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In this work, generalized gradient approximation (GGA) and the Heyd-Scuseria-Ernzerhof (HSE) hybrid functional within the framework of density functional theory (DFT) are used to investigate the structural, electronic and optical properties of Ag2MgSn(S/Se)4 quaternary chalcogenides in kesterite and stannite phases. The kesterite and stannite phases of Ag2MgSn(S/Se)4 are optimized and the values of lattice constants are calculated. The predicted energy bandgaps are found to be direct in nature along the Γ direction, with highest bandgap energy of less than 1.64 eV for Ag2MgSnS4 in kesterite phase. The total and partial density of states are analysed in detail. The optical properties such as imaginary and real parts of dielectric function, refractive index, reflectivity and extinction coefficient are also discussed. Further, in order to understand the light trapping capacity, we examine the absorption coefficients of Ag2MgSnS4 and Ag2MgSnSe4 materials and explore their applicability as solar cell absorber layers. The predicted values of all parameters will help researchers to carry out further investigations on these materials for photovoltaic applications.

Pure and gallium (Ga)-doped CH3NH3PbCl3 perovskites are systematically prepared via a simple solution-processed technique. The as-synthesized perovskites are then analysed for their structural, optical, morphological, elemental and electronic properties using X-ray powder diffraction (XRD), UV–Vis diffuse reflectance spectroscopy (UV–Vis-DRS), field emission gun-scanning electron microscopy (FEG-SEM), energy-dispersive spectroscopy (EDS) and photoluminescence spectroscopy (PL), respectively. The detailed structural study reveals the formation of the cubic structure with space group pm3m for pristine and Ga-doped CH3NH3PbCl3 perovskites. Microstrain and lattice dislocation density of doped perovskites increase with increasing Ga composition, compared to the undoped CH3NH3PbCl3. Optical properties show the bandgap narrowing up to 10% Ga doping, and any further increase in doping concentrations again increases the bandgap. This blue shift in absorption edge, i.e. bandgap widening behaviour, of highly doped CH3NH3PbCl3 (20% and 30%) perovskites justifies the Burstein–Moss effect in doped semiconductors. The highest Urbach tail energy is observed for 10% Ga-doped compound, which in turn results in the highest electron–phonon interaction. Morphological imaging shows that optimum Ga doping (10%) can improve the characteristic in terms of homogeneity and defect-free surface, compared to pristine perovskite. However, doping beyond the optimal value can further deteriorate the surface morphology by enhancing the surface inhomogeneity and defects. XRD and EDS both confirm the purity of the synthesized materials. Here, doping increases non-radiative recombination which suppresses the radiative recombination of pure CH3NH3PbCl3. These observations unfold the prospect for a new insight of post-transition metals, to fabricate lead-free perovskite materials with advanced optoelectronic properties.

In this work, mechanical and thermodynamic properties and phonon calculations of quaternary chalcogenide material Ag2MgSn(S/Se)4 in kesterite and stannite phases are calculated using density functional theory with generalized gradient approximation (GGA) functional. Elastic constants are calculated for all the four crystal structures, and it is found that they are mechanically stable in accordance with Born–Huang stability criterion. Also, it is observed that the strength of bonds along the [1 0 0] and [0 1 0] crystalline directions is as strong as the bonds in the [0 0 1] crystalline direction for all structures. The sum of elastic constants C11 and C12 is greater than C33 showing that elastic modulus calculated in the (0 0 1) plane is more compared to its values along the c-axis. With Pugh’s theory analysis, it is found that the B/G ratio is greater than 1.75 for all four structures, and they are ductile in nature. Using the Debye model, vibrational heat capacity at constant volume and coefficient of thermal expansion are studied in the temperature range of 0–1200 K for all four structures. Also, the vibrational modes and phonon dispersion curve along the high symmetry point (Z-Γ-X-P-Γ-N) are analysed to investigate the stability of the structures. These findings should be useful in the fabrication of thin-film solar cells using these materials as absorber layer.

Silicon photonics technology is on its last hurdle to complete the system with active research on enhancing the light extraction efficiency of silicon. Silicon has a very poor radiative emission efficiency due to its indirect bandgap, thus making the probability of radiative recombination to be very low. The periodic quantum confinement structures such as photonic crystals (PhCs) can be tailored to increase the radiative recombination probability at the desired wavelengths. In this paper, we have optimized the silicon photonic crystal (Si PhCs) parameters to obtain luminescence at silicon bandgap and telecommunication wavelength using FDTD method. The extraction of photons is mostly conquered in the silicon structure that has lattice constant, a: 480 nm with radius, r: 140 nm and a: 500 nm with r: 160 nm. We have also observed the emissive photon luminescence that emerges in the most stable state of optical communication wavelength at 1310 nm.

At present, silicon solar cells are predominantly commercialized in the market because of low cost, reliable and well-established technology, with a solar module efficiency of 16% to 22%. However, perovskite is cheaper to produce than silicon and has much better light absorption properties. It is known that silicon solar cells show highest efficiency in the 800-1100 nm range while perovskite solar cells perform best in the 500-700 nm range. In this work, using numerical device simulation, we investigate a tandem structure with the upper part as perovskite solar cell and the lower part as silicon solar cell. These two solar cells are interconnected using a thin TiO 2 conducting layer of 20 nm which facilitates the tunneling of electrons. The simulated tandem cell structure is able to minimize thermalization losses associated with hot carriers, providing maximum efficiency of 25.4%. The tunneling mechanism is realized by COMSOL Multiphysics.

