Al掺杂原子分数及退火温度对ZnO薄膜光学特性的影响

 采用溶胶凝胶法在（0001）Al₂O₃衬底上制备了不同掺杂原子分数的ZnO:Al薄膜，在Ar气氛中进行了600～950 ℃不同温度的退火处理，研究了掺杂原子分数和退火温度对薄膜光致发光、光吸收和透射的影响。结果显示，薄膜的紫外峰强度随掺杂原子分数和退火温度的提高而增强，与缺陷相关的绿光强度却随着掺杂原子分数和退火温度的提高而降低；薄膜光学带隙随掺杂原子分数的提高从3.21 eV增大到3.25 eV；光吸收在可见光区随着退火温度的升高而增大，在紫外区却随着退火温度的升高而减小，透射与吸收的变化规律相反；薄膜吸收边随退火温度的升高出现轻微的红移。     

Sol-gel matrix modified microstructured optical fibre towards a fluoride sensitive optical probe

In this article, we report an optical fluoride probe based on microstructured polymer optical fibers (MPOFs) which is modified with morin-Al complex doped silica gel film. This probe is fabricated by sol-gel fluxion coating process. Sol solution doped with morin-Al is directly inhaled into array holes of MPOF and then forms morin-Al-gel matrix film in them. The sensing probe shows different fluorescence intensity to different fluoride ion concentrations in the aqueous solution. The range of response is 5-50 mmol/L, under the condition of pH 4.6.     

Flow Injection Small-volume Fiber-optic pH Sensor Based on Evanescent Wave Excitation and Fluorescence Determination

A small-volume fiber-optic pH sensor (FOEWS) based on evanescent wave excitation is developed and evaluated. The sensor is simply fabricated by inserting a decladded optical fiber into a transparent capillary tube. A microchannel between the optical fiber and the capillary inner wall was formed and acted as flow cell for solution flowing through. The pH-sensitive fluorophore of fluorescein can be excited by the evanescent wave field produced on the fiber core surface to produce emission fluorescence. pH value was then sensed by its enhancing effect on the emission fluorescence intensity. The response range of the sensor is from pH 2.09 to pH 8.85 and the linear range is from pH 3.25 to 8.85. The proposed sensor has a small detection volume of 2.5 μL and a short response time of 8 s. It has been applied to measure pH values of real water samples and was in good agreement with the results obtained by commercial pH meter.     

Optical characterization of sol gel TiO<Subscript>2</Subscript> monoliths doped with Brilliant Green

Amorphous titanium dioxide monoliths doped with brilliant green (BG) were synthesized by the sol-gel process. The optical properties of the monoliths were characterized by Photoacoustic Spectroscopy and Photoluminescence Spectroscopy. The absorption spectra for the BG-doped TiO₂ monoliths exhibited two well defined absorption regions: a band below 400 nm corresponding to TiO₂ absorption and three absorption bands centered at 424 nm, 588 nm, and 632 nm due to brilliant green. While the undoped TiO₂ monoliths showed no luminescence, the doped samples showed a strong luminescence band at 673 nm, which increased its intensity for increasing organic dye doping.     

聚对苯撑亚乙烯/SiO2块状溶胶-凝胶非线性光学材料的研究

我们制作了一种由π－共轭聚合物聚对苯撑亚乙烯（PPV）均匀掺杂SiO2的块状溶胶－凝胶材料，该材料具有良好的光学品质和光学加工性能。通过扫描隧道显微镜（STM），紫外－可见吸收光谱和付氏红外光谱（FTIR）等方法研究了它的非线性光学特性。在对材料进行的光学两波耦合实验中，观察到了非对称能量耦合现象，并对此进行了分析。从吸光度和两波耦合衍射效率两方面对比了含PMMA和不含PMMA的两批不同掺杂浓度的PPV／SiO2 sol-gel材料的不同特性。     

