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), MoS2/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.
In this work, real-time morphological evolution occurring on the GeSn(111) surface during in-situ annealing in a N2 environment is examined using a phase contrast optical microscope equipped with a heating stage. Apart from isolated immobile Sn-rich dot-like islands, mobile teardrop-shaped islands are also found at the moving boundary separating the smooth and roughen regions on the surface. As the boundary grows, Sn-poor wire-like feature emerges. The rate of growth occurs with an activation energy of ~1.4eV and appears to be akin to liquid phase epitaxy where the Sn-rich droplets leads the formation of wire-like features and the movement is due to the directional flow of Ge atoms through the droplet. DFT calculations suggest that the morphological instability is thermodynamically driven, where the relaxation of the inherent strain occurs with Sn atoms preferentially segregating from the bulk-lattice and agglomerating at the surface. The formation of these heterogeneous surfaces would restrict the thermal budget for GeSn alloys to be monolithically integrated into Silicon or Germanium devices.
Wire bonding is an important process of semiconductor assembly by providing electrical connection between integrated circuit and the external leads of semiconductor package. Wire bonding on none-flat surface is uncommon and less exploration as compare to flat surface bond pad. In certain circumstances, wire bonding is required to conduct on none-flat surface. Bond pad with concave surface is initially designed for solder bumping. Nevertheless, assembly flexibility to conduct wire bonding on concave bond pad is required in certain product application. In view of this, bondability study of concave bond pad was conducted by applying conventional thermasonic wire bonding. It was discovered that concave bond pad displayed a unique behavior in term of ball bond deformation. Ball bond diameter increment rate of concave bond pad is lower than flat bond pad. Difference in term of ball bond deformation eventually lead to distinctive ball shear respond and process parameter window on concave bond pad. Wire pull test and ball bond cross section analysis also included in this study to complete the evaluation. Despite of differences between flat and concave bond pad, standard methodology of wire bond process characterization on concave bond pad is still applicable.
The paper presents the feasibility of a packaged interferometric photonics micro-taper sensor to be used for accurate measurement of curvature on cold-formed steel (CFS) roof truss structural monitoring. The interferometric photonics micro-taper sensor is protected within a polypropylene package to survive in harsh, in-the-field conditions. After installing both the interferometric photonics micro-taper sensor and linear variable displacement transducers (LVDTs) on a CFS roof truss, fatigue tests were conducted on the truss and the curvature is characterized. The accuracy of curvature measurement results is further verified by obtaining correlation coefficient of 0.9973 which shows excellence agreement between LVDT and interferometric photonics micro-taper sensor measurement. Furthermore, the sensor is highly sensitive to curvature which is -0.0372 μW/km -1 for the curvature range of 1.880 km -1 to 3.324 km -1 .
Lifetime of packaged Phosphor- Quantum dot (QDs) based white LEDs is studied. Various stress parameters such as blue light luminance, temperature and moisture are considered and their effect on the performance of the Phosphor- QD based LED is investigated. The lumen degradation rate and degradation trend for LEDs is observed to be different under varying stress conditions. Lumen recovery process is also observed under light stress test.
Manganite based Resistance Random Access Memories (RRAM) are attractive as they are non-volatile, area-scalable, with fast switching and large endurance and retention. However, the cross-point RRAM array implementation has sneak path current leakage. To avoid this issue, a selector device with high nonlinearity is used in series with a memory device. This addition of the selector device leads to a higher voltage requirement. Further, the integration of memory and selector is challenging and leads to higher circuit complexity. To resolve this issue, a single device is extensively explored to work as a selector-less RRAM. Recently, we have experimentally demonstrated a nanoscale PrMnO 3 (PMO) based selector-less RRAM with record memory window (MW) and non-linearity (NL). Along with MW and NL, the devices should operate at lower voltages to reduce power consumption in large memory array. To address this issue, in this paper, first, we experimentally demonstrate the switching voltage scaling (40 % reduction) in PMO selector-less RRAM using N 2 :O 2 partial pressure dependent annealing in the fabrication process. Further, this voltage reduction is attributed to the lowering of trap density in as-fabricated devices with higher O 2 concentration annealing. Finally, the trap density is extracted which shows the dependence where reduced trap density leads to lower operational voltages. This experimental voltage scaling of selector-less RRAM will provide a significant power performance improvement in the large cross-point memory array and neuromorphic computing applications.
Junctionless FETs have been extensively studied due to its remarkable feature to avoid the need of forming the ultra-steep junctions as in case of conventional transistors; however high doping concentration is required for proper operation of Junctionless FETs. In order to acquire high doping concentration using ion-implantation results in 2-D non-uniform doping profile which includes vertical as well as lateral spreading. In this work, the effect of lateral spreading of the dopants in non-uniform doped Junctionless FinFETs is analyzed through 3-D numerical simulation. The device short channel performance due to variations in the projected range (R p ), lateral straggle (ΔR t ) and dose (Q 0 ) of the implanted ions is demonstrated using Sentauras TCAD device simulator.
