Effect of Mo capping layers thickness on the perpendicular magnetic anisotropy in MgO/CoFeB based top magnetic tunnel junction structure

A detailed study of the magnetic characterizations of the top structure MgO/CoFeB/Mo is presented.The samples show strong perpendicular magnetic anisotropy(PMA) when the thickness of CoFeB is 0.9 nm and 1.1 nm.The saturation magnetic moment and interface anisotropy constant are 1566 emu/cm~3 and 3.75 erg/cm~2,respectively.The magnetic dead layer(MDL) is about 0.23 nm in this system.Furthermore,strong capping layer thickness dependence is also observed.The strong PMA of 1.1 nm CoFeB only exists in a Mo cap layer thickness window of 1.2-2 nm.To maintain PMA,the metal layer could not be too thin or thick in these multilayers.The oxidation and diffusion of the metal capping layer should be respectively responsibility for the degradation of PMA in these thin or thick metal capping layer samples.     

Non-linear effects of TMS capping on dimethyloctyl HPLC stationary phases

Co-bonding ligands on the same support to produce “blended” HPLC stationary phases is most commonly carried out in the form of capped reversed-phase materials. Non-additive retention properties were observed over a range of trimethylsilane/dimethyloctylsilane ratios. In addition, the increase in retention per mole of bonded trimethylsilane was greatest at the highest dimethyloctylsilane coverages.     

Synthesis,characterization, and hydrolysis of PVAc-PS-PVAc via charge transfer polymerization

An ABA triblock copolymer of polyvinyl acetate-b-polystyrene-b-polyvinyl acetate (PVAc-PS-PVAc) was successfully synthesized with a binary system composed of polystyrene with N,N-dimethylaniline end groups (PS_da) and benzophenone to initiate the polymerization of vinyl acetate under UV irradiation. The PS_da was obtained by capping the living polystyrene macrodianion with p-(dimethylamino) benzaldehyde in excess. The PVA-PS-PVA could then be obtained by hydrolysis of PVAc-PS-PVAc in the sodium ethoxide benzene solution. The intermediates and desirable copolymers were characterized by GPC, IR, and ¹H-NMR in detail. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2595–2600, 1999     

不同水环境对纳米银颗粒聚集体粒径大小及界面电势的影响

研究了不同水环境对无稳定剂与PVP为稳定剂的纳米银颗粒的物化性能的影响。结果表明:随着电解质浓度的增加,纳米银颗粒的粒径与界面电势逐步增大;二价阳离子比一价阳离子更能有效地使纳米银粒径与界面电势增加;稳定剂PVP,腐植酸及其他天然有机物能够增加纳米银溶胶的稳定性;在天然水体中,纳米银在海水中的粒径颗粒与界面电势比湖水中更大。     

A Modified Sequential Deposition Route for High-Performance Carbon-Based Perovskite Solar Cells under Atmosphere Condition

Carbon-based hole transport material (HTM)-free perovskite solar cells have exhibited a promising commercialization prospect, attributed to their outstanding stability and low manufacturing cost. However, the serious charge recombination at the interface of the carbon counter electrode and titanium dioxide (TiO₂) suppresses the improvement in the carbon-based perovskite solar cells’ performance. Here, we propose a modified sequential deposition process in air, which introduces a mixed solvent to improve the morphology of lead iodide (PbI₂) film. Combined with ethanol treatment, the preferred crystallization orientation of the PbI₂ film is generated. This new deposition strategy can prepare a thick and compact methylammonium lead halide (MAPbI₃) film under high-humidity conditions, which acts as a natural active layer that separates the carbon counter electrode and TiO₂. Meanwhile, the modified sequential deposition method provides a simple way to facilitate the conversion of the ultrathick PbI₂ capping layer to MAPbI₃, as the light absorption layer. By adjusting the thickness of the MAPbI₃ capping layer, we achieved a power conversation efficiency (PCE) of 12.5% for the carbon-based perovskite solar cells.     