Reversible UV degradation of PMMA plastic optical fibers

Laser-induced fluorescence, Raman and absorption spectroscopy are used to investigate reversible degradation of transmission in PMMA optical fibers. When exposed to 254 nm UV light, optical transmission of PMMA plastic optical fiber in 400-800 nm range shows a significant increase in attenuation for shorter wavelengths. Over a period of 10 days following UV exposure, the transmittance of the plastic fiber recovers to a significant fraction of its pre-exposure value. UV-exposed fiber exhibits strong laser-induced fluorescence with 488 nm argon-ion laser. This fluorescence spans a spectral region between 450 nm and 750 nm with a peak around 580 nm. The fluorescence intensity decreases over several days following UV exposure. Likewise, Raman is also used to investigate degradation process. Freshly UV-exposed fiber shows total absence of Raman spectrum of PMMA. Following UV exposure, recovery of Raman signal over several days is correlated to the recovery of fiber transmittance as well as the decay of laser-induced fluorescence. A widely believed plausible explanation for UV-induced increase of attenuation involves formation of different macro radicals which recombine progressively after UV is stopped. Laser-induced fluorescence over several days is reported here providing direct evidence for molecular-level deterioration and recovery of PMMA.     

Effect of Mn doping on the structural and optical properties of sol-gel derived ZnO nanoparticles

Un-doped and Mn-doped ZnO nanoparticles were successfully synthesized in an ethanolic solution by using a sol-gel method. Material properties of the samples dependence on preparation conditions and Mn concentrations were investigated while other parameters were controlled to ensure reproducibility. It was observed that the structural properties, particle size, band gap, photoluminescence intensity and wavelength of maximum intensity were influenced by the amount of Mn ions present in the precursor. The XRD spectra for ZnO nanoparticles show the entire peaks corresponding to the various planes of wurtzite ZnO, indicating a single phase. The diffraction peaks of doped samples are slightly shifted to lower angles with an increase in the Mn ion concentration, signifying the expansion of the lattice constants and increase in the band gap of ZnO. All the samples show the absorption in the visible region. The absorbance spectra show that the excitonic absorption peak shifts towards the lower wavelength side with the Mn-doped ZnO nanoparticles. The PL spectra of undoped ZnO consist of UV emission at 388 nm and broad visible emission at 560 nm with varying relative peak intensities. The doping of ZnO with Mn quenches significantly the green emission while UV luminescence is slightly affected.     

MgxZn1-xO薄膜的光致发光性能研究

用溶胶-凝胶旋涂的方法在Si(100)衬底上成功制备了MgxZn1-xO薄膜.通过对样品的X射线衍射花样进行分析,发现制得的样品都有明显的C轴取向.掺入Mg后C轴参数逐渐变小,这表明Mg离子进入了ZnO晶格.随着镁的掺入,其光致发光谱中的紫外发射峰的峰位发生明显蓝移,从3.28eV线性地变化到3.45eV.值得注意的是,掺入镁离子后,薄膜的紫外发光和可见发光的强度都显著高于ZnO.     

Photoluminescence characteristics of ZnS nanocrystallites doped with Ti3+and Ti4+

Direct synthesis of ZnS nanocrystallites doped with Ti³⁺ or Ti⁴⁺ by precipitation has led to novel photoluminescence properties. Detailed X-ray diffraction (XRD), fluorescence spectrophotometry, UV–vis spectrophotometry and X-ray photoelectron spectroscopy (XPS) analysis reveal the crystal lattice structure, average size, emission spectra, absorption spectra and composition. The average crystallite size doped with different mole ratios, estimated from the Debye–Scherrer formula, is about 2.6±0.2 nm. The nanoparticles can be doped with Ti³⁺ and Ti⁴⁺ during the synthesis without the X-ray diffraction pattern being altered. The strong and stable visible-light emission has been observed from ZnS nanocrystallites doped with Ti³⁺ (its maximum fluorescence intensity is about twice that of undoped ZnS nanoparticles). However, the fluorescence intensity of the ZnS nanocrystallites doped with Ti⁴⁺ is almost the same as that of the undoped ZnS nanoparticles. The emission peak of the undoped sample is at 440–450 nm. The emission spectrum of the doped sample consists of two emission peaks, one at 420–430 nm and the other at 510 nm. Received: 27 April 2001 / Accepted: 16 August 2001 / Published online: 17 October 2001     

