Narin Atiwongsangthong

Synthesis of Monodispersed Perovskite Barium Zirconate (BaZrO3) by the Sonochemical Method

Barium zirconate (BaZrO3) was synthesized successfully by the sonochemical method. The monophase of BaZrO3 was formed completely in short irradiation time without the calcination process. X-ray diffraction, Fourier transform and Raman spectroscopy were used to characterize formation of the perovskite BaZrO3 phase, which occurs in a 60 minute single phase with a cubic crystal structure at room temperature. Therefore, sonochemical irradiation could accelerate the formation of BaZrO3 particles significantly. Furthermore, scanning electron microscopy investigated the uniform shape and size. The size distribution became narrow with increasing time, as a function of irradiation.

Extraction of mobility degradation, effective channel length and total series resistance of NMOS at elevated temperature

This article describes the extraction of total series resistance, effective channel length and low field effective channel mobility degradation parameter at temperature in the range of 25°C–125°C of NMOS device. The relation of I<inf>DS</inf> and V<inf>GS</inf> in a linear region was used with a different of channel length. The procedure is based on the measurement of the transconductance characteristics of MOSFET in the linear region. The transconductance characteristics is determine for the several devices of difference drawn channel length. The results shows that, the effective channel length is increased in a range of 5×10⁻¹⁰ m/°C. The low field mobility degradation parameter is decreased by the factor of 0.733. The total series resistance is increased in the range of 1.4 Ω-µm/°C. The errors between the predicted model and measured of I<inf>DS</inf>&V<inf>GS</inf> in linear region is approximately 3 %

A novel power output model for photovoltaic system

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.

Carrier Lifetime of Platinum Doped P-N Diode after Irradiation by Soft X-Ray

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 (τg) 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.

Improvement of Independent Directional Magnetic Field Measurement Technique with Hall Sensors

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.

Nanocrystalline Barium Zirconium Titanate Synthesized by the Sonochemical Process

Nanocrystalline barium zirconium titanate, BaZr0.4Ti0.6O3, was synthesized successfully via the sonochemical process. The effects of reaction time on the precipitation of Ba(Zr,Ti)O3 particles were investigated briefly. The crystal structure as well as molecular vibrations and morphology were investigated. X-ray diffraction indicated that the powders exhibited a single phase perovskite structure, without the presence of pyrochlore or unwanted phases at the reaction time of 60 min. Nanocrystals were formed before being oriented and aggregated into large particles in aqueous solution under ultrasonic irradiation. A scanning electron microscopy (SEM) photograph showed the BZT powder as spherical in shape with uniform nanosized features.

Investigations of Nanostructure and Photoluminescence Properties of Nanoporous Silicon

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.

Photocurrent Enhancement between Two Coplanar Schottky-Barriers on Silicon MSM Photodetector

Gain properties of dc and ac photocurrent generated between two Schottky barriers coplanarly placed on silicon metal-semiconductor-metal photodetector have been investigated experimentally. The test structure has two square Mo/n-Si Schottky barrier junctions on an n-type silicon substrate with a resistivity of 9-12 Ω-cm and the junction internal separation is 20 m. The current-voltage (I-V) characteristics under illumination in visible range showed a rapid increase in the photocurrent at higher bias region. From the I-V characteristics and noise measurements, increase in photocurrent was ascribed to avalanche multiplication of carriers photogenerated in the reverse-biased Schottky junction. From observation of optical signal demodulation at low frequencies (10 kHz and 50 kHz), it was found that multiplication factor larger than 100 at 10 kHz and 30 at 50 kHz was achieved respectively.

Defects Study by Activation Energy Profile for Lowering Leakage Current in P-N Junction

Diode leakage current consists of diffusion (Id) and generation current (Ig), which is strongly sensitive to the residual defect density. These defects can be studied by activation energy (Ea). 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 Igcan 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 (Ea) is derived from slope of an Arrhenius plot of Ig. To derive the correct slope the temperature dependence of the depletion width, which is obtained from the corrected volume capacitance has been applied. The Ea profile below junction has been shown. The lower Ea value has been found near the junction, which may relate to the junction implantation.

Nanoporous silicon metal-semiconductor-metal visible light photodetector

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.