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    A planar nanoporous silicon metal-semiconductor-metal visible light photodetector
    (2013-11-01)
    In this work, the nanoporous silicon layer is prepared through the simple electrochemical etching of p-type crystalline silicon wafer in a hydrofluoric acid solution under various anodization conditions such as the resistivity of the silicon wafer, current density, concentration of the hydrofluoric acid solution and anodization time. The gravimetric method and SEM images have been used to characterize the morphological on the various porosity of nanoporous silicon layer. Two square Al Schottky contacts were thermally deposited on the nanoporous silicon layer with the electrode spacing is 500 μm to form a planar nanoporous silicon metal-semiconductor-metal (MSM) visible light photodetector. In experiment, we investigated photoresponse and the response time of a planar nanoporous silicon MSM visible light photodetector which was fabricated on the various porosity of a nanoporous silicon layer. It is found that when devices are fabricated on a higher porosity nanoporous silicon layer, the photoresponse of the device will expand toward the shorter-wavelengths and the bandwidth of the spectrum response will cover visible light. In addition, it is found that the response time of the device decreases. © 2013 American Scientific Publishers All rights reserved.
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    Improvement of independent directional magnetic field measurement technique with Hall sensors
    (2013-11-04)
    Mano, Athirot
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    Titiroongruang, Wisut
    The independent directional magnetic field measurement is a new technique for magnetic flux density measurement with high accuracy. This technique can reduce the limitation in term of angle that magnetic flux lines interact with Hall sensors. However, the original system limits the uniformity and symmetry of magnetic field patterns, which can cause an error for measurement system. Therefore, the aim of this research is to present the method to increase measurement accuracy of system, by improve magnetic field uniformity which can be done by using electromagnet instead of permanent magnet. The system is also improved the mechanical circle motion by using stepping motor, it is used to rotate Hall sensors in magnetic field which is generated by electromagnet. The result from experiment has shown of this method that can reduce the error percentage as 5% compare with original system. This method is shown 0.99997 of coefficient of determination, which represents to accuracy in magnetic flux density measurement range 0-1350 Gauss. © (2013) Trans Tech Publications, Switzerland.
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    A novel power output model for photovoltaic system
    (2017-10-19)
    Kittisontirak, Songkiate
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    Dawan, Promphak
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    Titiroongruang, Wisut
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    Chinnavornrungsee, Perawut
    This paper proposed the novel concept model for forecasting the PV power output. The model was used two meteorology to input model which are solar irradiance and module temperature. This model was improve the accuracy of model from simplified model is 1D5P by using the weight function. The proposed model was verified by comparison with measured data. The results showed that the model has high accuracy. The RMSE ranges from 0.02 to 0.07 and average RMSE is 0.04.
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    Application of chicken eggshell waste as a starting material for synthesizing calcium niobate (Ca4Nb2O9) powder
    (2015-07-01)
    Kamkum, Phonphan
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    ; ;
    This study focused on the possibility of using CaCO<inf>3</inf> from chicken eggshell waste as a starting material for synthesizing Ca<inf>4</inf>Nb<inf>2</inf>O<inf>9</inf> powder via a conventional solid state reaction. The heat behavior of CaCO<inf>3</inf> and Nb<inf>2</inf>O<inf>5</inf> raw material mixture was studied by thermogravimetric analysis (TGA). Phase formation of Ca<inf>4</inf>Nb<inf>2</inf>O<inf>9</inf> was studied as a function of calcination conditions by Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy and X-ray diffraction (XRD). The morphology and microstructure were charaterized via Scanning electron microscope (SEM). The X-ray fluorescence (XRF) results showed that the chicken eggshell contained more than 96.0% of CaCO<inf>3</inf> by weight. The XRD pattern peaks matched the peaks of calcite CaCO<inf>3</inf> ICDD No. 85-11108 very well. Furthermore, the XRD results and Rietveld refinement analysis confirmed that the purity and single phase of Ca<inf>4</inf>Nb<inf>2</inf>O<inf>9</inf> corresponded to the monoclinic structure (ICDD: 49-0911) obtained after the calcination process. The non-isothermal kinetic of Ca<inf>4</inf>Nb<inf>2</inf>O<inf>9</inf> also was investigated by the Ozawa methods. This study indicated that CaCO<inf>3</inf> from chicken eggshell waste is an alternative starting material for synthesizing Ca<inf>4</inf>Nb<inf>2</inf>O<inf>9</inf> powder.
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    Nanoporous silicon metal-semiconductor-metal visible light photodetector
    (2010-01-01)
    In this research, we present the study on the application of nanoporous silicon for optoelectronic device which called nanoporous silicon metal-semiconductor-metal (MSM) visible light photodetector in this paper. This device was fabricated on nanoporous silicon layer which was formed by electrochemical etching of silicon wafer in hydrofluoric acid solution under various anodization condition such as the resistivity of silicon wafer, current density, concentration of hydrofluoric acid solution and anodization time. The structure of this device has two square Al/nanoporous silicon Schottky-barrier junctions on the silicon substrate and the electrode spacing is 500 μm. The experiment will study on photoresponse and responsetime of nanoporous silicon MSM photodetector which was fabricated on various porosity of nanoporous silicon layer. It is found that when devices fabricated on higher porosity nanoporous silicon layer, the photoresponse of device will expand toward the short-wavelength and bandwidth of spectum response will cover visible light. In addition, it is found that responsetime of device decreases. ©ICROS.
