals. FESEM image of the surface of the ZnO reveal the flowerlike vertical nanorods with hexagonal crossection. The samples with higher roughness analyzed from AFM images indicate that the sample have larger grain. AFM results are found in good agreement and supported the FESEM results.

Studies of surface morphology and optical properties of ZnO nanostructures grown on different molarities of TiO2 seed layer

Titanium dioxide (TiO2) seed layer was prepared by using sol-gel spin-coating technique, followed by growth of 0.01 M of Zinc oxide (ZnO) nanostructures by solution-immersion. The molarities of TiO2 seed layer were varied from 1.1 M to 0.100 M on glass substrates. The nanostructures thin films were characterized by Field Emission Scanning Electrons Microscope (FESEM), Photoluminescence (PL) spectroscopy and Ultraviolet-Visible (UV-Vis) spectroscopy. FESEM images demonstrate that needle-like ZnO nanostructures are formed on all TiO2 seed layer. The smallest diameter of needle-like ZnO nanostructures (90.3 nm) were deposited on TiO2 seed layer of 0.100 M. PL spectra of the TiO2: ZnO nanostructures thin films show the blue shifted emissions in the UV regions compared to the ZnO thin film. Meanwhile, UV-vis spectra of films display high absorption in the UV region and high trasparency in the visible region. The highest absorbance at UV region was recorded for sample which has 0.100 M of TiO2 seed layer.

The growth of ubiquitous ZnO rods on PMMA-coated substrate by solution-immersion method at different annealing temperatures

In this work, solution-immersion method was used to grow ZnO rods on PMMA-coated substrate. For this purpose, 0.15 M of zinc nitrate hexahydrate (Zn(NO3)2.6H2O) and hexamethylenetetramine (C6H12N4) were used to growth of ZnO films at different annealing temperatures (room temperature, 80, 100, 120 and 140 °C). The morphology of the films was investigated by Scanning Electron Microscope (SEM) and optical properties were studied by Ultraviolet (UV-Vis) Spectroscopy. SEM analysis showed ubiquitous growth of ZnO rods that became better aligned and more closely-packed as the annealing temperature increased. As the annealing temperature exceeds 100 °C, the rods tend to merge to adjacent particles and the UV absorption decreased for the sample at higher temperatures (120 °C and 140 °C). Good absorption and better orientation of ZnO was obtained for the sample annealed at 100 °C due to the film possess better distribution and these improved orientation of particles caused the light to be effectively scattered on ...

Growth mechanism, surface and optical properties of ZnO nanostructures deposited on various Au-seeded thickness obtained by mist-atomization

In this paper, growth mechanisms of ZnO nanostructures on non-seeded glass, 6 nm and 12 nm Au seed layer obtained by mist-atomization was proposed. ZnO films were successfully deposited on glass substrate with different thickness of Au seed layer i.e. 6 nm and 12 nm. The surface and optical properties of the prepared samples were investigated using Field emission scanning electron microscopy (FESEM) and photoluminescence (PL). FESEM micrograph show that ZnO nanostructure deposited on 6 nm Au seed layer has uniform formation and well distributed. From PL spectroscopy, the UV emission shows that ZnO deposited on 6 nm Au seed layer has the more intense UV intensity which proved that high crystal quality of nanostructured ZnO deposited on 6 nm Au seed layer.