表面钝化前后Al0.22Ga0.78N/GaN异质结势垒层应变的高温特性

用高分辨X射线衍射仪(HRXRD)研究了表面钝化前后Al_0.22Ga_0.78N/ GaN异质结势垒层应变的高温特性，温度变化范围从室温到813K.结果表明，对未钝化的异质 结，当测试温度高于523K时，Al_0.22Ga_0.78N势垒层开始出现应变 弛豫；钝化后，在Al_0.22Ga_0.78N势垒层中会产生一个附加的平面 拉伸应变，并随着温度的增加，势垒层中的平面拉伸应变会呈现出一个初始的增加，接着应 变将减小，对100nm厚的Al_0.22Ga_0.78N势垒层，应变只是轻微地减 小，但对于50nm厚的Al_0.22Ga_0.78N势垒层，则出现了严重的应变 弛豫现象. 关键词： 0.22Ga_0.78N/GaN异质结')" href="#">Al_0.22Ga_0.78N/GaN异质结 应变 3 N₄钝化')" href="#">Si₃ N₄钝化 高温XRD     

Synthesis and application of Vis/NIR dialkylaminophenylbuta-1, 3-dienyl borondipyrromethene dyes

Mono- and bis-dialkylaminophenylbuta-1,3-dienyl boron-dipyrromethenes(BODIPYs) 1–12 were synthesized in 36%–42% yields by a Knoevenagel-type condensation. The absorption and emission maxima(labs= 614–739 nm; lem= 655–776 nm in CHCl3) of 1–12 covered from the visible to the nearinfrared region. Probe 1 was ratiometric Vis p H probes. Such probe was almost non-fluorescent. Upon the protonation of the tertiary amine function of 1, the strong fluorescence(Φf= 0.97) was released and the florescence intensity was dramatically increased by one thousand folds. The sharp isosbestic points were discovered at 590 nm, which was a ratiometric p H probe.     

用于紫外探测器DBR结构的高质量AlGaN材料MOCVD生长及其特性研究

利用MOCVD方法在(0001)取向的蓝宝石衬底上实现了不同工艺条件下的高质量AlGaN材料的制备.得到了无裂纹的全组分Al_xGa_1-xN(0<x<1)薄膜.通过XRD，SEM，AFM等测量分析方法系统研究了生长工艺参数对材料的结构质量、组分、厚度和表面形貌的影响.分析了不同生长工艺对AlGaN材料特性的影响.研制的高质量AlGaN材料在紫外探测器的DBR结构应用中得到比较好的特性.     

导电聚合物P3MT的荧光光谱

本文报道了导电聚合物P3MT的荧光光谱及其随样品掺杂浓度、激光强度和温度的变化。实验表明在基态非简并的导电聚合物P3MT中可同时存在三种不同的辐射跃迁:电子-空穴的带间直接复合,激子复合以及带边和双极化子能级之间的辐射跃迁。 关键词：     

Breakdown characteristics of AIGaN/GaN Schottky barrier diodes fabricated on a silicon substrate

In this work, the breakdown characteristics of AlGaN/GaN planar Schottky barrier diodes （SBDs） fabricated on the silicon substrate are investigated. The breakdown voltage （BV） of the SBDs first increases as a function of the anodeto-cathode distance and then tends to saturate at larger inter-electrode spacing. The saturation behavior of the BV is likely caused by the vertical breakdown through the intrinsic GaN buffer layer on silicon, which is supported by the post-breakdown primary leakage path analysis with the emission microscopy. Surface passivation and field plate termination are found effective to suppress the leakage current and enhance the BV of the SBDs. A high BV of 601 V is obtained with a low on-resistance of 3.15 mΩ·cm^2.     

