AlN纳米线阵列的光学性质及第一原理计算

为了制备均匀的宏观AlN纳米线阵列,采用化学气相沉积法在二次模板上成功地合成了AlN纳米线宏观阵列.利用X射线衍射仪、扫描电子显微镜、电子能谱仪和紫外-可见光光度仪测试了AlN纳米线阵列的结构、形貌和紫外发光性能.结果表明,AlN纳米线阵列分布均匀,AlN纳米线的平均直径与平均长度分别约为41 nm和1. 8μm. AlN纳米线的分布密度约为5. 4×107mm-2,其覆盖率约为7. 1%. AlN纳米线在150～310 nm范围内具有很好的吸光性能.利用第一原理计算得到的AlN纳米线光学性质与实验结果相符.     

氮化铝纳米线的合成与表征

在氮气和氨气气氛(P_N2∶P_NH3=1∶1，总压强为8×10⁴Pa,电压为20～28 V,电流为60～62 A的条件下，采用直流电弧等离子体法成功地制备出直径为20～200 nm、长度达到20 μm的AlN纳米线.利用x-射线衍射仪、扫描电镜、高分辨透射电镜和x-射线能谱仪等仪器对AlN纳米线形貌及结构进行观测与分析.AlN纳米线为六方晶态，属钎锌矿结构，并对AlN纳米线生长机理进行了研究.     

金银铜复合纳米线阵列的制备及其SERS效应研究

传统的拉曼增强基底均匀性差,排列无序等缺点限制了表面增强拉曼散射的广泛应用,文中选取Rb_4Cu_(16)Cl_(13)I_7快离子导体薄膜,在4μA外加直流电场作用下,利用固态离子学方法和真空热蒸镀法,制备了厘米级金银铜复合纳米线阵列.利用扫描电子显微镜(SEM)观测金银铜复合纳米线阵列的表面形貌,利用能量色散光谱仪(EDS)测量金银铜复合纳米线的化学成分,并选取罗丹明6G水溶液作为检测拉曼增强性能的探针分子,利用拉曼光谱仪测量金银铜复合纳米线基底的拉曼增强能力.结果表明:制备的金银铜复合纳米结构呈竹节状生长,微观形貌具有长程有序和短程有序结构,纳米线直径分布范围为45～95nm;纳米线表面均匀分布着直径为?20nm左右的纳米颗粒,从而使得其表面具有很高的粗糙度;纳米线中金银铜的近似摩尔比为2∶3∶15;制备的金银铜复合纳米线阵列作为表面增强拉曼散射基底测量罗丹明6G溶液的极限浓度是10~(-14) mol·L~(-1).     

反钙钛矿晶体Sc3AlN电子结构和光学性质的第一性原理研究

采用基于密度泛函理论的第一性原理的分子动力学方法,对立方反钙钛矿Sc3AlN的电子结构和光学性质进行了计算．系统分析了Sc3AlN电子结构和成键情况,并利用计算的能带结构和态密度分析了Sc3AlN的介电函数实部和虚部以及由它们派生出来的光学常数,即折射率、反射谱、吸收谱、光电导率和能量损失函数等．计算结果表明Sc3AlN属于导体材料,其价带主要由Al的2s2p,Sc的3d态电子构成,导带主要由Sc的3d态电子构成,静态介电常数ε1（O）=22．1,折射率n（0）=4．7．     

AlN晶体声子谱及其热学性能的第一原理计算

针对AlN晶体的声子谱和热学性能,采用密度泛函理论、第一性原理以及ABINIT软件进行了理论计算,得到了AlN晶体的声子谱以及内能、质量定容热容、熵和自由能与温度的关系曲线,并对曲线进行了理论分析.计算结果表明：AlN晶体的声子谱有12条曲线,其中3支为声学波,9支为光学波,并且形成了一光学带隙.AlN晶体的内能随着温度的增加而增加;质量定容热容起初随着温度的增加而较快地增加,后来逐渐达到稳定值;熵随着温度的增加也在增加,并且关系曲线有一定的弯曲;自由能随着温度的增加在不断地减小.以上计算结果与物理规律具有一致性.     

