Al/GaSb异质结的慢正电子研究

用单能慢正电子束和 X 射线衍射方法研究了 Al/n-GaSb 金属半导体异质结在不同温度退火的情况下的演变.采用三层模型既 Al/界面/GaSb 对 S-E 实验数据进行拟合.结果发现在未退火样品的 Al 和 GaSb 之间存在一个厚度大约5nm 的界面层.在经过400℃退火后,该界面厚度增加到约400nm,且 S 参数下降.这可能是由于在退火过程中,界面区域的原子在界面处相互扩散所引起的.Al 膜的 S_(Al)参数降低且效扩散长度 L_(Al)增加,说明 Al 膜内的空位缺陷经过退火被消除且进行结构重整,晶格结构不断变好的结果.衬底 GaSb 的 S_B 参数和有效扩散长度 L_B 的演变表明,经过250℃退火后,原有的正电子捕获中心消失：但是经进一步400℃退火,又产生了新的正电子捕获中心.这可能来源于其他类型的与 V_(Ga)相关缺陷的正电子捕获以及 Ga_(Sb)晶格反位引起的正电子浅捕获.X 射线衔射的测量结果证实了正电子方法的结论.     

Refractive index changes due to F → M conversion in KBr single crystals and their applications in holography

Refractive index changes due to the F → M colour centre conversion in a KBr crystal are given as a function of angular frequency and temperature. The applicability of the results obtained for holographic recording is discussed.     

Spectral diffusion broadening by soft local modes in Sm-doped sodium borate glass

An explanation for the anomalous temperature broadening of zero-phonon transition corresponding to ⁷F₀↔⁵D₀ electronic transition in Sm²⁺-doped sodium borate glasses is given. The main broadening mechanism is spectral diffusion induced by thermal fluctuation of long-living soft localized modes over the whole studied temperature region 5-293 K.     

Microwave saturation of EPR spectra of oxidised coal

Microwave saturation of multi-component EPR spectra of oxidized lignite Mequinenza (Spain) with a carbon content of 65.1 wt % and with a high sulphur content of 10.3 wt % was studied. The coal was oxidized with nitric acid (NHO₃), peroxyacetic acid (PAA), and in O₂/Na₂CO₃ system. Three different groups of paramagnetic centres exist in the coal samples analyzed. The EPR spectrum of the demineralised coal was a superposition of broad Gauss (ΔB _pp = 0.75 mT), broad Lorentz 1 (ΔB _pp = 0.42 mT) and narrow Lorentz 3 lines (ΔB _pp = 0.08 mT). The three EPR components with linewidths: 0.58–0.77 mT (Gauss line), 0.30–0.39 mT (Lorentz 1 line) and 0.05–0.06 mT (Lorentz 3 line) were recorded for the oxidized coal. The g-values were obtained for the samples studied in the ranges 2.0043–2.0046 (Gauss lines), 2.0035–2.0038 (Lorentz 1 lines) and 2.0032–2.0034 (Lorentz 3 lines). The broad Gauss and Lorentz 1 lines saturate at low microwave powers. The narrow Lorentz 3 lines of demineralised coal were not saturated at microwave power from the range considered. After the coal oxidation with HNO₃, PAA and in O₂/Na₂CO₃ system, the microwave saturation of the narrow Lorentz 3 lines was also observed, which indicated a degradation of the multi-ring aromatic structures upon oxidation.      

Rotaxane Formation of Multicyclic Polydimethylsiloxane in a Silicone Network: A Step toward Constructing “Macro-Rotaxanes” from High-Molecular-Weight Axle and Wheel Components

Rotaxanes consisting of a high-molecular-weight axle and wheel components (macro-rotaxanes) have high structural freedom, and are attractive for soft-material applications. However, their synthesis remains underexplored. Here, we investigated macro-rotaxane formation by the topological trapping of multicyclic polydimethylsiloxanes (mc-PDMSs) in silicone networks. mc-PDMS with different numbers of cyclic units and ring sizes was synthesized by cyclopolymerization of a α,ω-norbornenyl-functionalized PDMS. Silicone networks were prepared in the presence of 10–60 wt % mc-PDMS, and the trapping efficiency of mc-PDMS was determined. In contrast to monocyclic PDMS, mc-PDMSs with more cyclic units and larger ring sizes can be quantitatively trapped in the network as macro-rotaxanes. The damping performance of a 60 wt % mc-PDMS-blended silicone network was evaluated, revealing a higher tan δ value than the bare PDMS network. Thus, macro-rotaxanes are promising as non-leaching additives for network polymers.     

Sequenced cyclizations involving intramolecular capture of alkyl-oxyaminyl radicals. Synthesis of heterocyclic compounds

A cascade radical cyclization process involving oxime ethers tethered to a brominated phenyl and an activated olefin moiety is described. The generated aryl radicals using tri-n-butyltin hydride react with the CN bond to yield neutral alkyl-oxyaminyl radicals, which were then simultaneously captured by the activated double bond to provide heterocyclic systems with a pyrrolidinic nucleus.     

Al3+对Ge/Al-SiO2薄膜光致发光的影响

采用磁控溅射及后退火技术制备了不同组份和不同退火温度的Ge、Al共掺SiO₂薄膜。通过对样品的X射线光电子能谱(XPS)测试,确定了薄膜的成分和结构特征;同时还测试了样品的光致发光谱(PL谱),得到了峰值位于420 nm附近的紫光发射峰和峰值位于470 nm的蓝光发射峰。实验结果表明, Al的掺杂不仅可以显著地提高GeNOV中心和SiNOV中心的光发射效率,还可以促进GeNOV缺陷和SiNOV缺陷中心的形成,进而有利于薄膜的光致发光。     

A BN-Doped U-Shaped Heteroacene as a Molecular Floating Gate for Ambipolar Charge Trapping Memory

Two wide-band gap U-shaped polycyclic aromatic hydrocarbons with/without boron and nitrogen (BN-) doping ( BN-1 and C-1 ) were synthesized to tune the electronic features to suit the performance requirements for organic field-effect transistor memory (OFET-NVM). The chemical structures were characterized by scanning tunneling microscopy and single-crystal diffraction. Owing to the electron-donor effect of N and the high electron affinity of B, the BN-1 -based OFET-NVM displays large ambipolar memory windows and an enhanced charge storage density compared to C-1 and most reported small molecules. A novel supramolecular system formed from BN-1 and PMMA contributes to fabricating uniform films with homogeneous microstructures, which serve as a two-in-one tunnelling dielectric and charge-trapping layer to realize long-term charge retention and reliable endurance. Our results demonstrate that both BN doping and supramolecular engineering are crucial for the charge trapping of OFET-NVM.