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Alcubierre's warp-drive was the first to introduce superluminal travel from different approaches. Instead of creating a shortcut through spacetime via a wormhole, geometrodynamics of simultaneously contracting and expanding spacetime were conjectured. However, both methods require exotic matter that violates energy conditions. In this paper, we employ the concept of braneworld that naturally influences spacetime geometrodynamics. Starting from defining and developing the spacetime metric of the braneworld warp bubble, the expression for energy densities as a function of relevant parameters which contributes to the braneworld approach of superluminal travel by hyperspace-drive was derived. [ABSTRACT FROM AUTHOR]

The deformation temperature is an important factor influencing the thermal deformation behavior of alloys. In this paper, thermal compression tests of Mg-Gd-Nd-Zr alloy were carried out at 350 ∼ 500 °C using the Gleeble-3800 thermal simulator, and the dynamic recrystallization (DRX) mechanism and microstructure evolution of the alloy were investigated by electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). The results show that the basal slip a and pyramidal slip a + c were consistently high activity at the test temperatures. As the temperature increased, the pyramidal slip a was gradually activated. At 350 °C, monolayer necklace-like dynamic recrystallized (DRXed) grains were formed around the initial grains via discontinuous dynamic recrystallization (DDRX). At 400 ∼ 450 °C, the monolayer DRXed grains expanded into the initial grain via continuous dynamic recrystallization (CDRX) to form multilayer necklace-like DRXed grains. However, at 500 °C, no necklace-like structure was formed around the initial grains. The initial grains were split into subgrains by low angle grain boundaries (LAGBs), which continuously absorbed dislocations and rotated for DRX. In addition, at 350 ∼ 400 °C, the alloy produced significant precipitation bands (mainly β phase). Above 450 °C, the dynamic precipitation was significantly attenuated. Precipitates greater than 200 nm could well impede dislocation movement and induce DRX nucleation. Nevertheless, the precipitates at the grain boundaries of the DRXed grains in turn pined the grain boundaries, refining the DRXed grains. • At 350 °C, monolayer necklace-like DRXed grains were formed around the initial grains via DDRX. • At 400 ∼ 450 °C, the monolayer DRXed grains expanded into the initial grain via CDRX to form multilayer necklace-like DRXed grains. • At 500 °C, dislocations within the deformed grains preferentially form low-angle grain boundaries and split the grains into sub-grains, which in turn form DRXed grains. [ABSTRACT FROM AUTHOR]

Methanesulfonic acid (MSA) has been widely used in the electroplating step at a backend semiconductor assembly process. This process comes after component encapsulation, which serves primarily to protect internal components of a device as well as to prevent ingression of chemical byproducts. The objective of this article is to study sulfur (S) ingression activities with respect to both electroplating and encapsulation processes and their effect on leadframe surface conditions. This can be achieved through observation of leadframe surface condition on samples prepared through laser ablation or mechanical decapsulation. Results from 17 engineering lots show that 25% of samples analyzed were observed with leadframe surface irregularities. The energy-dispersive X-ray spectroscopy (EDX) analysis confirmed the trace of S element on the area with surface irregularities, which can be linked to S ingression based on the trace of its path from outside, probably due to the existence of a microgap on the package. These findings provide a clearer understanding of the ingression path of S for encapsulated copper (Cu) leadframe. Even though ingression of S does not directly cause a failure, it is thought that this could act as a precursor to further failure mechanisms such as corrosion-like phenomena. [ABSTRACT FROM AUTHOR]

This paper aims to study the effect of ultrasonic aluminum (Al) bonding and lamination processes on the electrical performance of copper indium gallium (di)selenide (CIGS) thin film photovoltaic (TFPV) solar panels. Ultrasonic Al bonding on the MoSe2 layer of the CIGS TFPV solar panel was performed in three configurations: eight bonds, 16 bonds, and parallel configurations. The lamination process was performed on the Al bonds with MoSe2 layers of the CIGS TFPV solar panel. Ultrasonic bonding and lamination processes significantly affect the electrical performance of CIGS TFPV solar panels. Open circuit voltage, Voc is the least affected electrical characteristic with the application of ultrasonic bonding and lamination processes as compared to short circuit current (Isc), current density (Jsc), maximum power (Pmpp), fill factor (FF), and efficiency. 8-bonds configuration has the highest efficiency, ranging from 11.45% to 13.86% throughout unique connections of I-V measurement, compared to 16-bonds ranging from 7.99% to 10.77%, and parallel configurations, ranging from 9.14% to 11.92%. The notable variations in electrical properties with the processes used to create laminated CIGS TPFV solar panels with ultrasonic Al bonding can be explained by physical examination and lock-in infrared (IR) thermography. The ultrasonic Al bond is best suited to be used as the interconnection mean in the CIGS TFPV solar panel compared to that of conductive adhesive that has been widely applied nowadays. [ABSTRACT FROM AUTHOR]

