Kevin Alvin Eswar

Annealing Heat Treatment of ZnO Nanoparticles Grown on Porous Si Substrate Using Spin-Coating Method

ZnO nanoparticles were successfully deposited on porous silicon (PSi) substrate using spin-coating method. In order to prepare PSi, electrochemical etching was employed to modify the Si surface. Zinc acetate dihydrate was used as a starting material in ZnO sol-gel solution preparation. The postannealing treatments were investigated on morphologies and photoluminescence (PL) properties of the ZnO thin films. Field emission scanning electron microscopy (FESEM) results indicate that the thin films composed by ZnO nanoparticles were distributed uniformly on PSi. The average sizes of ZnO nanoparticle increase with increasing annealing temperature. Atomic force microscopic (AFM) analysis reveals that ZnO thin films annealed at 500°C had the smoothest surface. PL spectra show two peaks that completely correspond to nanostructured ZnO and PSi. These findings indicate that the ZnO nanostructures grown on PSi are promising for application as light emitting devices.

Surface Morphology of Seeded Nanostructured ZnO on Silicon by Sol-Gel Technique

Nanostructured ZnO as a seeded was prepared by sol-gel technique on p-type silicon in various low molarities. Zinc acetate, Diethanolamine (DEA), and isopropyl were use as starting material, stabilizer, and solvent respectively. Atomic Force Microscopy (AFM) analysis shows smooth surface and uniform layer were produced in low molarities of precursor. The surface morphology of nanostructured ZnO was analyzed by Field Emission Scanning Electron Microscopic (FESEM). It is found that the nanostructured ZnO were successfully deposited on the silicon substrate with size ~10 nm to ~35 nm. Photoluminescence spectroscopy was employed to study the band gap in room temperature. It shows that very low intensity of PL in 0.05m and 0.1 m. PL intensity become more obvious starting from 0.15 m of precursor concentration.

Synthesis of ZnO Thin Film on Porous Silicon by Spin Coating in Various Low Molarities Precursor

Zinc acetate dehydrate as starting material along with diethanolamine as stabilizer, and isopropyl as a solvent were used to synthesis ZnO thin films in different low molarities. Sol-gel spin coating method was used in depositing ZnO on porous silicon substrate surface. In other to prepare substrate, p-type silicon wafer was etched by dilute hydrofluoric acid to modify the surface becomes porous. Field Emission Scanning Electron Microscopy (FESEM) was employed to study the surface morphology. It is found that ZnO thin films were successfully deposited on the substrates which are composed of ZnO nanoparticles with size ~16 nm to ~22nm. Atomic Force Microscopy (AFM) was used to investigate the surface roughness of thin film. The result shows that the surface roughness is increase as the increases of molarities. Photoluminescence (PL) spectra were done in range of 350 nm to 800 nm. The result shows peaks belonging to ZnO, ZnO defects, and porous silicon respectively are appeared.

Optical Properties of Nano-Porous Structure ZnO Prepared by Catalytic-Immersion Method

This paper presents an efficient method to prepare ZnO nano-porous structure via immersion of Si substrate with catalyst assistance (gold) in the mixture of zinc nitrate hexahydrate (Zn(NO3)2.6H2O) and urea (CH4N2O). Photoluminescence (PL) spectra of nano-porous ZnO revealed it had strong UV emission with low oxygen defect. Optical properties are found to be significantly affected by varying the Zn2+: urea ratio but from surface morphology observation, the porous structure was stabile and seemingly unchanged.

Synthesis of spin-coated nanostructured ZnO on P-type silicon and temperature dependence of I-V characteristic

Sol-gel spin coating deposition method was used to deposits nanostructured ZnO on P-type silicon. Zinc acetate, diethanolamine, and isopropyl were used as starting material, stabiliser and solvent respectively. Surface morphology was studied by field emission scanning electron microscopy (FESEM). It was found that nanostructured ZnO was distributed uniformly over the P-type Silicon substrate. This was supported by atomic force microscopy (AFM) image which shows the all the surfaces are covered by nanoparticle of ZnO. X-ray diffraction (XRD) was employed to analyse the structural and crystalline of nanostructured ZnO. Three peak (100), (002) and (101) correspond to nanostructed ZnO are appear. Temperature dependence I-V characteristic was investigated in range of 25 K to 300 K by using close cycle cryostat and using helium as cooler agent. It is found that the resistance were decrease toward the higher temperature. The result shows that resistivity gradually decreased due to increases of temperature.

ZnO nanostructures on different silicon–based substrate via simple sol–gel immersion method

In this work, ZnO nanostructures using zinc nitrate as starting material grown on different silicon–based substrate were studied. Porous silicon was prepared by electrochemical etching to modify the silicon surface. Field emission scanning electron microscopy (FESEM) displays different distribution and nanostructures of ZnO on different substrate. The seeded substrates show the better site for the growth of ZnO nanostructure due to presence of nucleation site. Crystalline of ZnO nanostructure were investigated by X–ray diffraction (XRD) grating. It is found that the hexagonal wurtzite of ZnO nanostructures were produced for all samples. The peaks (100), (002) and (101) are dominating for all samples prove that hexagonal structures of ZnO were formed. Photoluminescence spectra were employed in order to study the optical properties. The peak centred at 395-398 nm corresponds to free–exciton recombination ZnO nanostructures are found in silicon and porous silicon, respectively.

Utilization of urea in the synthesization ZnO-based thin film

The photoluminescence, morphology and structural properties of nanostructured ZnO synthesized from different molar ratio of precursor and stabilizer by a solution-immersion method were investigated. ZnO was successfully grown on gold-seeded Si substrate using a mixture of an aqueous solution of zinc nitrate hexahydrate (Zn(NO3)2.6H2O) with a non-toxic, odourless urea (CH4N2O) as a stabilizer. Solution-immersed method was adopted with the intention to develop a large area deposition at low-temperature benign method of preparation. A unique development of size and growth orientation is seemingly affected by the change in molarities of urea. Photoluminescence, structural properties and surface morphology are found to be significantly affected by varying the Zn2+:urea ratio. The chemical equations governed by urea are suggested.

Porosity and thickness effect of porous silicon layer on photoluminescence spectra

The porous silicon nanostructures was prepared by electrochemical etching of p-type silicon wafer. Porous silicon prepared by using different current density and fix etching time with assistance of halogen lamp. The physical structure of porous silicon measured by the parameters used which know as experimental factor. In this work, we select one of those factors to correlate which optical properties of porous silicon. We investigated the surface morphology by using Surface Profiler (SP) and photoluminescence using Photoluminescence (PL) spectrometer. Different physical characteristics of porous silicon produced when current density varied. Surface profiler used to measure the thickness of porous and the porosity calculated using mass different of silicon.Photoluminescence characteristics of porous silicon depend on their morphology because the size and distribution of pore its self will effect to their exciton energy level. At J=30 mA/cm2 the shorter wavelength produced and it followed the trend of porosi...

Optical properties of nanoporous structure ZnO

This paper presents an efficient method to prepare ZnO nanoporous structure via immersion of Si substrate with catalyst assistance (gold) in the mixture of zinc nitrate hexahydrate (Zn(NO3)2.6H2O) and urea (CH4N2O). Photoluminescence (PL) spectra of nanoporous ZnO revealed it had strong UV emission with low oxygen defect. Optical properties are found to be significantly affected by varying the Zn2+: urea ratio but from surface morphology observation, the porous structure was stable and seemingly unchanged.

Optical Properties and Raman Scattering Investigation of Ag Doped ZnO Thin Film Prepared by Two-Step Solution-Based Deposition Method

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.