采用紫外光照法在磷酸盐玻璃中合成CdS/Ag复合微粒

掺杂有Ⅱ-Ⅵ族半导体纳米颗粒(如CdS)或者过渡金属(如Ag)的玻璃由于其较大的非线性光学效应而引起人们的极大兴趣,而同时掺杂有半导体/金属的复合微粒则可以进一步增强玻璃的三阶非线性效应,因此成为目前的研究热点。我们利用玻璃沉淀技术及随后的热处理和紫外光还原技术制备了含高浓度(1%)Ag微粒的玻璃,并采用X射线衍射分析了其物相,用高分辨扫描电镜分析了其形貌,以及测试了其吸收和发光性能。从CdS/Ag复合微粒的扫描照片可以发现晶粒均匀分布在玻璃中,尺寸约为1μm。X射线衍射发现经过热处理和紫外光照的样品衍射峰中含有CdS和Ag,而只进行热处理的样品则只含有CdS,未处理的样品则显非晶态。CdS/Ag复合微粒的吸收峰呈现典型的表面等离子共振峰(420nm)以及CdS的峰(600nm),只含有CdS微粒的样品的吸收峰则在480nm附近,未处理的样品在320nm附近有一个吸收峰,这可能是由于样品在快速冷却过程中的微小晶化造成的。只含有CdS微粒的样品有三个明显的发光峰,然而CdS/Ag复合微粒的发过峰则消失。我们提出了共振能量转移机制来解释该现象。讨论了紫外光照还原Ag微粒的机制。可以认为通过紫外光照,CdS表面的电子被激发出来还原Ag+,从而形成银颗粒,伴随着空穴则被表面缺陷所捕获。     

Investigation of the influence of silver and tin on the luminescence of trivalent europium ions in glass

Europium-doped aluminophosphate glasses prepared by the melt-quenching technique have been studied by photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS). The effects of silver and tin doping, and of further thermal processing on Eu³⁺ ions luminescence have been assessed. For the glass system containing only europium, Eu³⁺ PL observed under UV excitation is suggested to occur through energy transfer from the excited glass host. After silver and tin doping, an enhanced UV excited Eu³⁺ PL has been indicated to occur essentially due to radiative energy transfer from isolated Ag⁺ ions and/or two fold-coordinated Sn centers. Since thermal processing of the material leads to a quenching effect on Eu³⁺ PL and Ag nanoparticles (NPs) formation due to reduction of silver ions by tin, XPS was employed in order to investigate the possibility for Eu³⁺→Eu²⁺ reduction during HT as a potential source of the PL decrease. The data points towards Ag NPs as main responsible for the observed weakening of Eu³⁺ PL.     

Synthesis of silver nanocomposites by SCF impregnation of matrices of synthetic opal and Vycor glass by the Ag(hfac)COD precursor

Silver-containing nanocomposites were prepared by impregnating Vycor glass (a pore diameter of 4 nm) and synthesized opal matrices (an interstitial void size of 40 nm) with cyclooctadiene complex of silver hexafluoroacetylacetonate (Ag(hfac)COD), a silver precursor, dissolved in supercritical carbon dioxide and were examined by optical absorption spectroscopy, atomic force microscopy, and electron spin-resonance spectroscopy. It was demonstrated that the absorption spectra of Vycor glass and opal matrices impregnated with Ag(hfac)COD molecules and subjected to thermal treatment in air at temperatures above 50°C exhibit plasmon resonances characteristic of Ag nanoparticles at 420–430 nm. The peculiarities of the plasmon resonance band for both types of samples were attributed to the morphology of the pore space in which silver particles are formed. Paramagnetic Cu(hfac)₂ molecules (copper hexafluoroacetylacetonate) were used as a spectroscopic probe for estimating the distribution of the precursor in the pores of Vycor glass and opal matrices during supercritical fluid impregnation.     

Photoluminescence enhancement induced from silver nanoparticles in Tb3+ -doped glass ceramics

We experimentally verify that surface plasmon (SP) enhances the photoluminescence (PL) of visible light from Tb3+ -doped 60SiO2 -20Al2O3 -20CaF2 :0.3Tb 3+ , 20Yb 3+ glass ceramics by using electron beam lithography to fabricate silver nanoparticles on the surface of the glass ceramics. Numerical calculation for the SP enhancement spectroscopy is achieved by using the finite-difference time-domain algorithm. A PL enhancement of Tb3+ by as much as 1.6 times is observed. The PL enhancement is mainly due to the coupling of excitation from 7 F 6 to 5 D 4 transition dipole of Tb 3+ ion with SP mode induced from the silver nanoparticles.     