The evaluation of the manufacturability, bondability, and reliability performances of the granular capillary is required to produce high-quality wire bonds. In this paper, two different types of wire bonding capillaries, namely, granular and conventional capillaries, were used for the gold (Au) wire bonding process. The wire pulling test was performed on the Au wire bonds created by both types of capillaries right after the wire bonding process and after the Au wire bonds were gone through accelerated tests of high-temperature storage and temperature cycling tests. It is noted that wire pull strengths were increased with the usage of the granular capillary compared to that of the conventional capillary for all five samples due to the occurrence of intimate bond between Au wedge bonds and bond pads. The increase of yield and the occurrence of consistence with one type of the failure mode for the Au wedge bonds that used granular capillary are due to the increment of scrubbing surface area between Au wire bonds and bond pads. The reduction of wire bonder stoppage with the usage of the granular capillary is due to the reduction of the short tail failure mode occurrence. This can be seen through the increment of the average yield percentage. It is observed that the granular capillary has the highest number of touchdowns or lifetimes compared to that of the conventional capillary. It is also found that the created wire bonds that used granular capillary have good bondability and reliability. These findings are based on the evaluation of the bonding interface thickness and distribution. [ABSTRACT FROM AUTHOR]

Alloying studies of Mg-Gd system alloys are an important way to improve alloy properties, reduce Gd content, and thus cost and density. Nd is excellent in promoting aging precipitation and enhancing heat resistance properties. In this work, low Gd content Mg-7Gd- x Nd-0.5Zr (x = 0, 0.5, 2, 3.5 wt%) alloys were prepared by melting casting and processed by solution aging. The effects of Nd on the microstructure and mechanical properties of the aged alloys were investigated by SEM, XRD, EDS, TEM, and electron tensile testing machine. The findings show that the Nd-free alloy consists mainly of α-Mg and Mg 5 Gd, and after Nd addition, a new phase Mg 41 Nd 5 is generated and the precipitation of the Mg 5 Gd phase is promoted, and due to the heterogeneous nucleation ability of Mg 41 Nd 5 particles leads to grain refinement. The principal precipitate phases in the matrix and grain boundaries of Nd-containing alloys are the β′ phase, which is the alloy's primary strengthening phase. Due to the influence of fine grain strengthening and precipitation strengthening, the ultimate tensile strength of the Mg-7Gd-2Nd-0.5Zr alloy achieves a maximum of 328 MPa and 294 MPa at ambient temperature and 250 °C, respectively. • Nd can promote the precipitation of Mg 5 Gd and generate Mg 41 Nd 5 with heterogeneous nucleation ability. • The main strengthening phase of the aged alloy is β′ phase. • The Mg-7Gd-2Nd-0.5Zr alloy achieves the maximum UTS (UTS 25 °C = 328 MPa, UTS 250 °C = 294 MPa). [ABSTRACT FROM AUTHOR]

Quasi-vertically aligned zinc oxide nanorod (ZnO NR) arrays were synthesized via hydrothermal processing on glass substrates coated with a conductive layer of aluminium-doped zinc oxide (AZO). Different characterization techniques were used to study the phase structures, surface morphology and elemental composition of the prepared nanorods, including X-ray diffraction (XRD), field emission scanning microscopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS). The sensing behaviour of the ZnO NR arrays has been demonstrated toward different concentrations of 2-methoxyethanol solvent, a highly toxic organic compound. The sensitivity of the prepared sensor is 24 nA/(ppm cm-2) and 60 nA/(ppm cm-2) at applied voltages of 5 V and 10 V, respectively. Its limit of detection (LoD) is 190 ± 5 ppm independently of the applied voltage. The mechanism of the sensing behaviour was explained based on the charge-transfer mechanisms. [ABSTRACT FROM AUTHOR]

Highlights: [•] Zinc oxide (ZnO) nanorods were prepared via low temperature hydrothermal process on a p-type silicon. [•] The prepared heterojunction shows an excellent rectifier behavior with high break voltage. [•] The prepared photodiode ZnO/p Si heterojunction shows interesting UV sensing properties with a visible blind behavior. [•] The prepared photodiode shows a high repeatability with different UV light pulse duration that makes it suitable for optical switching applications. [Copyright &y& Elsevier]

