Ultrafast Electrochemical Growth of Lithiophilic Nano-Flake Arrays for Stable Lithium Metal Anode

Lithium dendrites caused by nonuniform Li⁺ flux leads to the capacity fade and short-circuit hazard of lithium metal batteries. The solid electrolyte interface (SEI) is critical to the uniformity of Li⁺ flux. Here, an ultrafast preparation of uniform and vertical Cu₇S₄ nano-flake arrays (Cu₇S₄ NFAs) on the Cu substrate is reported. These arrays can largely improve the lithiophilicity of the anode and form Li₂S-enriched SEI due to the electrochemical reduction of Cu₇S₄ NFAs with lithium. A further statistical analysis suggests that the SEI, with a higher content of Li₂S, is more effective to inhibit the formation of lithium dendrites and yields less dead lithium. A quite stable coulombic efficiency of 98.6% can be maintained for 400 cycles at 1 mA cm^–2. Furthermore, at negative to positive electrode capacity ratio of 1.5 (N/P = 1.5), the full battery of Li@Cu₇S₄ NFAs||S shows 83% capacity retention after 100 cycles at 1 C, much higher than that of Li@Cu||S (33%). The findings demonstrate that high Li₂S content in the SEI is crucial for the dendrite inhibition to achieve better electrochemical performance.     

Theoretical design study on the origin of the improved phosphorescent efficiency of DPEphos quinoline-substituted derivatives for OLEDs

Various tetrahedral heteroleptic Cu(I) complexes, as red organic light-emitting diodes (OLEDs), show a concern of maximizing the quantum yield (QY) in order to improve the optoelectronic performance. Herein, three experimental [Cu(N^N) (bis [2-(diphenylphosphino)phenyl]ether)]⁺ (named 1, 2 and 3) were selected as the jumping-off point, following two complexes (named 4 and 5) were successfully designed by introducing bulky electron-donating substituents into N^N ligands continuously. As expected, the QY of designed complexes 4 (0.26) and 5 (0.13) exhibit over twice higher than that of 3 (5.4 × 10⁻²). This can be attributed to the enhanced electron-donating property of N^N ligand, which accelerated the radiative transition rate (k_r) through the apparently elevated energy level of the lowest triplet excited state (T₁) and strengthened transition dipole moments, even though the spin-orbit coupling (SOC) effect is weakened. Simultaneously, the tetrahedral geometric distortion could be effectively restrained by the bulky N^N ligands, but the high vibrational freedom of the terminal substituents could also bring in some unfavorable intra-ligand deformation, resulting in an upward of the nonradiative transition rate (k_nr) at 5 (k_nr: 0.30 × 10⁵ s⁻¹ for 4; 0.95 × 10⁵ s⁻¹ for 5). Therefore, it's worth noting that the balance of excited state energy level, SOC effect as well as the reorganization energy ought to be elaborately regulated to achieve the optimal QY. This detailed investigation on the microscopic mechanism of these Cu(I) complexes can provide instructive inspiration for experimentalists.     

Luminescent cationic/neutral Cu(I) complexes for use in light-emitting diodes: Synthesis,structural characterization,DFT studies and properties

Cationic and neutral mononuclear Cu(I) complexes, [Cu(PPh₃)₂(PmH)]BF₄ (1a), [Cu(DPEphos) (PmH)]BF₄ (2a), [Cu(Xantphos) (PmH)]BF₄ (3a), [Cu(PPh₃)₂(Pm)] (1b), [Cu(DPEphos) (Pm)] (2b) and [Cu(Xantphos) (Pm)] (3b) (PPh₃ = triphenylphosphine, DPEphos = bis(2-diphenylphosphinophenyl)ether, Xantphos = 9, 9-dimethyl-bis(diphenylphosphino)xanthenes, PmH = 2-(pyridin-2-yl)benzimidazole, Pm=(2-(Pyridin-2-yl)benzimidazolate), have been prepared and characterized by IR, ¹H NMR, ¹³C NMR, ³¹P NMR, XRD, elemental analysis and X-ray crystal structure analysis. The structural analysis shows that each of Cu(I) complexes includes a tetrahedral [Cu(NN) (PP)]⁺ moiety, and temperature variation from 99 K to 298 K leads to the change of bonds lengths, angles and weak interactions. Meanwhile, theoretical calculations indicate that the differences between cationic and neutral Cu(I) complexes affect the composition of HOMO and LUMO orbitals, and the effect of temperature on Mülliken atomic charges is limited. Furthermore, neutral Cu(I) complexes 1b–3b show better luminescence in comparison to cationic Cu(I) complexes 1a-3a at room temperature, and temperature variations from 99 K to 298 K result in changing photoluminescence to some extent, which partly agrees with the related calculation results. In these cationic and neutral Cu(I) complexes, the maximum phosphorescent lifetime and quantum yield reach respectively 137 μs and 42% at room temperature. Moreover, cationic and neutral Cu(I) complexes are utilized to fabricate the monochromatic LEDs, showing favorable electroluminescence with the maximum EQE of 7.10%.     

