Electrical Characterization of Different Passivation Treatments for Long-Wave Infrared InAs/GaSb Strained Layer Superlattice Photodiodes

Silicon dioxide (SiO₂), silicon nitride (Si _x N _y ), and zinc sulfide (ZnS) with ammonium sulfide [(NH₄)₂S] as a prepassivation surface treatment were compared as passivants for InAs/GaSb strained layer superlattice detectors with a 0% cutoff wavelength of ∼10 μm. SiO₂ did not show significant improvement and the zero-bias resistance-area product (R ₀ A) was 0.72 Ω-cm² at 77 K. Si _x N _y passivation showed a nominal improvement with an R ₀ A value of 4.1 Ω-cm² at 77 K. ZnS with (NH₄)₂S treatment outperformed others significantly, improving the R ₀ A value to 492 Ω-cm² at 77 K. Variable-area diode measurements indicated a bulk-limited R ₀ A value of 722 Ω-cm². ZnS-passivated diodes exhibited maximum surface resistivity with a value of 2500 Ω-cm.     

Implementation of enhanced forward pointer-based mobility management scheme for handling internet and intranet traffic in wireless mesh network

To implement WMN, IEEE 802.11s has been developed. The routing protocol for selecting a path between two mesh stations in IEEE 802.11s is hybrid wireless mesh protocol (HWMP). But mobility of external stations has not been considered in IEEE 802.11s. For handling movement of clients, many mobility management schemes have been proposed. Some of such schemes are: ANT, Mesh Mobility Management (M\(^{3})\), Infrastructure Mesh (iMesh), SMesh, MEsh networks with MObility management (MEMO), Wireless mesh Mobility Management (WMM), Static Anchor Scheme, Dynamic Anchor Scheme, LMMesh, Session-to-Mobility-Ratio based Scheme and Forward Pointer-Based Mobility Management Scheme (FPBR). But none of the schemes except FPBR have been integrated with IEEE 802.11s for providing mobility support to the external stations. FPBR has been proposed to enhance IEEE 802.11s for providing mobility support to external stations, but it can support internet traffic only. In WMN both internet and intranet traffic to and from the external station is important. In this paper, an improved version of FPBR named Enhanced FPBR (EFPBR) Scheme has been introduced to handle both internet and intranet traffic. Both EFPBR and HWMP have been numerically analyzed. HWMP and EFPBR schemes are simulated and the performances are compared. From the performance comparison, it can be observed that EFPBR performs better than that of IEEE 802.11s concerning throughput, end-to-end delay, routing overhead and average handoff cost. The number of route management packets transferred per handoff measured from numerical analysis and simulation has also been compared.     

Analysis of intermittent timing fault vulnerability

Continuous scaling of transistor feature size rapidly increases the effect of intermittent faults. These faults manifest as timing violations due to the combined effects of process variation, circuit wear-out, and variation in environmental conditions. In this paper, we combine all critical sources of intermittent faults in a comprehensive framework. Our experiments with the MIPS-789 processor reveal that at the 22nm technology node, the combined effect of all the factors can degrade the delay by 2.5X. Such gross delay degradation extending more than two cycles can render many recently proposed time borrowing techniques ineffective. We analyze three architectural techniques to mitigate intermittent faults and evaluate them using full system architectural simulation.     

Bifunctional Carbon Nanotubes by Sidewall Protection

A vertically aligned array of multiwalled carbon nanotubes (MWCNTs) impregnated with polystyrene is utilized to independently functionalize each end of the MWCNTs. The presence of the polystyrene matrix prevents sidewall oxidation of the CNTs, resulting in carboxylate derivatization at the CNT tips during processing via plasma oxidation. The membrane is subsequently dissolved in toluene, resulting in a suspension of CNTs with carboxylate‐derivatized tips. The CNT tips are further functionalized using carbodiimide‐mediated linking of carboxylate at the CNT tips with an amine of 2‐aminoethanethiol. This treatment results in thiol functionality and Fourier‐transform infrared (FT‐IR) studies confirm amide‐bond formation. Gold nanoparticles that are readily observed using transmisison electron microscopy (TEM) are then covalently linked to the thiol functional groups. Estimates of the average nanoparticle density are observed to decrease from ～ 526 particles μm^–1 near the CNT tips to negligible values (< 7 particles μm^–1) at locations beyond 700 nm from the CNT tips. This is consistent with a membrane geometry where CNTs tips are above the polystyrene surface owing to differing oxidation rates. Bifunctional CNTs (with different chemical functionality at either end of each CNT) is achieved by thiol functionalization on only one side of the oxidized CNT membrane floating on top of a 2‐aminoethanethiol functionalization reaction solution. After dissolution of the polystyrene matrix, TEM analysis shows gold‐nanoparticle decoration at the thiol‐functionalized end of the CNT.     

