ویژگی های بصری و ساختاری نوار نازک ZNO با روش اسپاترینگ

Structural and optical characterization of ZnO thin films

for optoelectronic device applications by RF sputtering technique

ویژگی های بصری و ساختاری نوار نازک ZNO برای کاربردهای دستگاه آپتوالکترونیک

با روش اسپاترینگ RF

ABSTRACT

This work reports structural and optical study of ZnO thin films grown over p-type silicon (Si) and glass substrates by RF magnetron sputtering technique. Surface morphological and optical properties of thin film have been studied using X-ray Diffraction (XRD), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray (EDX), ellipsometry and photoluminescence (PL) spectroscopy. Strong diffraction peak (002) obtained from XRD spectra of ZnO thin film indicates a preferential growth of single crystalline thin film along the c-axis oriented phase of hexagonal wurtzite structure. Surface morphological feature reveals uniform growth of undoped ZnO thin film over the substrate. Different important microstructural parameters for the film such as grain size, lattice parameters, defect density, stress and strain have been obtained. Optical properties such as transmittance, reflectance, absorption coefficient, refractive index and dielectric constant for a spectral range of 300–800 nm have been evaluated. A good optical transmittance of 83–92% has been observed for visible region, and the optical bandgap of ZnO films was found to be 3.23 eV. Energy Loss Function (ELF) and photoluminescence (PL) spectra for ZnO thin film has also been analyzed and reported.

 

سنتز هیدروترمال و شناسایی لایه های ZnO با نانوساختارهای مختلف

Hydrothermal synthesis and characterization of

ZnO films with different nanostructures

سنتز هیدروترمال و شناسایی لایه های ZnO با نانوساختارهای مختلف

ABSTRACT

ZnO nanomaterials were grown on the F-doped SnO2 glass substrate by a two-step hydrothermal method [14]. Firstly, ZnO buffer layer was modified on FTO substrates by spin-coating. Secondly, hydrothermal method was employed to synthesize ZnO materials. ZnO buffer layer was obtained by the following procedure. Zinc acetate was dissolved in the mixed solution of ethanolamine and 2- methoxyethanol with a concentration of 0.75 M. The mixture was then agitated at 60 ◦C for 30 min to yield a homogeneous and stable colloid solution. The procedure was the same as Ref. [27]. After coated with the above colloid solution by spin-coating, FTO substrates were annealed at 300 ◦C to get ZnO buffer layer.

 

سنتز نانو میله های ZnO با اندازه ی بزرگ با روش تبخیر حرارتی ساده

Synthesis of large size ZnO microrods by a simple way of

thermal evaporation

سنتز نانو میله های ZnO با اندازه ی بزرگ با روش تبخیر حرارتی ساده

ABSTRACT

Large sizeneedle-like ZnO microrods with diameters around 100 μm and length of up to2.5 mm have been achieved by asimple method of thermal evaporation of ZnO powder discs in the open air. Metallic catalysts and vacuum condition are not necessary. Both the micro-sized and nano-sized ZnO rods were grown vertically at different sites of the substrate. Theas-synthe sized micro rod sand nanorods are pure ZnO without any other element, and both of them consist of single crystalline cores with hexagonal cross sections.

 

سنتز دما پایین فیلم های نازک ZnO دوپ شده با سدیم و آلومینیوم

Low temperature synthesis wide optical band gap Al and

Al, Na) co-doped ZnO thin films)

سنتز دما پایین فیلم های نازک ZnO داپ همزمان شده با Al و Na

با باندگپ نوری گسترده

ABSTRACT

With a wide bandgap of 3.37 eV and a large exciton binding energy of 60meV at room temperature, zinc oxide (ZnO), like GaN, is considered as an important material for blue and ultra-violet optical devices. Its research interest arisen again since 1957, the New Jersey Zinc Company published a book entitled “Zinc Oxide Rediscovered” to promote the material’s “frontier” properties (such as semiconductor, luminescent, catalytic, ferrite, photoconductive, and photochemical properties) and illustrative applications. Recently, research focused mainly on fabrication of high quality single crystals and epitaxial layers, in order to fully realize ZnObased electronic and optoelectronic devices.

 

روش جدید سنتز لایه های نازک ZnO: ریزساختار، خواص الکتریکی و اپتیکی

New process for synthesis of ZnO thin films: Microstructural, optical

and electrical characterization

روش جدید سنتز لایه های نازک ZnO: ریزساختار، خواص الکتریکی و اپتیکی

ABSTRACT

Zinc oxide (ZnO) is an interesting wide-band-gap semiconductor material with a direct band gap of 3.36 eV [1] at room temperature and exciton binding energy of 60 meV. It has crystalline structure of the wurtzite type and the unit cell with the constants a = 3.24 ˚A and c = 5.19A˚ . Thin films of ZnO are utilized for a wide variety of electronic and opto-electronic applications, such as surface acoustic wave devices [4], transparent conducting electrodes [2], heat mirrors [3]. Nanoscale porous structures of ZnO with a high surface area find their application in chemical sensors [5] and dye-sensitised solar cells [6]. Various techniques have been used to deposit undoped and doped ZnO films on different substrates, including spray pyrolysis [7], organometallic chemical vapor deposition [8], pulsed laser deposition [9], sputtering [10], and sol–gel process [11].