In this paper, a Kretschmann based surface plasmon resonance sensor using silver (Ag) and indium tin oxide (ITO) on chromium (Cr)-coated BK7 substrate has been analyzed for refractive index sensor. By numerical simulations, the thickness of the ITO layer along with Ag thin film have been optimized to achieve the best performance of the sensor in terms of sensitivity and Figure of Merit (FOM). The best sensor performance was achieved by Cr(0.5 nm/Ag(30 nm) with sensitivity value of 69.88°/RIU and FOM of 15.19 whereas Cr(0.5 nm)/Ag(30 nm)/ITO(10nm) gave sensitivity and FOM of 68.77°/RIU and 11.26, respectively. The deposition of Cr enhanced the attachment of Ag layer to prism whereas incorporating ITO on Cr/Ag sensor interface helps to protect the Ag layer from oxidation and preserve its sharp optical signal. Hence, this Ag based SPR interface with ITO coated can be useful for sensing refractive index changes for analyte detection.

Taguchi’s L9 static design was employed to determine the robust design of a zinc oxide (ZnO) nanofilm surface plasmon resonance (SPR) bimetallic sensor. The control factors such as incident wavelength and different thicknesses of silver, gold and ZnO layers were selected. Noise factors include thickness of the chromium layer and the diameter of the biomolecules (i.e. urea) which were simulated using Finite-Difference-Time-Domain (FDTD). Results obtained show that the thickness of the gold layer has a 41.32% dominant factor effect on the minimum reflectance of light $(\mathbf{R}_{\mathbf{min}})$ , whereas the incident wavelength has a 73.15% dominant factor effect on the full-width-at-half-maximum (FWHM) of the SPR signal. The confirmation tests carried out show that the values of $\mathbf{R}_{\mathbf{min}}$ and FWHM were optimized using Taguchi's orthogonal array method leading to a robust design of the SPR sensor.

A Kretschmann-based surface plasmon resonance (SPR) sensing method was used to determine the refractive index and thickness of graphene thin films. The measured complex refractive index (n,k) values of graphene on Au at 670 nm and 785 nm wavelength are 2.85,0.74 and 3.1, 1.19 respectively. In further analysis, the analysis of sensing performance of graphene on Au SPR sensor for ethanol detection was obtained using Finite Difference Time Domain (FDTD) method. With the addition of graphene layers, the sensitivity, detection accuracy and quality factor of the SPR sensor increased at 670 nm.

In the current work, the sol-gel synthesis method was used to synthesize both undoped and gallium (1%-Ga) doped TiO2 nanoparticles. The as-deposited materials were calcined at 400–500 °C with a temperature variation rate of 5 °C per minute. The crystallographic properties of the semiconductor materials were determined from X-ray diffraction (XRD) which showed the formation of anatase TiO2. The average crystallite sizes, determined from the widths of the XRD reflections, were 11 and 4 nm for undoped and Ga-doped TiO2, respectively. The materials were further studied by density functional theory with meta-generalized gradient approximation exchange–correlation functional. Supercell systems consisting of 24 and 48 atoms were created to form 12.5% and 6.25% Ga dopant substitution, respectively. These structures were optimized to obtain the ground state properties. Transmission electron microscopy showed polycrystalline, spherical powders, with grain sizes comparable to those found using XRD. The surface morphology of the doped TiO2 obtained from scanning electron microscopy showed an improved surface structure compared to pristine TiO2. Moreover, the electronic states of the materials were investigated using X-ray photoelectron spectroscopy. Energy dispersive X-ray spectroscopy verified the elemental composition of titanium, oxygen, and Ga present in the nanoparticles. The surface chemical bonds were analyzed by Fourier-transform infrared spectroscopy. Ultraviolet diffused reflectance spectra analysis was used to examine their optical properties. The experimentally obtained bandgaps of pristine and 1% Ga-doped TiO2 nanoparticles were 2.9 and 3.09 eV, respectively. The optical properties were further analyzed by computing the band structures and density of states using density functional theory. Similar to the experimental results, these electronic structures showed an increase in bandgap after 6.25% Ga incorporation. However, with 12.5% doping, there was a decrement in the bandgap. The analysis showed that, with an appropriate amount of substitution, Ga-doped TiO2 semiconductor material can be used in the electron transport layer and many other fields of photoelectric cells.

The purpose of this study was to design a model for microring resonators (MRRs) for biochemical detection. As a model, two types of MRRs were proposed. The Lumerical application software was used to optimize and analyze the design of MRRs device. Several parameters influencing the detection process were investigated, including the gap separation, the ring radius, the waveguide width and the etching depth dimension of MRRs. The results showed that these parameters highly influenced the condition of MRRs. The optimum parameters yielding optimum detection of biochemical are 4.5 um, 90 nm, 470 nm and 220 nm, corresponding to ring radius, separation gap, waveguide width and etching depth, respectively. The both models of MRRs proposed in this paper yield large values of FSR (free spectral range) and Q-factor therefore are suitable for biochemical detection.