帽层对极紫外多层膜反射特性影响分析

介绍了在极紫外波段，利用帽层材料来减少多层膜反射镜因外部环境干扰而造成的反射率降低，使多层膜光学元件能够长时间稳定工作.计算了在139nm波长处Mo/Si极紫外多层膜反射镜在表面镀制不同帽层材料时的理论最大反射率，利用单纯形调优法，对帽层和多层膜的周期厚度进行优化，同时把分层理论用于多层膜帽层优化,可使多层膜的反射率得到进一步提高.分析了在加入帽层前后多层膜外层电场强度的分布变化情况. 关键词： 多层膜 反射率 帽层 极紫外     

Synthesis of End‐capped Regioregular Poly(3‐hexylthiophene)s via Direct Arylation

The synthesis of regioregular head‐to‐tail poly(3‐hexylthiophene)s capped with aryl groups (Ar‐HT‐P3HTs) has been accomplished by palladium‐catalyzed polycondensation of 2‐bromo‐3‐hexylthiophene ( 1 ) via direct arylation. A variety of aryl groups are installed at the initiated end in 86%–98% selectivity using aryl bromides and iodides as capping agents. The polymerization proceeds via a two‐stage process. Before monomer 1 is consumed, the competitive formation of end‐capped and non‐capped HT‐P3HTs is operative, where the molecular weight increases linearly with monomer conversion. After 1 is consumed, the resulting polymers are coupled with each other to afford highly end‐capped HT‐P3HTs.     

Enhanced rear‐side reflection and firing‐stable surface passivation of silicon solar cells with capping polymer films

Low refractive index polymer materials have been investigated with a view to form the back surface mirror of advanced silicon solar cells. SiO_x:H or AlO_y SiO_x:H polymer films were spun on top of an ultra‐thin (<10 nm) atomic‐layer‐deposited (ALD) Al₂O₃ layer, itself deposited on low‐resistivity (1 Ω cm) p‐type crystalline silicon wafers. These double‐layer stacks were compared to both ALD Al₂O₃ single layers and ALD Al₂O₃/plasma‐enhanced chemical vapour deposited (PECVD) SiN_x stacks, in terms of surface passivation, firing stability and rear‐side reflection. Very low surface recombination velocity (SRV) values approaching 3 cm/s were achieved with ALD Al₂O₃ layers in the 4–8 nm range. Whilst the surface passivation of the single ALD Al₂O₃ layer is maintained after a standard firing step typical of screen printing metallisation, a harsher firing regime revealed an enhanced thermal stability of the ALD Al₂O₃/SiO_x:H and ALD Al₂O₃/AlO_y SiO_x:H stacks. Using simple two‐dimensional optical modelling of rear‐side reflection it is shown that the low refractive index exhibited by SiO_x:H and AlO_y SiO_x:H results in superior optical performance as compared to PECVD SiN_x, with gains in photogenerated current of ～0.125 mA/cm² at a capping thickness of 100 nm. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Gold Nanoparticle Assemblies on Surfaces: Reactivity Tuning through Capping‐Layer and Cross‐Linker Design

The immobilization of metal nanoparticles (NPs) with molecular control over their organization is challenging. Herein, we report the formation of molecularly cross‐linked AuNP assemblies using a layer‐by‐layer approach. We observed four types of assemblies: 1) small aggregates of individual AuNPs, 2) large aggregates of individual AuNPs, 3) networks of fused AuNPs, and 4) gold islands. Interestingly, these assemblies with the different cross‐linkers and capping layers represent different stages in the complete fusion of AuNPs to afford islands of continuous gold. We demonstrate that the stability toward fusion of the nanoparticles of the on‐surface structures can be controlled by the reactivity of the cross‐linkers and the hydrophilicity/hydrophobicity of the nanoparticles.     

Size control of spherical metallic nanocrystals

In this review, we show that the use of AOT reverse micelles favors the formation of spherical metallic nanomaterials, magnetic or not, such as cobalt and copper. The size is controlled by varying different parameters like the water content of the micelles, the intermicellar interactions, the capping with the AOT surfactant and the reducing agent concentration. As expected theoretically, the change in size of copper nanocrystals induces changes in their optical properties. By controlling both the size and the size distribution of cobalt nanocrystals, well-defined, two-dimensional superlattices can spontaneously form.