 

سنتز نانو ورقه های ZnO از طریق روش الکترورسوبی

Synthesis of ZnO nanosheets via electrodeposition method and

their optical properties, growth mechanism

سنتز نانو ورقه های ZnO از طریق روش الکترورسوبی ، خواص نوری و مکانیزم رشد

ABSTRACT

ZnO nanosheets were prepared by electrochemical deposition method at 80 C on seeded Indium Tin Oxide conducting glass substrates. The seed layer was coated on ITO by spin coating and annealed at 350 C for 30 min prior to electrochemical deposition growth. X-ray diffraction patterns (XRD) and field emission scanning electron microscope (FESEM) images confirmed that the ZnO nanosheets consist of polycrystalline structures. Room temperature photoluminescence spectra (PL) of the ZnO nanosheets exhibited band-edge ultraviolet (UV) and visible emission (blue) indicating the ZnO nanosheets had excellent optical properties. The UV–Vis absorption spectrum of ZnO nanosheets was shown a strong absorption at 300 nm. The ZnO nanosheets structure demonstrated higher photocatalytic activity during degradation of aqueous methylene blue under visible-light irradiation. Moreover, the growth mechanism of the ZnO nanosheets had been discussed.

 

سنتز نانو ورقه های ZnO از طریق روش الکترورسوبی

Synthesis of ZnO nanosheets via electrodeposition method and

their optical properties, growth mechanism

سنتز نانو ورقه های ZnO از طریق روش الکترورسوبی ، خواص نوری و مکانیزم رشد

ABSTRACT

ZnO nanosheets were prepared by electrochemical deposition method at 80 C on seeded Indium Tin Oxide conducting glass substrates. The seed layer was coated on ITO by spin coating and annealed at 350 C for 30 min prior to electrochemical deposition growth. X-ray diffraction patterns (XRD) and field emission scanning electron microscope (FESEM) images confirmed that the ZnO nanosheets consist of polycrystalline structures. Room temperature photoluminescence spectra (PL) of the ZnO nanosheets exhibited band-edge ultraviolet (UV) and visible emission (blue) indicating the ZnO nanosheets had excellent optical properties. The UV–Vis absorption spectrum of ZnO nanosheets was shown a strong absorption at 300 nm. The ZnO nanosheets structure demonstrated higher photocatalytic activity during degradation of aqueous methylene blue under visible-light irradiation. Moreover, the growth mechanism of the ZnO nanosheets had been discussed.

 

جوشکاری آلیاژ Al–Cu–Mg–Mn به روش تیگ

Effect of welding parameters on the solidification microstructure

of autogenous TIG welds in an Al–Cu–Mg–Mn alloy

تاثیر پارامترهای جوشکاری بر میکروساختار انجمادی جوش های TIG

بدون ماده پر کننده در یک آلیاژ Al–Cu–Mg–Mn

ABSTRACT

The weld metal microstructures of autogenous TIG welds have been investigated for a range of welding conditions using an Al–Cu–Mg–Mn alloy. It was found that a combination of high welding speeds and low power densities provide the thermal conditions required for the nucleation and growth of equiaxed grains in the weld pool, providing heterogeneous nucleation sites are available. The most likely origin of the nucleants is from a combination of dendrite fragments and TiB2 particles that survive in the weld pool. The finest microstructure was observed in the centre of the weld and is attributed to the higher cooling rates which operate along the weld centreline. Composition profiles across the dendrite side arms were measured in the TEM and were found to follow a Scheil type segregation behaviour where there is negligible back diffusion in the solid. The measured core concentration of the dendrite side arms was found to rise with increasing welding speed and was attributed to the formation of significant undercoolings ahead of the primary dendrite tip, which enriched the liquid surrounding the dendrite side arms.

 

اثر ارتعاش مکانیکی روی ریزساختار ماده‎ی جوشکاری

Studies on the Effect of Mechanical Vibration on 

the Microstructure of the Weld Metal

تحقیقات در مورد اثر ارتعاش مکانیکی روی ریزساختار ماده‎ی جوشکاری

ABSTRACT

The solidification process in the weld metal produces solidification structure. The solidification process depends on the thermal gradient, solidification speed and the alloy content. These structures can be planar, cellular, columnar dendritic and equiaxed dendritic. The solidification process may change from planar to cellular, columnar dendritic and equiaxed dendritic across the weld metal zone as shown in fig.1. Three grains are shown to grow epitaxially from the fusion line. A short distance away from the fusion line, solidification changes to the cellular mode. Further away from the fusion line, the solidification changes to columnar dendritic mode. Near the weld centre line equiaxed dendrites nucleate and grow, blocking off the columnar dendrites. Each one of these structures would affect the hot cracking susceptibility in greater or smaller extent.

 

مشخصه یابی فولاد یاتاقان Characteristics of 100Cr6 bearing steel

Characteristics of 100Cr6 bearing steel after thixoforming process performed 

with prototype device

مشخصه یابی فولاد یاتاقان 100Cr6 بعد از فرایند thixoforming انجام شده با ابزار مدل اولیه

ABSTRACT

A device based on a high pressure die-casting(HPDC) machine was constructed, with a capacity to produce thixo-casts from steel. After inductive heating to the required semi-solid temperature range, the samples were transported in a protective argon atmosphere to a cylinder of modified HPDC and injected into a pre-heated die. Bearing steel 100Cr6 (after forging) was used as the feedstock material. The metallographic analysis of the steel showed a homogenous structure within a whole volume characterized by a grain size between 2 μm and 8 μm. Differential scanning calorimetry (DSC) analysis allowed to estimate the process temperature for thixoforming at 1 390 °C which was attributed to about 45% of a liquid phase.