Comparative study of ZnO nanostructures grown on silicon (100) and oxidized porous silicon substrates with and without Au catalyst by chemical vapor transport and condensation (original) (raw)
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Growth of ZnO Nanostructures on Porous Silicon and Oxidized Porous Silicon Substrates
Brazilian Journal of Physics, 2011
We have investigated an oxidation of substrate effect on structural morphology of zinc oxide (ZnO) rods. ZnO rods are grown on porous silicon (PS) and on thermally oxidized porous silicon substrates by carbothermal reduction of ZnO powder through chemical vapour transport and condensation. Porous silicon is fabricated by electrochemical etching of silicon in hydrofluoric acid solution. The effects of substrates on morphology and structure of ZnO nanostructures have been studied. The morphology of substrates is studied by atomic force microscopy in contact mode. The texture coefficient of each sample is calculated from X-ray diffraction data that demonstrate random orientation of ZnO rods on oxidized porous silicon substrate. The morphology of structures is investigated by scanning electron microscopy that confirms the surface roughness tends to increase the growth rate of ZnO rods on oxidized PS compared with porous silicon substrate. A green emission has been observed in ZnO structures grown on oxidized PS substrates by photoluminescence measurements.
Photoluminescence Spectra of ZnO Thin Film Composed Nanoparticles on Silicon and Porous Silicon
Advanced Materials Research, 2013
ZnO thin film was successfully deposited on different substrate by sol-gel spin coating. Zinc acetate dihydrates, diethanolamine and isopropyl were used as starting material, stabilizer and solvent respectively. Two different substrate used in this work are p-type silicon wafer and porous silicon. Porous silicon was prepared by electrochemical etching. In order to study the surface morphology, field emission scanning electron microscopy (FESEM) was employed. It is found that, ZnO thin film was composed by ZnO nanoparticles. The averages size ZnO nanoparticle is 23.5 nm on silicon and 17.76 nm on porous silicon. Based on Atomic Force Microscopy (AFM) topology analysis, surface of ZnO thin films on porous silicon was rougher compared to ZnO thin films on silicon due to substrate surface effect. Photoluminescence spectra shows two peaks are appear for ZnO thin film on silicon and three peaks are appear for ZnO thin film on porous silicon. PL spectra peaks of ZnO thin film on silicon ar...
Seeded Porous Silicon Preparation as a Substrate in the Growth of ZnO Nanostructures
Applied Mechanics and Materials, 2015
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 suc...
Optical Properties and Field Emission of ZnO Nanorods Grown on p-Type Porous Si
N-type ZnO nanorods were grown on p-type porous silicon using a chemical bath deposition (CBD) method (p-n diode). The structure and geometry of the device were examined by field-emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) while the optoelectronic properties were investigated by UV/Vis absorption spectrometry as well as photoluminescence and electroluminescence measurements. The field emission (FE) properties of the device were also measured and its turn-on field and current at 6 V/µm were determined. In principle, the growth of ZnO nanorods on porous siicon for optoelectronic applications is possible.
Formation of ZnO Nanostructures Grown on Si and SiO2 Substrates
ZnO nanorods are grown on Si-based substrate by chemical bath deposition method in aqueous solution using zinc nitrate hexahydrate. Various substrates having different surface morphology are used to evaluate their effect on growing ZnO nanorods, such as flat Si wafer, small and large textured-Si wafer, porous silicon, flat SiO 2 wafer, small and large textured-SiO 2 wafer. The length, diameter, geometry, and coverage density of ZnO nanorods are investigated by field-emission scanning electron microscopy and summarized. SiO 2 is a preferred substrate for the growth of ZnO nanorods to Si if the surface morphology of substrate is same, and the textured surface has much higher coverage density (> 95%) than the flat surface. Each nanorod is vertically grown along the c-axis on the top of each pyramid face for textured substrate, and forms the 3D sea sponge-like ZnO structure. The characteristics of ZnO nanorods grown on various substrates are analyzed by grazing-angle X-ray diffraction (XRD) and photoluminescence (PL) measurements.
Post annealing effect on thin film composed ZnO nano-particles on porous silicon
Zinc acetate dihydrate as a starting material was used in precursor preparation. In order to prepare porous silicon (Psi) substrates, electrochemical etching was employed to modify the silicon surface. ZnO thin films were successfully deposited on porous silicon substrate by spin-coating technique. Post annealing temperatures were varied in a range of 300°C to 700°C to investigate its effect on morphologies and photoluminescence properties of the ZnO thin films. Field Emission Scanning Electron Microscopy (FESEM) results revealed that the thin films are composed of ZnO nano-particles and distributed uniformly on Psi surface. ZnO nano-particle sizes are varied from 21.3 nm to 25.9 nm when annealed in different temperatures. Atomic Force Microscopic (AFM) analysis was carried out to study the surface morphology. It was found that the lowest average surface roughness of ZnO thin films is obtained at an annealing temperature of 500°C, which is 1.46 nm. Photoluminescence (PL) spectroscopy was conducted in the range of 350 nm to 900 nm. The result shows three distinct peaks at 410 to 420 nm, 525 to 600 nm and 625 to 725 nm, which are attributed to nano-structured ZnO, ZnO defects and porous silicon respectively.