The solid state structure of [b(10)h(11)](-) and its dynamic NMR spectra in solution

The structure of [PPh(3)(benzyl)][B(10)H(11)] was determined at -123 degrees C and 24 degrees C by single-crystal X-ray analyses. The B(10) core of [B(10)H(11)](-) is similar in shape to that of [B(10)H(10)](2)(-). The 11th H atom asymmetrically caps a polar face of the cluster and shows no tendency for disorder in the solid state. Variable temperature multinuclear NMR studies shed light on the dynamic nature of [B(10)H(11)](-) in solution. In addition to the fluxionality of the cluster H atoms, the boron cage is fluxional at moderate temperatures, in contrast to [B(10)H(10)](2)(-). Multiple exchange processes are believed to take place as a function of temperature. Results of ab initio calculations are presented. Crystal data: [PPh(3)(benzyl)][B(10)H(11)] at -123 degrees C, P2(1)/c, a = 9.988(2) A, b = 18.860(2) A, c = 15.072(2) A, beta = 107.916(8) degrees, V = 2701.5(7) A(3), Z = 4; [PPh(3)(benzyl)][B(10)H(11)] at 24 degrees C, P2(1)/c, a = 10.067(5) A, b = 19.009(9) A, c = 15.247(7) A, beta = 107.952(9) degrees, V = 2775(2) A(3), Z = 4.     

Ionic effect on combing of single DNA molecules and observation of their force-induced melting by fluorescence microscopy

Molecular combing is a powerful and simple method for aligning DNA molecules onto a surface. Using this technique combined with fluorescence microscopy, we observed that the length of lambda-DNA molecules was extended to about 1.6 times their contour length (unextended length, 16.2 microm) by the combing method on hydrophobic polymethylmetacrylate coated surfaces. The effects of sodium and magnesium ions and pH of the DNA solution were investigated. Interestingly, we observed force-induced melting of single DNA molecules.     

Highly regioselective synthesis of polysubstituted pyrroles through three-component reaction induced by low-valent titanium reagent

1,2,3,5-Tetrasubstituted and 1,2,3,4,5-pentasubstituted pyrroles may be synthesized through three-component reaction of 1,3-diketones, aldehydes, and amines induced by low-valent titanium reagent. High regioselectivity was achieved. Compared with the classical synthetic method, this new method has the advantages of short reaction time (15 min), high yields, convenient manipulation, and high regioselectivity.     

Simulation of diagnostic ultrasound image pulse sequences in cavitation bioeffects research

Research on cavitational bioeffects of diagnostic ultrasound (DUS) typically involves a diagnostic scanner as the exposure source. However, this can limit the ranges of exposure parameters for experimentation. Anesthetized hairless rats were mounted in a water bath and their right kidneys were exposed to ultrasound. Amplitude modulation with Gaussian envelopes simulated the image pulse sequences (IPSs) produced by diagnostic scanning. A 10 mulkgmin IV dose of Definity((R)) contrast agent was given during 1-5 min exposures. Glomerular capillary hemorrhage was assessed by histology. A stationary exposure approximated the bioeffects induced by DUS within the beam area. However, the use of five closely spaced exposures more faithfully reproduced the total effect produced within a DUS scan plane. Single pulses delivered at 1 s intervals induced the same effect as the simulated DUS. Use of 100 ms triangle-wave modulations for ramp-up or ramp-down of the IPS gave no effect or a large effect, respectively. Finally, an air-backed transducer simulating DUS without contrast agent showed a zero effect even operating at twice the present DUS guideline upper limit. Relatively simple single-element laboratory exposure systems can simulate diagnostic ultrasound exposure and allow exploration of parameter ranges beyond those available on present clinical systems.     

Topologically decoherence-protected qubits with trapped ions

We show that trapped ions can be used to simulate a highly symmetrical Hamiltonian with eigenstates naturally protected against local sources of decoherence. This Hamiltonian involves long-range coupling between particles and provides a more efficient protection than nearest neighbor models discussed in previous works. Our results open the perspective of experimentally realizing, in controlled atomic systems, complex entangled states with decoherence times up to 9 orders of magnitude longer than isolated quantum systems.