纳米PbS/SiO_2气凝胶介孔组装体的制备及光学特性

对用自行研制的ＳＣＤ－Ｉ型高压釜制备的ＳｉＯ２气凝胶与用胶体化学方法制备的ＰｂＳ纳米粒子的组装体系的光学性质进行了研究．用透射电镜观察了其形貌,用光吸收谱仪及荧光光谱仪测定其光吸收谱及荧光谱．发现样品的光吸收边随退火温度升高由可见逐渐移到红外波段．样品的光致发光强度随退火温度上升先增强直至５７３Ｋ,而后随退火温度上升而减弱．我们认为光吸收边红移是由量子限域效应引起的,而荧光强度变化与ＰｂＳ表面缺陷及激子的复合几率变化有关．     

(Ca,Sr,Ba)3V2O8的制备和发光性能研究

采用微波辅助溶胶-凝胶法制备了自激发钒酸盐A3(VO4)2(A:Ca,Sr,Ba)。采用X射线衍射仪、傅里叶变换红外光谱仪、扫描电镜、透射电子显微镜、荧光谱仪对样品各项参数进行了表征,研究了A3(VO4)2的光致发光特性,探讨了不同制备工艺条件对其发光性质的影响。实验结果表明,Sr3V2O8样品发光强度随退火温度而变化,在680～900℃时,其发射光谱强度随温度上升而单调下降,达到1000℃时开始上升;pH值为4时,样品的发射光谱强度最大。     

退火气氛对镶嵌在SiO2中Ag纳米颗粒热演变影响效应的研究

将70 keV的Ag离子以5×10¹⁶ cm^-2的剂量注入到SiO₂基底中, 随后分别在400~800℃的Ar、N₂、空气气氛中退火, 详细研究了样品的表面形貌、光吸收特性、结构及成分随退火气氛及退火温度的变化规律。原子力显微镜、紫外-可见分光光度计及掠入射X射线衍射仪的测试结果显示: Ar气氛退火样品中形成的Ag纳米粒子(NPs)细小均匀, 其颗粒密度在700℃时达到最大值, 光吸收性能最佳; N₂气氛退火引发Ag纳米颗粒的团聚生长, 在样品近表面形成较大的Ag NPs, 其颗粒密度也在700℃时达到最大值; 而空气中退火后, 由于AgO的形成、分解, 样品的光吸收强度随退火温度升高持续下降。最后, 卢瑟福背散射研究结果表明, 样品的这些变化主要归因于Ag原子在不同退火气氛下随退火温度的扩散行为不同。     

掺Er-Al2O3薄膜发光特性的研究

通过离子束辅助沉积(IBAD)在热氧化SiO2上沉积Al2O3薄膜,在120keV下注入5×10115cm-2Er离子,Ar气氛下773～1273K退火1h.低温下测试PL谱线,随退火温度升高,发光强度上升.973K退火下发光强度特别低,并观察到Si衬底的1140nm峰.光透射谱表明几乎在所有的测试范围内尤其在1530nm处973K退火样品的透射谱强度最强,波导损耗最低.1530nm发光强度随退火温度的变化跟发光强度的变化相反.说明Er离子在514.5nm泵谱吸收界面σ跟Al2O3的光吸收损耗有一定关系.     

热历史对磺化聚苯乙烯钠盐离聚体动态力学性能的影响

用动态粘弹谱（ＤＭＡ）考察了经不同热处理后的磺化聚苯乙烯钠盐离聚体（ＮａＳＰＳ）的动态力学性能，发现热历史对离聚体玻璃化温度无明显影响，淬火能有效增加离子簇数量从而使粘弹谱的橡胶台平变宽。玻璃化温度以上退火有助于形成稳定的离子簇。玻璃化温度以下退火则由于形成不稳定的离子簇导致二次升温过程中发生结构重组，淬火能有效减小这种现象。首次发现ＮａＳＰＳ有一定随热历史而变的β松驰，认为该松驰是由非受限键层局     

Al2O3薄膜的发光性能及其结构研究

以高纯铝为靶材,在不同氧氩比例下,采用直流反应磁控溅射法制备了Al2O3薄膜。用F-4500型荧光分光光度计测量其荧光光谱,观察到416 nm和438 nm处的光致发光发射谱（PL）,是由于氧空位充当的色心所致,且随着氧氩比例的增加,峰的位置基本不变,强度先上升后下降,这是由于氧氩比例的改变导致氧空位浓度变化引起的。通过对未退火及不同温度退火样品的XRD分析发现：室温沉积的Al2O3薄膜为非晶态,400℃退火开始有晶体出现,且退火温度越高,结晶性能越好。     

Ag离子注入单晶MgO光吸收和透射电镜研究

能量为200kev的Ag离子注入到单晶MgO中，透射电镜明场像和高分辨像证明了该样品中形成了Ag纳米颗粒,未退火样品以及还原气氛下退火样品的光吸收谱都观察到Ag的吸收峰,发现随退火温度的升高，Ag的吸收峰先向短波方向移动，随退火温度的进一步升高又向长波移动，退火温度达到900℃时吸收峰红移到未退火前的位置,由透射电镜明场像和相应的选区电子衍射花样发现，由于离子辐照效应使得Ag离子注入单晶MgO非晶化，且注入层被部分损伤。     