宏观树枝状铜纳米线的制备及分形学研究

为了进一步揭示固态离子学方法制备铜纳米线的生长机理,选取具有高离子电导率的快离子导体Rb_4Cu_(16)Cl_(13)I_7薄膜,利用固态离子学方法在外加恒定电流3μA作用下,制备厘米级铜纳米线.采用扫描电子显微镜对其微观形貌进行了表征和分析,利用能量色散光谱仪确定纳米线的化学成分.结果表明:制备的铜纳米线呈现宏观树枝状结构,在靠近阴极位置整齐排布,长度约为2 mm,且排布比较紧密,部分纳米线在生长过程中出现分形生长,最长分支长度约为1 cm,排布比较稀疏;铜纳米线呈长程无序短程有序,直径分布范围为90~100 nm,纳米线表面铜纳米颗粒直径分布范围为10~20 nm,树枝状铜纳米线的分形维数为1.35,说明树枝状铜纳米线较少,铜纳米线的生长机理分析表明,树枝状结构的出现与纳米线"顶端生长优势"有关.     

单晶氮化硅纳米线的合成制备与光致发光性能研究

本文采用氮气保护高能球磨及硅粉直接氮化工艺制备高纯、单晶氮化硅纳米线。使用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、高分辨率透射电子显微镜(HRTEM)和激光共聚焦显微拉曼光谱仪对实验产物的物相结构、微观结构及光学性能进行分析。在室温下使用325nm激光对样品进行激发,观察到样品具有较宽的发射光谱,波长范围为350~670nm;发光光谱中存在三个由缺陷跃迁引起的发光峰。     

基于等效介质理论的纳米线黑硅光学特性研究

为了研究不同形貌下纳米线黑硅阵列的减反射性能,文中采用金属辅助催化刻蚀法在硅基底表面制备大面积排列有序的硅纳米线,即纳米线黑硅。研究了刻蚀溶液中氧化剂的比例对其生长过程、表面形貌及光学特性的影响。通过亚波长光栅原理和等效介质理论计算了纳米阵列结构在特定波长下的抗反射性能的最佳参数,使用FDTD Solutions仿真软件系统模拟了宽光谱照射下尺寸参数对纳米线黑硅微结构阵列反射率的影响。研究结果表明:通过测试样品可见光到近红外波段(380～900 nm)的光学特性,相较于抛光硅片,表面存在纳米线黑硅阵列的硅片吸光度得到有效提升。通过改变刻蚀溶液中氧化剂的比例,可以定量地调控薄膜的吸光度。结合光学测试结果进行理论计算,能够提供纳米线黑硅衍射级次的变化规律,归一化周期T/λ比值持续增加,高阶级次的衍射光会逐渐出现。通过控制硅线周期来避免出现高级次衍射光,提升薄膜的减反射性能。     

海洋光学推出QE Pro高性能光谱仪

美国海洋光学公司新推出配备了背照薄型CCD阵列的高灵敏度光谱仪——QE Pro高性能光谱仪。     

环境折射率变化对纳米线光纤场强分布的影响

基于光学倏逝波的光纤或波导传感器是目前的重要发展方向之一． 从Maxwell 方程出发,得 到由于周围环境折射率变化而引起的光纤场强分布的变化． 结果表明: 纳米线光纤中的光场场强分 布跟环境折射率有较为敏感的关系． 在相同的外界环境下,纳米线光纤直径D 大的光纤纤芯内光 场能量较强,纳米线光纤直径D 小的光纤纤芯内光场能量较弱; 对相同直径D 的纳米线光纤,随着 外界折射率的增大,光损耗越来越强． 这为纳米线波导在光传感领域的应用提供了有力的证据．     

Study of buffer and epitaxy technology in two-step growth of aluminium nitride

AlN (aluminium nitride) films were prepared by metalorganic chemical vapor deposition (MOCVD) on c-plane sapphire (α-Al₂O₃) substrates. By means of studying the traces of in-situ optical reflectivity, it was found that the AlN nucleation layer showed a specific (0001) lattice orientation, which differed from the GaN nucleation layer on (0001) sapphire substrates. The AlN buffer suffered the compressive stress at the initial stage of nucleation. And the compressive strain was relaxed gradually along with the thickness of buffer increasing and consequently annealing. Optical transmission spectra revealed that in the process of growing AlN epilayers, higher V/III ratio could improve the crystal quality but reduce the growth rates. In addition, proper doping of silane (SiH₄) could improve the surface morphology of AlN film.     