Al-Mg-Si (AA6061) Al alloy plates were joined by the method of gas metal arc welding using Al-5Mg (ER5356) filler metal and were subjected to the oxidation test in flowing air environment at 600°C from 8 to 40 hours and the weight gain was measured. The characteristic of oxide grown on welded zone surface was examined by SEM/EDS, XRD, and XPS. Oxide was observed to grow on the fused metal surface suggesting the possibility of modifying the oxide chemistry under high temperature environment. It was found that the oxidation behavior of fused metal affected by the nature of their oxide growth and morphology, was influenced by their welding process and the difference in the chemical composition. [ABSTRACT FROM AUTHOR]

Abstract: The evaluation of gold, Au ball bond requires a new approach to obtain a more localized and detailed result. This is due to the limited data in terms of quality and quantity obtained from conventional tests. The nanoindentation test is proposed in order to evaluate the quality of ball bond in more detail. The nanoindentation test was carried out to analyze the strengthening of Au ball bond after being subjected to high temperature storage, HTS. It was observed that Au and intermetallic compounds, IMC, have a higher creep behavior compared to that of silicon, Si. The dislocation glide was the responsible indentation creep mechanism for Au and IMC of ball bond that have been subjected to 0 and 1000h of HTS. It was observed that the variation of creep behavior of Au ball bond was reduced after being subjected to 1000h of HTS. The variation of creep behavior of IMC decreased after being subjected to 1000h of HTS. It was also noted that the creep behavior of both Au and IMC decreased with the increase of HTS time interval. It was found that the hardness value for Au decreased with the increase of HTS time interval, whereas, the hardness value of IMC increased with the increment of HTS time interval. Based on the results obtained, it was indicated that the nanoindentation test has the ability to evaluate the strengthening of Au ball bond in a localized manner and in more detail compared to that of the conventional tests. [Copyright &y& Elsevier]

The most common environmental stress tests that are commonly used for corrosion risk assessment study or package integrity qualification qualifier as part of AEC-Q101E requirement are Unbiased highly accelerated stress test (u-HAST) and Unbiased humidity test(Moisture Soak). In this paper, this study is initiated due to abnormal situation whereby the failure could not be detected at 0 h as this corrosion symptom takes place after several months of storage (4 to 6 months) and failure can be only detected during customer board assembly process after subsequent period of storage. Objective of this paper is to develop a novel methodology by identifying an optimum environmental stress test condition which can replicate an early detection method to put in evidence the onset of corroded wedge on Cu-Ag system on a copper wire-bonded semiconductor device. The approach used was by subjecting the components to two different unbiased environmental stress methods, i.e., u-HAST and Moisture Soak. Pre- and post-electrical testing will be done after each interval for each stress tests. In the event if there are no electrical failures observed, post-mechanical decapsulation analysis results will be used instead. Upon mechanical decapsulation, the visual inspection on the wedge surface area and periphery of Ag plating was performed through optical inspection. x-ray Photoelectron Spectroscopy (XPS) will complement the Energy Dispersive x-ray (EDX) analysis to confirm the corrosion product on the wedge surface area and periphery of Ag plating area surrounding the wedge surface. Based on the evaluation results, Moisture Soak, clearly demonstrated a better leading indicator compared to u-HAST for the activation of corrosion. Moisture Soak (55 °C/85%RH) showing a consistent trend of higher corrosion detection on SOT23 package compared to u-HAST. [ABSTRACT FROM AUTHOR]

Purpose: Reflow solder joint quality is significantly affected by the ability of the solder to perfectly fill pad space and retain good solder joint shape. This study aims to investigate solder joint quality by quantitatively analyzing the stencil printing-deposited solder volume, solder height and solder coverage area. Design/methodology/approach: The dispensability of different solder paste types on printed circuit board (PCB) pads using different stencil aperture shapes was evaluated. Lead-free Type 4 (20–38 µm particle size) and Type 5 (15–25 µm particle size) solder pastes were used to create solder joints according to standard reflow soldering. Findings: The results show that the stencil aperture shape greatly affects the solder joint quality as compared with the type of solder paste. These investigations allow the development of new strategies for solving solder paste stencil printing issues and evaluating the quality of solder joints. Originality/value: The reflow soldering process requires the appropriate selection of the stencil aperture shape according to the PCB and the solder paste according to the particle-size distribution of the solder alloy powder. However, there are scarce studies on the effects of stencil aperture shape and the solder alloy particle size on the solder paste space-filling ability. [ABSTRACT FROM AUTHOR]

