Cathodoluminescent and nonlinear optical properties of undoped and erbium doped nanostructured ZnO films deposited by spray pyrolysis

We have deposited zinc oxide (ZnO) and erbium doped zinc oxide (ZnO:Er) thin films on heated glass substrates using spray pyrolysis technique. The effect of erbium dopant on structural, morphological, luminescent and nonlinear optical properties was studied. The deposited films have been analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), ex situ compositional analysis (ESCA), profilometry, cathodoluminescence (CL) and third harmonic generation (THG) measurements. All films were polycrystalline, having a preferential growth orientation along the ZnO (0 0 2) plane, with a corresponding average crystallite size of less than 41 nm. Addition of erbium can effectively control the film surface morphology and its cathodoluminescent properties. The films containing low erbium concentration show a uniform surface covered with hexagonal shaped grains and a strong UV light emission intensity as well as TH response. In contrast, when the erbium doping ratio exceeds 3%, a porous surface with columnar textural growth becomes more pronounced, and a substantial reduction of the cathodoluminescent and TH response. A strong TH signal was obtained for the film with good crystalline quality at the concentration of 2%. Third order nonlinear optical susceptibility (χ^〈3〉) values of the studied materials were in the remarkable range of 10⁻¹² esu.     

铒掺杂硼酸盐玻璃中的激发态阱

铒掺杂硼酸盐玻璃广泛应用于发光材料中,研究其发光动力学性质对于优化和提高其发光效率具有重要意义. 本文采用传统的熔融淬火法合成了摩尔比为2%的掺铒硼酸盐玻璃,并在低于硼酸盐玻璃转变温度(260 °C)下退火,退火处理后的掺铒硼酸盐玻璃光学性质得到了一定程度的提高. 硼酸盐玻璃未掺杂和掺杂Er³⁺的热性能采用差示扫描量热法以10 °C/min的速度进行测量. 同时还测量了掺铒硼酸盐玻璃发光机理的吸收光谱、激发光谱、稳态发射光谱、瞬态发射光谱和衰减动力学曲线. 实验结果表明Er³⁺在不同激发波长下556 nm处发射时具有不同的寿命,在掺铒硼酸盐玻璃中可能存在激发态阱,利用实验数据得到了激发态阱的深度为0.14 eV.     

1.54 μm Emission of pulsed-laser deposited Er-doped films on Si

We investigate the photoluminescence properties of Er-doped SiO₂ and glass films fabricated by pulsed-laser deposition (PLD) for different deposition parameters and erbium host materials. The luminescence yield of SiO₂ : Er films increases strongly with increasing oxygen background pressure during laser ablation. We compare SiO₂ and soda-lime glass as host materials for erbium ions. Under identical growth conditions and the same erbium concentrations in both targets, films deposited from the soda-lime glass show a much higher luminescence yield. This enhancement is attributed to a higher concentration of optically active erbium in the multicomponent glass environment.     

Properties of mixed molybdenum oxide-iridium oxide thin films synthesized by spray pyrolysis

Molybdenum-doped iridium oxide thin films have been deposited onto corning glass- and fluorine-doped tin oxide coated corning glass substrates at 350 °C by using a pneumatic spray pyrolysis technique. An aqueous solution of 0.01 M ammonium molybdate was mixed with 0.01 M iridium trichloride solution in different volume proportions and the resultant solution was used as a precursor solution for spraying. The as-deposited samples were annealed at 600 °C in air medium for 1 h. The structural, electrical and optical properties of as-deposited and annealed Mo-doped iridium oxide were studied and values of room temperature electrical resistivity, and thermoelectric power were estimated. The as-deposited samples with 2% Mo doping exhibit more pronounced electrochromism than other samples, including pristine Ir oxide.     

Erbium partitioning in a heavily doped transparent glass ceramic

An erbium-doped transparent glass ceramic, consisting of LaF3 nanocrystallites with a characteristic length of approximately 20 nm embedded in an aluminosilicate glass matrix and exhibiting infrared-to-green up-conversion, has been studied. The degree of erbium partitioning into the nanocrystallite phase was found using energy transfer coefficients determined from bulk Er3+:LaF3 samples. This transparent glass ceramic sample was found to have a partitioning fraction of 19 +/- 5%.     

Optimization of erbium-doped waveguide amplifier

Based on the combined model of erbium-doped waveguide amplifier with high erbium ion concentration, the rate equation and evolution equation is solved numerically. The waveguide parameters such as doping concentration, waveguide length are optimized in this paper. With pumping power of 150 mW, the optimal erbium doping concentration and waveguide length is 6×10²⁶ m⁻³, 15 cm or so, respectively. The amplifier with these optimal parameters may reach gain more than 35 dB.     

