不同金属缓冲层对GaN薄膜的光学及电学性能的影响

本文以金属Ga和NH3为原料,Al、Ni和Fe为金属缓冲层,采用化学气相沉积法(CVD)在Si(100)衬底上合成了GaN微米薄膜。利用X射线衍射仪(XRD)、场发射扫描电子显微镜(FESEM)、能量弥散X射线谱(EDS)、光致发光光谱(PL)和霍尔效应测试仪(HMS-3000)等对GaN微米薄膜进行表征。结果表明,所有样品均为六方纤锌矿结构;样品均出现了很强的近带边紫外发射峰和半峰宽较大的中心波长为672 nm红光发射峰;不同样品的电学性能差异较大。最后对合成的GaN微米薄膜的可能形成机理进行了简单分析。     

不同金属缓冲层对GaN薄膜的光学及电学性能的影响

本文以金属Ga和NH₃为原料,Al、Ni和Fe为金属缓冲层,采用化学气相沉积法(CVD)在Si(100)衬底上合成了GaN微米薄膜。利用X射线衍射仪(XRD)、场发射扫描电子显微镜(FESEM)、能量弥散X射线谱(EDS)、光致发光光谱(PL)和霍尔效应测试仪(HMS-3000)等对GaN微米薄膜进行表征。结果表明,所有样品均为六方纤锌矿结构;样品均出现了很强的近带边紫外发射峰和半峰宽较大的中心波长为672nm红光发射峰;不同样品的电学性能差异较大。最后对合成的GaN微米薄膜的可能形成机理进行了简单分析。     

利用Pd催化合成单晶GaN纳米线的光学特性(英文)

基于金属元素钯具有的催化特性,采用射频磁控溅射方法,在Si(111)衬底上沉积Pd:Ga2O3薄膜,然后在950℃下对薄膜进行氨化,制备出大量GaN纳米线.采用扫描电子显微镜(SEM)、X射线衍射(XRD)、透射电子显微镜(TEM)和高分辨透射电子显微镜(HRTEM)等技术手段对样品的结构、形貌和成分进行分析.结果表明,制备的样品为具有六方纤锌矿结构的单晶GaN纳米线,直径在20-60nm范围内,长度为几十微米,表面光滑无杂质,结晶质量较高.用光致发光光谱对样品的发光特性进行测试,分别在361.1、388.6和426.3nm处出现三个发光峰,且与GaN体材料相比近带边紫外发光峰发生了较弱的蓝移.对GaN纳米线的生长机制也进行了简单的讨论.     

6H-SiC/3C-SiC/6H-SiC量子阱结构制备及其发光特性

利用固源分子束外延(SSMBE)生长技术, 在1350K的衬底温度下, 通过改变Si束流强度, 在6H-SiC(0001)面上外延生长6H-SiC/3C-SiC/6H-SiC量子阱结构薄膜, 并用反射高能电子衍射(RHEED)与光致发光(PL)谱对生长的薄膜的晶型和发光特性进行表征. RHEED 结果显示生长的薄膜为6H-SiC/3C-SiC/6H-SiC量子阱结构薄膜. 室温下He-Gd激光激发的光致发光(PL)谱显示, 薄膜在480-600 nm范围内存在衬底未观察到的较强发光. 拟合得到的发光峰与依据量子阱结构模型计算出的发光位置较为一致. 由此表明, 该强发光带可能是6H-SiC/3C-SiC/6H-SiC量子阱结构的发光.     

硼离子对铕掺杂SiO2干凝胶发光性能的影响

采用溶胶-凝胶法制备了Al单掺和B，Al共掺的Eu掺杂SiO2干凝胶。利用荧光光谱、IR，XRD，DSC，TG／DTG等技术研究了硼离子、退火温度对样品发光性质的影响。经500℃以上退火处理用248nm激发的样品，产生Eu^3＋离子^5D0→^7FJ的特征发射，^5D0→^7F1的跃迁分裂为两个峰。比较615nm处的发光强度，掺硼酸样品的发光强度是不加硼酸发光强度的3．3倍。这是因为B离子的加入，在材料中形成了Si—O—B键，破坏了网络的对称性，加强了Eu^3＋的红光发射。当退火温度上升到850℃用350nm激发时，样品有很强的Eu^2＋蓝光发射。Al单掺的发射中心在437nm处，发射半峰宽约为70nm，而B，Al共掺样品的发光中心蓝移到425nm处，单掺样品的蓝光强度几乎是共掺样品强度的2倍。这是由于硼酸的加入改变了基质的网络结构，从而导致单掺和共掺样品发射峰位和强度的改变。     

扩镓Si基溅射Ga2O3氮化反应生长GaN薄膜

采用射频磁控溅射在扩镓硅基上溅射Ga2O3氮化反应生长GaN薄膜。用X射线衍射(XRD)、扫描电镜(SEM)、选区电子衍射(SAED)、光电能谱(XPS)和荧光光谱(PL)对样品进行结构、形貌、组分和发光特性的分析。XRD、SAED和XPS分析证明,采用此方法得到六方纤锌矿结构的GaN多晶膜。SEM显示薄膜由均匀、结合紧密的纳米微晶粒组成,其直径约为50～100nm。PL发光谱显示位于344nm处,相对于365nm明显蓝移的带边峰,此发光峰应归功于自由载流子的复合。     

GaN纳米棒的催化合成及其发光特性

使用稀土元素Tb作催化剂, 通过氨化溅射在Si(111)衬底上的Ga2O3/Tb薄膜, 成功制备出GaN纳米棒. X射线衍射测试显示, GaN纳米棒具有六方结构. 利用扫描电子显微镜和高分辨透射电子显微镜观察分析得出, 纳米棒为单晶GaN, 纳米棒的直径为50-150 nm, 长度约10 μm. 光致发光谱在368.6 nm处有一强的紫外发光峰, 说明纳米棒具有良好的发光特性. 讨论了GaN纳米棒的生长机制.     

