Powderless processing of ceramics: Thin-layer electroceramics

A review is made of progress on the sol-gel processing of dense insulating electroceramics by polymeric condensation routes. Up until the past ten years, powders and porous coatings were principally made for optical and conductive applications. Much effort was expended on silica (SiO₂) and silicate-based systems. Recently, these approaches have been extended to non-silicate systems [1]. In this paper information is presented for the powderless processing of selected electroceramics in thin-layer form. Materials include PbTiO₃, BaTiO₃, Ba_1–x Pb _x TiO₃, PbZrO₃, Pb(Zr_1–y Ti _y )O₃ and (Pb_1–x La _x )(Zr_1–y Ti _y )O₃ which find applications in ceramic capacitors, piezoelectric transducers and electrooptic modulators. The approach is to avoid powders, and the attendent problems of powder handling, flow, packing, etc., and make use of polymerization condensation reactions to form extended networks with chemical linkage. Data are reported for the synthesis and low temperature processing routes for amorphous and polycrystalline ceramics.     

Utilization of TXRF analytical technique in order to improve front-end semiconductor processing

In this paper, we summarize how the introduction of in-line TXRF monitoring provides detailed analytical information on aluminum, titanium and molybdenum contamination levels in order to improve several process steps from front-end processing, minimize product yield loss and make it possible to successfully manufacture multiple products and process geometries in the same fabrication platform.     

Observation of π Berry phase in quantum oscillations of three‐dimensional Fermi surface in topological insulator Bi2Se3

We report the quantum transport studies on Bi₂Se₃ single crystal with bulk carrier concentration of ～10¹⁹ cm^–3. The Bi₂Se₃ crystal exhibits metallic character, and at low temperatures, the field dependence of resistivity shows clear Shubnikov–de Haas (SdH) oscillations above 6 T. The analysis of these oscillations through Lifshitz–Kosevich theory reveals a non‐trivial π Berry phase coming from three‐dimensional (3D) Fermi surface, which is a strong signature of Dirac fermions with three‐dimensional dispersion. The large Dingle temperature and non zero slope of Williamson–Hall plot suggest the presence of enhanced local strain field in our system which possibly transforms the regions of topological insulator to 3D Dirac fermion metal state. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Proximity-Effect-Induced Superconductivity in Nb/Sb2Te3-Nanoribbon/Nb Junctions

Nanohybrid superconducting junctions using antimony telluride (Sb₂Te₃) topological insulator nanoribbons and Nb superconducting electrodes are fabricated using electron beam lithography and magnetron sputtering. The effects of bias current, temperature, and magnetic field on the transport properties of the junctions in a four-terminal measurement configuration are investigated. Two features are observed. First, the formation of a Josephson weak-link junction. The junction is formed by proximity-induced areas in the nanoribbon right underneath the inner Nb electrodes which are connected by the few tens of nanometers short Sb₂Te₃ bridge. At 0.5 K a critical current of 0.15 µA is observed. The decrease of the supercurrent with temperature is explained in the framework of a diffusive junction. Furthermore, the Josephson supercurrent is found to decrease monotonously with the magnetic field indicating that the structure is in the small-junction limit. As a second feature, a transition is also observed in the differential resistance at larger bias currents and larger magnetic fields, which is attributed to the suppression of the proximity-induced superconductive state in the nanoribbon area underneath the Nb electrodes.     

绝缘子切槽成型机的研制

本文介绍一种自行研制的绝缘子切槽成型机的结构和工作原理.一个气缸的双向运动代替两个执行元件的直线运动使其经济合理结构紧凑;气动系统回路的安全保护措施使应用更为可靠.     

Balance-equation approach to impact ionization induced by an intense terahertz radiation: Application to InAs/AlSb heterojunctions

We have extended the balance equations to account for conduction-valence interband impact ionization (II) process induced by an intense terahertz (THz) electromagnetic irradiation in semiconductors, and applied them to study the II effect on electron transport and electron-hole pair generation-recombination rate in THz-driven InAs/AlSb heterojunctions (HJ). As many as needed multiphoton channels are self-consistently taken into account for yielding a given accuracy. The time evolution of transport state including THz-radiation-induced II process are monitored in details by an extensive time-dependent analysis. Two different physical stages, the quasi-steady state and the complete steady-state, are clearly identified from the present calculations. Intersubband electron transfer rate and net electron-hole generation rate are derived as functions of the THz radiation strength E _ac for various radiation frequencies from f _ac = 0.42 to 6 THz at lattice temperatures T = 6 K. It's indicated that the THz radiation with a larger E _ac or a lower f _ac, has a stronger effect on electron transport and II process. Qualitative agreement is obtained between the calculated electron-hole generation rate and the available experimental data for InAs/AlSb HJ's at T = 6 K. Received 24 May 2002 / Received in final form 26 August 2002 Published online 31 October 2002 RID="a" ID="a"e-mail: jccao8@hotmail.com