Structural and optical properties of ZnO film by plasma-assisted MOCVD

High quality ZnO film was deposited by plasma-assisted metal-organic chemical vapor deposition (MOCVD). We observed a dominant peak at 34.6° due to (0 0 2) ZnO, which indicated that the growth of ZnO film was strongly C-oriented. The full-width at half-maximum (FWHM) of the -rocking curve was 0.56° indicating relatively small mosaicity. Photoluminescence (PL) measurement was performed at both room temperature and low temperature. Ultraviolet (UV) emission at 3.30 eV was found with high intensity at room temperature while the deep level transition was weakly observed at 2.513 eV. The ratio of the intensity of UV emission to that of deep level emission was as high as 193, which implied high quality of ZnO film. From PL spectrum at 10 K, we observed A-exciton emission at 3.377 eV and D°X bound exciton transition at 3.370 eV. The donor–acceptor transition and LO phonon replicas were observed at 3.333 and 3.241 eV respectively. Raman scattering was performed in back scattering at room temperature. The E₂, A_1(LO) and A_1(TO) mode was seen at 437.6, 575.8 and 380 cm^–1 respectively. In comparison with Raman spectrum of ZnO powder, we found that ZnO film was nearly free of strain, which indicated high crystal quality.     

离子注入诱导量子阱界面混合效应的光致荧光谱研究

采用多元芯片方法获得了一系列不同离子注入剂量的GaAsAlGaAs非对称耦合量子阱单元,通过光致荧光谱测量,研究了单纯的离子注入导致的界面混合效应.荧光光谱行为与有效质量理论计算研究表明,Al原子在异质结界面的扩散在离子注入过程中已基本完成,而热退火作用主要是去除无辐射复合中心. 关键词： 量子阱 离子注入 光致荧光谱 界面混合     

Fluorinated Eu‐Doped SnO2 Nanostructures with Simultaneous Phase and Shape Control and Improved Photoluminescence

Fluorinated Eu‐doped SnO₂ nanostructures with tunable morphology (shuttle‐like and ring‐like) are prepared by a hydrothermal method, using NaF as the morphology controlling agent. X‐ray diffraction, field‐emission scanning electron microscopy, high‐resolution transmission electron microscopy, X‐ray photoelectron spectroscopy, and energy dispersive spectroscopy are used to characterize their phase, shape, lattice structure, composition, and element distribution. The data suggest that Eu³⁺ ions are uniformly embedded into SnO₂ nanocrystallites either through substitution of Sn⁴⁺ ions or through formation of Eu‐F bonds, allowing for high‐level Eu³⁺ doping. Photoluminescence features such as transition intensity ratios and Stark splitting indicate diverse localization of Eu³⁺ ions in the SnO₂ nanoparticles, either in the crystalline lattice or in the grain boundaries. Due to formation of Eu‐F and Sn‐F bonds, the fluorinated surface of SnO₂ nanocrystallites efficiently inhibits the hydroxyl quenching effect, which accounts for their improved photoluminescence intensity.     

Semipolar (11\bar 2\bar 2) ZnO thin films grown on LaAlO3‐buffered LSAT (112) single crystals by pulsed laser deposition

Semipolar (11\bar 2 \bar 2) ZnO was successfully grown on (112) LaAlO₃/(LaAlO₃)_0.29(Sr₂AlTaO₆)_0.35 substrate by pulsed laser deposition. The epitaxial relationship is [11\bar 23]_{\rm ZnO} // [11\bar 1]_{\rm LAO/LSAT} with the polar axis of [000\bar 1]_{\rm ZnO} pointing to the surface. For ZnO films with thickness of 1.6 μm, the threading dislocation density is ～1 × 10⁹ cm^–2, and the density of basal stacking faults is below 1 × 10⁴ cm^–1. The (11\bar 2 \bar 2) ZnO exhibits strong D⁰X emissions with a FWHM of 9 meV and very few green–yellow emissions in the low‐temperature (10 K) and room‐temperature photoluminescence spectra, respectively.

