Effect of Substrate Temperature on the Structural,Electrical and Optical Properties of Nanocrystalline Silicon Films in Hot-Filament Chemical Vapor Deposition

Hydrogenated nanocrystalline silicon fi1ms are deposited onto glass substrates at different substrate temperatures(140-400℃)by hot-filament chemical vapor deposition.The effect of substrate temperature on the structural properties are investigated.With an increasing substrate temperature,the Raman crystalline volume fraction increases,but decreases with a further increase.The maximum Raman crystalline volume fraction of the nanocrystalline silicon 61ms is about 74%and also has the highest microstructural factor(R=0.89)at a substrate temperature of 250℃.The deposition rate exhibits a contrary tendency to that of the crystalline volume fraction.The continuous transition of the fi1m structures from columnar to agglomerated is observed at a substrate temperature of 300℃.The optical band gaps of the grown thin 61ms declines(from 1.89 to 1.53 eV)and dark electrical conductivity increases(from about 10-10 to about 10-6 S/cm)with the increasing substrate temperature.

基于镍钴层状双氢氧化物生长在氧化铟锡纳米线和炭布复合物上的高性能微型锌电池

人类需求推动了微型储能器件的快速发展,开发高性能、绿色和安全的小型化电子器件势在必行。近年来,平面叉指型可充电锌微电池(MB)因其易于串并联集成、灵活性和可去除传统隔膜而受到广泛关注。本文使用激光蚀刻技术合成了一种水基高安全性的负极Zn、正极NiCo-LDH@ITO NWs@CC的微型锌电池。由于使用高导电性的ITO NWs@CC集流体,基于锌箔负极和NiCo-LDH正极的叉指型微型电池表现出优异的性能。平面叉指微型电池在碱性水系电解质中、电流密度1 mA cm^(−2)下具有453.5 mAh g^(−1)(对应于0.56 mAh cm^(−2))的高比容量。值得注意的是,微型锌电池表现出优异的能量密度(798.4μWh cm^(−2),对应于649.9 Wh kg^(−1))和功率密度(4.1 mW cm^(−2),对应于3282.7 mW kg^(−1))。微型电池也表现出非常好的长期循环稳定性(在5 mA cm^(−2)下经4000次循环后容量保持率为216%)。此外,串并联测试进一步表明微型电池良好的一致性。

Growth of Graphene Nanoribbons and Carbon Onions from Polymer

Graphene nanoribbons and carbon onions are directly prepared by electron beam irradiation of polyacrylonitrile and expanded polystyrene nanofibers,respectively.By controlling the irradiation process in a high resolution transmission electron microscope,the number of layers of the graphene nanoribbons,as well as the dimension of the carbon onions,can be controlled.It is found that the initial diameter of the nanofiber has a strong effect on the final results.A mechanism is proposed to explain the transformation of polymer nanofibers to carbon nanostructures under electron beam irradiation.This supposes that the polymer nanofibers are first carbonized and then graphitized as a result of the high energy electrons.According to the mechanism,it is believed that all polymer nanofibers could be carbonized and then converted to graphene nanoribbons by proper electron beam irradiation.

A Novel Model of the H Radical in Hot-Filament Chemical Vapor Deposition

Amorphous hydrogenated and crystalline silicon thin films were prepared by hot-filament chemical vapor deposition.A structural transformation from amorphous phase to crystalline phase by increasing the filament temperature Tfil from 1600℃ to 1650℃ was observed.This phenomenon may result from the associated abundance of H radicals participating in the growth of the Silms.A probability distribution model of the H radical is proposed to elucidate this phenomenon.According to this model,the phase transition is due to a distinct difference in the probability distribution of the H radicals,which seems to be dependent upon Tfil.