S. Shaari

FABRICATION OF ZINC OXIDE-BASED DYE-SENSITIZED SOLAR CELL BY CHEMICAL BATH DEPOSITION

Zinc oxide film has been fabricated by converting flower-like structure of zinc carbonate hydroxide made by chemical bath deposition technique. Flower-like structure is employed as charge transport network of dye-sensitized photoanode. Analysis of current density–voltage characteristic shows deposition temperature and deposition time of chemical bath deposition influence photovoltaic performance. Analysis of electrochemical impedance spectroscopy reveals short electron lifetime and high effective electron diffusion coefficient of zinc oxide-based dye-sensitized solar cell.

Angle Shifting in Surface Plasmon Resonance: Experimental and Theoretical Verification

This paper discussed a sensing property of the SPR sensor to detect changes in refractive index of the dielectric medium. The resonant angle shifting was observed as the dielectrics medium was changed from air to SiO2 thin film. The effect of a free space wavelength to the excitation of SPP was investigated by employing laser sources with wavelengths transmission of 545nm and 632.8nm. In comparison with 545nm of wavelength transmission, we revealed that He-Ne laser source with wavelength of 632.8nm is suitable to produce a strong SPR signal due to its high Q-factor. To avoid misinterpretation between the destructive interference and SPR phenomenon, we proposed a simple theoretical approach using momentum conservation principle which concerning the wavevector values to validate the experimental results. By ignoring the imaginary part of the dielectric function of gold, we proved that this theoretical approach is still acceptable due to the excellent agreement between the theoretical and simulation approaches.

Design configuration of encoder and decoder modules for modified double weight (MDW) code spectral amplitude coding (SAC) optical code division multiple access (OCDMA) based on fiber Bragg gratings

In this work, we are proposing the serial and parallel configurations of encoder and decoder modules to encode and decode a new developed spectral amplitude coding (SAC) known as modified double weight (MDW) code for optical code division multiple access (OCDMA) system. This coding scheme is designed in a way to decrease the number of FBGs used in the encoder and decoder modules and to maintain the cross-correlation parameter to 1.

Design and optimization of 22 nm gate length high-k/metal gate NMOS transistor

In this paper, we invented the optimization experiment design of a 22 nm gate length NMOS device which uses a combination of high-k material and metal as the gate which was numerically developed using an industrial-based simulator. The high-k material is Titanium dioxide (TiO2), while the metal gate is Tungsten Silicide (WSix). The design is optimized using the L9 Taguchi method to get the optimum parameter design. There are four process parameters and two noise parameters which were varied for analyzing the effect on the threshold voltage (Vth). The objective of this experiment is to minimize the variance of Vth where Taguchis nominal-the-best signal-to-noise ratio (S/N Ratio) was used. The best settings of the process parameters were determined using Analysis of Mean (ANOM) and analysis of variance (ANOVA) to reduce the variability of Vth. The results show that the Vth values have least variance and the mean value can be adjusted to 0.306V ±0.027 for the NMOS device which is in line with projections by the ITRS specifications.

Modeling And Analysis Of Lateral Doping Region Translation Variation On Optical Modulator Performance

In this paper, we design and discuss the performance of a silicon phase modulator integrated in a silicon‐on‐insulator (SOI) waveguide. The modulator employing the p‐i‐n diode structure will be working at 1.55 μm optical telecommunications wavelengths. The lateral translation of doping regions of p+ and n+ doping regions are varied, and the refractive index change, phase modulation efficiency and also the absorption loss of the modulator are investigated. Our simulation shows that moving the lateral translation of the doping regions closer to the rib waveguide sidewall, the change of the refractive index increases, resulting better modulation efficiency but experiences more absorption loss.

