Crystalline silicon surface passivation investigated by thermal atomic-layer-deposited aluminum oxide

Atomic-layer-deposited(ALD) aluminum oxide(Al_2O_3) has demonstrated an excellent surface passivation for crystalline silicon(c-Si) surfaces, as well as for highly boron-doped c-Si surfaces. In this paper, water-based thermal atomic layer deposition of Al_2O_3 films are fabricated for c-Si surface passivation. The influence of deposition conditions on the passivation quality is investigated. The results show that the excellent passivation on n-type c-Si can be achieved at a low thermal budget of 250℃ given a gas pressure of 0.15 Torr. The thickness-dependence of surface passivation indicates that the effective minority carrier lifetime increases drastically when the thickness of Al_2O_3 is larger than 10 nm. The influence of thermal post annealing treatments is also studied. Comparable carrier lifetime is achieved when Al_2O_3 sample is annealed for 15 min in forming gas in a temperature range from 400℃ to 450℃. In addition, the passivation quality can be further improved when a thin PECVD-SiN_x cap layer is prepared on Al_2O_3, and an effective minority carrier lifetime of2.8 ms and implied Voc of 721 mV are obtained. In addition, several novel methods are proposed to restrain blistering.     

基于石墨烯电极的Co-Salophene分子器件的自旋输运

采用基于非平衡格林函数结合第一性原理的密度泛函理论的计算方法,研究了基于锯齿型石墨纳米带电极的Co-Salophene分子器件的自旋极化输运性质.计算结果表明,当左右电极为平行自旋结构时,自旋向上的电流明显大于自旋向下的电流,自旋向下的电流在[-1V,1V]偏压下接近零,分子器件表现出优异的自旋过滤效应.与此同时,在自旋向上电流中发现负微分电阻效应.当左右电极为反平行自旋结构时,器件表现出双自旋过滤和双自旋分子整流效应.除此之外,整个分子器件还表现出较高的巨磁阻效应.通过分析器件的自旋极化透射谱、局域态密度、电极的能带结构和分子自洽投影哈密顿量,详细解释该分子器件表现出众多特性的内在机理.研究结果对设计多功能分子器件具有重要的借鉴意义.     

孔性介质负载下的络合氢化物及其储氢特性*

络合氢化物具有较高的重量储氢密度,已成为国内外研究的热点。孔性介质由于高比表面积、孔径均匀可调以及良好热稳定性而备受关注。研究表明,实现孔性介质负载的络合氢化物可有效地改善其储氢性能。本文简述了孔性介质的结构特征和物化特性,着重阐述了孔性介质负载催化络合氢化物的制备方法、脱/加氢性能的影响及其催化机理的研究进展,并指出了需要研究的科学问题。