Photoluminescence Spectroscopy Studies of InGaAsN Quantum Wells

我们测量了低N组分的InGaAsN/InGaAs/GaAs量子阱材料的光致发光(PL)谱,测量温度范围从13K到300K。实验结果显示,InGaAsN的PL谱的主峰值的能量位置随温度的变化呈现出反常的S型温度依赖关系。用Varshni经验公式对实验数据进行拟合之后,发现在低温下InGaAsN量子阱中的载流子是处于局域态的。此外,我们还测量了样品在不同的温度、不同的能量位置的瞬态谱,结果进一步证实了:在低温下,InGaAsN的PL谱谱峰主要是局域态激子的复合发光占据主导地位,而且InGaAsN中的载流子局域态主要是由N等电子缺陷造成的涨落势引起的。The photoluminescence (PL) spectroscopy in InGaAsN/InGaAs/GaAs quantum wells (QWs) with low-nitrogen composition has been measured in the temperature range 13-300K. The peak position energies of InGaAsN as measured by PL exhibit anomalous inverted S-shape-like temperature dependence. Fitting with Varshni empirical relation to PL data, we have found that carriers in InGaAsN QWs are localized at low temperatures. Moreover, Time-resolved photoluminescence (TRPL) measurements, performed for various temperatures and different PL energy position, further proved that the broad PL emission of InGaAsN at low temperature is mainly dominated by strong localization, which arises from nitrogen-induced fluctuating potential in quantum wells

中央苏区图书馆文献资源的采集工作研究

中央苏区时期,面对敌人的经济封锁和刚起步的图书出版发行工作,图书馆文献资源采集工作异常艰难。在党和苏维埃政府颁布的一系列法规和指令下,中央苏区的工作者明确了文献资源的采集原则,开拓多方渠道加强了文献资源采集工作,为当今图书馆文献资源采集工作提供借鉴和参考

Oxidative dehydrogenation of ethane to ethylene in the presence of HCl over CeO_2-based catalysts

报道了一种HCl存在时温和条件下的乙烷氧化脱氢制乙烯催化转化新途径.研究发现,在多种金属氧化物催化剂中,CEO2呈现最佳乙烯生成的催化性能.与纳米粒子相比,具有棒状和立方体状形貌的CEO2纳米晶具有较高的乙烷转化率和乙烯选择性.以MnOX修饰CEO2可进一步提高催化性能.在8 WT%MnOX-CEO2催化剂上,723 k反应2 H时乙烷转化率和乙烯选择性分别为94%和69%.该催化剂性能稳定,反应100 H乙烯收率可保持在65%–70%.HCl的存在对乙烯的选择性生成起着至关重要的作用,一部分乙烯来自于氯乙烷的脱HCl反应.This article reports a new catalytic route for the oxidative dehydrogenation of ethane to ethylene in the presence of HCl at moderate temperatures.CeO2 was found to be the most efficient catalyst for the production of ethylene from the variety of metal oxides examined in this work.CeO2 nanocrys‐tals with rod and cube morphologies showed higher ethane conversions and ethylene selectivities than CeO2 nanoparticles.The modification of CeO2 by MnOx further enhanced the catalytic perfor‐mance.Ethane conversion of 94% and ethylene selectivity of 69% were obtained after 2 h of reac‐tion at 723 K over an 8 wt% MnOx-CeO2 catalyst.This catalyst was stable and the ethylene yield could be sustained at 65%–70% over 100 h of reaction.The presence of HCl played a key role in the selective production of C2H4, and some of the C2H4 was probably formed from chloroethane by de‐hydrochlorination.supportedbytheNationalBasicResearchProgramofChina(973Program;2010CB732303); theNationalNaturalScienceFoundationofChina(21033006); theProgramforChangjiangScholarsandInnovativeResearchTeaminUniversity(IRT1036)~

CdS量子点表面巯基酸分子排列方式的宽带和频光谱研究

巯基酸是一种常用的量子点表面配体，对量子点的光电属性和催化活性具有重要影响。用宽带和频光谱（BB-SFG）研究巯基酸分子(HS-(CH2)n-COOH，n = 2，5，10)在金膜和硫化镉（CdS）量子点表面的排列方式。结果表明：在金表面上3种自组装巯基酸单分子膜，都可以检测到与巯基和羧基相连的两个亚甲基的C-H振动和频谱峰。而在CdS量子点表面，短链的HS-(CH2)2-COOH和HS-(CH2)5-COOH处于较无序的混乱包覆状态，检测不到C-H振动和频谱峰；但长链的HS-(CH2)10-COOH在CdS量子点表面是较有序的类似反胶束状的排列，可以检测到与羧基相连的亚甲基的C-H振动谱峰。国家重点研发计划项目(2017YFA0206500,2016YFA0200702)国家自然科学基金(21327901)