Silver aggregates and twofold-coordinated tin centers in phosphate glass: A photoluminescence study

The optical properties of silver species in various oxidation and aggregation states and of tin centers in melt-quenched phosphate glasses have been assessed by optical absorption and photoluminescence (PL) spectroscopy. Glasses containing silver and tin, or either dopant, were studied. Emission and excitation spectra along with time-resolved and temperature-dependent PL measurements were employed in elucidating the different emitting centers observed and investigating on their interactions. In regard to silver, the data suggests the presence of luminescent single Ag⁺ ions, Ag⁺-Ag⁺ and Ag⁺-Ag⁰ pairs, and nonluminescent Ag nanoparticles (NPs), where Ag⁺-Ag⁰→Ag⁺-Ag⁺ energy transfer is indicated. Tin optical centers appear as twofold-coordinated Sn centers displaying PL around 400 nm ascribed to triplet-to-singlet electronic transitions. The optically active silver centers were observed in glasses where 8 mol% of both Ag₂O and SnO, and 4 mol% of Ag₂O were added. Heat treatment (HT) of the glass with the high concentration of silver and tin leads to chemical reduction of ionic silver species resulting in a large volume fraction of silver NPs and the vanishing of silver PL features. Further characterization of such heat-treated glass by transmission electron microscopy and X-ray photoelectron spectroscopy appears consistent with silver being present mainly in nonoxidized form after HT. On the other hand, HT of the glass containing only silver results in the quenching of Ag⁺-Ag⁰ pairs emission that is ascribed to nonradiative energy transfer to Ag NPs due to the positioning of the pairs near the surface of NPs during HT. In this context, an important finding is that a faster relaxation was observed for this nanocomposite in relation to a heat-treated glass containing both silver and tin (no silver pairs) as revealed by degenerate four-wave mixing spectroscopy. Such result is attributed to Ag NP→Ag⁺-Ag⁰ plasmon resonance energy transfer. The data thus indicates that energy transfer between Ag⁺-Ag⁰ pairs and NPs is bi-directional.     

Formation of silver nanoparticles on the silicate glass surface after ion exchange

It has been experimentally shown that water vapor thermal treatment of silicate glasses with silver ions introduced by ion exchange leads to the formation of a silver nanoparticle layer with a high packing density on the glass surface. The results of studying the morphology of samples by atomic force and electron microscopy and X-ray spectral analysis of the composition of nanoparticles, as well as the optical density and luminescence spectra in different stages of the treatment, are presented. Mechanisms explaining the processes responsible for silver nanoparticle formation upon water vapor thermal treatment on the glass surface after ion exchange are proposed.     

Thermal effects on optical properties of silver ruby glass

2 O·10 CaO·74 SiO₂ mol%) glass doped with 0.11 and 0.35 wt.% silver are investigated. Heating treatments are carried out in a temperature range between 400 and 575 °C for times ranging from 30 to 300 min in different atmospheres and cooling rates. The starting glasses show a colourless and transparent appearance, but after thermal treatments under a reducing atmosphere become coloured, confirming the presence of silver colloids related to the 410-nm absorption band. On the other hand, the main effects of thermal treatments on the PL spectra concern those from samples treated in a reducing atmosphere. Thus, the intensity of both excitation and emission spectra chiefly diminishes in the 220–230 nm and 325–350 nm ranges, respectively. In addition, time-resolved spectra show the main ultraviolet (UV) emission centred above 330 nm upon excitation with 228-nm light. In contrast to the starting glass, we notice no shift or even slight shifts of the peak position to longer wavelengths with increasing delay time after pulse excitation, even for delay times as short as 0.01 ms. The results are discussed on the basis of transitions in which Ag⁺ ions are involved. Received: 6 February 1998/Accepted: 9 March 1998     

On the mechanism of gray scale patterning of Ag-containing As2S3 thin films

We demonstrate an application of photo-induced silver diffusion into chalcogenide glass thin film for gray scale lithography. The gray scale chalcogenide glass masking layer generated in the present experiments was dry etched using reactive ion etching. The etching rate increases almost linearly with the total dose of absorbed light, thus forming the basis of gray scale lithography. Chemical composition as well as electronic structure on the surface of chalcogenide glassy film has been determined by high-resolution X-ray photoelectron spectroscopy (XPS) of the film at different stages of the patterning process. Influence of thermal annealing of chalcogenide film before Ag deposition has been investigated using scanning electron microscopy (SEM) and XPS techniques. It is observed that thermal annealing of the chalcogenide film slows the process of silver diffusion during the proposed processing procedure. A mechanism is proposed to explain the stages of gray scale lithography based on chalcogenide glass photoresists.     