The rapid spread of severe acute respiratory syndrome coronavirus 2 (SARS CoV-2) infections that were first detected in Wuhan, China, at the end of 2019 led to the state of the global COVID-19 pandemic declared by the World Health Organization in March 2020. Thus, the world faces a new challenge to control the spread of the virus. The pandemic highlighted the need for rapid detection of infections that would be able to accurately screen the population much more rapidly and economically than the gold standard molecular biology-based tools such as quantitative real-time reverse transcription polymerase chain reaction. Such screening measures would be able to isolate infected individuals, including those showing no symptoms, and provide early treatments before more serious complications develop, thus allowing for the spread of infections to be better controlled without the implementation of socioeconomically crippling lockdowns. In this review, we present a comprehensive overview of the major advances in the use of electrolyte-gated field effect transistor-based biosensors for the detection of viruses, including their use for SARS-CoV-2 detection. We describe the main types of bioreceptors used for the detection of viruses in general and those used for COVID-19 in detail. [ABSTRACT FROM AUTHOR]

The early corrosion detection of a semiconductor package is the desired goal for industrial semiconductor manufacturing owing to its capability to predict corrosion activity before the product leaves the assembly line. However, the standard procedure for early correction detection always faces great challenges and is yet to be available. Usually, the detected corrosion activities show some degree of failure. Leadframe discoloration provides insights into early corrosion detection in a semiconductor package. This study adopted an unbiased highly accelerated stress test (uHAST) to induce discoloration by promoting the suitable equilibrium moisture content (EMC). The wedge bond of Cu wire onto the Ag-plated Cu leadframe was used. To obtain the actual EMC, dew-point analysis was performed by dry- and wet-bulb data collection. The semiconductor package was subjected to several sets of uHAST condition comprising different combinations of temperature and relative humidity (RH) for 168 h. Mechanical decapsulation was used to expose the wedge bond of Cu wire onto the Ag-plated Cu leadframe followed by qualitative and X-ray photoelectron spectroscopy (XPS) analysis. We found that a higher percentage of EMC facilitated the discoloration of Cu-wedge bond. XPS analysis further confirmed that the discoloration was associated with early corrosion activities. Therefore, uHAST may be used as an early corrosion detection procedure by considering the combination effect of RH and temperature through EMC analysis. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to analyze the effect of surface roughness and hardness of leadframe on the bondability of gold (Au) wedge bond using in situ inspection of laser interferometer and its relationship with the deformation and wire pull strength. Design/methodology/approach: The in situ inspection of ultrasonic vibration waveform through the changes of vertical axis (y-axis) amplitude of wire bonder capillary was carried out using laser interferometer to analyze the formation of Au wedge bond. The relationship between the changes of ultrasonic waveform of capillary with the deformation and the pull strength was analyzed to evaluate the bondability of Au wedge bonds. Findings: It was observed that the changes in vertical axis amplitude of ultrasonic vibration waveform of wire bonder capillary can be used to describe the process of bonding formation. The loss of ultrasonic energy was exhibited in ultrasonic vibration waveform of wire bonding on leadframe that has higher value of roughness (leadframe A) as compared to that of leadframe that has lower value of roughness (leadframe B). The lower pull strength obtained by Au wedge bond further confirms the reduction of bond formation because of the higher deformation on leadframe A as compared to that of leadframe B. Originality/value: The relationship between in situ measurement using laser interferometer with the bondability or deformation and wire pull strength of Au wedge bonds on different surface roughness and hardness of leadframes is still lacking. These findings provide a valuable data in analyzing the bonding mechanisms that can be identified based on the in situ measurement of ultrasonic vibration and the bondability of Au wedge bonds. [ABSTRACT FROM AUTHOR]

This study investigated the effectiveness of heat shield placement locations during the rework process to avoid thermal and mechanical damage to adjacent ball grid array components and their solder joints on double-sided printed circuit board assembly. Three types of heat shield placement locations were used: sample X, individual heat shield placement on adjacent components of the rework location; sample Y, a U-shaped, and sample Z, a square-shaped heat shield placed respectively at the heat source location. The dye and pull test results, infrared thermography, and temperature measurements were analysed to understand the relationship between the location of the heat shield and solder joint damage during rework. Heat shield placement at the heat source location on the reworked component can reduce the peak temperatures on the adjacent rework component locations by up to 8.18%. The peak temperatures of the centre and corner of the BGA component can be maintained below 195 °C and 210 °C, respectively to improve the adjacent rework component locations' solder joint quality by reducing solder joint damage by more than 50% solder cracks. This is useful for thermal management during rework involving high-density ball grid array component placements on double-sided printed circuit board assembly. [ABSTRACT FROM AUTHOR]