In this work the one dimensional device simulation of lead-free perovskite solar cell of CH 3 NH 3 SnI 3 absorber perovskite material is performed. The parameters which affect the overall performance of the solar cell are investigated and it is observed that the absorber thickness, doping concentrations of HTM (hole transport material), ETM (electron transport material) and perovskite absorber and temperature, influence the solar cell performance. The optimized performance of the perovskite solar cells with PCE (power conversion efficiency) of 30.59%, is obtained when the thicknesses of perovskite was 300nm and the doping concentrations of Cu2O, PCBM and perovskite were 9×1021cm-3, 1×1021cm-3 and 1×1013cm-3 respectively. It is observed that suitable optimization of material parameters and device dimensions may lead to high efficiency Perovskite solar cell.

Kretschmann-based surface plasmon resonance (K-SPR) sensing approach using planar thin metal films offer distinct advantages over other label-free sensing techniques in the visible region. SPR phenomenon occurs due to the propagation of electromagnetic waves along the surface of the thin metal layers. Practically, some refractive index changes on the dielectric sample layer will cause changes in surface plasmon polaritons (SPP). The main purpose of using this coupling technique is to match the light-wave vector wave with the SPP vector wave. This paper will give an overview of the design and development of SPR-based sensors utilizing the angular interrogation Kretschmann configuration for detecting the presence of various analytes such as urea, creatinine, glucose, ethanol and uric acid in the visible region. Various sensor layers such as 50-nm thick gold (Au), MoS 2 /graphene, Au/graphene oxide, Ag/ITO and Au/Ag/ZnO thin films were used to detect the analytes at 633 nm, 670 nm and 785 nm visible electromagnetic wavelengths. Output characteristics such as the reflectivity, full width at half maximum (FWHM), sensitivity, Q factor and Figure of merit (FOM) of the sensors were analyzed. Results of this study was obtained using Lumerical's Finite Difference Time Domain (FDTD) and experimental characterization was obtained using Bionavis SPR equipment; available at IMEN, UKM.

First principle calculations on pure and germanium (Ge) incorporated tin (IV) oxide (SnO2) are performed to understand their structural, electronic, and optical properties at the microscopic level. The optimized ground state structures exhibited a reduction in their lattice parameters as well as total energy with increasing germanium concentration. From the band structures of the pristine and doped SnO2, we have observed a reduction in the energy gap due to the incorporation of germanium into stannic oxide (SnO2). As conduction band minimum near Fermi level reaching a lower energy level with an increase in doping concentration, the electron affinity is increasing. The calculated band gaps of pure, 6.25 %, 12.5 % and 25 % ‘Ge’ incorporated tin (IV) oxides are 1.76, 1.73, 1.56 and 1.53 eV, respectively, and all are direct in nature. Further, the calculated electron effective mass at the conduction band minimum is lower than the hole effective mass at the valence band maximum. Hence, the mobility of electrons is found to be higher, suggesting the n-type semiconducting property. The contributions of different atoms on valence and conduction band are studied by calculating the density of states spectra. Optical properties, such as real and imaginary dielectric constants, absorption, reflectivity, refraction and extinction coefficient, loss function, real and imaginary optical conductivity are calculated. The calculated optical absorption shows that both un-doped and doped materials preserve the optical transparency in the infra-red region. Our analysis shows that Ge-doped SnO2 has a tunable band gap and work function, which makes it suitable for applications in photovoltaic devices.

The paper reports scattering of plane waves by elliptical/circular homogenous, isotropic, and non-magnetic dielectric cylinders coated with chiral medium and surrounded by a perfectly electrical conducting sheath helix structure. The effect of pitch angle on the echo width under the assumption of parallel polarization is discussed, and the results are compared taking into account dielectric cylinders of different dimensions. The introduction of negative refraction in chiral mediums, and its effects on both the elliptical- and circular-shaped scattering objects are evaluated. The results indicate significant impact of the used chiral medium coating as well as the embedded sheath helix structure to alter the bi-scattering echo width of the object.

Diabetes mellitus is a disease of metabolic disorders where human blood contains a high amount of sugar level for a prolonged period. This study aims to simulate how effective sensor based on MRR and SPR for the purpose of diabetes monitoring. The results show that sensor based on MRR and SPR provides the ability to detect low level of glucose concentration as low as 7 mmol/L (0.13%) and the ability to detect resonance shift for very small glucose concentration change. Therefore, the sensor based on MRR and SPR can be used for diabetes monitoring. The sensitivity of the sensor based on MRR and SPR is 85.84 nm/RIU and 116.69 °/RIU respectively. These findings are important for the development of diabetes monitoring based on MRR or SPR.