This paper presents an exhaustive TCAD based optimization of a π - Gate AlGaN/GaN HEMT for improved cutoff frequency and device reliability. The device was tuned for high cut - off frequency by varying the pillar height and using gate recess technique. Comparisons demonstrate 25% improvement in cut - off frequency while maintaining similar device power and I ON /I OFF of 10 12 . In order to assess the reliability, performance of the devices, has been compared at different operating temperature. Also, the channel temperature has been evaluated by using thermal simulation. Device simulator tool ATLAS from Silvaco has been employed for all performance analysis.
This paper proposes an electrical model of Pt/Ta 2 O 5 /TaO x /Pt Resistive Random-Access Memory (RRAM) device encompassing the current conduction mechanism beyond the RESET phase by considering the current conduct through outside of the filament (OCF), which is modelled by incorporating the tunneling mechanism assisted by oxygen vacancy traps. For this, triangular barrier dependent trap assisted tunneling (TAT) is implemented and the model is improvised by considering the electron tunneling through the trapezoidal barrier by adopting the generalized TAT (GTAT) mechanism. Further, to enhance the model, the effect of oxygen vacancy diffusion on current conduction is modelled with Fick's law. To deploy the tunneling mechanisms, the model facilitates voltage controlled current sources and voltage sources available in SPICE tool and the characteristics obtained from the proposed model shows well matching with experimental results with maximum current at RESET phase is ~ 80μA at 3V. Moreover, the influence of oxygen vacancy diffusion on the resistance of the device beyond RESET phase is noticed and a ~ 20 K Ohm decrease in resistance is observed while increasing the input voltage from 2V to 3 V. In addition, the model is tested with the rectangular as well as the triangular pulse and results captures the current conduction beyond resetting.
In advanced non-planar MOSFETs architecture, the reliability issue is the primary concern by most researchers due to aggravated local self-heating arising from the enhanced active power dissipation inside the device structure. In this work, 3-D quantum-corrected electrothermal (ET) simulation based analysis is performed to have an insight into the self-heating effect (SHE) in ultra-thin junctionless gate-all-around FETs. The effect of quantum confinement on the carrier distribution due to the ultra-thin channel region is also considered. Through coupled hydrodynamic and thermodynamic carriers transport models, we demonstrate the influence of SHE on the drive current capability, negative output conductance and reliability of the device structure. The ET simulation results also establish the fact that the thermal contact resistance (R th ) strongly influence the device lattice and carriers temperature and the overall performance of the device. Finally, the reliability issues or degradation mechanism of SHE with on-chip ambient temperature variations has also been investigated.
When graphene supported on SiO 2 is fluorinated, XPS reveals an increase in concentration of chemically-adsorbed fluorine (higher F/C ratio with C-CF, C-CF 2 , C-F and C-F 2 but no C-F 3 ) on the graphene surface with time. Raman I D /I G ratio, i.e. a measure of non-sp 2 to Sp 2 bonding states, increases with time before showing a decrease suggesting a surface morphology change owing to C-F bonding followed by disordering of the π-electron system. AFM surface morphology scans reveal that defects (holes), which increases in size with time, are observed to form preferentially at the boundary of the graphene flakes. Synchronized Kelvin-Probe Force-Microscopy (KPFM) mapping of the graphene region surrounding these holes shows a higher work-function, φ, giving rise to a donut-shape contact potential difference (CPD) which increases from 4.9 ± 0.1 eV to 5.4 ± 0.1 eV with fluorination. Together with XPS and Raman results, the increase in φ can be attributed to the presence of a higher concentration of fluorine in the graphene region (C-F/C-F 2 bonds) surrounding these holes. The formation of the hole-defects on graphene and its subsequent increase in size with fluorination is thus a result of aggregation of adsorbed fluorine and removal of carbon likely in the form of CF 4 or C 2 F 4 .
As the field of electronics is advancing; the rigid devices are being replaced by flexible systems, which in turn are opening applications in smart wearables and textiles. This put additional limitations on the manufacturing processes that need to be compatible with flexible and low-temperature substrates. Direct-write techniques enable alternate field of printed electronics that provide low resolution, low-cost and conformal printing for more ergonomical devices. This review focuses on aspects of printed electronics for application in wearables. Different printing techniques are discussed and related research is discussed. Different types of materials available to fabricate smart textiles and wearables are discussed. A perspective on future road map is provided while discussing existing challenges in the field.
A flexible pressure sensor with bendable and distortable sensor arrays for force detection in knee arthroplasty were fabricated and characterized. The internal pressure of prosthesis knee joint can be effectively detected through real-time detection for sensor array output voltages. The pressure device shows good repeatability, consistency, small hysteresis in large detection range and stability in dynamic response which indicate promising potential in applications of knee arthroplasty.
