Study of the GaN Film by Spectroscopic Ellipsometry

【中文摘要】 采用椭圆偏振光谱法,在1.50～6.50 eV光谱内,研究了在蓝宝石衬底(0001)面上使用金属有机化学气相沉积(MOCVD)的方法制备的非掺杂纤锌矿结构GaN薄膜的光学性质。建立GaN表面层/外延层/缓冲层/衬底四层物理结构模型。与Cauchy和Sellmeier色散公式比较后选择了Tanguy Extended色散公式来分析GaN薄膜的光学性质。椭圆偏振光谱拟合结果表明,Tanguy Extended色散公式能更准确、方便地描述GaN薄膜在全波段(特别是带隙及带隙之上波段)的色散关系。提供了GaN薄膜在1.50～6.50 eV光谱范围内的寻常光(o光)和非寻常光(e光)折射率和消光系数色散关系,为定量分析GaN薄膜带边附近各向异性的光学性质提供了依据。 【英文摘要】 Optical property of wurtzite GaN film was investigated by spectroscopic ellipsometry(SE) in the spectrum range of 1.50~6.50 eV.Unintentionally doped wurtzite GaN film was fabricated by metal-organic chemical vapor deposition(MOCVD) on(0001) sapphire.Four-layer physical structure model including surface layer,epilayer,buffer layer and substrate was built by analysis.Compared with common dispersion formulas such as Cauchy and Sellmeier,Tanguy Extended dispersion formulas was used to characterize optical prope...国家自然科学基金重点专项(60827004);国家自然科学基金(60776066);国家863计划项目资助项目(2011AA03A110

石墨烯/三元乙丙橡胶纳米复合材料的制备与性能研究

文中将石墨烯与三元乙丙橡胶(EPDM)进行机械共混,制得石墨烯/EPDM纳米复合材料,研究了石墨烯含量对复合材料的导电、导热、力学性能以及相形态的影响。结果表明:石墨烯可以显著地改善复合材料的导电、导热和力学性能。复合材料的电导率和导热系数均随石墨烯含量增加而增大,经推算其导电逾渗阈值为1.3%(体积分数)。随石墨烯含量增加,复合材料的杨氏模量和定伸应力随之逐渐增大;而拉伸强度、撕裂强度、断裂伸长率都呈现先增大后减小的趋势。复合材料的储能模量在很宽的温度范围内也显著提高,且随石墨烯含量的增加而增大;而玻璃转化区tanδ值随石墨烯含量增加而下降。经复合材料脆断面观察,石墨烯在EPDM基体中达到了良好的分散

JUNO Sensitivity on Proton Decay p→νˉK+p\to \bar\nu K^+ Searches

The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator detector designed to explore many topics in fundamental physics. In this paper, the potential on searching for proton decay in $p\to \bar\nu K^+$ mode with JUNO is investigated.The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification. Moreover, the excellent energy resolution of JUNO permits to suppress the sizable background caused by other delayed signals. Based on these advantages, the detection efficiency for the proton decay via $p\to \bar\nu K^+$ is 36.9% with a background level of 0.2 events after 10 years of data taking. The estimated sensitivity based on 200 kton-years exposure is $9.6 \times 10^{33}$ years, competitive with the current best limits on the proton lifetime in this channel

JUNO sensitivity on proton decay p → ν K + searches*

The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator detector designed to explore many topics in fundamental physics. In this study, the potential of searching for proton decay in the $p\to \bar{\nu} K^+$ mode with JUNO is investigated. The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification. Moreover, the excellent energy resolution of JUNO permits suppression of the sizable background caused by other delayed signals. Based on these advantages, the detection efficiency for the proton decay via $p\to \bar{\nu} K^+$ is 36.9% ± 4.9% with a background level of $0.2\pm 0.05({\rm syst})\pm$$0.2({\rm stat})$ events after 10 years of data collection. The estimated sensitivity based on 200 kton-years of exposure is $9.6 \times 10^{33}$ years, which is competitive with the current best limits on the proton lifetime in this channel and complements the use of different detection technologies