A comparative study on structural and optical properties of ZnO and Al-doped ZnO thin films obtained by ultrasonic spray method using different solvents

Transparent conducting ZnO and Al doped ZnO thin films were deposited on glass substrate by ultrasonic spray method. The thin films with concentration of 0.1 M were deposited at 350 °C with 2 min of deposition time. The effects of ethanol and methanol solution before and after doping on the structural, optical and electrical properties were examined. The DRX analyses indicated that ZnO films have nanocrystalline nature and hexagonal wurtzite structure with (1 0 0) and (0 0 2) preferential orientation corresponding to ZnO films resulting from methanol and ethanol solution, respectively. The crystallinity of the thin films improved with methanol solution after doping to (0 0 2) oriented. All films exhibit an average optical transparency about 90%, in the visible range. The band gaps values of ZnO thin films are increased after doping from 3.10 to 3.26 eV and 3.27 to 3.30 eV upon Al doping obtained by ethanol and methanol solution, respectively. The electrical conductivity increase from 7.5 to 15.2 (Ω cm)⁻¹ of undoped to Al doped ZnO thin films prepared by using ethanol solution. However, for the methanol solution; the electrical conductivity of the film is stabilized after doping.     

Spectroscopic and lasing properties of Er3+:Yb3+-doped fluoride phosphate glasses

Er³⁺ emission and lasing properties at 1.5 μm were studied in fluoride phosphate glasses (FP20) with different doping concentrations as well as in a commercial phosphate glass (Kigre QX). Emission decay behaviour at 1 μm and 1.5 μm was examined with respect to energy transfer between ytterbium and erbium. Emission cross-sections were determined using the reciprocity and Füchtbauer–Ladenburg methods. Gain spectra were calculated for the glasses and related to differences in the tuning curves and lasing properties. The temperature rise due to the quantum defect was determined via the ratios of green upconversion luminescence for different pump powers. The results from the laser and tuning experiments indicate that the FP20 glass offers good possibilities in broadband amplification and the generation of ultrashort pulses. Received: 24 August 2000 / Revised version: 27 October 2000 / Published online: 7 February 2001     

OH-对磷酸盐铒玻璃光谱性质的影响

本文系统研究了Yb³⁺、Er³⁺共掺磷酸盐铒玻璃中OH^-含量与铒玻璃荧光寿命和光谱性质的关系.结果表明OH^-基团的存在使得Er³⁺离子的荧光强度显著降低,荧光寿命大大缩短.比较了三种不同Al₂O₃含量(5mol%,8mol%和13mol%)的铒玻璃在2.9μm波长处的红外吸收系数与铒离子荧光寿命的关系,发现玻璃中OH^-在2.9μm的吸收系数和Er³⁺的⁴Ⅰ_13/2能级离子衰减速率成线性关系,不同Al₂O₃含量的玻璃具有不同Er³⁺和OH^-基团的相互作用参量和不同的荧光寿命值及量子效率.并从玻璃结构上解释了Al₂O₃含量对除水机制和光谱性质的影响.经过充分除水后的铒玻璃荧光寿命可达到9.1ms.     

Influence of the ion synthesis and ion doping regimes on the effect of sensitization of erbium emission by silicon nanoclusters in silicon dioxide films

The photoluminescence spectra of erbium centers in SiO₂ films with ion-synthesized silicon nanoclusters under nonresonant excitation were investigated. Erbium was introduced into thermal SiO₂ films by ion implantation. The dependences of photoluminescence intensity on the dose, the order of ion implantation of Si and Er, the annealing temperature, and additional Ar⁺ and P⁺ ion irradiation regimes, i.e., factors determining the influence of radiation damage and doping on sensitization of erbium luminescence by silicon nanoclusters, were determined. It was found that the sensitization effect and its amplification due to doping with phosphorus are most pronounced under the conditions where nanoclusters are amorphous. The quenching of photoluminescence due to radiation damage in this case manifests itself to a lesser extent than for crystalline nanoclusters. The role of various factors in the observed regularities was discussed in the framework of the existing concepts of the mechanisms of light emission and energy exchange in the system of silicon nanoclusters and erbium centers.     