Green Emitting Cerium Doped CaS Whiskers Grown by Solid State Diffusion Method

Undoped and cerium doped Calcium sulfide (CaS) phosphors were synthesized using solid state diffusion method. The X-ray diffraction pattern revealed that both undoped and doped CaS crystallites have cubic structure with average crystallite size varying from 20 to 30 nm. Scanning electron micrographs indicated that Ce doped CaS phosphors were composed of whiskers with different dimensions and orientations. The optical properties of undoped and Ce doped particles were characterized using Photoluminescence (PL) and UV-Vis absorption spectroscopy. The PL emission spectrum of cerium doped CaS phosphors for an excitation wavelength 465 nm showed a main peak at 500 nm and a shoulder peak at 556 nm due to 5d?→?4f transition in Ce³⁺ ions. The variation of PL intensity with cerium concentration was investigated and the maximum PL intensity was obtained for a doping concentration of 3 wt.%. The optical band gap of the samples was estimated from the diffuse reflectance spectrum and was found to increase with increase in cerium concentration. The enhanced optical properties of these phosphors can be exploited in various optoelectronic devices including displays and bioimaging techniques.     

Zn掺杂β-Ga2O3薄膜的制备和特性研究

β-Ga₂O₃是一种宽带隙半导体材料,能带宽度E_g≈5.0eV,在光学和光电子学领域有广泛的应用。用射频磁控溅射方法在Si衬底和远紫外光学石英玻璃衬底制备了本征β-Ga₂O₃薄膜及Zn掺杂β-Ga₂O₃薄膜,用紫外 可见分光光度计、X射线衍射仪、荧光分光光度计对本征β-Ga₂O₃薄膜及Zn掺杂β-Ga₂O₃薄膜的光学透过、光学吸收、结构和光致发光进行了测量,研究了Zn掺杂和热退火对薄膜结构和光学性质的影响。退火后的β-Ga₂O₃薄膜为多晶结构,与本征β-Ga₂O₃薄膜相比,Zn掺杂β-Ga₂O₃薄膜的β-Ga₂O₃(111)衍射峰强度变小,结晶性变差,衍射峰位从35.69°减小至35.66°。退火后的Zn掺杂β-Ga₂O₃薄膜的光学带隙变窄,光学透过降低,光学吸收增强,出现了近边吸收,薄膜的紫外、蓝光及绿光发射增强。表明退火后Zn掺杂β-Ga₂O₃薄膜中的Zn原子被激活充当受主。     

Excellent UV absorption in spin-coated thin films of oleic acid modified zinc oxide nanorods embedded in Polyvinyl alcohol

The aim of the study is to investigate the optical properties of spin-coated, highly transparent nanocomposite films of oleic acid modified ZnO (Zinc oxide) nanorods embedded in Polyvinyl alcohol (PVA) matrix. Pristine and oleic acid (OA) modified ZnO nanorods have been prepared by wet chemical synthesis and are characterized by X-ray diffraction, FESEM, TEM and FT–IR spectroscopy techniques. The optical properties of ZnO/PVA films are studied using UV–visible absorption and Photoluminescence (PL) spectroscopy. The results show that the optical absorption of the films in the UV region is quite high and more than 95% absorption is observed in films prepared from OA modified ZnO nanorods. The excellent UV absorption at around 300 nm offers prospects of applications of these films as efficient UV filters in this wavelength region. The PL spectrum of pristine ZnO nanorods shows almost white light emission whereas OA modified ZnO nanorods have a more intense peak centered in the blue region. The PL emission of OA modified ZnO/PVA film shows appreciable increase in intensity compared to the film obtained with pristine ZnO. The surface modification of ZnO by the polymer matrix removes defect states within ZnO and facilitates sharp near band edge PL emission at 364 nm.     

