Impact of wide bandgap p-type nc-Si on the performance of a-Si solar cells

This paper reports the impact of a wide bandgap p-type hydrogenated nanocrystalline silicon (nc-Si:H) on the performances of hydrogenated amorphous silicon (a-Si:H) based solar cells. The player consists of nanometer-sized Si crystallites and has a wide effective bandgap determined mainly by the quantum size-confinement effect (QSE). By incorporation of this p-layer into the devices we have obtained high performances of a-Si:H top solar cells with V-infinity=1.045 V and FF=70.3 %, and much improved mid and bottom a-SiGe:H cells, deposited on stainless steel (SS) substrate. The effects of the band-edge mismatch at the p/i-interface on the I-V characteristics of the solar cells arc discussed on the bases of the density-functional approach and the AMPS model.

Influence of crystal perfection on the reverse leakage current of the SiGe Si p-n heterojunction diodes

Double-crystal X-ray diffraction and I-V characterization have been carried out on the GSMBE grown SiGe/Si p-n heterojunction materials. Results show that the SiGe alloys crystalline quality and the misfit dislocations are critical influences on the reverse leakage current. The crystal perfection and/or the degree of metastability of the Sice alloys have been estimated in terms of the model proposed by Tsao with the experimental results. High-quality p-n heterojunction diodes can be obtained by optimizing the SiGe alloy structures, which limit the alloys in the metastable states. (C) 1999 Elsevier Science B.V. All rights reserved.

Origin of flat-band voltage sharp roll-off in metal gate/high-k/ultrathin- SiO2/Si p-channel metal-oxide-semiconductor stacks

The origin of the flat band voltage roll-off (V-FB roll-off) in metal gate/high-k/ultrathin-SiO2/Si metal-oxide-semiconductor stacks is analyzed and a model describing the role of the dipoles at the SiO2/Si interface on the V-FB sharp roll-off is proposed. The V-FB sharp roll-off appears when the thickness of the SiO2 interlayer diminishes to below the oxygen diffusion depth. The results derived using our model agree well with experimental data and provide insights to the mechanism of the V-FB sharp roll-off.

长期施肥对农田土壤N、P���化酶活性的影响

本试验利用国家黑土肥力与肥料效益长期定位监测基地为平台，研究了多种施肥方式（包括休闲、不施肥、氮、氮钾、氮磷钾、秸秆配施化肥、猪粪配施化肥等）对参与土壤氮转化过程的蛋白酶 、脲酶、硝酸还原酶、氨氧化酶以及参与土壤有机磷矿化的磷酸三酯酶、磷酸二酯酶和磷酸单酯酶活性和动力学特性的作用，以探讨不同施肥方式对氮磷转化酶活性的影响，得出如下结果： 1. 不同施肥处理对土壤氮转化酶促过程影响不同，有机肥配施化肥处理显著增强了蛋白酶、脲酶、氨氧化酶活性。有机肥配施化肥处理土壤速效氮含量高于化肥处理，硝态氮积累量较大，铵态氮含量差异不显著，有机肥配施化肥能够显著促进尿素水解和硝态氮的积累，表明有机肥配施化肥有机氮的矿化强度及硝化作用强于化肥处理。施肥对硝酸还原酶活性没有显著影响。相关分析表明，土壤蛋白酶、脲酶和氨氧化酶活性与微生物量碳呈显著正相关，氨氧化酶活性与脱氢酶呈显著正相关。 2. 有机肥配施化肥处理显著提高了土壤速效磷的含量，增强了土壤磷酸二酯酶和中性磷酸单酯酶活性，土壤速效磷含量过高的情况下，速效磷对中性磷酸单酯酶产生一定程度的抑制作用。与对照相比，化肥处理显著增高了中性磷酸单酯酶活性，但是对磷酸二酯酶有一定的抑制作用。相关分析表明，土壤磷酸二酯酶活性与土壤脱氢酶、速效磷呈显著正相关，中性磷酸单酯酶与速效磷含量呈负相关。