Influence of Triangle Structure Defect on the Carrier Lifetime of the 4H-SiC Ultra-Thick Epilayer

Effect of triangle structure defects in a 180-μm-thick as-grown n-type 4H-SiC homoepitaxial layer on the carrier lifetime is quantitatively analyzed, which is grown by a horizontal hot-wall chemical vapor deposition reactor.By microwave photoconductivity decay lifetime measurements and photoluminescence measurements, the results show that the average carrier lifetime of as-grown epilayer across the whole wafer is 2.59μs, while it is no more than 1.34μs near a triangle defect(TD). The scanning transmission electron microscope results show that the triangle structure defects have originated from 3C-SiC polytype and various types of as-grown stacking faults.Compared with the as-grown stacking faults, the 3C-SiC polytype has a great impact on the lifetime. The reduction of TD is essential to increasing the carrier lifetime of the as-grown thick epilayer.     

硫酸铵-乙醇-铬天青S体系萃取分离铝

研究了硫酸铵-乙醇-铬天青S体系萃取分离和富集铝的行为及与一些金属离子分离的条件。硫酸铵能使乙醇的水溶液分成两相,在分相过程中,Al3+和铬天青S(CAS)生成的Al(CAS)2-能被乙醇相完全萃取,Pb2+、Pd2+、Cr3+、Ru3+、Ir4+、Ni2+、Mg2+、Co2+和Fe2+不被萃取而和Al3+分离。     

用于人类脂肪干细胞的纯化和体外长期培养的聚合物涂层

采用紫外固化法制备了基于丙烯酸酯类水凝胶的聚合物涂层(PC),并用X射线光电子能谱(XPS)、水接触角(WCA)和原子力显微镜(AFM)分别对PC进行了化学组成和表面性能的表征.在PC表面进行了人类脂肪干细胞(h ASC)的体外长期培养扩增,得到的第3代细胞的生物学表征结果表明,干细胞在PC表面能正常黏附生长,流式细胞仪检测发现干细胞对特征标记物CD49d,CD73,CD105的阳性显性比例较高,对HLA-DR和CD31几乎不显性,说明扩增的干细胞具有h ASC特征.对PC上扩增的干细胞进行诱导分化,并用油红O、茜素红和阿利新蓝分别进行染色分析,结果表明,该干细胞保留了h ASC的多能特性:能分化为成脂、成骨和成软骨细胞.含有单体甲基丙烯酰氧乙基三甲基氯化铵(DMC)、甲基丙烯酸环己酯(CHMA)和甲基丙烯酸-2-(二乙氨基)乙酯(DEAEMA)的PC2(质量比为3∶1∶2)在用于h ASC体外长期培养时,比其它PC和TCP更有利于细胞的黏附和增殖,纯化细胞,保持其多能性.实时荧光定量PCR(RT-q PCR)的分析表明PC2上得到的细胞更容易向成骨和成软骨细胞分化.     

气相分子吸收光谱法快速测定土壤中亚硝酸盐氮

建立气相分子吸收光谱法快速测定土壤中亚硝酸盐氮的方法。土壤样品采样用200 mL 1 mol/L的氯化钾溶液浸提,于20℃恒温条件下震荡60 min,静置离心。在0.5 mol/L柠檬酸+30%乙醇介质中,用气相分子吸收光谱法测定亚硝酸盐氮含量。结果显示,在0～2.0 mg/L范围内亚硝酸盐氮质量浓度与吸光度呈良好的线性关系,线性相关系数为0.999 9,方法检出限为0.010 mg/L,相对标准偏差为1.32%(n=6),样品加标回收率为93.0%～97.0%。该方法具有操作简单、分析快速准确、干扰少等优点,适用于土壤中亚硝酸盐氮的测定。     

利用水浴振荡器对土壤中砷测定的优化

利用水浴振荡器进行土壤消解,实现对传统消解方法的优化.对不同类型标准土样及实际土样,按40r/min的转速消解60min后测定砷含量,可取得满意的准确度和精密度.     

广西污水中汞、砷检测能力验证结果分析

利用能力验证计划,对广西全区检验检测机构的污水中汞、砷分析能力进行对比和评价。采用单因子方差对考核样品进行均匀性检测,对全区144家检验检测机构的检测结果进行四分位稳健统计分析,用Z比分值绘制柱状图直观评定各检测机构的测试结果。污水中汞检测结果合格率为77.0%,砷检测结果合格率为84.8%。广西检验机构的汞、砷总体检测能力较强,少数检测机构的检测能力和水平有待提高。     

气相色谱-负化学电离质谱法(GC-NCI MS)对虫螨腈在茄子和土壤中残留的分析

虫螨腈(chlorfenapyr),又名溴虫睛;化学名称:4-溴-2-(4-氯苯基)-1-乙氧基甲基-5-三氟甲基吡咯-3-腈;CAS登记号:122453-73-0;分子式:C15H11BrClF3N2O;相对分子质量:407.62;结构式如图1,是由美国氰胺公司开发的一种新型的杀虫、杀螨剂,其作用机理新颖,杀虫谱广、对常规农药无交互抗性,并对人、鸟、鱼、蚕低毒[1].     

基于非线性回归模型的中国电力需求、资源、环境分析

中国电力需求的持续增长,给资源和环境带来了巨大的压力,而经济增长及其增长方式是电力需求发生变化的原因.中国从1995年以来GDP和全社会用电量时序统计结果具有明显的非线性变化特征,因而基于非线性回归模型的GDP、电力需求、资源和环境分析,可以为解决中国电力可持续发展问题提供一个理论依据.     

Passivation effects of phosphorus on 4H-SiC(0001) Si dangling bonds: A first-principles study

The effect of phosphorus passivation on 4H-SiC(0001) silicon(Si) dangling bonds is investigated using ab initio atomistic thermodynamic calculations. Phosphorus passivation commences with chemisorption of phosphorus atoms at high-symmetry coordinated sites. To determine the most stable structure during the passivation process of phosphorus, a surface phase diagram of phosphorus adsorption on SiC(0001) surface is constructed over a coverage range of 1/9–1 monolayer(ML). The calculated results indicate that the 1/3 ML configuration is most energetically favorable in a reasonable environment. At this coverage, the total electron density of states demonstrates that phosphorus may effectively reduce the interface state density near the conduction band by removing 4H-SiC(0001) Si dangling bonds. It provides an atomic level insight into how phosphorus is able to reduce the near interface traps.