Isostructural series of CH3NH3Pb(1 − x)SnxCl3 (x = 0%, 0.5%, 2.5%, 10%, 20%, and 33%) perovskites are prepared by the solution processing method. The synthesized perovskites are investigated in terms of their structural, optoelectronic, morphological, elemental, and thermal properties. The improved crystallinity and enhanced absorption edge toward longer wavelength are observed due to the increased amount of tin (Sn) in the Pb site of CH3NH3PbCl3. The bandgap is reduced from 2.93 eV to 2.83 eV when one third atomic percentage (at. %) of Pb is replaced with Sn. Further, elemental analysis confirms the successful doping of Sn in the host perovskite without the presence of any impurity. The thermogravimetric study of the prepared samples shows that the thermal stability is improving up to 20 at. % Sn doping, whereas the stability starts deteriorating for 33 at. % doping. The obtained results reveal that less toxic, better crystallinity, enhanced optoelectronic properties can be achieved by partial doping of Sn in CH3NH3Pb(1 − x)SnxCl3 perovskites. This work offers a new reference for exploring the use of Sn-doped CH3NH3PbCl3 perovskite materials in optoelectronic devices.

The link power improvement in a coarse wavelength division multiplexing (CWDM) system which is transmitted using a hybrid erbium-doped fiber amplifier (EDFA) and semiconductor optical amplifier (SOA) scheme as a pre-amplifier, is discussed. The network is designed for amplifying 8 CWDM channels ranging from 1471 nm to 1611 nm. The hybrid amplifiers’ gain measurement is obtained from experimental work with gain peak at 22 dB which is observed at 1531 nm. The amplifiers also caused power increment of 5.06 dB in the transmission link before the signal is split individually at the receiving end. Based on the higher gain peaks and power spectrum at 1531 nm and 1551 nm wavelengths, the proposed amplified link would be useful for the transmission of video applications.

In this article, scattering from silver metal cylinder due to L-nihility, coated with dielectric material that encapsulates perfectly electric conducting sheath helix structure, is presented. The orientation of helix can be altered, and the cases of both the parallel (TM) and the perpendicular (TE) polarizations of electromagnetic (EM) waves are analyzed. Co- and cross-polarized fields for different values of pitch angle are formulated under oblique angle of incidence. The bi-static echo width of the scatterer is investigated as a function of at the L-nihility frequency which lies within the optical frequency range. The results are compared with those obtained for perfect electric conductor (PEC) at different values of the angle of incidence. It is observed that the considered guiding structure behaves identically with the simple PEC cylinder under the situation when the helix structure is oriented parallel to the axial direction of the guide. However, for the other forms of the helix orientation, the str...

This paper reports on the effects of the Halo structure variations on threshold voltage ( V th ) in a 22 nm gate length high-k/metal gate planar NMOS transistor. Since the V th is one of the important physical parameter for determining the functionality of complementary metal-oxide–semiconductor device, this experiment will focus on finding the best combination on process parameter to achieve the best value of V th . The Halo structure variable process parameters are the Halo implantation dose, the Halo implantation tilting angle, the Source/Drain implantation dose and the compensation implantation dose. The design of the planar device consists of a combination of high permittivity material (high-k) and a metal gate. Titanium dioxide was used as the high-k material instead of the traditional SiO 2 dielectric and tungsten silicide was used as the metal gate. The optimization process was executed using Taguchi's L 9 array to obtain a robust design. Taguchi's Nominal-the-Best signal-to-noise ratio was used in an effort to minimize the variance of V th . The results show that the V th values have least variance and the mean value can be adjusted to 0.289 V±12.7% which is in line with projections made by the International Technology Roadmap for Semiconductors.

Microring resonator (MRR)-based channel dropping filters have been extensively explored because of the high quality factor, compact size, and easy integration of fabrication. In order to design an excellent MRR wavelength filter, optimization of the design parameters are essential. In this paper, the design trade-off ofMRR-based channel dropping filter was statistically studied by employing the Taguchi method. Four control factors considered were width of rings and channels, radii of the microring, upper rib waveguide height, and gap size. The analysis of variancewas adopted to analyze significant trends that occurred on the free spectral range (FSR) and insertion loss (IL) performance under different sets of control factor combinations. The best parametric combination of control factors was identified in order to achieve a balance performance between large FSR and low IL using Finite-Difference Time Domain (FDTD) simulation by RSoft Inc. After optimization, the value of FSR and IL obtained was 17nm and 0.245 dB, respectively. Confirmation tests were carried out to verify the optimized parametric combinations and a new parametric combination considering both outputs were 16nm and 0.215 dB. The optimal combinations were 6 mm ring radius with the separation gap of 50 nm and 350 nm350 nm rib waveguide cross section. Copyright © 2013 John Wiley & Sons, Ltd.

Microring resonators (MRR) have been extensively explored due to the high quality factor, compact size and easy integration of fabrication. By tailoring microring dimensions, resonator can be tuned to support the desired spectrum of optical modes. This enhancing the development of new types of planar lightwave circuits (PLC) devices for wavelength-division-multiplexed (WDM) networks such as optical filters, sensors, modulators and switches. In this paper, we carry out a quick analysis to investigate a MRR based wavelength filter which will be working around 1.55 μm wavelength. In order to design an excellent MRR filter, optimization of the design parameters are crucial. The FDTD simulation by RSoft is employed to design and characterized the wavelength filter performance. Optimization of design parameters such as size of rings and channels, resonant order, radii of microring and gap size are determined. Multiple serially cascaded microrings are also studied. The device is designed to satisfy single mode behavior for small SOI waveguide. Optimum device parameters are obtained and the key issues affecting the resonator design such as free spectral range (FSR), insertion loss and Quality Factor (Q-factor) are discussed.