退火温度对硅基溅射银膜微结构和应力的影响

用直流溅射法在硅(111)基底上制备银膜，膜厚为380nm。用BGS6341型电子薄膜应力分布测试仪对膜应力随退火温度的变化进行了研究，结果表明：膜应力随着退火温度的升高而增大，在400℃退火温度下膜应力变化明显。用MXP18AHF型X射线衍射仪测量了膜的衍射谱，对膜微结构随退火温度的变化进行了讨论。制备的Ag膜仍为面心立方结构，呈多晶状态，平均晶粒尺寸为23．63nm，薄膜晶格常数(0．40805nm)比标准样品晶格常数(0．40862nm)稍小。     

退火对两种硅基薄膜的结构及发光影响

采用双离子束共溅射沉积方法制备了两种复合硅基薄膜SiOxCy和SiOxNy薄膜,对两种薄膜进行后退火处理,并分别对样品进行PL、FTIR、XPS谱测试分析,比较退火前后的发光及结构的变化。两种样品的光致发光测试谱(PL)表明:退火前后都有两个发光峰位-都存在470nm的发光峰位,它来自于硅基薄膜中中性氧空位缺陷(O3≡Si-Si≡O3),是由于氧原子配位的二价硅的单态-单态之间的跃迁所致,其发光强度随退火温度的升高而变化。进一步的FTIR和XPS的测试谱表明另外一个发光峰位420nm(SiOxCy薄膜)和400nm(SiOxNy薄膜)分别来自于掺杂杂质(C和N)与硅基薄膜中的Si、O组成的复合结构。而两种样品经过退火处理后掺杂所引起的发光峰位强度随退火温度的升高而增强,说明退火温度的升高有利于发光机制的形成。     

ATS／PEEK共混物的结晶熔融行为

用ＤＳＣ研究了ＰＥＥＫ和ＡＴＳ／ＰＥＥＫ共混物的结晶熔融行为。ＰＥＥＫ的结晶熔融行为取决于其物理状态、熔融、退火结晶和固相处理条件。ＡＴＳ的加入使ＰＰＳ的冷结晶温度Ｔ∝提高，Ｔｃ和Ｔｍ降低。固相处理引起ＰＥＥＫ无定形区热氧化交联，淬火样品退火结晶后出现双熔融峰，随退火温度提高，高温峰Ｔｍ２基本不变，低温峰Ｔｍ１移向高温，最后与Ｔｍ２重迭成单峰。ＡＴＳ对ＰＥＥＫ的Ｔｍ１影响不大，但使其Ｔｍ２降低。     

退火CdS/SiO2介孔组装体系光吸收的行为

用溶胶-凝胶法获得多孔SiO2载体，浸泡合成法得到不同复合量的CdS/SiO2块材料介孔组装体系。研究了复合量、气氛条件及退火温度对其光吸收特征的影响，发现吸收边随复合量增加往长波方向移动；在氮气和空气中退火时，随退火温度升高前者表现为红移而后者表现为蓝移，这归属于量子尺寸效应。     

退火CdS/SiO2介孔组装体系光吸收的行为

用溶胶-凝胶法获得多孔SiO₂载体,浸泡合成法得到不同复合量的CdS/SiO₂块材介孔组装体系.研究了复合量、气氛条件及退火温度对其光吸收特性的影响,发现吸收边随复合量增加往长波方向移动;在氮气和空气中退火时,随退火温度升高前者表现为红移而后者表现为蓝移,这归属于量子尺寸效应.     

Chemical synthesis, structural and optical properties of quantum sized semiconducting tin(II) selenide in thin film form

A chemical route to nanocrystalline photoconducting tin(II) selenide quantum dots in thin film form was developed and the structural and optical properties of the synthesized materials were studied. The synthesized SnSe nanocrystals deposited as thin films belong to the orthorhombic crystalline system. Unit cell parameters of the as-deposited and thermally treated semiconducting quantum dots in thin film form were determined from experimental X-ray diffraction data employing multiple regression analysis technique. An average crystal size of 14.8 nm was estimated for as-deposited SnSe quantum dots using the Debye-Scherrer approach which increases to 23.3 nm upon annealing. Average crystal size increase upon thermal treatment is accompanied by slight enlargement of the unit cell parameters. On the basis of optical absorption studies of the SnSe films, conclusions regarding the band structure of this material in reciprocal space were derived. The as-deposited films are characterized by indirect band gap energy of 1.20 eV which exhibits a slight red shift to 1.10 eV upon annealing. Additional electronic transition of a direct type was found to occur at 1.74 eV in the case of as-deposited films, shifting to 1.65 eV in the course of annealing. All these values are blue-shifted with respect to the macrocrystalline material ones, which along with the red shift detected upon annealing, is a strong indication of the three-dimensional confinement effects in the studied nanocrystals.     