Conductive Anodic Filament Failures in Fine-Pitch Through-Via Interconnections in Organic Package Substrates

Failures due to conductive anodic filament (CAF) formation in copper-plated through-vias have been a concern in printed wiring boards since the 1970s. With the continuous reduction in through-via pitch to meet high circuit density demands in organic packages, the magnitude of CAF failures is expected to be significantly higher. In this study, an accelerated test condition [130°C, 85% relative humidity (RH), and 100 V direct current (DC)] was used to investigate CAF in two organic package substrates: (1) cyclo-olefin polymer–glass fiber composite (XR3) and (2) epoxy–glass fiber composite (FR4). Test coupons with through-via spacing of 100 μm and 200 μm were investigated in this study. CAF failures were not observed in either substrate type with spacing of 200 μm. With spacing of 100 μm, insulation failures were observed in FR4, while XR3 exhibited stable insulation resistance during the test. The substrates were characterized using gravimetric measurement, and XR3 was found to exhibit significantly lower moisture absorption compared with FR4. The CAF failures in FR4 were characterized using scanning electron microscopy and energy-dispersive x-ray spectroscopy. The results suggest a strong effect of moisture sorption of organic resins on CAF failure at smaller through-via spacing in package substrates.     

Selective Zinc(II)‐Ion Fluorescence Sensing by a Functionalized Mesoporous Material Covalently Grafted with a Fluorescent Chromophore and Consequent Biological Applications

A highly ordered 2D‐hexagonal mesoporous silica material is functionalized with 3‐aminopropyltriethoxysilane. This organically modified mesoporous material is grafted with a dialdehyde fluorescent chromophore, 4‐methyl‐2,6‐diformyl phenol. Powder X‐ray diffraction, transmission electron microscopy, N₂ sorption, Fourier transform infrared spectroscopy, and UV‐visible absorption and emission have been employed to characterize the material. This material shows excellent selective Zn²⁺ sensing, which is due to the fluorophore moiety present at its surface. Fluorescence measurements reveal that the emission intensity of the Zn²⁺‐bound mesoporous material increases significantly upon addition of various concentrations of Zn²⁺, while the introduction of other biologically relevant (Ca²⁺, Mg²⁺, Na⁺, and K⁺) and environmentally hazardous transition‐metal ions results in either unchanged or weakened intensity. The enhancement of fluorescence is attributed to the strong covalent binding of Zn²⁺, evident from the large binding constant value (0.87 × 10⁴ M ^?1). Thus, this functionalized mesoporous material grafted with the fluorescent chromophore could monitor or recognize Zn²⁺ from a mixture of ions that contains Zn²⁺ even in trace amounts and can be considered as a selective fluorescent probe. We have examined the application of this mesoporous zinc(II) sensor to cultured living cells (A375 human melanoma and human cervical cancer cell, HeLa) by fluorescence microscopy.     

Analytical Performance Evaluation of a STBC Coded OFDM FSO Communication System over Turbulent Atmospheric Channel

Journal of Communications Technology and Electronics - An analytical approach is presented for an optical IM/DD system with STBC coded OFDM RF subcarrier modulation over a free space optical...     

Rheological and gelling properties of a novel glucan from Leuconostoc dextranicum NRRL B-1146

The glucan produced by glucansucrase by the bacterial strain Leuconostoc dextranicum NRRL B-1146 was purified and characterized for its certain properties. The glucan was precipitated by ethanol and further purified by size exclusion chromatography. The purified glucan was homogenous and free of protein. The rheological properties of glucan were studied. The steady shear measurements for the semi-dilute glucan solution indicated that the viscosity (η) of the glucan solution decreased with the increase in shear stress (τ) and exhibited typical non-Newtonian pseudoplastic behavior, indicating branched nature of glucan. The surface morphology studied using Scanning Electron Microscopy revealed that the glucan has a porous structure. This glucan can be used as thickening or gelling agent in food or in the sourdoughs in bakery applications.     

Dielectric Properties and Leakage Current Characteristics of Sol-Gel Derived (Ba0.5Sr0.5)TiO3:MgTiO3 Thin Film Composites

(Ba_1-xSr_x)TiO₃ (BST) is a suitable material for microelectronic device applications due to its high response of the dielectric permittivity to an applied electric field. However, the large dielectric constants found in this system limit its usefulness at microwave frequencies. In our recent studies sol-gel prepared Ba_0.5Sr_0.5TiO₃:MgO heterostructured thin films have shown an increase in the figure of merit (tunability/loss) compared to pure Ba_0.5Sr_0.5TiO₃ films, but the leakage characteristics of these films did not improve significantly. Moreover, due to the hygroscopic nature of MgO, the BST:MgO heterostructured films may suffer with longer period of time instability. In this paper we used the low loss and non-hygroscopic MgTiO₃ for the fabrication of the Ba_0.5Sr_0.5TiO₃:MgTiO₃ (BST50:MT) heterostructured thin films by sol-gel technique and studied the effects of MgTiO₃ layers on the structural, physical, dielectric properties, and leakage current behavior of the BST:MT films. The X-ray studies indicated that both MT and Ba_0.5Sr_0.5TiO₃ are highly oriented and remain as two distinct individual entities in the composite films and a considerable reduction in the dielectric loss and leakage currents has been observed. High frequency phase shifter studies (at low voltage) suggest that these films are suitable for the tunable microwave device applications.