蓝相液晶光电特性研究

蓝相液晶由于其特有的扭曲双螺旋结构,具有快速响应特性与宏观上的光学各向同性。通过聚合物稳定的方法,可以提升其热稳定性,但是也导致了驱动性能下降,磁滞效应增强等问题。文章通过研究手性掺杂和聚合物网络对蓝相液晶材料体系的作用以及不同温度下的磁滞效应,探索蓝相液晶器件光电特性的影响因子,为改善蓝相液晶材料的光电特性提供理论上的支持。     

Magnesium vacancies and hydrogen doping in MgH2 for improving gravimetric capacity and desorption temperature

Performing an ab initio analysis, we inspect the effect of magnesium vacancies and hydrogen doping on the magnesium hydride (MgH₂). The Korringa – Kohn – Rostoker method integrated with the coherent potential approximation is used to perform our calculations. In particular, we find that the gravimetric capacity of MgH₂ increases from 7.658 to 9.816 wt% when the concentrations of magnesium vacancies and hydrogen dopant atoms increase from 0 to 10%. Concretely, the results reveal that the magnesium vacancies and the hydrogen doping have a beneficial effect on the hydrogen storage properties of the hydride by decreasing its desorption temperature and stability. This decrease can be explained on the one hand by the diminution of the number of Mg atoms that establish strong bonds with H atoms, and on the other hand by using the density of states, which indicates that when the concentrations increase, the Mg and H states shift to the conduction band. We also obtain that the value of the desorption temperature can be controlled by varying the concentrations of magnesium vacancies and hydrogen dopant atoms from 4.2 to 5.8% in order to reach the optimum range 289–393 K for the practical use of fuel cell vehicles.     

不同掺杂剂对磷矿碳热还原反应的影响

对比分析了分别以K₂CO₃、Na₂CO₃、NiSO₄、K₂CO₃-NiSO₄为掺杂剂的不同磷矿碳热还原反应体系，结果表明，1200℃时，掺杂碱金属的体系由于其更易产生液相，利于扩散，因此，其反应进度比其他体系略好；对比掺杂物体系和无掺杂体系的各温度XRD图谱可知，掺杂物只是强化了反应的进度，并未有新的物质产生。添加掺杂物后残渣的流动温度也有明显差异，1250℃时，掺杂碱金属的残渣其流动温度较低，而随着温度的升高，残渣的流动温度均下降；但1350℃时，混合掺杂体系和掺杂硫酸镍体系的流动温度却低于碱金属体系；从1300℃下残渣的SEM图谱分析可知，具有掺杂物体系的残渣外观形态与无掺杂体系基本一致，说明添加掺杂物并没改变残渣的外观形态，均是固体残渣，符合窑法磷酸固态排渣的要求。     

Highly efficient bluish green phosphorescent organic light-emitting diodes based on heteroleptic iridium(III) complexes with phenylpyridine main skeleton

A new series of heteroleptic iridium(III) complexes, bis(2-phenylpyridinato-N,C2′)iridium (2-(2′,4′-difluorophenyl)-4-methylpyridine), (ppy)₂Ir(dfpmpy) and bis(2-(2′,4′-difluorophenyl)-4-methylpyridinato-N,C2′)iridium (2-phenylpyridine) (dfpmpy)₂Ir(ppy), have been synthesized by using phenylpyridine as a main skeleton for bluish green phosphorescent organic light-emitting diodes (PhOLEDs). The Ir(III) complexes showed high thermal stability and high photoluminescent (PL) quantum yields of 95% ± 4% simultaneously. As a result, the PhOLEDs with the heteroleptic Ir(III) complexes showed excellent performances approaching 100% internal quantum efficiency with a very high external quantum efficiency (EQE) of ∼27%, a low turn-on voltage of 2.4 V, high power efficiency of ∼85 lm/W, and very low efficiency roll-off up to 20,000 cd/m².     

SIMS quantification of As and In in Hg1−xCdxTe materials of different x values

This paper presents a study of Secondary Ion Mass Spectrometry (SIMS) quantification of As and In in Hg_1–xCd_xTe materials. The SIMS results show that for Hg_1-xCd_xTe with x from 0.2 to 0.8, As and In quantification is independent of the x-values (0.2–0.8). The relative sensitivity factors (RSF) for In and As derived from the standard of one x value can be used to accurately quantify unknown samples of different x value(s). We also determined the dependence of sputtering rate vs. x values under oxygen beam bombardment.     

Improved Gettering Efficiency of Ni from Nickel-Mediated Crystallization Silicon Using Phosphorus-Doped Amorphous Silicon

Ni-metal-induced lateral crystallization (NILC) has been utilized to fabricate polycrystalline silicon thin-film transistors. However, the NILC process often leads to Ni and NiSi₂ precipitates being trapped. In this study, two kinds of films were used as gettering layers: (1) amorphous Si and (2) phosphorus-doped amorphous Si. After annealing at 550°C for 12 h, it was found that phosphorous dopant did improve the gettering efficiency of amorphous Si.     

SiC中基态施主能级分裂对杂质电离的影响

对SiC中基态施主能级分裂对杂质电离的影响,与温度、掺杂浓度和杂质能级深度的关系进行了系统研究.发现只有在高温且掺杂浓度低的情况下,能级分裂的影响很小可忽略不计,其他条件下均需考虑能级分裂因素.随掺杂浓度的增加,能级分裂的影响增强;随温度的升高,能级分裂影响的整体趋势下降,但存在峰值.当杂质能级深度发生变化时,能级分裂的影响显得比较复杂;曲线上的峰值随着能级深度的增加而向高温方向移动,能级越浅峰就越小;并且在高于某一温度时,随能级的加深能级分裂的影响逐渐增强.     

The origin of electrical property deterioration with increasing Mg concentration in ZnMgO:Ga

Transparent conductive Ga-doped Zn_1 − xMg_xO (ZnMgO:Ga) films were epitaxially grown via Pulsed Laser Deposition on sapphire by optimizing the substrate temperature and other parameters of deposition. Zn_0.68Mg_0.31Ga_0.01O/sapphire films deposited at 400 °C have a Hall mobility (μ) of 9.2 ± 0.5 cm² V^− 1 s^− 1 and a free electron density (n) of 1.79 × 10²⁰ ± 0.06 × 10²⁰ cm^− 3, yielding an electrical conductivity (σ) = 262 ± 22 S/cm. Zn_0.90Mg_0.09Ga_0.01O/sapphire films, deposited under the same growth conditions, have similar crystalline quality, but significantly better electrical properties (σ = 1450 ± 10 S/cm, μ = 24.5 ± 2.5 cm² V^− 1 s^− 1, n = 3.81 × 10²⁰ ± 0.20 × 10²⁰ cm^− 3). This comparison provides evidence of electrical property deterioration in doped ZnMgO bulk material with increasing Mg content, independent of crystalline quality. Electrical properties of ZnMgO:Ga are further deteriorated by the decrease of the crystalline quality. Polycrystalline Zn_0.90Mg_0.09Ga_0.01O/a-SiO₂ samples deposited under identical conditions on amorphous silica substrates had both inferior crystal quality and inferior transport properties (μ = 2.5 ± 0.2 cm² V^− 1 s^− 1, n = 2.04 × 10²⁰ ± 0.20 × 10²⁰ cm^− 3, σ = 80 ± 8 S/cm) compared to their epitaxial counterparts. Overall, the results of this study indicate that both bulk material properties and crystalline quality influence the electrical properties of single-phase ZnMgO:Ga thin films.