The attraction towards two-dimensional optical code division multiple access (2D-OCDMA) systems has increased due to its potential in enhancing the performance of optical access networks and producing optical code-based signals. 2D-OCDMA network systems enable better bit-error-ratio (BER) performance as well as increase the number of supportable users in the optical network. Time-spreading wavelength-hopping is one of the many techniques that has been proposed for 2D-OCDMA. In this paper, we present the simulative study of a 2D-OCDMA system. The developed time-spreading, wavelength-hopping network utilizes enhanced double weight (EDW) code which has enhanced properties such as a cross-correlation value of 1 and has a simple encoder/decoder design. The output BER was satisfactory at above 10 −9 at data rate of 1.25 Gbps for 20 km distance with the ITU-T G.652 standard single mode optical fiber for 3 users.

We present a detailed fabrication process of silicon optical waveguide with a depth of 4μm via simulation and experiment. An anisotropic wet etching using Potassium Hydroxide (KOH) solutions was selected to study the influence of major fabrication parameters such as etch rate, oxidation time and development time to the fabrication performance. The fabrication of the silicon waveguide with the orientation of was modeled using ATHENA from 2D Silvaco software and was later compared with the actual fabricated device. Etching time of 4 minutes was required to etch the Si to the depth of 4μm to obtain a perfectly trapeizoidal optical waveguide structure. Our results show that the simulation model is trustworthy to predict the performance of the practical anisotropic wet etching fabrication process. The silicon-based waveguide components are targeted to be employed in realizing future photonic devices such as optical modulators.

In this paper, we presented the performance analysis of Silicon- on- Insulator (SOI) based, four channels optical wavelength demultiplexer using microrings. The characterizations are done employing Finite- Difference Time- Domain (FDTD) mode simulations from RSOFT. Serially cascaded microring arrays up to the third order are demonstrated to discuss the design issues of the laterally coupled wavelength demultiplexer. Characteristics like the Free Spectral Range (FSR), crosstalk and insertion loss losses are studied.

The fitted parameters for the analytic function used to specify the doping dependence of minority carrier lifetimes for In0.53Ga0.47As (InGaAs) is described in this paper. This model together with other carrier models was used to develop an interdigitated lateral PIN photodiode utilizing InGaAs as the absorbing layer. We propose the usage of spin-on chemicals such as spin-on dopants and spin-on glass to form the p+ wells, n+ wells and the surface passivation layer of the device hence providing a cheap and easy solution versus the conventional epitaxial growth methodology. The modeled device achieved dark currents of 0.21 nA and capacitance of 2.87 nF at an operating voltage of 5 V. Optical illumination at a wavelength of 1550 nm and power of 10 W/cm2 enabled the device to achieve responsivity of 0.56 A/W and external quantum efficiency of 44%. The −3 dB frequency response of the device was at 8.93 GHz and signal-to-noise ratio is 36 dB. The developed device shows close correlation with experimentally developed devices developed using other fabrication methodologies. The results of this work would be useful in the thorough development of InGaAs-based devices based on spin-on chemical fabrication methodology using commercial device simulation packages. Copyright © 2010 John Wiley & Sons, Ltd.

The fitted parameters for the analytic function used to specify doping- and temperature-dependent low-field mobilities for In0.53Ga0.47As is described in this paper. The developed model was compared with other mobility models as well as measured Hall data from periodical literature and very good agreement is observed. The result of this work was used to develop an In0.53Ga0.47As interdigitated lateral p-i-n photodiode (ILPP) model and good correlation was obtained when compared with the experimentally developed device. The results of this work would be useful in the development of In0.53Ga0.47As-based devices using commercial device simulation packages.

This paper presents an inclusive study and analysis of graphene-based MOSFET device at 32nm gate length. The analysis was based on top-gated structure which utilized Hafnium Dioxide (HfO 2 ) dielectrics and metal gate. The same conventional process flows of a transistor were applied except the deposition of bilayer graphene as a channel. The analytical expression of the channel potential includes all relevant physics of bilayer graphene and by assuming that this device displays an ideal ohmic contact and functioned at a ballistic transport. Based on the designed transistor, the on-state current (I ON ) for both GNMOS and GPMOS shows a promising performance where the value is 982.857uA/um and 99.501uA/um respectively. The devices also possess a very small leakage current (I OFF ) of 0.289578nA/um for GNMOS and 0.130034nA/um for GPMOS as compared to the conventional SiO 2/ Poly-Si and high-k metal gate transistors. However, the devices suffer an inappropriate subthreshold swing (SS) and high value of drain induced barrier lowering (DIBL).

This paper aims to study the effect of process parameter variation on a nano-scaled planar p-type MOSFET (metal-oxide-semiconductor field-effect transistor) device for 22 nm technology using Taguchi's L9 orthogonal array. The device was constructed with high-k/metal gate consisting of Titanium dioxide (TiO2) and Tungsten silicide (WSix) metal gate using an industrial-based numerical simulator. Using Taguchi's Signal-to-noise ratio (SNR) of nominal-the-best (NTB), the compensation implantation has been as identified as the dominant factor influencing the Vth value with 67.77% while the Halo implantation tilting angle has been identified as the adjustment factor. Upon optimization, the Vth value is −0.29538 V which is within the requirements of the International Technology Roadmap for Semiconductors (ITRS) 2012 which is −0.289 V ± 12.7 %.