大尺度NiS2纳米线的超声喷雾热解制备

以NiCl2·6H2O和硫脲为前驱液,在350℃的玻璃衬底上,通过超声喷雾热解技术与软模板相结合,成功地制备了产率较高的二硫化镍大尺度纳米线．利用X射线衍射仪（XRD）、透射电子显微镜（TEM）、偏光显微镜分别对产物的物相和形貌进行了表征．结果表明：所制备的NiS2纳米线沿（200）晶面具有明显的取向生长,长径比约为25：1,并对其生长机理做了初步的探讨．     

Influence of InAs deposition thickness on the structural and optical properties of InAs quantum wires

The influence of InAs deposition thickness on the structural and optical properties of InAs/InA1As quantum wires （QWR） superlattices （SLS） was studied. The transmission electron microscopy （TEM） results show that with increasing the InAs deposited thickness, the size uniformity and spatial ordering of InAs QWR SLS was greatly improved, but threading dislocations initiated from InAs nanowires for the sample with 6 monolayers （MLs） InAs deposition. In addition, the zig-zag features along the extending direc- tion and lateral interlink of InAs nanowires were also observed. The InAs nanowires, especially for the first period, were laterally compact. These structural features may result in easy tunneling and coupling of charge carders between InAs nanowires and will hamper their device applications to some extent. Some suggestions are put forward for further improving the uniformity of the stacked InAs QWRs, and for suppressing the formation of the threading dislocations in InAs QWR SLS.     

AlN粉末在氮氧混合气氛下抗水解性能的研究

研究了在高氮/低氧混合气氛下热处理(500~700℃)对AlN(氮化铝)粉体表面特性及粉体抗水解性能的影响.实验结果表明:在高氮/低氧混合气氛保护下的AlN粉末表面覆盖了氧化铝薄膜层结构,有效地抑制了AlN与水的反应,阻碍了水分子向AlN粉末表面侵蚀的作用,提高了AlN粉末在潮湿环境中的抗水化能力,且热处理后粉末在水溶液中高剪切应力球磨过程中具有非常好的稳定性.     

Effects of microstructure modification on properties of AlN/BN composites

It is very difficult to prepare full-densified aluminum nitride-boron nitride （AIN/BN） composite ceramics with homogeneous microstructure and high thermal conductivity. Spark plasma sintering （SPS） was used to fully densify the AIN/BN composites in this work. Microstructure, mechanical properties and thermal conductivity of the SPS sintered AIN/BN composites with 5-30 vol% BN were investigated. The results show that the microstructure of composites is fine and homogenous, and the AIN/BN composites exhibit high mechanical properties. To promote the growth of AIN grains and modify the distribution of grain boundary in AIN/BN composites, a heat treating methodology was introduced through gas pressure sintering （GPS）. This processing was significantly beneficial to enhancing the thermal conductivity of the specimen. The thermal conductivity of AIN/BN composites with 5-30 vol% BN reached 60 W/m K after the samples were treated by GPS.     

Structural and optical properties of periodically ordered ZnO nanowires

Periodically ordered ZnO nanowire arrays were fabricated by a combination of soft templates created by electron beam lithography and an electrochemical process. Individual ZnO nanowires were precisely placed in desired locations to form two-dimensional periodic structures with specific patterns. Scanning electron microscopy and light diffraction measurements confirmed the long-range ordered structures in the nanowire arrays. Variable temperature photoluminescence revealed both band edge and defect emissions. The obtained photonic structures may have potential applications in optical and optoelectronic devices.     

Structural and optical characteristics of Al_xGa_(1-x)N/AlN superlattice

AlN/Al0.3Ga0.7N superlattices were grown on (0001) sapphire substrate by metal-organic chemical vapor deposition (MOCVD). The superlattice period varies from 6 to 30. The layer thickness of different period stack was designed. GaN or AlGaN template was employed for growing AlN/AlGaN superlattices. Reflectivity, SEM, AFM and XRD data of the AlxGa1-xN/AlN superlattices are presented. It is found that the templates used have an intensive impact on surface roughness and interfacial properties of following AlN/AlGaN superlattices. The result of atomic force microscopy indicates that AlN/AlGaN superlattices grown on GaN template exhibit quasi-two-dimensional growth mode. The resulting superlattice has a smooth surface morphology and distinct interface. No crack is observed in the area of a 2-inch wafer.