Double-pass erbium-doped zirconia fiber amplifier for wide-band and flat-gain operations

The double-pass erbium-doped zirconia fiber amplifier (EDZFA) is proposed and demonstrated to provide a wide-band amplification as well as flat-gain operation in both the C- and L-band regions using only a single-gain medium. The proposed amplifier utilizes an erbium-doped zirconia fiber (EDZF) with erbium ion concentration of 2800 ppm as a gain medium. The medium is fabricated in a ternary glass host, zirconia-yttria-aluminum codoped silica fiber through solution doping technique along with modified chemical vapor deposition (MCVD). Compared to a single-pass operation, the double-pass EDZFA shows a better gain performance. At input signal power of 0 dBm and the optimum EDZF length of 2 m, a flat gain of around 16 dB is achieved by the proposed double-pass amplifier with gain variation of approximately 2.5 dB throughout the wavelength range from 1530 to 1590 nm. However, the noise figure of the double-pass amplifier is slightly higher than that of the single-pass due to inefficient population inversion at the input part of the amplifier.     

K9玻璃薄膜对离子交换磷酸盐玻璃波导表面保护的优化研究

采用镀K9玻璃薄膜方法来解决离子交换掺铒磷酸盐玻璃波导表面的侵蚀问题,对K9玻璃薄膜的厚度进行了优化研究。测量分析了样品的荧光光谱和荧光寿命,采用光学显微镜和棱镜耦合技术对不同K9玻璃薄膜厚度下制备波导的表面形貌和导光特性进行了表征和测试。结果表明,与掺铒磷酸盐玻璃原材料相比,镀K9玻璃薄膜后荧光光谱保持不变,荧光寿命稍有下降(约0.2 ms);K9玻璃薄膜的厚度在60~80 nm的范围内保护效果最佳。为下一步制备掺铒有源玻璃光波导器件奠定了良好的实验基础。     

Spectral luminescence and information characteristics of transparent lead fluoride nano-glass-ceramics doped with erbium ions

Spectral luminescence properties of synthesized transparent nano-glass-ceramics doped with erbium ions are studied. It is shown that, as a result of the secondary heat treatment of nano-glass-ceramics, the width of the luminescence spectrum at half maximum increases more than by 15 nm. Luminescence life-time dependences of erbium ions in studied samples are measured, their absorption cross-sections are determined, and their emission cross-sections are calculated by the McCumber method. Spectral and ultimate information characteristics of erbium-doped fiber amplifiers based on synthesized nano-glass-ceramics are numerically simulated. It is shown that, in the unsaturated gain regime, a substantial ripple of the absorption and emission cross-section spectra and shorter lifetime of the metastable level of the erbium ion reduce the pumping radiation power that is required for obtaining the given peak gain, narrow the gain spectra, and lower the transmission capacity of devices based on nano-glass-ceramics compared to the initial glass. Conversely, fiber amplifiers based on calcium fluoride glass-ceramics, for which the lifetime of the metastable level increases with increasing annealing temperature, have an advantage in the transmission capacity over devices based on the primary glass.     

Er3+注入CdTe薄膜的结构和光电性能研究

采用离子注入技术对近距离升华制备的CdTe薄膜进行Er³⁺掺杂研究.讨论了不同掺Er³⁺浓度对CdTe薄膜的结构和光电性能的影响.利用X射线衍射仪、扫描电子显微镜、紫外-可见分光光度计、霍耳效应测试系统和复阻抗分析仪对样品进行测试.结果表明，适当的掺杂量可以改善CdTe薄膜的结晶性能，降低晶界势垒高度，提高其导电性能.在一定掺杂范围内掺Er³⁺对CdTe薄膜的光能隙影响不大. 关键词： CdTe薄膜 离子注入 晶界势垒 光能隙     

Efficient one-pot synthesis of Ag nanoparticles loaded on N-doped multiphase TiO2 hollow nanorod arrays with enhanced photocatalytic activity

The simultaneous Ag loaded and N-doped TiO₂ hollow nanorod arrays with various contents of silver (Ag/N-THNAs) were successfully synthesized on glass substrates by one-pot liquid phase deposition (LPD) method using ZnO nanorod arrays as template. The catalysts were characterized by Raman spectrum, field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscope (HRTEM), ultraviolet-vis (UV-vis) absorption spectrum and X-ray photoelectron spectroscopy (XPS). The results suggest that AgNO₃ additive in the precursor solutions not only can promote the anatase-to-rutile phase transition, but also influence the amount of N doping in the samples. The photocatalytic activity of all the samples was evaluated by photodegradation of methylene blue (MB) in aqueous solution. The sample exhibited the highest photocatalytic activity under UV light illumination when the AgNO₃ concentration in the precursor solution was 0.03 M, due to Ag nanoparticles acting as electron sinks; When the AgNO₃ concentration was 0.07 M, the sample performed best under visible light illumination, attributed to the synergetic effects of Ag loading, N doping, and the multiphase structure (anatase/rutile).     

