Counterdoping of MOS channel (CDC)-a new technique of improvingsuppression of latching in insulated gate bipolar transistors

A novel technique of improving suppression of latching in insulated-gate bipolar transistors (IGBTs) is proposed and experimentally verified. By counterdoping the channel of the DMOS cell, the doping of the p-base can be increased up to a factor of two. Dynamic latching improvement of 40-80%, corresponding to the p-base doping increase, has been obtained. The degradation in forward blocking voltage was observed when the counterdoping dosage exceeds about 2×10¹² cm^-2 for 600-V devices     

The effect of substrate doping on the performance of anode-shortedn-channel lateral insulated-gate bipolar transistors

The performance of n-channel lateral-insulated-gate bipolar transistors (n-LIGBTs) with anode shorts on p^- epi/p⁺ substrates is compared to that of anode-shorted n-LIGBTs on p^- substrates, as well as to that of conventional n-LIGBTs on either substrate. It is shown that both forward-voltage drop and turn-off time are better for anode-shorted devices fabricated on p^- epi/p⁺ substrate than for those on p^- substrates, due to a larger percentage component of vertical bipolar current and a lower collector resistance. Forward-voltage drops of 3.05 and 3.3 V at 133 A/cm² and turn-off times of 400 and 750 ns have been measured for devices on p^- epi/p⁺ and p ^- substrates respectively. All the LIGBTs showed current limiting at two to four times the ON-state conduction current during dynamic switching     

Knoevenagel condensation reaction over acid–base bifunctional nanocrystalline CexZr1−xO2 solid solutions

Highly thermally stable three-dimensional spongelike mesoporous Ce_xZr_1?xO₂ solid solutions consisting of nanometer size particles with different Ce/Zr compositions were synthesized by a modified sol–gel procedure using a triethanolamine/water mixture as a solvent to be used in liquid Knoevenagel condensation reaction. These materials were investigated in detail by means of X-ray diffraction (XRD), Raman spectroscopy, chemical analysis, X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), UV–Vis spectroscopy, Fourier transform infrared spectroscopy (FT-IR) and adsorption microcalorimetry. The XRD, HRTEM and XPS studies proved the presence of nanocrystalline Ce_xZr_1?xO₂ solid solutions. These solid solutions showed excellent chemoselectivity in the classical Knoevenagel reaction. The large pore sizes (around 10 nm) highlight the possibility of using Ce_xZr_1?xO₂ as a support material for versatile catalytic systems. The results obtained from NH₃ and SO₂ adsorption microcalorimetry experiments successfully demonstrated the incorporation of ZrO₂ into the CeO₂ lattice resulting in both acidic and basic surface sites in a mixed oxide matrix.     

Structural,Electrical, and Optical Behavior of Strontium Bismuth Titanate Ceramic

In this report, we present the structural, electrical, and optical study of layer-structured SrBi₄Ti₄O₁₅ (SBT) ceramic prepared by solid-state reaction route. The X-ray diffraction and Rietveld refinement studies show a single-phase orthorhombic structure with space group A₂₁am. The scanning electron micrograph shows plate-like grains. The various Raman peaks originated due to the TiO₆ octahedron confirm the orthorhombic structure. The temperature-dependent dielectric study shows a normal ferroelectric phase transition with a transition temperature at 813 K (540 °C). Impedance studies show a non-Debye-type relaxation and relaxation frequency shift to higher side with increase in temperature. The Nyquist plot shows overlapping semicircles which results the existence of both for grain and grain boundary effect in SBT ceramic. The frequency-dependent AC conductivity at different temperatures indicates that the conduction process is thermally activated and the spectra follow the universal power law. The variation of DC conductivity confirms that the SBT ceramic exhibits negative temperature coefficient of resistance behavior. The Ferroelectric behavior is studied by hysteresis loop. The optical band gap is found to be 2.93 eV from the UV–Visible spectroscopy study. The room-temperature photoluminescence study shows a strong red emission.     

Highly sensitive detection of exocytotic dopamine release using a gold-nanoparticle-network microelectrode

Here we report a new type of microelectrode sensor for single-cell exocytotic dopamine release. The new microsensor is built by forming a gold-nanoparticle (AuNP) network on a carbon fiber microelectrode. First a gold surface is obtained on a carbon fiber microdisk electrode by partially etching away the carbon followed by electrochemical deposition of gold into the pore. The gold surface is chemically functionalized with a sol-gel silicate network derived from (3-mercaptopropyl)trimethoxysilane (MPTS). A AuNP network is formed by immobilizing Au nanoparticles onto the thiol groups in the sol-gel silicate network. The AuNP-network microelectrode has been characterized by scanning electron microscopy (SEM) and steady-state voltammetry. The AuNP-network microelectrode has been used for amperometric detection of exocytotic dopamine secretion from individual pheochromocytoma (PC12) cells. The results show significant differences in the kinetic peak parameters including shorter rise time, decay time, and half-width as compared to a bare carbon fiber electrode equivalent. These results indicate AuNP-network microelectrodes possess an excellent sensing activity for single-cell exocytotic catecholamine release, specifically dopamine. Moreover, key advantageous properties inherent to bare carbon fiber microelectrodes (i.e., rigidity, flexibility, and small size) are maintained in addition to an observed prolonged shelf life stability and resistance to cellular debris fouling and dopamine polymerization.