Enhanced quantum-well photoluminescence in InGaAs/InGaAsP heterostructures following excimer-laser-assisted surface processing

The influence of excimer-laser-assisted surface processing on quantum-well photoluminescence (QW PL) has been investigated in InGaAs/InGaAsP heterostructures capped with a thin layer of In_0.53Ga_0.47As. The PL mapping measurements carried out on samples before they were processed in a rapid thermal annealer indicated no significant differences in the QW PL signal intensity measured at the excimer-laser-processed sites and in their vicinity. However, a large difference in the QW PL signal, with its intensity significantly enhanced at the laser-processed sites, was observed after 10 s of rapid thermal annealing (RTA) at 750 °C. The largest contrast in the PL signal (an intensity difference up to about 100%) was obtained for a site processed with 50 pulses and a laser fluence of 123 mJ/cm². The changes in the QW PL signal intensity have been found to coincide with the changes in the surface chemical composition that were detected with Auger electron spectroscopy. The main difference concerns the development of a GaO_x layer on the laser-processed In_0.53Ga_0.47As surface.     

Synthesis and photoluminescence properties of silver nanowires

Silver nanowires of 50–190 nm in diameters along with silver nanoparticles in the size range of 60–200 nm in prismatic and hexagonal shapes are synthesized through chemical process. The lengths of the silver nanowires lie between 40 and 1000 μm. The characterizations of the synthesized samples are done by X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV–visible absorption spectroscopy. The syntheses have been done by using two processes. In the first process, relatively thicker and longer silver nanowires are synthesized by a soft template liquid phase method at a reaction temperature of 70 °C with methanol as solvent. In the second process, thinner silver nanowires along with silver nanoparticles are prepared through a polymer mediated polyol process at a reaction temperature of 210 °C with ethylene glycol as solvent. The variations of photoluminescence (PL) emission from the silver nanocluster dispersed in methanol as well as in ethylene glycol are recorded at room temperature under excitation wavelengths lying in between 300 and 414 nm. The blue–green PL emission is observed from the prepared samples and these emissions are assigned to radiative recombination of Fermi level electrons and sp- or d-band holes.     

Frequency upconversion properties of Ag: TeO<Subscript>2</Subscript>–ZnO nanocomposites codoped with Yb<Superscript>3+</Superscript> and Tm<Superscript>3+</Superscript> ions

Yb³⁺–Tm³⁺ codoped tellurite glasses containing silver nanoparticles (NPs) were synthesized and characterized using transmission electron microscopy and optical techniques. The samples’ composition and the nucleation of NPs were investigated using electron diffraction and energy dispersive spectroscopy. For the optical experiments, the samples were excited using a diode laser operating at 980 nm, in resonance with the Yb³⁺ transition ²F_7/2→²F_5/2. Photoluminescence (PL) bands corresponding to Tm³⁺ transitions were observed at 480, 650, and 800 nm due to the Yb³⁺→ Tm³⁺ energy transfer. PL enhancement was achieved by heat-treatment of the samples at 325°C during different time intervals. The growth of the PL bands correlates with the increase of the silver NPs concentration. The relevant mechanisms contributing for the PL characteristics are discussed.     

碱石灰玻璃表面长方形银纳米颗粒的制备与表征

采用离子交换结合热处理的方法在碱石灰玻璃表面制备了银纳米颗粒。通过紫外-可见分光光度计、X射线衍射仪、扫描电子显微镜对样品进行了表征。结果表明:热处理时,银离子在玻璃表面成核并生长成近似长方形的纳米颗粒。吸收光谱在416nm附近出现明显的银纳米颗粒表面等离子体共振吸收特征峰。     

On the nature of photoluminescence and EPR centers in glassy Ge2S3in terms of positron annihilation

The results of positron annihilation studies are discussed together with photoluminescence (PL) and EPR data for similar samples. The correlation between changes in e⁺-annihilation lifetime parametors, PL and EPR characteristics under doping of Ge₂S₃ glass with metals confirms the idea that these effects are related to point charged defects. The results obtained permit concluding that these defects (charged dangling bonds in the EPR and “fatigue of PL” cases) are situated at the boundaries of microinclusions. PL centers are probably associated with internal structure of the inclusions.     

两片掺铒玻璃样品级联荧光光谱的实验研究

介绍一种掺铒玻璃样品的制作方法，实验测量了单片及两片掺铒玻璃样品的荧光特性.结果表明：两片掺铒玻璃样品级联的荧光强度比单片掺铒玻璃样品的荧光强度高，半值宽度与高浓度单片样品的半值宽度近似相等；在两片掺铒玻璃样品级联的形式中，浓度高的样品靠近抽运光源时的荧光强度比浓度低的样品靠近抽运光源时的荧光强度高；两种低浓度样品组合的荧光强度相对于其单片样品荧光强度的增幅比两种高浓度样品组合的荧光强度相对于其单片样品荧光强度的增幅要高. 关键词： 掺铒玻璃样品 级联 荧光光谱强度 半值宽度     