The polysilicon is a material widely used in an many electronic components. When circuits are placed underneath the bond pads, it is expected that their electrical properties are not impacted by any kind of thermo-mechanical stress. This paper presents detailed investigation of such various Back End Of Line (BEOL) stress impacts on a polysilicon material. A meander shaped polysilicon resistor was used as a test vehicle. In this paper, various factors (number of probe insertions, probing temperature and wire bond material) were investigated to determine the impact on the electrical properties of the polysilicon circuit. The change in resistance of the polysilicon resistors after probing and wire bonding were measured. The change in resistance was observed to be negligible after probing. After wire bonding there was a significant change but seen only ~ 3%. However, it must be noted that this percentage change in resistance is still well within the reliability specification limit, which have been followed by industry.
Recently transparent conductive electrodes (TCEs) have attracted the interest of researchers due to their outstanding optical and electrical properties. Indium tin oxide (ITO) is an oxide material that combines the criteria of high conductance and transmittance. However, ITO is a non-flexible, brittle and expensive material. TCEs are commonly embedded in solar cells to perform high photon absorption and electron collection instantaneously. In this paper, an optimized TCE network is proposed to maintain TCEs' conductivity and transparency and to improve their flexibility and ability to handle mechanical forces. The network is designed by aligning multi-walled carbon nanotubes (MWCNTs) on ITO speckled surface to form ITO-CNT grid. The alignment mechanism is achieved through dielectrophoretic (DEP) force, where an electric field of 10V and 105 Hz is subjected to an ethanol/ MWCNT suspension to assemble the CNT across ITO's floating electrodes.
Electrical signal transmission in conductive channels would entail the phenomenon of electromagnetic wave propagation. In nerve fibers, however, the established Hodgkin-Huxley model treats the saltatory conduction between nodes-of-Ranvier separated by Myelin sheaths as a purely electric-field capacitive charging-discharging effect. The celebrated model could accurately explain most of the experimental observations of simple nerve fibers found in squids, shrimps and earthworms, but may fail to explain some of the observations for complex mammalian nerve fibers. In this talk, we explore some of the alternative models and analyze their advantages and disadvantages, while proposing that electromagnetic transmission models may be more suitable to explain nerve conduction in myelinated nerve fibers.
In this work, tungsten disulphide (WS2) based heterojunction photodetector device is fabricated on top of silicon (Si) substrate by using simple drop casting method. The device is characterised for its optoelectronic properties in the visible range of light illumination at 465 nm. The current-voltage (I-V) measurement is performed to attain I-V curves of various laser powers (282.6 μW, 589.2 μW, 889.9 μW, 1.07 mW and 1.265 mW). The photocurrent is found to be highly dependent on the laser power. Time based responses are calculated at 3.0 V DC bias voltage for various modulation frequencies (1 Hz, 50 Hz, 100 Hz, 500 Hz, 1 kHz, 3 kHz and 5 kHz). The fabricated device has high responsivity of 66.85 mA/W for an incident laser power of 1.265 mW and detectivity of 1.1763 × 10 9 Jones for an incident laser power of 282.6 μW. Raman shifts are observed at 351.38 cm -1 and 420.54 cm -1 , confirming the successful growth of WS 2 and verification of a non-stoichiometric WS 2 layer by the energy-dispersive X-ray (EDX) spectroscopy. These results are very promising towards further development for optoelectronic applications.
With CMOS device scaling slowing down, exploring new devices' working principles becomes paramount. The electron spin, as a complement to the charge, attracts much attention. The electron spin is characterized by the two well-defined projections on a given axis and is suitable for digital applications. Magnetic tunnel junctions (MTJs) feature different resistances in parallel and antiparallel magnetization configuration and enable spin-based types of non-volatile magnetic memories. MTJs are quite CMOS compatible as they are fabricated with a CMOS-friendly process. The relative magnetization configuration is manipulated by means of a spin-transfer torque (STT) acting on the free layer. The electrically addressable non-volatile STT memory is nearing mass production for stand-alone and embedded applications. The current status and modeling approaches of state-of-the art STT and spin-orbit torque memory are briefly reviewed.
Organic thin film gas sensor based on Zinc hexadecafluorophthalocyanine (ZnPcF 16 ) have been fabricated by spin-coating method. The thin film was then used to study the absorption spectra and morphology using UV-VIS spectrometer. Then the fabricated film has been used as a chemical sensing material for the detection of VOCs (ammonia, acetone, ethanol and methanol) by using a low-cost optical measurement. For getting more insight, Quantum mechanical calculation based on DFT was employed to investigate the interactions between VOCs and sensing molecules.
An improved atmospheric packaged SOI resonant pressure sensor is presented. A special anchor structure using suspended connecting truss is developed to suppress the vertical position shift of the resonator when the diaphragm deflects, and a stress isolating structure is introduced to improve the performance of the resonant pressure sensor. Experimental results show that the vertical position shift of the resonator is reduced to only 7.3% compared with conventional anchor design. Over the full scale pressure range of 3.5–280 kPa, the pressure sensitivity is 10.86 Hz/kPa, with the nonlinearity is 0.0138%FS, the hysteresis error is 0.0047%FS, the repeatability error is 0.0071%FS, and the accuracy is better than 0.02%FS.