An accelerated reliability testing via thermal cycling test (TCT) was used to test ball grid array (BGA) components’ reliability. Five variables were observed; control sample J and samples K, L, M, and N were BGA component samples that have been exposed to TCT between 500 and 1250 cycles with the TCT profile in the range of 0 °C–100 °C. The crack orientation of the individual solder joint was analyzed along with the propagation path pattern on the solder array of the BGA component pad by analyzing the dye and pull test results that were then mapped and analyzed using the cardinal and ordinal directions approach. This is to determine the crack propagation path direction in the solder array and track the potential of warpage on the BGA package as the TCT cycles progressed. A cross section was performed on sample M with the 3-D X-ray and scanning electron microscopy (SEM) analysis to observe the solder joints’ fracture lines and surface topographies. The results showed that individual solder joint crack orientation is correlated to the crack propagation location on the BGA package. The solder joint from northwest (NW), northeast (NE), southeast (SE), and southwest (SW) of the BGA package is prone to solder crack compared to the solder joint array in the middle. A solder grain structure coarsening occurred at the crack propagation due to the high cyclic strain from the TCT. [ABSTRACT FROM AUTHOR]

Purpose -- This paper aims to analyze the effect of Au wire size and location of hook during wire pulling test to identify the variation of results obtained. Design/methodology/approach -- Two hook locations, namely, location A and location B were used to analyze the effect of hook location. Location A was the same as the hook location required by MIL-STD-883E standard, whereas location B was located near to the second bond. The correlation between new purposed failure modes and MIL-STD-883E standard was developed to reflect on the pull strength with the physical failure. Findings -- It was observed that fine pitch Au wire has higher variation and lower process capability of pull strength. Au wire pulled by the hook at location B provides a more representative result compared to that at location A. Fifty per cent or more of Au remnant is required to be considered as a good and reliable Au wedge bond based on the new purposed failure modes. Originality/value -- The evaluation of gold (Au) wedge bond requires a new proper wire pulling test method. This is due to the large variation obtained from the application of current practice of wire pulling test. [ABSTRACT FROM AUTHOR]

Abstract: The effect of gamma radiation on the mechanical and structural properties of gold ball bonds was investigated. Gold wires from thermosonic wire bonding were exposed to gamma rays from a Cobalt-60 source at a low dose (5Gy). The load–depth curve of nanoindentation for the irradiated gold wire bond has an apparent staircase shape during loading compared to the as-received sample. The hardness of the specimens calculated from the nanoindentation shows an increase in value from 0.91 to 1.09GPa for specimens after exposure. The reduced elastic modulus for irradiated specimens significantly increased as well, with values from 75.18 to 98.55GPa. The change in intrinsic properties due to gamma radiation was investigated using dual-focused ion beam and high-resolution transmission electron microscope analysis. The dual-focused ion beam and high-resolution transmission electron microscope images confirmed the changes in grain structure and the presence of dislocations. The scanning electron microscope micrographs of focused ion beam cross sections showed that the grain structure of the gold became elongated and smaller after exposure to gamma rays. Meanwhile, high-resolution transmission electron microscopy provided evidence that gamma radiation induced dislocation of the atomic arrangement. [Copyright &y& Elsevier]

Abstract: This paper characterizes die damage resulting from various wafer thinning processes. Die fracture strength is measured using ball breaker test with respect to die surface finish. Further study on surface roughness and topography of each surface finish is obtained by atomic force microscopy (AFM) and scanning electron microscopy (SEM) techniques. Stress relief process with 25μm removal is able to strengthen 100μm wafer by 20.4% using chemical wet etch and 75μm wafer by 36.4% with plasma etch. Relatively, plasma etching shows higher fracture strength and flexibility compared to chemical wet etch. This is due to topography of the finished surface of plasma etch is smoother and rounded, leading to a reduced stress concentration, hence improved fracture strength. [Copyright &y& Elsevier]

Abstract: This paper discusses on the surface characteristics of each of the seven set-up process steps prior completion of under bump metallurgy (UBM) deposition. The Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) techniques were used to obtain the surface roughness and morphology of each deposition process. The elemental analysis using Energy Disperse X-Ray (EDX) and precision micro-cross-section using Focus Ion Beam (FIB) was also used in this study. The first zincation process has high surface roughness but preserved surface morphology of initial thin-film surface. The second zincation provides the improved surface roughness due to the replacement aluminum layer with ion zinc in the solution. Smooth surfaces leads to better shear strength. However, second zincation will affect the Al thickness, hence excessive attacks on Al layer may cause reliability problem. [Copyright &y& Elsevier]