Photoluminescence spectroscopy study on tris(8-hydroxyquinoline) aluminum film

In situ photoluminescence spectroscopy (PL) measurements of tris(8-hydroxyquinoline) aluminum (Alq₃) film were carried out. Upon deposition of Alq₃ on the glass substrate, the PL intensity changes dramatically, while the peak position of Alq₃ emission shows a sharp red-shift from 524 nm at the initial deposition of Alq₃, and tends to a saturation value of 536 nm for the film thickness range from 2 to 500 nm. This red-shift is associated with the change from the 2D to 3D exciton state with increasing Alq₃ film thickness. Temperature dependent PL spectra of Alq₃ films showed, besides the changes in the PL intensity, clearly a blue-shift of Alq₃ emission about 9 nm for the film annealing up to 150 °C, while no any shift of Alq₃ emission was observed for the film annealing below 130 °C. Both changes in PL intensity, and especially in the peak position of Alq₃ emission were attributed to crystallization (thermal) effect of Alq₃ film upon annealing.     

Photoluminescent properties of silicon carbide and porous silicon carbide after annealing

Photoluminescent (PL) p-type 6H porous silicon carbides (PSCs), which showed a strong blue-green photoluminescence band centered at approximately 490 nm, were annealed in Ar and vacuum conditions. The morphological, optical, and chemical states after annealing are reported on electrochemically etched SiC semiconductors.The thermal treatments in the Ar and vacuum environments showed different trends in the PL spectra of the PSC. In particular, in the case of annealing in a vacuum, the PL spectra showed both a weak red PL peak near 630 nm and a relatively intense PL peak at around 430 nm in the violet region. SEM images showed that the etched surface had spherical nanostructures, mesostructures, and islands. With increasing annealing temperature it changes all spherical nanostructures. The average pore size observed at the surface of the PSC before annealing was of the order of approximately 10 nm.In order to investigate the surface of a series of samples in detail, both the detection of a particular chemical species and the electronic environments at the surface are examined using X-ray photoelectron spectroscopy (XPS). The chemical states from each XPS spectrum depend differently before and after annealing the surface at various temperatures. From these results, the PL spectra could be attributed not only to the quantum size effects but also to the oxide state.     

非晶Si/SiO2超晶格的制备及其光谱研究

用磁控溅射方法在玻璃基底上制备了非晶Si/SiO₂超晶格.利用透射电子显微镜 (TEM) 和X射线衍射技术对其结构进行了分析,结果表明,超晶格中Si层大部分区域为非晶相,局域微区呈现有序结构,其厚度由1.8—3.2nm变化,SiO₂层厚度为4.0nm.并采用多种光谱测量技术,如吸收光谱、光致发光光谱和Raman光谱技术,对该结构的光学性质进行了系统研究.结果表明,随纳米Si层厚度的减小,光学吸收边以及光致荧光峰发生明显蓝移,Raman峰发生展宽,即观测到明显的量 关键词：     

Thermally induced native defect transform in annealed GaSb

Undoped p-type Ga Sb single crystals were annealed at 550–600?C for 100 h in ambient antimony. The annealed Ga Sb samples were investigated by Hall effect measurement, glow discharge mass spectroscopy(GDMS), infrared(IR)optical transmission and photoluminescence(PL) spectroscopy. Compared with the as-grown Ga Sb single crystal, the annealed Ga Sb samples have lower hole concentrations and weak native acceptor related PL peaks, indicating the reduction of the concentration of gallium antisite related native acceptor defects. Consequently, the below gap infrared transmission of the Ga Sb samples is enhanced after the thermal treatment. The mechanism about the reduction of the native defect concentration and its influence on the material property were discussed.     

Solgel synthesis and structural characterization of silver-silica nanocomposites

The solgel process has been successfully used to prepare silver/silica nanocomposites. After drying in air at 50°C for 30 min, samples were heat treated in air, at 100, 200, 400 and 500°C for the formation of silver nanoparticles. Evolution of silver nano-particles in the amorphous SiO₂ matrix as a function of annealing temperature has been studied. Characterizations were made by X-ray diffraction, ultraviolet-visible, and infrared spectroscopy. Mechanisms of silver clusters formation in the densified silica matrix with respect to thermal treatment are discussed.     

Thickness effect on the evolution of morphology and optical properties of ZnO films

N-Al co-doped ZnO films with various thicknesses were deposited on glass substrates by ultrasonic spray pyrolysis (USP). The crystalline microstructure, morphology, distribution of elements and photoluminescence properties of ZnO films were characterized by X-ray diffraction (XRD), field emission scanning microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS) and photoluminescence (PL) spectroscopy. The XRD and FESEM results show that with the increase of film thickness the grain size increases and the grain shape changes from regular hexagonal sheet-like to wedge-shaped, even pyramidal. The PL spectra illustrate that there is an obvious red-shift for the emission center from ultraviolet to blue region, and the intensities of defects emissions increase with the increase of thickness. In addition, the electrical properties are proved to be strongly affected by film thickness.