气相传输平衡技术制备LiGaO2薄膜

为获得与GaN薄膜晶格失配小的衬底材料，报道了利用气相传输平衡技术（VTE）在（100）β-Ga2O3单晶衬底上制备高度[001]取向LiGaO2薄膜的方法。经过X射线衍射分析表明得到的薄膜是由单相LiGaO2组成。利用扫描电镜（SEM）观察表面形貌，发现经气相传输平衡技术处理得到的薄膜表面形貌主要受温度的影响，表面晶粒尺寸随温度上升而增大。而X射线衍射测试表明随着温度上升，所得到的薄膜也从多晶向单晶化转变。在经过退火处理后，通过观察吸收谱发现LiGaO2薄膜中产生色心，并且色心的种类与温度有关。表明可以

γ-LiAlO_2晶体的生长及掺镓研究

由于与GaN晶格失配小(约1．4％)，γ-LiAlO2单晶有望成为GaN外延衬底材料。本文首先使用提拉法生长出了尺寸达φ45×50mm^3的γ-LiAlO2单晶，然后采用Ga2O3作为掺杂剂，仍用提拉法生长出了三种不同掺镓浓度的LiAl1-xGaxO2(x=0．1，0．2，0．3)晶体，并用X射线粉末衍射(XRPD)分别对晶体及坩锅中剩余的熔体的成份进行了表征。结果表明LiAl1-xGaxO2(x=0，0．1，0．2，0．3)晶体归属于γ-LiAlO2结晶结构，Ga^3+离子部分地取代Al^3+离子，发生

Studies of magnetic interactions in Mn-doped β-Ga2O3 from first-principles calculations

The magnetic behavior of Mn-doped beta-Ga2O3 is Studied from first-principles calculations within the generalized gradient approximation method. Calculations show that ferromagnetic ordering is always favorable for configurations in which two Mn ions substitute either tetrahedral or octahedral sites, and the ferromagnetic ground state is also sometimes favorable for configurations where one Mn ion substitutes a tetrahedral site and another Mn ion substitutes an octahedral site. However, the configurations of the latter case are less stable than those of the former. (c) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Large-scale synthesis of single-phase, high-quality GaN nanocrystallites

Large-scale synthesis of high-quality GaN nano-crystallites has been achieved by direct reaction of a 4:1 molar Ga/Ga2O3 mixture with ammonia at 950degreesC. X-ray diffraction, transmission electron microscopy, selected-area electron diffraction and high-resolution transmission electron microscopy revealed that the produced GaN nanocrystallites were single hexagonal wurtzite structure with an average particle size around 45 nm. A sharp near band edge emission peak and a blue light emission peak were observed in photoluminescence spectroscopy. The synthesis approach is simple and easy to be commercialized.

Interface of wet oxidized AlGaAs/GaAs distributed Bragg reflectors

The interface of wet oxidized Al0.97Ga0.03As/GaAs in a distributed Bragg reflector (DBR) structure has been studied by means of transmission electron microscopy and Raman spectroscopy. With the extension of oxidation time, the oxide/GaAs interfaces are not abrupt any more. There is an amorphous film near the oxide/GaAs interface, which is Ga2O3 related to the prolonged heating. In the samples oxidized for 10 and 20 min, there are some fissures along the oxidized AlGaAs/GaAs interfaces. In the samples oxidized or in situ annealed for long time, no such fissures are present due to the complete removal of the volatile products.

Preparation and characterization of GaN films by radio frequency magnetron sputtering and carbonized-reaction technique

Radio frequency magnetron sputtering/post-carbonized-reaction technique was adopted to prepare good-quality GaN films on Al2O3(0 0 0 1) substrates. The sputtered Ga2O3 film doped with carbon was used as the precursor for GaN growth. X-ray diffraction (XRD) pattern reveals that the film consists of hexagonal wurtzite GaN. X-ray photoelectron spectroscopy (XPS) shows that no oxygen can be detected. Electrical and room-temperature photoluminescence measurements show that good-quality polycrystalline GaN films were successfully grown on Al2O3(0 0 0 1) substrates. (c) 2005 Elsevier B.V. All rights reserved.

Magnetism and photoluminescence in manganese-gallium oxide nanowires with monoclinic and spinel structures

Manganese-gallium oxide nanowires were synthesized via in situ Mn doping during nanowire growth using a vapor phase evaporation method. The microstructure and composition of the products were characterized via transmission electron microscopy (TEM), field emission scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy. The field and temperature dependence of the magnetization reveal the obvious hysteresis loop and large magnitude of Curie-Weiss temperature. The photoluminescence of the manganese-gallium oxide nanowires were studied in a temperature range between 10 and 300 K. A broad green emission band was observed which is attributed to the T-4(1)-(6)A(1) transition in Mn2+ (3d(5)) ions. (c) 2005 Elsevier B.V. All rights reserved.