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    Carrier lifetime of platinum doped P-N diode after irradiation by soft X-ray
    (2013-08-30)
    Nararug, Budsara
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    Srithanachai, Itsara
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    Ueamanapong, Surada
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    Khunkhao, Sanya
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    Janprapha, Supakorn
    This paper analyzes the effect of X-ray irradiation on the electrical properties of Pt-doped p-n diode. X-ray energy irradiated on Pt-doped P-N diode with 70 keV with time 205 sec. After irradiations, the current-voltage (I-V) characteristics and capacitance-voltage (C-V) characteristics and carrier degeneration lifetime (τ<inf>g</inf>) were investigated. The results show that the leakage current is slightly increased after the diodes were exposed X-ray and affect higher degeneration carrier lifetime. The effects after X-ray irradiation indicated that the defects of the diode have been changed. © (2013) Trans Tech Publications Switzerland.
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    Study on structure and optical properties of thin-film zinc oxide spin coating under the conditions of annealing temperature of zinc acetate dihydrate
    (2018-01-01)
    Pornprasit, Weerachai
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    In this research we investigated the effect of anneal temperature change on the structure and optical properties of thin zinc oxide film by rotating sol-gel coating on glass substrate. 300°C, 400°C, 500°C and 600°C respectively. Crystal structure analysis with X-ray diffractometer Scherrer equation was used to determine the size of the crystals. The size of the crystals was 30-48 nm. The surface of the film was scanned by scanning electron microscope. Analysis of optical properties with UV spectrometer. It was found that the effect of anneal temperature variation on the light transmission and absorption of the film was 80-90%. The wavelength ranges from 300 to 375 nm. Finally, the gap between the energy bands is between 3.20 and 3.24 electron volts(eV).
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    Investigations of nanostructure and photoluminescence properties of nanoporous silicon
    (2013-10-04)
    In this paper, the nanoporous silicon layer was formed by electrochemical etching of silicon wafer in hydrofluoric acid solution. The purpose of this research, the nanoporous silicon layer were investigated the nanostructure and photoluminescence properties. We report the investigation on nanostructure of nanoporous silicon by using SEM, the gravimetric and fourier transform Raman spectroscopy (FT-Raman) technique. It is found that increasing the constant current density between electrochemical etching have effect to increasing porosity of nanoporous silicon. And increasing porosity of nanoporous silicon is effect from decreasing average size of silicon crystallites in nanoporous silicon which can confirm with Raman spectroscopy. The Changes in the photoluminescence intensity of nanoporous silicon samples are studied during nanoporous silicon stored in various ambient gases such as air, nitrogen, oxigen and vacuum. From data of this experiment when nanoporous silicon were stored in ambient air for a long time, the photoluminescence intensity of nanoporous silicon will decrease. In addition, we found strongly decreasing in its photoluminescence intensity when nanoporous silicon were stored in ambient of oxygen which can confirm by using fourier transfrom infrared spectroscopy (FT-IR) technique. © (2013) Trans Tech Publications, Switzerland.
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    Effect of Forming Porous Silicon with Different Electrochemical Etching Cell to Porosity Layer Under Various Anodization Current Density
    (2017-01-01)
    Intasom, Jiramet
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    In this research is purpose to study effect of forming porous silicon with different electrochemical etching cell to porosity layer under various anodization current density (10, 15, 20 and 25 mA/cm<sup>2</sup>). Three method of forming porous silicon were prepared by forming in single tank electrochemical etching cell without coating Al at backside of silicon wafer, forming in single tank electrochemical etching cell with coating Al at backside of silicon wafer and forming in double tank electrochemical etching cell without coating Al at backside of silicon wafer. After that investigate porous silicon by test photoluminescence with irradiate UV- Light on samples. The porosity of porous silicon was measure by gravimetric method. The result was found that the porous layer from forming by double tank electrochemical etching cell without coating Al at backside are most homogeneity and porosity of porous silicon are increase with the increase of current density.
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    Defects study by activation energy profile for lowering leakage current in p-n junction
    (2011-01-01)
    Srithanachai, Itsara
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    Ueamanapong, Surada
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    Rujanapich, Poopol
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    Niemcharoen, Surasak
    Diode leakage current consists of diffusion (I<inf>d</inf>) and generation current (I<inf>g</inf>), which is strongly sensitive to the residual defect density. These defects can be studied by activation energy (E<inf>a</inf>). Therefore, this paper presents a method for calculating activation energy of silicon p-n junctions from volume generation current. It combines temperature-dependent current-voltage (I -V) and capacitance- voltage (C-V) measurements of diodes. The I<inf>g</inf> can be found from the volume leakage current by subtraction of the volume diffusion current, which is calculated while the depletion width is zero. The activation energy (E<inf>a</inf>) is derived from slope of an Arrhenius plot of I<inf>g</inf>. To derive the correct slope the temperature dependence of the depletion width, which is obtained from the corrected volume capacitance has been applied. The E<inf>a</inf> profile below junction has been shown. The lower E<inf>a</inf> value has been found near the junction, which may relate to the junction implantation. © (2011) Trans Tech Publications.