Optimization of electro-optical characteristics of GaAs-based oxide confinement VCSEL

An experimental study has been presented of the oxide-confined vertical-cavity surface-emitting lasers (VCSEL) operating in the 850 nm region of the electromagnetic spectrum. In this regard, various relevant VCSEL samples with numerous oxide aperture sizes have been fabricated and characterized. Thorough investigations of the electrical as well as optical characteristics of the fabricated samples have been performed which includes the overall device performance as a function of the oxidize aperture sizes. It is reported that the VCSEL with oxide aperture size <10 μm require low threshold currents (<1 mA). Further, the differential quantum efficiencies up to 28% were measured for a number of these devices. It is found that devices employing oxide aperture of 10 to 15 μm shows promising electro-optical characteristics for 850 nm oxide VCSEL optimization.

Improved efficiency of GaAs-based VCSEL by utilizing fan-pad metallization and trench patterning

Emphasizing the Vertical-Cavity Surface-Emitting Laser (VCSEL) device packaging, fan-pad metallization and trench patterning are demonstrated for VCSEL operating at 850 nm of the electromagnetic spectrum. The fabricated devices are observed to exhibit low threshold current and series resistance, contributing thereby to higher VCSEL efficiency. It is also observed that the output spectral characteristics of the fabricated device show stable multimode operation. The results indicate that the proposed VCSEL packaging exhibits superior device performance as compared to the VCSEL device packaged with square-pad metal.

Performance of OCDMA Systems Using AND Subtraction Technique

A new detection scheme, namely AND subtraction technique is proposed and presented in this paper. The theory is being elaborated and experimental results have been done by comparing double-weight (DW) code against the existing code, Hadamard. In this paper we have proved that AND subtraction technique gives better bit error rates (BER) performance than Complementary subtraction technique against the received power level.

Absorption Characteristics of Ruthenium (Ru)-II Nanoparticles as a Dissolved Oxygen Sensing Material

Ruthenium (Ru)-II complexes such as the Ruthenium-tris(4,7-diphenyl-1,10-phenanthroline)dichloride (Ru(dpp)32+)is commonly used for dissolved oxygen sensing because of their profound advantages such as visible absorption, a large Stokes’ shift, good fluorescence quantum yields, long excitation lifetimes and good oxygen quenching efficiency. In this study, we report on the absorption characteristics of (Ru(dpp)32+) when it is exposed to dissolved oxygen where the absorption was determined using ultraviolet-visible (UV-Vis) absorbance spectroscopy. The results show that by decreasing the concentration ofRu(ddp)32+, the absorbance remained constant at optical wavelength of 455nm while the intensity changes with the presence of dissolved oxygen. The sensitivity of detecting dissolved oxygen was proven to improve by increasing the amount of Ru(ddp)32+ used.

Optical and structural properties of Zn(1-x)FexS nanoparticles synthesized by chemical bath deposition method

Nanoparticles of Zn(1-x)FexS with x = 0.0, 0.05, 0.1, 0.15, 0.2 and 0.3 were synthesized using the chemical bath deposition method, using tri-sodium citrate as a complexion agent. These nanoparticles were characterized using XRD, SEM, optical absorbance and photoluminescence. SEM micrographs of the films revealed the combination of Zn(1-x)FexS nanoparticles with an average particle size D ~ 60.3 to 19.3 nm ± 0.01 nm for x = 0.0 to 0.3. X-ray diffraction patterns confirmed the nanocrystalline cubic ZnS phase formation. UV-visible spectrometer measurement showed high absorbance for Fe concentration x ≥ 0.15 in the wavelength range 325–800 nm. However, for x ≤ 0.1, the absorbance of the films decreased with further increase of Fe concentration. From the absorbance data, the direct bandgap values have been calculated to be in the range Eg = 3.5 to 2.23 eV for x = 0.0 to 0.3. The bandgap decreased with the increase of Fe concentration in the films. The photoluminescence spectra of the films showed two emission peaks, the first in the low wavelengths due to band-to-band transition, and the second in the high wavelengths due to the transitions probabilities and to the concentration of Fe ions. Due to the quenching effect, the intensity of PL spectra decreased on further increase of Fe doping.