• A method of removing CIGS layers up until MoSe 2 of TFPV using mechanical brushing and scribing was found to be plausible method before ultrasonic bonding application. • Ultrasonic Al bond on Mo back contact layer has higher bondability as compared to that of ultrasonic Al bond on MoSe 2 in terms of electrical (contact resistance) and mechanical (peel strength) performances. • The creation of micro weld between ultrasonic Al bonds with Mo can be identified through the identification of failure modes from load-distance profile of peel test. • Rigidity and stress distribution experienced during lamination process determine the panel construction CIGS TFPV selection. This paper aims to study the bondability of ultrasonic Aluminum, Al bonds on Mo and MoSe 2 layers of back-contact metal of copper indium gallium (de)selenide (CIGS) thin film photovoltaic (TFPV) solar panel. The bondability of ultrasonic Al bonds were evaluated based on the contact resistance, R c , peel strength and electrical characteristics measured using transmission line method (TLM), peel test, and current–voltage (I-V) measurement, respectively. Besides, the qualitative results of load-distance profiles from tensile test also have been used to evaluate the bondability of the ultrasonic Al bonds. Two type of lamination constructions namely construction 1 and construction 2 were built on the CIGS TPFV solar panel with ultrasonic Al bonds on Mo and MoSe 2. It was noted that the new method of removing CIGS layer up until MoSe 2 is the plausible technique to be used. Ultrasonic Al bond on Mo layer has higher bondability as compared to that of ultrasonic Al bond on MoSe 2 through the quantitative results of R c , peel strength and qualitative result of load-distance profile. CIGS TFPV solar panel with construction 2 is the suitable construction for the CIGS TFPV solar panel due to the higher rigidity, and even stress distribution experienced during lamination process as compared to that of construction 1. It is noted that steps taken from ultrasonic bonding until lamination process has increased the cumulative contact area and decreased the R c and consequently increased the efficiency of CIGS TFPV solar panel with ultrasonic Al bond on MoSe 2 layer. [ABSTRACT FROM AUTHOR]

In this study, porous silicon (PSi) was prepared and tested as an extended gate field-effect transistor (EGFET) for pH sensing. The prepared PSi has pore sizes in the range of 500 to 750 nm with a depth of approximately 42 μm. The results of testing PSi for hydrogen ion sensing in different pH buffer solutions reveal that the PSi has a sensitivity value of 66 mV/pH that is considered a super Nernstian value. The sensor considers stability to be in the pH range of 2 to 12. The hysteresis values of the prepared PSi sensor were approximately 8.2 and 10.5 mV in the low and high pH loop, respectively. The result of this study reveals a promising application of PSi in the field for detecting hydrogen ions in different solutions. [ABSTRACT FROM AUTHOR]

Purpose The purpose of this paper is to analyse the operation of p-type side gate junctionless silicon transistor (SGJLT) in accumulation region through experimental measurements and 3-D TCAD simulation results. The variation of electric field components, carrier’s concentration and valence band edge energy towards the accumulation region is explored with the aim of finding the origin of SGJLT performance in the accumulation operational condition.Design/methodology/approach The device is fabricated by atomic force microscopy nanolithography on silicon-on-insulator wafer. The output and transfer characteristics of the device are obtained using 3-D Technology Computer Aided Design (TCAD) Sentaurus software and compared with experimental measurement results. The advantages of AFM nanolithography in contact mode and Silicon on Insulator (SOI) technology were implemented to fabricate a simple structure which exhibits the behaviour of field effect transistors. The device has 200-nm channel length, 100-nm gate gap and 4 μm for the distance between the source and drain contacts. The characteristics of the fabricated device were measured using an Agilent HP4156C semiconductor parameter analyzer (SPA). A 3-D TCAD Sentaurus tool is used as the simulation platform. The Boltzmann statistics is adopted because of the low doping concentration of the channel. Hydrodynamic model is taken to be as the main transport model for all simulations, and the quantum mechanical effects are ignored. A doping dependent Masetti mobility model was also included as well as an electric field dependent model with Shockley–Read–Hall (SRH) carrier recombination/generation.Findings We have obtained that the device is a normally on state device mainly because of the lack of work functional difference between the gate and the channel. Analysis of electric field components’ variation, carrier’s concentration and valence band edge energy reveals that increasing the negative gate voltage drives the device into accumulation region; however, it is unable to increase the drain current significantly. The positive slope of the hole quasi-Fermi level in the accumulation region presents mechanism of carriers’ movement from source to drain. The influence of electric field because of drain and gate voltage on charge distribution explains a low increasing of the drain current when the device operates in accumulation regime.Originality/value The proposed side gate junctionless transistors simplify the fabrication process, because of the lack of gate oxide and physical junctions, and implement the atomic force microscopy nanolithography for fabrication process. The optimized structure with lower gap between gate and channel and narrower channel would present the output characteristics near the ideal transistors for next generation of scaled-down devices in both accumulation and depletion region. The presented findings are verified through experimental measurements and simulation results. [ABSTRACT FROM AUTHOR]

