GaN基LED低温空穴注入层的MOCVD生长研究

针对GaN基LED空穴注入效率低的问题,在量子阱与电子阻挡层之间插入低温空穴注入层（LT-HIL）,实验研究了MOCVD生长LT-HIL时二茂镁（Cp₂Mg）流量和生长温度的影响。结果表明：随着Cp₂Mg流量的增加,外延薄膜晶体质量下降,外延片表面平整度和均匀性降低;而受Mg掺杂时补偿效应的影响,主波长先红移后蓝移,芯片的输出光功率先升高后降低,正向电压先降低后升高。相比于无LT-HIL的样品,在20 mA工作电流下,Cp₂Mg流量为1.94 μmol/min时制备的芯片的输出光功率提升20.3%,而正向电压降低0.1 V。在Cp₂Mg流量较大时,LT-HIL的渐变式生长温度对外延质量有所改善,但不是主要影响因素。     

Magnesocene‐Based Electrolytes: A New Class of Electrolytes for Magnesium Batteries

Unlike ferrocene, bis(η⁵‐cyclopentadienyl)magnesium (magnesocene, MgCp₂) is slightly dissociated in solvents, such as ethers, resulting in electrolyte solutions with low conductivity. MgCp₂/tetrahydrofuran solutions make possible reversible magnesium plating and stripping with low over‐potentials for many cycles. The Mg deposits appear with a cauliflower‐like morphology. IR and NMR spectroscopy confirm that the electrolyte is stable and not decomposed during prolonged cycling. The anodic stability limit is in the range of 1.5 V (at platinum) and 1.8 V versus Mg/Mg²⁺ (at stainless steel), which may be sufficient for low‐voltage cathode materials. MgCp₂ is a first example of a completely new class of halide‐free electrolytes, which may open up a new research direction for future magnesium metal and magnesium‐ion batteries.     

Infrared spectroscopy of van der Waals modes in the intermolecular potential of Ar-CO: The K a, = 0 combination of stretch and bending

Using our diode laser spectrometer a new subband of Ar^?CO in the 2167 cm^?1 region has been detected. We have assigned 18 rotational transitions to a thus far unobserved K _a = 0 van der Waals mode at 23.927cm^?1 above the ground state. An exact analysis yields a Coriolis coupling of this new observed state to a previously detected van der Waals state at 26.187cm^?1 [10]. The measurements and a complete analysis are presented.     

One-Step Synthesis and Schlenk-Type Equilibrium of Cyclopentadienylmagnesium Bromides

In the in situ Grignard metalation method (iGMM), the addition of bromoethane to a suspension of magnesium turnings and cyclopentadienes [C₅H₆ (HCp), C₅H₅-Si(iPr)₃ (HCp^TIPS)] in diethyl ether smoothly yields heteroleptic [(Et₂O)Mg(Cp^R)(μ-Br)]₂ (Cp^R=Cp ( 1 ), Cp^TIPS ( 2 )). The Schlenk equilibrium of 2 in toluene leads to ligand exchange and formation of homoleptic [Mg(Cp^R)₂] ( 3 ) and [(Et₂O)MgBr(μ-Br)]₂ ( 4 ). Interfering solvation and aggregation as well as ligand redistribution equilibria hamper a quantitative elucidation of thermodynamic data for the Schlenk equilibrium of 2 in toluene. In ethereal solvents, mononuclear species [(Et₂O)₂Mg(Cp^TIPS)Br] ( 2’ ), [(Et₂O)_nMg(Cp^TIPS)₂] ( 3’ ), and [(Et₂O)₂MgBr₂] ( 4’ ) coexist. Larger coordination numbers can be realized with cyclic ethers like tetrahydropyran allowing crystallization of [(thp)₄MgBr₂] ( 5 ). The interpretation of the temperature-dependency of the Schlenk equilibrium constant in diethyl ether gives a reaction enthalpy ΔH and reaction entropy ΔS of −11.5 kJ mol⁻¹ and 60 J mol⁻¹, respectively.