One reasonable and cost-effective method to sense chemicals such as ammonia is to use optical waveguides. In this work, the simulation of an optical single-mode splitter waveguide was executed to detect ammonia on the sensing arm. OptiBPM and Ionex softwares were used for the waveguide and ion exchange simulations respectively. The deepest and widest optical channel was produced when a concentration of Ag+ of 0.2 moles/m3 was used at a temperature of 350°C for duration of 35 minutes. The optical splitter designed in OptiBPM showed a change in the optical power with the presence of ammonia on the gold-coated sensing arm of the splitter. Therefore, the thermal ion change method is an alternative cost-effective method for the fabrication of optical biosensors.

This paper investigates and analyzes an Optical Interconnect (OI) link using external (indirect) modulation technique. A Continuous Wave (CW) light source with a Mach Zehnder (MZ) modulator is used in the transmitter part and a Si-based waveguide is used as a transmission path. Indium Gallium Arsenide (InGaAs) and Germanium (Ge) materials were applied to observe the performance of Avalanche Photodiode (APD) and P-I-N Photodiode (PIN). In order to evaluate the performance of OI link using external (indirect) modulation, the model of OI link was designed and simulated using OptiSPICE tools. Simulation results on the performance of MZ modulator, power degradation of OI link and receiver sensitivity are reported in this paper.

The complementary metal-oxide-semiconductor field effect transistor (CMOSFET) has become major challenge to scaling and integration. Innovation in transistor structures and integration of novel materials are necessary to sustain this performance trend. CMOS variability in the scaling technology becoming very important concern due to limitation of process control; over statistically variability related to the fundamental discreteness and materials. Minimizing the transistor variation through technology optimization and ensuring robust product functionality and performance is the major issue.In this article, the continuation study on process parameters variations is extended and delivered thoroughly in order to achieve a minimum leakage current (ILEAK) on PMOS planar transistor at 22 nm gate length. Several device parameters are varies significantly using Taguchi method to predict the optimum combination of process parameters fabrication. A combination of high permittivity material (high-k) and metal gate are utilized accordingly as gate structure where the materials include titanium dioxide (TiO2) and tungsten silicide (WSix). Then the L9 of the Taguchi Orthogonal array is used to analyze the device simulation where the results of signal-to-noise ratio (SNR) of Smaller-the-Better (STB) scheme are studied through the percentage influences of the process parameters. This is to achieve a minimum ILEAK where the maximum predicted ILEAK value by International Technology Roadmap for Semiconductors (ITRS) 2011 is said to should not above 100 nA/µm. Final results shows that the compensation implantation dose acts as the dominant factor with 68.49% contribution in lowering the device’s leakage current. The absolute process parameters combination results in ILEAK mean value of 3.96821 nA/µm where is far lower than the predicted value.

Computer-aided diagnosis (CAD) of mammograms assists the radiologists to detect the mammographic mass presence. Since the variability of shapes of such breast masses occurs very frequently, it is more difficult to classify them into benign and malignant stages. One efficient approach to classify them is the fractal analysis by deriving their shape features. Various methods have been proposed for the fractal dimension (FD) computation of region of interest (ROI) in biomedical images. Among those, two methods, namely power spectral analysis (PSA) and differential box counting method (DBCM), are used here for the FD computation of breast contour margins. Fractal analysis by PSA method is a frequency-domain approach which is applied to the one-dimensional (1D) signatures of the two-dimensional (2D) breast mass contours. However, the DBCM model assigns the smallest number of boxes that cover the whole image surface. Finally, a comparative analysis is performed between the above-said two methods which show the PSA method yields better accuracy than the DBCM.

This paper provides the enhancement of 22nm planar PMOS transistor technology through downscaling, design parameter simulation and optimization process. The scaled down device is optimized for its process parameter variability using Taguchi method. The aim is to find the best combination of fabrication parameters in order to achieve the target value of the threshold voltage (V th ). A combination of high permittivity material (high-k) and metal gate is utilized simultaneously in replacing the conventional SiO 2 /Poly-Si technology. For this, Titanium dioxide (TiO 2 ) was used as the high-k material and tungsten silicide (WSi x ) was used as the metal gate. The simulation results show that the optimal threshold voltage (V th ) of −0.289 V ± 12.7% is achieved in accordance to the ITRS 2012 specifications. This provides a benchmark towards the fabrication of 22 nm planar PMOS in future work.

The evolution of MOSFET technology has been governed solely by device scaling, delivered an ever-increasing transistor density through Moore's Law. In this paper, the design, fabrication and characterization of 32nm HfO 2 /TiSi 2 PMOS device is presented; replacing the conventional SiO 2 dielectric and Poly-Silicon. The fabrication and simulation of PMOS transistor is performed via Virtual Wafer Fabrication (VWF) Silvaco TCAD Tools namely ATHENA and ATLAS. Taguchi L9 Orthogonal method is then applied to this experiment for optimization of threshold voltage (V TH ) and leakage current (I OFF ). The simulation result shows that the optimal value of V TH and I OFF which are 0.1030075V and 3.4264075×10−12A/um respectively are well within ITRS prediction.