Structural Studies of Zno Nanostructures on Porous Silicon: Effect of Post-Annealing Temperature
International Journal of Engineering & Technology
ZnO Nanostructures have been successfully deposited on of Porous silicon (PSi) via wet colloid chemical approach. PSi was prepared by electrochemical etching method. ZnO/PSi thin films were annealed in different temperature in the range of 300 °C to 700 °C. Surface morphology studies were conducted using field emission scanning microscopy (FESEM). Flower-like structures of ZnO were clearly seen at annealing temperature of 500 °C. The X-ray diffraction spectra (XRD) have been used to investigate the structural properties. There are three dominant peaks referred to plane (100), (002) and (101) indicates that ZnO has a polycrystalline hexagonal wurtzite structures. Plane (002) shows the highest intensities at annealing temperature of 500 °C. Based on plane (002) analysis, the sizes were in range of 30.78 nm to 55.18. In addition, it was found that the texture coefficient of plane (002) is stable compared to plane (100) and (101).
Journal of Electronic Materials, 2019
In the present work, a comparison between zinc oxide (ZnO) nanoflowers and nanorods for photovoltaic applications is presented. Using chemical bath deposition technique, ZnO nanoflowers were grown on porous silicon (PS) while ZnO nanorods were deposited on flat Si substrate. The morphology of ZnO/PS sample indicated the formation of nanoflowers by accumulation of ZnO nanorods on PS walls. The structural studies indicated that ZnO nanoflowers experienced a stress relief compared to ZnO nanorods which was due to the role of porous substrate for accommodating the lattice strain in order to obtain the subsequent ZnO nanoflowers with reduced strain. The optical results obtained from ZnO nanoflowers showed more intense photoluminescence and Raman peaks compared with nanorods. It was due to the higher specific surface area of nanoflowers which led to a higher absorption coefficient and increased the generation of electron-hole pairs in this sample. Due to their elevated specific surface area, ZnO nanoflowers can capture the incident light and reduce the reflection coefficient of silicon substrates. Thus, they can be considered as an effective antireflective layer to improve the efficiency of solar cells. The optoelectrical results showed an improvement in the efficiency of fabricated solar cells by use of ZnO nanoflowers on PS structures when compared to the conventional ones possessing ZnO nanorods on flat silicon substrates. Development of ZnO nanoflowers on PS substrates can further extend the applications of ZnO nanostructures in photovoltaic devices.
ZnO nanocoral reef grown on porous silicon substrates without catalyst
Journal of Alloys and Compounds, 2011
Porous silicon (PS) technology is utilized to grow coral reef-like ZnO nanostructures on the surface of Si substrates with rough morphology. Flower-like aligned ZnO nanorods are also fabricated directly onto the silicon substrates through zinc powder evaporation using a simple thermal evaporation method without a catalyst for comparison. The characteristics of these nanostructures are investigated using fieldemission scanning electron microscopy, grazing-angle X-ray diffraction (XRD), and photoluminescence (PL) measurements of structures grown on both Si and porous Si substrates. The texture coefficient obtained from the XRD spectra indicates that the coral reef-like nanostructures are highly oriented on the porous silicon substrate with decreasing nanorods length and diameter from 800-900 nm to 3.5-5.5 m and from 217-229 nm to 0.6-0.7 m, respectively. The PL spectra show that for ZnO nanocoral reefs the UV emission shifts slightly towards lower frequency and the intensity increase with the improvement of ZnO crystallization. This non-catalyst growth technique on the rough surface of substrates may have potential applications in the fabrication of nanoelectronic and nanooptical devices.
Growth of High-Density Zinc Oxide Nanorods on Porous Silicon by Thermal Evaporation
Materials, 2012
The formation of high-density zinc oxide (ZnO) nanorods on porous silicon (PS) substrates at growth temperatures of 600-1000 °C by a simple thermal evaporation of zinc (Zn) powder in the presence of oxygen (O 2) gas was systematically investigated. The high-density growth of ZnO nanorods with (0002) orientation over a large area was attributed to the rough surface of PS, which provides appropriate planes to promote deposition of Zn or ZnO x seeds as nucleation sites for the subsequent growth of ZnO nanorods. The geometrical morphologies of ZnO nanorods are determined by the ZnO x seed structures, i.e., cluster or layer structures. The flower-like hexagonal-faceted ZnO nanorods grown at 600 °C seem to be generated from the sparsely distributed ZnO x nanoclusters. Vertically aligned hexagonal-faceted ZnO nanorods grown at 800 °C may be inferred from the formation of dense arrays of ZnO x clusters. The formation of disordered ZnO nanorods formed at 1000 °C may due to the formation of a ZnO x seed layer. The