Thermoluminescence and dosimetric properties of bismuth doped CaS nanocrystalline phosphor

The irradiation effect on bismuth doped CaS nanocrystalline phosphors and their possible applications to solid state dosimetry have been studied. The wet chemical co-precipitation method has been used for preparation of nanocrystallites. In UV exposed CaS nanocrystallites, the thermoluminescence glow curve consists of two peaks at 439 and 561 K. The effect of different concentrations, dose dependence, fading and reusability in CaS:Bi nanocrystallites have been investigated. The high temperature peak (dosimetric peak) intensity is nearly linear in a wide range of UV exposure. A blue shift has been observed in photoluminescence spectra, which may be attributed to quantum size effect.     

Influence of pH in La-doped SnO2 nanoparticles towards sensor applications

The present investigation has been carried out to optimize the pH level of lanthanum (La)-doped tin dioxide (SnO₂) nanoparticles towards the potential application in gas sensor. The La-doped SnO₂ nanoparticles were synthesized by sol-gel method in different pH values varying from acidic to base nature. The synthesized nanoparticles were characterized by X-ray diffraction (XRD), ultraviolet (UV), photoluminescence (PL), and scanning electron microscopy (SEM) techniques. The XRD, UV, and PL analyses show the pH influences on the crystallite size of La-doped SnO₂ nanoparticles. The SEM images show the formation of porous structure at pH 11. Also, the electrical conductivity of 1 mol% La-doped SnO₂ at pH 3 and pH 11 were measured by impedance analyzer. In addition, we have fabricated and demonstrated device performance of synthesized La-doped SnO₂ nanoparticles for gas-sensing application. Real-time current response and long-time response to the gas sensing were also studied for the fabricated device.

     

Effect of the oxygen pressure on the microstructure and optical properties of ZnO films prepared by laser molecular beam epitaxy

A series of ZnO films were prepared on the Si (1 0 0) or glass substrate at 773 K under various oxygen pressures by using a laser molecular beam epitaxy system. The microstructure and optical properties were investigated through the X-ray diffraction, Raman spectrometer, scanning electron microscope, ultraviolet–visible spectrophotometer and spectrofluorophotometer. The results showed that ZnO thin film prepared at 1 Pa oxygen pressure displayed the best crystalinity and all ZnO films formed a columnar structure. Meanwhile, all ZnO films exhibited an abrupt absorption edge near the wavelength of 380 nm in transmission spectra. With increasing the oxygen pressure, the transmission intensity changed non-monotonically and reached a maximum of above 80% at 1 Pa oxygen pressure, based on which the band gaps of all ZnO films were calculated to be about 3.259–3.315 eV. Photoluminescence spectra indicated that there occurred no emission peak at a low oxygen pressure of 10⁻⁵ Pa. With the increment of the oxygen pressure, there occurred a UV emission peak of 378 nm, a weak violet emission peak of 405 nm and a wide green emission band centered at 520 nm. As the oxygen pressure increased further, the position of UV emission peak remained and its intensity changed non-monotonically and reached a maximum at 1 Pa. Meanwhile the intensity of green emission band increased monotonically with increasing the oxygen pressure. In addition, it was also found that the intensity of UV emission peak decreased as the measuring temperature shifted from 80 to 300 K. The analyses indicated that the UV emission peak originated from the combination of free excitons and the green emission band originated from the energy level jump from conduction band to O_Zn defect.     

Zn掺杂β-Ga2O3薄膜的制备和特性研究（英文）

β-Ga2O3是一种宽带隙半导体材料,能带宽度Eg≈5.0eV,在光学和光电子学领域有广泛的应用.用射频磁控溅射方法在Si衬底和远紫外光学石英玻璃衬底制备了本征β-Ga2O3薄膜及Zn掺杂β-Ga2O3薄膜,用紫外-可见分光光度计、X射线衍射仪、荧光分光光度计对本征β-Ga2O3薄膜及Zn掺杂β-Ga2O3薄膜的光学透过、光学吸收、结构和光致发光进行了测量,研究了Zn掺杂和热退火对薄膜结构和光学性质的影响.退火后的β-Ga2O3薄膜为多晶结构,与本征β-Ga2O3薄膜相比,Zn掺杂β-Ga2O3薄膜的β-Ga2O3(111)衍射峰强度变小,结晶性变差,衍射峰位从35.69°减小至35.66°.退火后的Zn掺杂β-Ga2O3薄膜的光学带隙变窄,光学透过降低,光学吸收增强,出现了近边吸收,薄膜的紫外、蓝光及绿光发射增强.表明退火后Zn掺杂β-Ga2O3薄膜中的Zn原子被激活充当受主.     