In this article, we examine the effect of four process parameters and two noise parameters on the threshold voltage (Vth) of a 22nm gate length PMOS device. The gate of the device uses titanium dioxide (TiO2) as the high permittivity material (high-k) layer to replace the traditional silicon dioxide (SiO2) dielectric layer. While the polysilicon (poly-Si) which is also known as self-aligned silicide (SALICIDE) layer, is deposited on top of the high-k dielectric layer and is used to reduce the gate electrode resistance. The virtual fabrication device was designed using the ATHENA and electrical characterization was simulated using ATLAS. These two simulators were combined with the L9 Taguchi's experimental design to aid in the design and optimization of the process parameters for a total of 36 simulation runs. The objective is to minimize the variance in Vth using Taguchi's nominal-the-best signal-to-noise ratio (SNR) analysis. Analysis of the mean (ANOM) was used to determine the best settings for the process parameters while Analysis of variance (ANOVA) was used to reduce the variability of Vth. The results show that the Vth values with the least variance is -0.289 V ± 12.7% which is well within the prediction by the International Technology Roadmap for Semiconductors (ITRS) 2011.

Fractal analysis can be used for the detection of masses exhibiting circular and lobulated shape margins in screening mammograms. Currently, mammograms have been one of the most versatile methods for the early detection of breast cancer. However, one of the characteristic lesions of breast cancer appears as dense regions of breast sizes and properties known as breast masses. To classify these breast masses into benign and malignant, fractal analysis can be used. The most versatile method for fractal analysis is based on Power Spectral Analysis (PSA) using the signatures of contours. The experimental results using fractal analysis provides an accuracy of 82% for circular and lobulated margin breast masses.

In this article, a network structure of passive optical network (PON) in conjunction with optical code division multiple access (OCDMA) technique is theoretically investigated using Modified Quadratic Congruence (MQC) codes as a signature sequence, and taking into account the effects of various noises such as shot noise, phase-induced intensity noise (PIIN), thermal noises and multiple access interference (MAI) noises. The system also has been simulated with 9 users simultaneously over a 20km channel length, utilizing spectral amplitude coding (SAC) detection scheme with fiber Bragg grating filters. The results show that, the system based on SAC scheme and MQC codes at 622Mb/s, was achieved the error free transmission (bit error rate BER

We present the modeling of a first order waveguide-coupled microring resonator (MRR) by coupled mode theory (CMT) using transfer matrix model. The design topology is based on the lateral coupling configuration and single mode propagation which is integrated on a Silicon-on-Insulator (SOI) platform. Performance parameters including Free Spectral Range (FSR) and Quality Factor (Q-factor) are investigated. For verification, we compare these results with the results obtained from the Finite Difference Time Domain (FDTD) commercially available software. We found that both results agree well with each other.

Long-wavelength VCSELs (LW-VCSEL) operating in the 1.55 μm wavelength regime offer the advantages of low dispersion and optical loss in fiber optic transmission systems which are crucial in increasing data transmission speed and reducing implementation cost of fiber-to-the-home (FTTH) access networks. LW-VCSELs are attractive light sources because they offer unique features such as low power consumption, narrow beam divergence and ease of fabrication for two-dimensional arrays. This paper compares the near field and far field effects of the numerically investigated LW-VCSEL for various design parameters of the device. The optical intensity profile far from the device surface, in the Fraunhofer region, is important for the optical coupling of the laser with other optical components. The near field pattern is obtained from the structure output whereas the far-field pattern is essentially a two-dimensional fast Fourier Transform (FFT) of the near-field pattern. Design parameters such as the number of wells in the multi-quantum-well (MQW) region, the thickness of the MQW and the effect of using Taguchi's orthogonal array method to optimize the device design parameters on the near/far field patterns are evaluated in this paper. We have successfully increased the peak lasing power from an initial 4.84 mW to 12.38 mW at a bias voltage of 2 V and optical wavelength of 1.55 μm using Taguchi's orthogonal array. As a result of the Taguchi optimization and fine tuning, the device threshold current is found to increase along with a slight decrease in the modulation speed due to increased device widths.

Code pulses of spectral amplitude coding (SAC)-optical code division multiple-access (OCDMA) are overlaid onto a multichannel wavelength division multiplexing (WDM) system. Modified quadratic congruence (MQC) codes are developed as the signature codes for the SAC/OCDMA system to avoid the overlapping between signals of both systems. In addition, simultaneous transmission of both optical CDMA users and WDM users on the same band is investigated using a network simulation. Our results are compared to traditional non-hybrid systems. It is concluded that the proposed hybrid scheme achieves performance that is slightly worse than that for the non-hybrid scheme. Furthermore, it provides enhanced data confidentiality as compared to the scheme with SAC/OCDMA only because WDM signals perform a partial masking over encoded signals.