TiO_2薄膜晶相转换的光谱分析

采用溶胶-凝胶法在石英玻璃衬底上用旋涂法制备了TiO2薄膜样品,对样品在800-1100℃范围内进行退火处理,并对样品进行了拉曼光谱、透射光谱和荧光发光(PL)光谱测试.拉曼谱测试表明,随退火温度的升高,样品由锐钛矿相经锐钛矿与金红石的混相最终变为金红石相.透射谱测试表明,样品的吸收带边随着样品的相转换而发生红移.在总的趋势上,样品的折射率n随相转换而升高,厚度d和带隙Eg随相转换而降低.荧光发光光谱测试表明,在557-570nm和794-812nm范围内出现了两个发光光谱带.随着相转换,557-570nm范围内的发光光谱强度由强到无,而794-812nm范围内的发光光谱强度由弱到强.     

蓝色磷光材料Flrpic的发光特性

研究了掺杂浓度及热退火对磷光材料双(4,6-二氟苯基吡啶-N,C2’)吡啶甲酰合铱(Flrpic)发光性能的影响.不同掺杂浓度的薄膜及有机电致发光器件(OELDs)的发光颜色部随Flrpic浓度的增大由蓝色逐渐变化到黄绿色.纯Flrpic薄膜的吸收光谱和光致发光(PL)光谱在440-480 nm范围内有明显的光谱重叠,476 nm处的发光强度随Flrpic掺杂浓度增大而降低主要是由自吸收效应引起的.测量了不同激发密度下的光致发光光谱和不同掺杂浓度下的电致发光(EL)光谱,发现530 nm处的发光强度随激发强度或掺杂浓度的增大而增强,证实了530 nm处的发光是来源于Flrpic分子间的激基缔合物发光.通过比较热退火前后薄膜微观形貌及电致发光器件光谱的变化,进一步证实了热退火促进Flrpic分子聚集,增强了Flrpic分子间的辐射跃迁发光.通过调控Flrpic掺杂浓度和优化器件结构,并对器件进行热退火处理得到一系列发光颜色从蓝色逐渐变化到黄绿色的有机电致发光器件.     

蓝色磷光材料FIrpic的发光特性

研究了掺杂浓度及热退火对磷光材料双(4,6-二氟苯基吡啶-N,C2?)吡啶甲酰合铱(FIrpic)发光性能的影响.不同掺杂浓度的薄膜及有机电致发光器件(OELDs)的发光颜色都随FIrpic浓度的增大由蓝色逐渐变化到黄绿色.纯FIrpic薄膜的吸收光谱和光致发光(PL)光谱在440-480nm范围内有明显的光谱重叠,476nm处的发光强度随FIrpic掺杂浓度增大而降低主要是由自吸收效应引起的.测量了不同激发密度下的光致发光光谱和不同掺杂浓度下的电致发光(EL)光谱,发现530nm处的发光强度随激发强度或掺杂浓度的增大而增强,证实了530nm处的发光是来源于FIrpic分子间的激基缔合物发光.通过比较热退火前后薄膜微观形貌及电致发光器件光谱的变化,进一步证实了热退火促进FIrpic分子聚集,增强了FIrpic分子间的辐射跃迁发光.通过调控FIrpic掺杂浓度和优化器件结构,并对器件进行热退火处理得到一系列发光颜色从蓝色逐渐变化到黄绿色的有机电致发光器件.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.     

Synthesis of pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles by Curtius reaction in Morita-Baylis-Hillman derivatives

Synthesis of substituted pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles from the Morita-Baylis-Hillman derivatives of acrylates via saponification followed by Curtius reaction is described.     

正丁胺对激光染料荧光谱影响的研究

用正丁胺作为碳源,采用射频辉光放电制备碳膜,选用激光染料R6G和聚乙二醇混合液作为蒸气源,采用单源热蒸发,在蒸发室与染料同时沉积得到混合膜,用拉曼光谱和红外光谱分析了碳膜的结构和键合方式,分析表明:碳膜中存在胺基团和氢原子.混合膜的荧光谱测量结果表明,认为正丁胺对染料荧光谱的影响是因为胺基和氢原子的存在.     

Cu0-catalysed 1,3-dipolar cycloadditions of α-amino acid derived N,N-cyclic azomethine imines to ynones

A series of 20 CuAIAC reactions between eight 4-acylamino substituted pyrazolidine-3-one-1-azomethine imines and four terminal ynones were performed using Cu⁰ as catalyst. The corresponding fluorescent cycloadducts were obtained in very high yields upon simple workup. Thus, Cu-metal turned out to be a better catalyst than Cu^I in terms of yield and ease of isolation. Availability of azomethine imines, mild reaction conditions, and simple workup enable a “click” access to libraries of densely substituted 2,3-dihydro-1H,5H-pyrazolo[1,2-a]pyrazol-1-ones. Reactivity of differently substituted dipoles was evaluated experimentally and by quantum chemical methods (DFT).     

Synthesis and antioxidative/anti-inflammatory activity of novel fullerene–polyamine conjugates

(E)-4-(Fullerenopyrrolidin-1-yl)-3-methylbut-2-enoic acid and its corresponding succinimidyl ester, readily obtained through Prato-type modification of C₆₀, were used for the selective N-acylation of polyamines. The thus obtained conjugates were evaluated for their antioxidative and anti-inflammatory activity and their cytotoxicity was determined. Members of this family of compounds showed interesting anti-lipid peroxidation, anti-lipoxygenase and anti-inflammatory activity and comparable cytocompatibility to spermidine.