Effect of strain in PbSe/ZnPc stacked layers prepared by thermal evaporation method

The article investigates the structural and optical properties of ZnPc/PbSe hybrid multilayer (HML) structure deposited by using thermal evaporation technique. The X-ray diffraction pattern reveals the formation of ZnPc–PbSe composite and strain induced quantum size effect. Scanning electron microscope image shows the spherical grains for as-deposited film and nanorod like structure for the annealed film. The rods are oriented along one direction and stacking axis changes with the function of annealing temperature. The optical spectra show strong absorption in UV–Visible region and the optical absorption edge was red shifted for annealed samples. The luminescence properties were enhanced with broad emission in the range of 375–400 nm in HMLs. The optical band gap values are calculated and it varies from 3.2 to 3.04 eV with the function of annealing temperature and the band gap splitting was observed for a higher temperature of annealed samples. Strain-induced effect on ZnPc/PbSe HML has been reported using Raman spectra.     

Emission wavelength trimming of self-assembled InGaAs/GaAs quantum dots with GaAs/AlGaAs superlattices by rapid thermal annealing

The effects of rapid thermal annealing on InGaAs quantum dots grown by atomic layer molecular beam epitaxy to the structural transformation and optical properties are investigated. No misfit dislocation was observed from either the as-grown or annealed dots. The size and composition of the quantum dots become more uniform upon annealing mainly from the height fluctuation as predicted by the theoretical model. Large bandgap blue shifts, resulted from the In and Ga interdiffusion, were observed with the preservation of three-dimensional carrier confinement. The GaAs/AlGaAs superlattice was found to minimize the defect diffusion and dot interdiffusion during the high-temperature epitaxial overgrowth.     

Formation of CdS nanoparticles by gas-diffusion method in sol–gel derived ureasilicate matrix

CdS nanoparticles (NPs) were prepared by exposing a hybrid ureasilicate gel containing cadmium (II) ions to H₂S gas at room temperature. Additional component (tetraethoxysilane) was introduced during the synthesis in order to improve the mechanical properties of the host matrix. The obtained material was subsequently subjected to an annealing treatment under an argon atmosphere at temperatures that varied from 43 to 102 °C. The size of the embedded NPs increased with thermal annealing. The optical absorption spectroscopy, photoluminescence (PL) and transmission electron microscopy (TEM) measurements confirmed the formation of CdS nanoparticles (NPs) exhibiting quantum confinement effect.     

Positron annihilation studies of defects and fine size effects in nanocrystalline nickel oxide

Ultrafine nickel oxide nanoparticles were prepared by sol–gel method using a solution of nickel nitrate hexahydrate and ammonium hydroxide and subsequently annealed in air at different temperatures in the range 200–275?°C for different hours to vary the particle sizes. They were characterised for phase, purity, structure and sizes by X-ray diffraction and high-resolution transmission electron microscopy. They were found polycrystalline in nature and possessed face-centred cubic (NaCl-type) structure with lattice parameter varying with annealing temperature. The ultrafine structure clearly revealed the formation of hexagons with average diameter about 5?nm. Ultraviolet–visible absorption spectroscopy was carried out to study the optical properties and for the estimation of the bandgap. The nanoparticles exhibited weak and strong quantum confinement in the size ranges of 10.47–8.47 and 6.57–5?nm. The samples were then investigated through positron annihilation spectroscopy to characterise and closely monitor the evolution of vacancy-type defects and defect clusters during particle growth in the samples. The positron lifetime drastically increased at very low particle sizes, supporting the confinement effects demonstrated by optical absorption studies. The results from coincidence Doppler broadening measurements were consistent and indicated changes also in the electron momentum distribution during the occurrence of these finite size effects in the nanoparticles.     

Optical properties of nanocrystalline SnS2 thin films

Thin films of nanocrystalline SnS₂ on glass substrates were prepared from solution by dip coating and then sulfurized in H₂S (H₂S:Ar = 1:10) atmosphere. The films had an average thickness of 60 nm and were characterized by X-ray diffraction studies, scanning electron microscopy, EDAX, transmission electron microscopy, UV-vis spectroscopy, and Raman spectroscopy. The influence of annealing temperature (150-300 °C) on the crystallinity and particle size was studied. The effect of CTAB as a capping agent has been tested. X-ray diffraction analysis revealed the polycrystalline nature of the films with a preferential orientation along the c-axis. Optical transmission spectra indicated a marked blue shift of the absorption edge due to quantum confinement and optical band gap was found to vary from 3.5 to 3.0 eV with annealing temperature. Raman studies indicated a prominent broad peak at ∼314 cm⁻¹, which confirmed the presence of nanocrystalline SnS₂ phase.     

ZnS/ SiO2 介孔组装体系的发光性质

通过Sol-gel 法得到SiO₂ 介孔固体, 浸泡热分解后获得ZnS/ SiO₂ 介孔组装体。吸收光谱和荧光光谱表明: 随复合量增大, 蓝移量减小; 在氮气中退火后, 吸收边位置和荧光谱中的峰位随退火温度升高向长波方向移动且发光增强, 450 ℃以后减缓。经计算, 颗粒尺寸的理论值与其自由激子半径相当, 说明吸收边的移动起因于量子尺寸效应。