Synthesis of GaN nanorods with vertebra-like morphology

GaN nanorods with vertebra-like morphology were synthesized by nitriding Ga2O3/ZnO films at 1000 degrees C for 20min. Ga2O3 thin films and ZnO middle layers were pre-deposited in turn on Si(111) substrates by r.f. magnetron sputtering system. In the flowing ammonia ambient, ZnO was reducted to Zn and Zu sublimated at 1000 degrees C. Ga2O3 was reducted to Ga2O and Ga2O reacted with NH3 to synthesize GaN nanorods in the help of the sublimation of Zn. The structure and morphology of the nanorods were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM), The composition of GaN nanorods was studied by energy dispersive spectroscopy (EDS) and fourier transform infrared (FTIR) system.

场发射(FED)用荧光粉的研制与改性

场发射平板显示器（Field Emission Displays, FED）是一种新发展起来的平板显示器，由于其在亮度、视角、响应时间、工作温度范围、能耗等方面具有优良的特性，成为近年新型显示器研究的热点之一。为实现高效的FED红、绿、蓝全色显示，荧光粉在其中起着十分重要的作用。制备性能优良的场发射用彩色荧光粉是决定将来FED技术成功与否的关键因素之一。 本论文研究的内容包括场发射(FED)用荧光粉的研制和改性工作。在场发射(FED)用荧光粉研制方面，采用溶胶-凝胶方法，制备了一系列新型场发射(FED)用荧光粉，包括稀土离子激活的镓酸镧 [(LaGaO3: Re3+ (Re = Eu, Tb, Dy, Tm, Sm)]体系、铟酸钙[(CaIn2O4: Re3+ (Re = Eu, Pr, Tb, Dy,)]体系、铟酸锶[(SrIn2O4: Re3+ (Re = Pr, Tb, Dy)]体系、镓酸镥[Lu3Ga5O12:Re3+ (Re = Eu, Tb，Pr)]体系，并研究了Pr, Sm, Eu, Tb, Dy, Tm等稀土离子在这些基质中的光致发光、低压阴极射线发光性质和能量传递等性质。在荧光粉的改性方面，采用喷雾热解法制备了Sr2CeO4球形场发射用荧光粉，研究了喷雾前驱体溶液中，聚乙二醇浓度、金属离子浓度、烧结温度对形貌及发光性能的影响；采用溶胶－凝胶方法成功将SiO2表明包覆一层CaTiO3:Pr3+, Y3Al5O12:Ce3+/Tb3+荧光粉，得到单分散，球形形貌，分布均匀，具有核/壳结构的球形荧光粉；另外研究了不同的制备方法对Ga2O3:Dy3+荧光粉的发光性能的影响。所得样品用XRD、FTIR、SEM、TEM、漫反射光谱、光致发光(PL)光谱、荧光寿命曲线、低压阴极射线(CL)光谱等进行表征。 在紫外光激发下，稀土离子激活的镓酸镧彩色荧光粉有基质(LaGaO3)的发射和稀土离子(Eu3+, Tb3+, Dy3+, Tm3+, Sm3+)的特征发射，研究表明在基质和稀土离子之间存在能量传递，其能量传递效率因离子而异。在阴极射线激发下，样品仅有稀土离子(Eu3+, Tb3+, Dy3+, Tm3+, Sm3+)的特征发射。如：LaGaO3: Eu3+发红光，LaGaO3: Dy3+发白光，LaGaO3: Tm3+发蓝光，LaGaO3: Sm3+发黄光，LaGaO3: Sm3+,Tb3+发白光。LaGaO3: Tb3+的发光颜色可通过不同Tb3+的掺杂浓度从蓝光到绿光进行调控。在相同的激发条件下，所制备的蓝光发射的LaGaO3: Tb3+和LaGaO3: Tm3+荧光粉与商业FED用蓝粉(Y2SiO5: Ce3+，日亚化学工业株式会社，NP-1047)相比具有更好的色纯度和更高的发光效率；所制备的黄光发射的LaGaO3: Sm3+荧光粉与商业低压黄色荧光粉((Zn,Cd)S: Ag，日亚化学工业株式会社，NP-1020)相比，色纯度接近，但具有更高的发光效率。并首次实现了单一基质中白光发射(LaGaO3: Sm3+,Tb3+), 所制备的稀土离子激活的镓酸镧彩色荧光粉[(LaGaO3: Re3+ (Re = Eu, Tb, Dy, Tm, Sm )]在场发射器件有潜在的应用。 在稀土离子掺杂的Sr/CaIn2O4荧光粉体系中，在基质Sr/CaIn2O4和掺杂离子Pr3+/Tb3+/Dy3+存在高效能量传递。基质Sr/CaIn2O4吸收能量向激活离子Pr3+/ Tb3+/Dy3+传递，发射为稀土离子Pr3+/Tb3+/Dy3+的特征发射，发光强度、荧光寿命等符合应用要求，在低压电子束激发下，Sr/CaIn2O4: Pr3+/Tb3+/Dy3+荧光粉为稀土离子的特征发射，其低压阴极射线发光(CL)光谱与光致发光(PL)发射光谱一致，CL强度随激发电压，电流密度增加而增强。 对于CaIn2O4:Eu3+荧光粉，进一步研究表明CaIn2O4:Eu3+荧光粉的光致发光和阴极射线发光颜色可以通过掺杂不同浓度的Eu3+从白光，黄光，到红光进行调控。低浓度掺杂发白光，高浓度掺杂发红光，适当的浓度发黄光。 在Lu3Ga5O12:Re3+ (Re = Eu, Tb，Pr)荧光粉体系中，在紫外（UV）和低压阴极射线激发下，所制备的荧光粉Lu3Ga5O12: Eu3+, Lu3Ga5O12: Pr3+为稀土离子Eu3+, Pr3+的特征发射，分别发黄光和绿光。Lu3Ga5O12:Tb3+的发光颜色因Tb3+掺杂浓度不同而不同，低浓度掺杂发蓝光，高浓度发绿光。 Sr2CeO4荧光粉在UV及低压阴极射线激发下发出强烈蓝光，源于配体到金属离子电荷迁移带跃迁(Ce4+-O2-)。其阴极射线发光强度与电压及灯丝电流呈良好的线性关系。 采用溶胶－凝胶方法的核壳结构的SiO2@CaTiO3:Pr3+和SiO2@Y3Al5O12: Ce3+/Tb3+荧光粉, FESEM和TEM结果表明这种核壳结构的发光材料表面致密，厚度均匀，保持了单分散SiO2微球的形貌特征。在UV及低压阴极射线激发下，SiO2@CaTiO3:Pr3+呈强红色发射，源于Pr3+ 的1D2—3H4 (612 nm)跃迁；SiO2@Y3Al5O12:Ce3+和SiO2@Y3Al5O12:Tb3+ 分别发黄绿光和绿光，源于Ce3+的5d-4f和Tb3+的5D4-7FJ (J = 6, 5, 4, 3)跃迁。PL强度可以通过包覆次数调控，CL强度随激发电压及灯丝电流增加而增强。 在Ga2O3:Dy3+荧光粉体系中，采用了溶胶-凝胶，氨水共沉淀，和高温固相法制备了Ga2O3:Dy3+荧光粉并比较了他们的结晶行为，形貌，光致发光和低压阴极射线发光性能。溶胶-凝胶法制备由于原料在分子层次上混合，可以得到纯相，氨水共沉淀和高温固相法原料不如溶胶凝胶法混合均匀，很难得到纯相。溶胶-凝胶和氨水共沉淀所得荧光粉为纳米级别大小，分别呈球形和玉米棒形状；高温固相法微米级别且呈不规则形状。Ga2O3向Dy3+传递能量效率依次按溶胶-凝胶，氨水共沉淀，和高温固相法逐渐降低。在紫外光激发下，分别发白光，蓝白光，蓝光。其低压阴极射线发光与光致发光类似。相比之下，溶胶-凝胶法制备Ga2O3:Dy3+荧光粉比氨水共沉淀和高温固相法制备要好。