Several types of metallization have been used in order to enhance the bondability of wire bond. The introduction of copper (Cu) wire bond further increases the requirement of finding the suitable metallization. In this paper, two types of metallization, namely silver (Ag) and nickel-palladium–gold-silver (Ni/Pd/Au/Ag), deposited on Cu substrate were used as the bond pad for the second Cu wire bond. Wire pulling test was conducted on the Cu second bond by placing the hook near the second bond in order to obtain consistence stich of Cu wire bond. The characteristic remaining area of stich was obtained using the image processing software Image J. It was observed that the pull strength of the Cu second bond was higher for Ag metallization compared with that of Ni/Pd/Au/Ag metallization. It was also shown that the Cu second bond on the Ag metallization has higher contact diameter compared with that of Ni/Pd/Au/Ag metallization. The contact diameter of the Cu second bond on Ag metallization has higher value and it can be correlated with its higher value of pull strength. The characteristic area was found to be proportionally related with the pull strength of second bond. [ABSTRACT FROM PUBLISHER]

Purpose – This paper aims to investigate the influence of temperature and lignin concentration on the inhibition of carbon steel corrosion in 1 M HCl. Design/methodology/approach – Weight loss corrosion tests were performed at different temperatures in the range of 30-70°C (303-343 K). Findings – It was found that the corrosion inhibition efficiency (IE) of lignin on the carbon steel decreased when the temperature was increased from 60 to 70°C. However, at lower temperatures ranging from 30 to 50°C, the IE improved, due to occurrence of lignin adsorption on the surface of metal specimens. The IE was higher with increasing lignin concentration, thus reducing the weight loss of the carbon steel. The adsorption phenomenon involved exothermic processes because the value of enthalpy of adsorption (ΔH°ads) < 0 and Gibbs free energy of adsorption (ΔG°ads) were less negative with increase in temperature. The entropy of adsorption (ΔS°ads) had negative values, representing the decrease in disorder of adsorption. The adsorption of lignin on the carbon steel surface in 1 M HCl was comprehensive, as deduced from kinetic and thermodynamic parameters. However, physisorption was the major contributor in the inhibition mechanism. The inhibitive features of carbon steel surfaces showed less damage once the steel was treated in lignin, as evident from macroscopy images. Practical implications – The use of lignin as an acid corrosion inhibitor at high temperature is practical in metal surface treatment process. Social implications – The use of organic compounds gives an advantage to the environment, universal health and save cost, as the compounds can be found in nature. Originality/value – Lignin can act as a flexible corrosion inhibitor within the temperature range of 30-70°C in 1 M HCl because it exhibits comprehensive adsorption (i.e. a combination of both physisorption and chemisorption) at specific concentrations. [ABSTRACT FROM AUTHOR]

The structural changes of radiolytically prepared aluminium-copper (Al-Cu) bimetallic nanoparticles by adjusting the precursors' mole ratio and gamma radiation dose were investigated by transmission electron microscopy, field emission scanning electron microscopy/energy dispersive spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), and X-band continuous wave electron paramagnetic resonance (EPR). The EPR spectrum was also analysed through the simulation of the powder-like EPR spectra. The results note that in prepared samples with higher Al contents, formation of core-shell structure is dominant, whereas in Cu-rich samples, the final structures are primarily in alloy and oxide forms. According to the analysis of data obtained from X-ray diffraction, FTIR, and EPR, we found that the unpaired electron of the Cu ion in various phases play the main role in structural phase transformation of Al-Cu nanoparticles. Additionally, based on the information extracted from simulated EPR peaks of Cu-Cu, the diameter of the Cu core in core-shell structures was obtained. We showed that by increasing the gamma radiation dose from 80 to 120 kGy, the overall size of nanoparticles decreases from 9.47 to 3.75 nm, but the contribution of copper core increases from 11 to 22 % of overall particle size. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes the behaviour of bioactive wollastonite materials containing Malaysian limestone and silica sand. Wollastonite, which is also known as calcium silicate (CaSiO3), is an industrial mineral composed of calcium, silicon and oxygen. Pseudowollastonite, which is a primary crystal of wollastonite, was synthesised via a solid-state reaction at a temperature of 1450°C. The in-vitro bioactivity of wollastonite was examined by soaking it in simulated body fluid (SBF) solution for 1–7 days at 36.5°C. The soaked wollastonite samples were characterised using XRD, SEM-EDX, FTIR and ICP analyses. Apatite particles precipitated on the surface of the wollastonite sample after the sample was soaked in the SBF. The XRD analysis indicated the presence of an increasing amount of the hydroxyapatite phase as the soaking time increased. The SEM and EDX analyses indicated the formation of granules of agglomerated apatite particles on the surface of the soaked wollastonite sample. During the formation of apatite, phosphate ions from the SBF solution were consumed. This process was confirmed by ICP, which revealed a decrease in ion concentration after the soaking process. The FTIR analysis indicated that the peaks of the phosphate ions increase when the apatite layer forms on the surface of the wollastonite sample. After the soaking process, a calcium deficient hydroxyapatite layer was observed on the wollastonite sample. The study concludes that wollastonite produced from Malaysian limestone and silica sand is bioactive and may be used as an implantable biomaterial. [Copyright &y& Elsevier]

