Comparison between N2 and O2 anneals on the integrity of an Al2O3/SiaN4/SiO2/Si memory gate stack

In this paper the endurance characteristics and trap generation are investigated to study the effects of different postdeposition anneals （PDAs） on the integrity of an Al2O3/Si3N4/SiOz/Si memory gate stack. The flat-band voltage （Vfb） turnarounds are observed in both the programmed and erased states of the N2-PDA device. In contrast, this turnaround is observed only in the erased state of the O2-PDA device. The Vfb in the programmed state of the O2-PDA device keeps increasing with increasing program/erase （P/E） cycles. Through the analyses of endurance characteristics and the low voltage round-trip current transients, it is concluded that in both kinds of device there are an unknown type of pre-existing characteristic deep traps and P/E stress-induced positive oxide charges. In the O2-PDA device two extra types of trap are also found： the pre-existing border traps and the P/E stress-induced negative traps. Based on these four types of defects we can explain the endurance characteristics of two kinds of device. The switching property of pre-existing characteristic deep traps is also discussed.     

Synthesis of 1-pyrroline 1-oxides analogous to pseudouridine

Pseudouridine (ψ-uridine, Ψ) aza′-analogues with a 5,5-bis(hydroxymethyl)-1-pyrrolin-2-yl 1-oxide as the glycone mimic were obtained by the addition of (2,4-dimethoxypyrimidin-5-yl)magnesium bromide to 1-aza-7,14-dioxadispiro[4.2.5.2]pentadec-1-ene 1-oxide (3), followed by oxidation and removal of the protecting groups. The analogous synthesis from (2,4-dimethoxypyrimidin-5-yl)lithium and 3 was less efficient; in the first step of the reaction sequence, competing dimerisation of 3 predominated over addition of the organolithium agent to 3.     

Laser Induced Marking of Polymer Chains with Radical Spin Traps

A pathway for marking of polymer chains with radical spin traps during pulsed laser polymerization in free radical polymerization is presented. By introducing a so‐called marker that forms a non‐propagating radical at (or shortly after) the incidence of a laser pulse, a polymer subdistribution is generated by specifically terminating propagating radicals via combination with such a marker radical. The generated polymer subdistribution can subsequently be imaged by modern soft‐ionization mass spectrometry. Herein, the general methodology of the method in which such marker is generated via reaction of an initiating radical with a nitrone is demonstrated on the examples of BA and VAc.

     

AlGaN/GaN高电子迁移率晶体管肖特基高温退火机理研究

在不同应力条件下,研究了AlGaN/GaN高电子迁移率晶体管高温退火前后的电流崩塌、栅泄漏电流以及击穿电压的变化.结果表明,AlGaN/GaN高电子迁移率晶体管通过肖特基高温退火以后,器件的特性得到很大的改善.利用电镜扫描(SEM)和X射线光电子能谱(XPS)对高温退火前、后的肖特基接触界面进行深入分析,发现器件经过高温退火后,Ni和AlGaN层之间介质的去除,并且AlGaN材料表面附近的陷阱减少,使得肖特基有效势垒提高,从而提高器件的电学特性. 关键词： AlGaN/GaN高电子迁移率晶体管 肖特基接触 界面陷阱     

Magnetic interactions of cold atoms with anisotropic conductors

We analyze atom-surface magnetic interactions on atom chips where the magnetic trapping potentials are produced by current carrying wires made of electrically anisotropic materials. We discuss a theory for time dependent fluctuations of the magnetic potential, arising from thermal noise originating from the surface. It is shown that using materials with a large electrical anisotropy results in a considerable reduction of heating and decoherence rates of ultra-cold atoms trapped near the surface, of up to several orders of magnitude. The trap loss rate due to spin flips is expected to be significantly reduced upon cooling the surface to low temperatures. In addition, the electrical anisotropy significantly suppresses the amplitude of static spatial potential corrugations due to current scattering within imperfect wires. Also the shape of the corrugation pattern depends on the electrical anisotropy: the preferred angle of the scattered current wave fronts can be varied over a wide range. Materials, fabrication, and experimental issues are discussed, and specific candidate materials are suggested.     

Titanium dioxide nanoparticles heavily doped with niobium: A light-induced electron paramagnetic resonance study

Light-induced electron paramagnetic resonance (EPR) spectra of titanium dioxide nanoparticles heavily doped with niobium(v) are studied. At low temperatures, the EPR signal caused by interband illumination is associated with paramagnetic Ti³⁺ sites in anatase, which, as the temperature rises above 210 K, are discharged to the non-paramagnetic Ti⁴⁺ state due to the escape of trapped photoelectrons and their recombination with holes. The temperature dependence of the integral EPR signal has a non-Curie character, especially in the temperature range where the discharge of Ti³⁺ centers is already significant.     

Symmetric Swallowtail Beams in the Rectangle Frame

A new type of symmetric swallowtail beam (SSB) in the rectangle frame is introduced here. These kinds of beams are highly tunable with multiple manipulation parameters. The focal length and the focus intensity can be controlled precisely. The SSBs can guide the off-axis vortex to their center. And the experimental results agree well with the numerical simulations. Besides, stable trapping of particles by utilizing the SSBs' auto-focusing property and rectangle symmetry is also observed.