Undoped and Mn doped ZnO films with different doping concentration were synthesized by sol gel method using the spin coating technique. Zn 1−x Mn x O thin films are prepared using 2-methoxyethanol solution of zinc acetate dehydrate and manganese acetate tetrahydrate. The quantity of Mn in the sol was varied for each experiment with an annealing temperature of 500°C. As to investigate the physical properties and microstructures, the samples are characterized using FESEM. The surface morphology showed spherical shaped nanoparticles and separated uniformly on the films. The quality surface degraded by doping with Mn but at until 8% of Mn, the surface become smoother. Meanwhile, the optical properties were characterized using UV-Vis where the absorbance spectra were affected by certain amount of Mn concentration. Four point probe is used to measure the resistivities of the samples. These films achieve tunable band gap characteristics by means of changing the dopant concentration.

We have analyzed and discussed the issues arising in the design of Silicon — on — Insulator (SOI) wavelength filters with different types of device geometry. Microring and microdisk geometries have been chosen as the device configurations and in order to demonstrate the device performance and potential, Free Spectral Range (FSR), and Q-factor values are computed. Studies of the transmittance characteristics are carried out using Finite-Difference Time-Domain (FDTD) methods by RSOFT Software. Results show that the microring-based wavelength filter has a FSR of 1.4 THz and a Q-factor value of 486. On the other hand, the microdisk based filter has a broader FSR with slightly smaller Q-factor.

Objective Data on the prevalence of hypovitaminosis D in Indians living in the western part of the country are limited. The authors aimed to study the vitamin D status and dietary intake of calcium and phytates in healthy adult volunteers from a city in the western part of India. Methods This cross-sectional study was conducted at a tertiary care centre in western India. A total of 1137 young (age: 25–35 years), healthy volunteers of both sexes were included in the study. All subjects were assessed for sun exposure, dietary intake of energy, protein, fat, calcium and phytates. Biochemical investigations included calcium, inorganic phosphorus, alkaline phosphatase, 25-hydroxyvitamin D (25(OH)D), intact parathyroid hormone (iPTH), total proteins, albumin and creatinine in serum and spot urinary calcium to creatinine ratio. Results The serum 25(OH)D concentration for the whole study population was low (17.4±9.1 ng/ml), and that for men and women were 18.9±8.9 ng/ml and 15.8±9.1 ng/ml, respectively. Seventy per cent of the study population had hypovitaminosis D (25(OH)D Conclusion Hypovitaminosis D, low dietary calcium and high phytate consumption are highly prevalent among young healthy adults in the western part of India.

Since 1980's, silicon photonic devices have been extensively studied, however a submicrometre-size photonic devices have been realized only in the last few years. Silicon properties namely the transparency in the range of optical telecommunications wavelengths and high index of refraction, have enabled the fabrication of low loss submicron waveguide. Photonic devices such as splitter, coupler, and filter have been demonstrated in silicon but once the device has been fabricated, the properties of the device are predetermined. A silicon based modulator can be used to control the flow of light, where the refractive index of the silicon waveguide can be varied thus, induce a change in the transmission properties.

Silicon as a photonic medium has a unique advantages. It is transparent in the range of optical telecommunications wavelengths (1.3 and 1.55µm) and has a high index of refraction, which allows for the fabrication of high-index-contrast submicrometer structures. The key elements for the development of silicon microphotonics is the silicon-based optical modulators which have earned a great interest in the recent years. High-speed optical modulation can be achieved by free carrier concentration variations. Electron and hole injection in PIN diodes has been widely used but generally leads to bandwidths lower than a few 100MHz.

Silicon high-speed waveguide-integrated electro-optic modulator is one of the critical devices for on-chip optical networks. The device converts data from electrical domain to the optical domain. Most studies for high speed modulation method in Si or Si based device are based on free carrier concentration variations (injection or depletion of free carriers) which are responsible for local refractive index variations and then phase modulation of a guided wave traveling through the active region. A change in the refractive index/absorption can be achieved by injection or depletion of both electron and holes into the intrinsic region of a silicon p-i-n diode.

The morphology and optical properties of Zn 1−x Mn x O films were synthesized by sol gel method using spin coating technique. Zn 1−x Mn x O thin films is prepared using 2-methoxyethanol solution of zinc acetate dehydrate and manganese acetate tetrahydrate. The solution is stabilized by MEA. The quantity of Mn in the sol was varied from x = 0,0.02, 0.04, 0.06 and 0.08 with annealing temperature of 600°C. Investigation of the physical properties and presence of nanostructures were executed using SEM and XRD characterization. Addition of Mn lead to the formation of nanosize rod structures. The optical properties were characterized using UV-Vis where the band gap and transmittance can be determined. Results show that the transmittance spectra and band gap reduces after a certain percentage of Mn addition. The variation of the band gap performance with dopant concentration is also examined.

Undoped and Mn doped ZnO films with different doping concentration were synthesized by sol gel method using a spin coating technique. Zn 1−x Mn x O thin films are prepared using 2-methoxyethanol solution of zinc acetate dehydrate and manganese acetate tetrahydrate. The solution was stabilized by MEA. The quantity of Mn in the sol was varied from x = 0, 0.02 and 0.04 with annealing temperature of 700°C. The samples were characterized using AFM to investigate the surface morphology and nanostructures. The XRD analysis shows the crystalline structure and orientation of the films. The films exhibit hexagonal wurtzite structure and improved crystalline quality by increasing the Mn doping. Meanwhile, the optical properties were characterized using UV-Vis where the transmittance and band gap decreases upon increment of Mn concentration.