Ge/GeO/多层石墨纳米复合物锂离子电池负极材料性能研究

由于其高容量、快速锂离子扩散速率和高电导性的优点,锗被认为是一种非常有前景的锂离子电池负极材料.本研究利用GeO2和石墨作为前驱体,通过水热法制备Ge/GeO/多层石墨复合物并将其应用于锂离子电池负极材料进行电化学性能研究.实验结果表明,Ge/GeO2纳米粒子的粒径约为40 nm.该复合物电极的第一次充放电容量分别是2045和1146 mA h g.1,库仑效率为56.0%.50圈充放电循环后,当电压范围为0.01.50 V时,容量保持在1008 mAhg.倍率实验表明,该电极在1C(1C=1000mAg)和2 C倍率大电流下,虽然容量略有衰减,但仍保持790和710 mAhg的高容量.教育部新世纪优秀人才计划(编号:NCET-13-0879)；福建省闽江学者特聘教授计划；泉州市桐江学者特聘教授计划；福建省自然科学基金(编号:2016J01069)资助项目

Selectivity control in photocatalytic valorization of biomass-derived platform compounds by surface engineering of titanium oxide

化学化工学院王野教授课题组与程俊教授课题组合作，在生物质光催化选择转化方面取得重要突破。研究团队发展了一种调控TiO2表面结构以控制生物质转化途径的新方法，率先实现多种木质纤维素平台分子的光催化还原选择性调控，获得高产率的加氢产物(精细化学品)或偶联产物(燃料前驱体)。该论文第一作者为化学化工学院2015级博士毕业生吴雪娇、2015级博士毕业生李洁琼和固体表面物理化学国家重点实验室谢顺吉博士。【Abstract】Photocatalysis has offered a promising opportunity for selective transformation of biomass to high-value chemicals or fuels under mild conditions. Whereas titanium oxide has been widely used for photocatalytic pollutant degradation, H2 evolution, and CO2 reduction, few studies have been devoted to TiO2-based photocatalytic valorization of biomass or biomass-derived platform compounds. Here, we report on surface-controlled photocatalysis of TiO2 for selective valorization of furfurals and vanillin that are lignocellulose-derived key platform compounds. The reaction can be switched from hydrogenation of aldehyde group to C–C coupling by manipulating exposed facets; furanic and aromatic alcohols or coupling products, which are fine chemicals or jet-fuel precursors, could be produced with high selectivity. Our studies elucidate that the facet-dependent density of oxygen vacancies governs the charge distribution and adsorption strength of surface species and thus controls product selectivity. The present work offers an example of selectivity control by engineering TiO2 surfaces for valorization of biomass-derived feedstocks.This work was supported by the National Natural Science Foundation of China (nos. 21690082 and 21972115). 论文中相关研究工作得到国家自然科学基金(21690082、21972115)等项目的资助

Spectral Study of InGaAs/GaAs Strained Quantum Wells

【中文摘要】 分别用光致发光谱(PL)、光伏谱(PV)及时间分辨谱(TRPL)的方法,测量了应变InGaAs/GaAs单量子阱和多量子阱在不同温度下的光谱,发现单量子阱与多量子阱有不同的光学性质。多量子阱PL谱发光峰和PV谱激子峰的强度与半高宽都比单量子阱的大,但单量子阱的半高宽随着温度的升高增大很快,这是由激子 声子耦合引起的。通过时间分辨谱研究发现了量子阱子能级之间的跃迁,多量子阱的发光寿命明显比单量子阱的长。我们利用形变势模型对量子阱的能带进行了计算,很好地解释了实验结果。 【英文摘要】 Methods of photoluminescence(PL) photovoltage(PV), and timeresolved spectrum(TRS) are applied to study InGaAs/GaAs strained quantum well. We discover singlequantum well(SQW) and multiquantum well(MQW) have different spectral properties; and spectral intensity of MQW is much higher and spectral full width at half maximum (FWHM) is larger than those of SQW, but spectral FWHM of SQW increases more quickly than that of MQW, which is caused by excitonLO phonon coupling. The peaking energy of 11H obtained fro...福建省自然科学基金重点资助项目(A992001

Study on Schottky barrier of 4H-SiC at different anealing temperature

采用磁控溅射的方法在4H-SiC样品上分别沉积四种金属薄膜(Ag,Cu,Ni,Cr)形成Schottky 接触,研究了不同温度退火对Schottky势垒高度的影响。通过对样品的I-V测试结果的拟合,得到各金属/4H-SiC Schottky接触的势垒高度以及理想因子。在反向偏压100V下,样品的反向漏电流小于10-10A,说明样品的反向特性良好。样品经过不同温度的退火后,发现Cu、Ni与4H-SiC的势垒高度(SBH)随退火温度的升高而提高,超过某一温度,其整流特性变差; Ag、Cr的SBH在退火后降低。SBH与金属功函数呈线性关系(Cr金属除外),斜率为0.11。Schottky barriers were formed by sputtering the metals on the front side of 4H-SiC(Si face) by magnetron sputtering to study the rectifying characteristics of the contacts between the metals and 4H-SiC. The infections of the annealing under different temperature were also studied. Schottky barrier height (SBH) of metal/4H-SiC was evaluated from I-V measurements. Under a reverse voltage about 100 V, the reverse leaky current is below 0.1 nA. After annealed, the SBH of Cu/, Ni/4H-SiC was increased, but the SBH of Cr/, Ag/4H-SiC contact was decreased. The relationship between the work function of metals and the SBH was presented. The barrier height depends on the metal work function with slopes of 0.1 to 0.2 (except metal Cr).福建省厦门市科技项目(3502Z20031076