MBE-grown Si: Er light-emitting structures: Effect of epitaxial growth conditions on impurity concentration and photoluminescence

The technology and properties of light-emitting structures based on silicon layers doped by erbium during epitaxial MBE growth are studied. The epitaxial layer forming on substrates prepared from Czochralski-grown silicon becomes doped by oxygen and carbon impurities in the process. This permits simplification of the Si: Er layer doping by luminescence-activating impurities, thus eliminating the need to make a special capillary for introducing them into the growth chamber from the vapor phase. The photoluminescence spectra of all the structures studied at 78 K are dominated by an Er-containing center whose emission line peaks at 1.542 μm. The intensity of this line measured as a function of the substrate and erbium dopant source temperatures over the ranges 400–700°C and 740–800°C, respectively, exhibits maxima. The edge luminescence and the P line observed in the PL spectra are excited predominantly in the substrate. The erbium atom concentration in the epitaxial layers grown at a substrate temperature of 600°C was studied by Rutherford proton backscattering and exhibits an exponential dependence on the erbium source temperature with an activation energy of ～2.2 eV.     

On the fluorescence enhancement mechanism of Er3+ in germanate glass containing silver particles

The spectral properties of trivalent erbium ions(Er3+) are systematically studied in a melt-quenched germanate glass(60 GeO2-20PbO-10BaO-10K2O-0.1Ag2O) containing silver(Ag) particles.Thermal treatment of the material leads to the precipitation of Ag particles as observed by transmission electron microscopy and confirmed by absorption spectrum for the obvious surface plasmon resonance peak of Ag particles.The fluorescence from Er3+ in the 10-min-annealed sample with Ag particles is found to be 4.2 times enhanced compared with the unannealed sample excited by 488-nm Ar+ laser.A comparison is made between a spectral study performed on the unannealed Er3+-doped sample and the one annealed for 20 min.The data of absorption cross section and Judd-Ofelt intensity parameters show the agreement between the two samples no matter whether there are Ag particles,indicating that the introduction of Ag particles by post-heat treatment has no effect on the crystal field environment of Er3+ ions.The fluorescence enhancement is attributed to the surface plasmon oscillations of Ag particles in germanate glass.     

Photoluminescence of porous silicon saturated with tungsten-tellurite glass with rare-earth metal impurities

It has been shown that the presence of silicon nanoparticles in a layer of porous silicon saturated with tungsten-tellurite glass causes an increase in the photoluminescence quantum efficiency of erbium (1530 nm) by an order of magnitude in the case of long-wavelength excitation and an enhancement of the ytterbium photoluminescence (980 nm) by almost 50 times and erbium photoluminescence by 25 times in the case of short-wavelength pumping. This luminescence enhancement is explained by the formation of additional channels of transfer of external excitation by silicon nanocrystallites in porous silicon to impurity ytterbium and erbium ions in tungsten-tellurite glass.     

Optical properties of erbium-doped porous silicon waveguides

Planar and buried channel porous silicon waveguides (WG) were prepared from p⁺-type silicon substrate by a two-step anodization process. Erbium ions were incorporated into pores of the porous silicon layers by an electrochemical method using ErCl₃-saturated solution. Erbium concentration of around 10²⁰ at/cm³ was determined by energy-dispersive X-ray analysis performed on SEM cross-section. The luminescence properties of erbium ions in the IR range were determined and a luminescence time decay of 420 μs was measured. Optical losses were studied on these WG. The increased losses after doping were discussed.     

Fluorine-doped zinc oxide transparent and conducting electrode by chemical spray synthesis

Highly transparent and conducting fluorine-doped zinc oxide thin films, consisting of spherical nanometer-sized grains, were synthesized onto soda-lime glass substrate by using a chemical spray unit. The effect of fluorine doping concentration in starting solution was investigated. Both doped and undoped films were preferentially oriented along [002] direction. Electrical resistivity decreases from 5.7 x 10^-2 to 8.6 x 10^-3 ohm-cm after 1 at.% fluorine doping, and increases for higher doping concentration. However, surface morphology of films obtained at 3 at.% fluorine doping appeared smooth and uniform. A shift of the edge of the optical transmission in the ultraviolet region as a result of fluorine doping was obtained.