XPS studies and photocurrent applications of alkali-metals-doped ZnO nanoparticles under visible illumination conditions

The present work is a study about a relationship between X-ray photoelectron spectrometer (XPS) results and photocurrent intensity of alkali-metals-elements doped ZnO nanoparticles, which is carried out under visible illumination conditions. The nanoparticles were synthesized by a simple sol–gel method. Structure and morphology studies of the NPs were carried out by X-ray diffraction analysis (XRD) and transmission electron microscopy (TEM). The effect of doping on the optical band-gap was investigated by using UV–visible spectrometer. The absorption peak of the doped ZnO NPs was red-shifted with respect to that of the undoped ZnO NPs. After that, the photocurrent application of the products was examined under a white light source at 2 V bias. The photocurrent results showed that, the current intensity of the ZnO NPs was increased by doping materials. However, K-doped ZnO NPs showed the highest photocurrent intensity. Finally, a discussion was carried out about the obtained photocurrent results by the O-1s spectra of the XPS of the samples. Our results suggest that the alkali-metals-doped ZnO NPs exhibit considerable promise for highly sensitive visible-light photodetectors.     

Effect of gamma ray irradiation on optical properties of Nd doped phosphate glass

The effect of gamma irradiation in the dose range of 5-500 kGy on the optical absorption and luminescence spectra of Nd doped phosphate glass is reported. The spectral absorption of this glass before and after gamma irradiation was measured in the spectral range 300-900 nm at room temperature using spectrophotometer and synchrotron beamline. Drastic increase in absorption was noted below 600 nm after gamma irradiation, which was dependent on the dose of irradiation. Additional absorption (AA) spectra of irradiated sample shows generation of two absorption bands below 600 nm, which finally became one very broad band peak with increased intensity at irradiation dose of 500 kGy. AA spectra also show the presence of negative peaks at the location of absorption peaks of Nd³⁺. Photoluminescence of Nd doped phosphate glass shows two strong bands which decreases to a very low intensity with a red shift after gamma irradiation. These results indicate that irradiation produces different kinds of defects in the glass material along with conversion of valence state of Nd³⁺ to Nd²⁺. This change was found irreversible at room temperature.     

Enhancement in UV emission and band gap by Fe doping in ZnO thin films

Enhancement of the optical band gap of ZnO from 3.14 to 3.29 eV has been obtained using Fe dopant. Undoped and doped ZnO films are deposited by sol-gel spin coating. XRD patterns indicate polycrystalline nature and hexagonal wurtzite structure of Zn_1?xFe_xO films. EDX analysis confirms the presence of iron dopant. The photoluminescence spectra show an ultraviolet emission peak at 398 nm (NBE emission) and defect emission peak at 485 nm. Intensity of the NBE emission is much higher for the doped samples with its ratio to defect emission intensity highest for 2 at. %doping. The NBE emission shifts to higher energy with increasing dopant concentration in a manner similar to that exhibited by the band gap. Surface morphology has been studied using FESEM.     

Influence of different stabilizers on the optical and nonlinear optical properties of CdTe nanoparticles

CdTe semiconductor nanocrystals were synthesized with three different stabilizers: Mercaptoacetic Acid (MAA), Mercaptopropionic Acid (MPA) and 2-Mercaptoethanol (ME) at pH ≈ 11.2 by wet chemical route using potassium tellurite and cadmium chloride as starting materials. The effect of capping agent on the preparation of these samples was evaluated using UV-Visible absorption and photoluminescence analysis. With the same reaction time but with different stabilizers, nanocrystals of different diameters were obtained. The average full width at half maximum of the photoluminescence spectra was about 69 nm which indicates that the monodispersity was quite good. The particle size was calculated by Debye-Scherrer equation from XRD data. Further characterization studies such as FT-IR and optical nonlinearity studies on the samples were carried out and the results are discussed.