     

Al掺杂四针状ZnO纳米结构的制备及其光致发光和场发射特性

采用热蒸发法成功制备了Al掺杂四针状ZnO纳米结构(T-AZO),利用扫描电子显微镜、X射线衍射仪、荧光光谱仪和场发射测试系统分别研究了不同Al摩尔分数对T-AZO纳米结构表面形貌、微结构、光致发光谱和场发射特性的影响。实验结果表明:T-AZO纳米结构呈现六角纤锌矿结构,Al掺杂对四针状ZnO纳米结构的形貌产生明显影响并且使紫外发射峰产生蓝移。实验中,当Al掺杂摩尔分数为3%时,场发射性能最好,其开启场强为1.33 V/μm,场增强因子为8 420。     

ZnAl2O4：Tb3+荧光粉的合成、结构及其光学性能研究

通过溶胶-凝胶法制备出不同Tb³⁺掺杂浓度和不同二次煅烧温度下的ZnAl₂O₄:Tb³⁺荧光粉, 并利用X射线衍射(XRD)和荧光光谱等对样品进行了表征。由XRD结果可知,当Tb³⁺掺杂的摩尔分数不大于9%,二次煅烧温度在600℃以上时,所得粉体为结晶性良好的尖晶石相。在紫外光激发下,ZnAl₂O₄:Tb³⁺荧光粉的发射光谱由位于488 nm(⁵D₄→⁷F₆)、542 nm(⁵D₄→⁷F₅)、587 nm(⁵D₄→⁷F₄ )和621.5 nm(⁵D₄→⁷F₃)的4个发射峰组成。研究发现,Tb³⁺的掺杂浓度和二次煅烧温度对样品发光强度有着重要影响,当Tb³⁺的摩尔分数为5%,二次煅烧温度为900℃时,ZnAl₂O₄:Tb³⁺荧光粉的发光最强,继续增加Tb³⁺掺杂浓度或提高煅烧温度,分别会出现浓度猝灭和温度猝灭现象。     

Resonant energy transfer from nanocrystal Si to β-FeSi2 in hybrid Si/β-FeSi2 film

The photoluminescence （PL） characteristics of hybrid β-FeSi2/Si and pure β-FeSi2 films fabricated by pulsed laser deposition at 20 K are investigated. The intensity of the 1.54-μm PL from the former is enhanced, but the enhancement vanishes when the excitation wavelength is larger than the widened band gap of Si nanocrystal. Time-resolved PL decay measurements reveal that the lifetime of the photo-excited carriers in the hybrid β-FeSi2/Si film is longer than that in the pure β-FeSi2 film, providing evidence that the PL enhancement results from the resonant charge transfer from nanocrystalline Si to β-FeSi2.     

Optical and magnetic properties of InFeP layers prepared by Fe~+ implantation

InFeP layers are prepared by ion implantation of InP with 100-keV Fe＋ ions to a dose of 5 ×10^16 cm-2 and investigated by optical, magnetic, and ion beam analysis measurements. Photoluminescence measurements show a deep-level peak at 1.035 eV due to Fe in InP and two exciton-related luminescences at 1.426 eV and 1.376 eV in the implanted samples annealed at 400℃. Conversion electron Mossbauer spectroscopy reveals a doublet corresponding to Fe3＋ ions in the indium sites. Atomic force microscopy and magnetic force microscopy show that magnetic clusters are formed in the annealing process. The magnetization-field hysteresis loops show ferromagnetic properties persisting up to room temperature with a coercive field of 100 0e （10e = 79.5775 A-m-1）, saturation magnetization of 4.35 × 10-5 emu, and remnant magnetization of 4.4× 10 6 emu.     

氩、氢混合等离子体处理对GaAs表面性质及发光特性的影响

介绍了一种氩、氢混合等离子体清洗GaAs基片的实验工艺,深入研究了氩、氢等离子体清洗GaAs表面污染物和氧化层,并活化表面性能的基本原理,同时讨论了气体流量、溅射功率和清洗时间等不同溅射参数对等离子体清洗效果的影响。结果表明,在氩气和氢气流量分别为10 cm³/min和30 cm³/min,溅射功率为20 W,清洗时间为15 min的条件下,GaAs样品的光致发光强度提高达139.12%,样品表面的As-O键和Ga-O键基本消失。     

共掺Mo6+离子的Ca4LaNbW4O20∶Eu3+荧光粉的发光特性

采用高温固相法制备了红色荧光粉Ca4LaNb(W1-x Mo x)4O20∶Eu3+并研究了样品的发光性质。Ca4LaNbW4O20∶Eu3+的激发光谱中包含一个宽的激发带,峰值位于275 nm,归属于WO2-4基团的电荷迁移跃迁。随着Mo6+离子的掺入,Ca4LaNbW4O20∶Eu3+位于275 nm处的吸收带变宽,其原因是O2--Eu3+的电荷迁移跃迁增强。在Ca4LaNb(W1-x Mo x)4O20∶Eu3+的发射光谱中,400~500 nm间较宽的发射带属于WO2-4基团的发射带,而位于591 nm和616 nm的尖锐的发射峰分别属于Eu3+的5D0→7F1磁偶极跃迁和5D0→7F2电偶极跃迁发射。随着Mo6+离子浓度的增加,WO2-4基团的发射带强度下降,从而提高了色纯度。