Ultrasmall Pd‐Cu‐Pt Trimetallic Twin Icosahedrons Boost the Electrocatalytic Performance of Glycerol Oxidation at the Operating Temperature of Fuel Cells

Recently, in order to improve the energy conversion efficiency of direct polyol fuel cells, the engineering of effective Pd‐ and/or Pt‐based electrocatalysts to rupture C? C bonds has received increasing attention. Here, an example is shown to synthesize highly uniform sub‐10 nm Pd‐Cu‐Pt twin icosahedrons by controlling the nucleation phase. Because of the synergies of the electronic effect, synergistic effect, geometric effect, and abundant surface active sites originating from the formation of near surface alloy and special icosahedral shape, the Pd‐Cu‐Pt twin icosahedrons exhibit excellent electrocatalytic performance in glycerol electrocatalysis at the operating temperature of direct alcohol fuel cells (70 °C) in KOH electrolyte. The Pd_50.2Cu_38.4Pt_11.4 icosahedrons show mass activities of 9.7 A mg^?1_Pd+Pt and 13.7 A mg^?1_Pd. Furthermore, the Pd_50.2Cu_38.4Pt_11.4 icosahedrons demonstrate long‐term durability in current–time test for 36 000 s and high in situ anti‐CO poisoning performance. In addition, the introduction of CO can enhance electro‐oxidation endurance on Pd_50.2Cu_38.4Pt_11.4 icosahedrons, and the peak mass activity can reach to 14.4 A mg^?1_Pd+Pt. The in situ Fourier transform infrared spectroscopy spectra indicate that the Pd_50.2Cu_38.4Pt_11.4 icosahedrons possess a high capacity to break C? C bonds and may efficiently convert glycerol into CO₂, thus improving the utilization efficiency of energy‐containing molecule glycerol.     

Impact of Transition-Metal Contamination on Oxygen Precipitation in Czochralski Silicon Under Rapid Thermal Processing

研究了快速热处理工艺下直拉单晶硅中过渡族金属铜、镍对内吸杂工艺中氧沉淀形成规律的影响.实验结果表明:在快速热处理工艺下,间隙铜对氧沉淀几乎没有影响,铜沉淀却能显著地促进氧沉淀的形成;而间隙镍或镍沉淀对氧沉淀的形成都没有影响.基于实验结果并结合氧沉淀的形核理论,对金属铜、镍对氧沉淀的影响机理进行了解释.     

铜锡合金纳米粒子的制备和性能研究

通过化学还原方法制备了铜锡合金纳米粒子,并研究分析了其的尺寸和热学性能。铜锡纳米粒子的X射线衍射分析结果显示,合成产物主要是锡纳米颗粒和铜锡合金(Cu6Sn5)纳米颗粒组成,且这些纳米粒子并未被氧化。其示差扫描量热法测得结果表明,本次合成的纳米颗粒的熔点为202.98 ℃,适合现代电子封装技术对低熔点封装材料的要求。     

Sn3.8Ag0.7Cu和Sn37Pb焊点界面显微结构研究

利用扫描电子显微镜（SEM）和透射电子显微镜（TEM）研究了Sn3.8Ag0.7Cu（Sn37Pb）/Cu焊点在时效过程中的界面金属间化合物（IMC）形貌和成份。结果表明：150℃高温时效50、100、200、500h后,Sn3.8Ag0.7Cu（Sn37Pb）/Cu焊点界面IMC尺寸和厚度增加明显,IMC颗粒间的沟槽越来越小。50h时效后界面出现双层IMC结构,靠近焊料的上层为Cu6Sn5,邻近基板的下层为Cu3Sn。之后利用透射电镜观察了Sn37Pb/Ni和Sn3.8Ag0.7Cu/Ni样品焊点界面,结果显示,焊点界面清晰,IMC晶粒明显。     

Microstructure characterization of Sn-Ag solder joints between stud bumps and metal pads

The microstructure of the flip-chip solder joints fabricated using stud bumps and Pb-free solder was characterized. The Au or Cu stud bumps formed on Al pads on Si die were aligned to corresponding metal pads in the substrate, which was printed with Sn-3.5Ag paste. Joints were fabricated by reflowing the solder paste. In the solder joints fabricated using Au stud bumps, Au-Sn intermetallics spread over the whole joints, and the solder remained randomly island-shaped. The δ-AuSn, ε-AuSn₂, and η-AuSn₄ intermetallic compounds formed sequentially from the Au stud bump. The microstructure of the solder joints did not change significantly even after multiple reflows. The AuSn₄ was the main phase after reflow because of the fast dissolution of Au. In the solder joints fabricated using Cu stud bumps, the scallop-type Cu₆Sn₅ intermetallic was formed only at the Cu interface, and the solder was the main phase. The difference in the microstructure of the solder joints with Au and Cu stud bumps resulted from the dissolution-rate difference of Au and Cu into the solder.     

Sn-3.0Ag-0.5Cu真空再流焊工艺技术研究

为了获得低热阻和解决不同焊接材料之间的热应力匹配问题,大功率DC-DC模块电源产品广泛采用了载体组件作为功率元器件热沉的散热方法。载体组件由金属基板和陶瓷基板焊接而成,为了得到无空洞的焊接界面,载体组件采用了真空再流焊工艺技术。文中从焊料形态、焊接表面处理、真空度等几个方面介绍了载体组件的Sn-3.0Ag-0.5Cu真...     

Barrier layers for Cu ULSI metallization

Barrier layers are integral parts of many metal interconnect systems. In this paper we review the current status of barrier layers for copper metallization for ultra-large-scale-integration (ULSI) technology for integrated circuits (ICs) manufacturing. The role of barrier layers is reviewed and the criteria that determine the process window, i.e. the optimum barrier thickness and the deposition processes, for their manufacturing are discussed. Various deposition methods are presented: physical vapor deposition (PVD), chemical vapor deposition (CVD), electrochemical deposition (ECD), electroless deposition (ELD), and atomic layer CVD (ALCVD) for barrier layers implementation. The barrier integration methods and the interaction between the barrier and the copper metallization are presented and discussed. Finally, the common inspection and metrology for barrier layer are critically reviewed.