This paper examines the impact of two important geometrical parameters, namely the thickness and source/drain extensions on the performance of low doped p-type double lateral gate junctionless transistors (DGJLTs). The three dimensional Technology Computer-Aided Design simulation is implemented to calculate the characteristics of the devices with different thickness and source/drain extension and based on that, the parameters such as threshold voltage, transconductance and resistance in saturation region are analyzed. In addition, simulation results provide a physical explanation for the variation of device characteristics given by the variation of geometric parameters, mainly based on investigation of the electric field components and the carries density variation. It is shown that, the variation of the carrier density is the main factor which affects the characteristics of the device when the device's thickness is varied. However, the electric field is mainly responsible for variation of the characteristics when the source/drain extension is changed. [ABSTRACT FROM AUTHOR]

The bonding mechanisms of gold, to give the desired strength of wire bonding, still require detailed investigation, including establishing adequate and reliable testing procedures. The current practices for analysing the mechanisms of wire bonding are inadequate and do not provide a comprehensive picture. This is because the focus of the tests is not clear, which causes variation in the results obtained, changing the conclusions about the responsible mechanism. Furthermore, as the size of Au wire bonds decreases, the mechanism responsible for thermosonic Au wire bonding may change. This paper provides a comprehensive analysis of the current and possible future methods for elaborating the bonding mechanism and strength of thermosonic Au wire bonds. We discuss the testing methods, their limitations and advantages, and suggest ways in which they can be improved. [ABSTRACT FROM AUTHOR]

This paper presents a durability analysis of two types of copper leadframe, i.e. the un-oxidised leadframe and the oxidised leadframe. Both leadframe types were used in the fabrication process of a Quad Flat No-Lead (QFN) package, which can be said as a recent type of the 3D stacked die semiconductor package. This study involved the durability test and analysis on QFN packages when these packages were subjected under constant cyclic loadings. In order to perform the cyclic test, the procedure of the three-point cyclic bending test has been employed on the packages. In addition, a strain gauge which was connected to the dynamic data acquisition system was used for each tested QFN package for determining the response of the captured cyclic strain signal. It has been found that the variable amplitude pattern of signal response has been obtained during the constant cyclic test. The obtained response signals for both type of leadframe were then analysed using the approaches of signal processing technique, which is relatively new in this field. The collected response signal were analysed using the normal statistical methods, the Power Spectrum Density (PSD) calculation and also the time-frequency localization analysis. From the detail signal analysis, it has been found that the un-oxidised leadframe showed a lower range of strain response compared to the oxidised leadframe, indicating higher lifetime. As a result, this finding lead to the durability conclusion, for which the un-oxidised leadframe has more durability effects and it also has higher lifetime compared to the oxidised leadframe. Finally, a micro-crack phenomenon at the epoxy interface between the die and the leadframe was also observed for the QFN package with the oxidised leadframe. [ABSTRACT FROM AUTHOR]

Abstract: ZnO thin films have been successfully synthesized by thermal evaporation of pure zinc at 900°C under the flow of different percentages of argon and oxygen gases. The films were characterized by X-ray diffraction (XRD), variable pressure scanning electron microscopy (VPSEM), energy dispersive X-ray spectroscopy (EDS) and UV–vis spectroscopy. The aim of this paper is to study the influence of the oxygen percentage on the structural and morphological properties of the ZnO films. VPSEM results show that very thick needle structures were produced at high oxygen percentages. EDS results revealed that only Zn and O are present in the sample, indicating a composition of pure ZnO. XRD results showed that the ZnO synthesized under different quantities of oxygen were crystalline with the hexagonal wurtzite structure. UV–vis spectroscopy results indicated that the optical band gap energies from the transmission spectrum are between 3.62 and 3.69eV for ZnO thin films. [Copyright &y& Elsevier]