ELECTRONIC SPECTROSCOPY STUDIES OF A P2S5NH4OH TREATED GAS(100) SURFACE

Microscopic characteristics of the GaAs(100) surface treated with P2S5/NH4OH solution has been investigated by using Auger-electron spectroscopy (AES) and x-ray photoemission spectroscopy (XPS). AES reveals that only phosphorus and sulfur, but not oxygen, are contained in the interface between passivation film and GaAs substrate. Using XPS it is found that both Ga2O3 and As2O3 are removed from the GaAs surface by the P2S5/NH4OH treatment; instead, gallium sulfide and arsenic sulfide are formed. The passivation film results in a reduction of the density of states of the surface electrons and an improvement of the electronic and optical properties of the GaAs surface.

Preparation and Luminescence Properties of YVO4:Ln and Y(V, P)O-4:Ln (Ln = Eu3+, Sm3+, Dy3+) Nanofibers and Microbelts by Sol-Gel/Electrospinning Process

One-dimensional YVO4:Ln and Y(V, P)O-4:Ln nanofibers and quasi-one-dimensional YVO4:Ln microbelts (Ln = Eu3+, Sm3+, Dy3+) have been prepared by a combination method of sol-gel process and electrospinning. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL), low-voltage cathodoluminescence (CL), and time-resolved emission spectra as well as kinetic decays were used to characterize the resulting samples.

One-Dimensional Ce3+- and/or Tb3+-Doped X-1-Y2SiO5 Nanofibers and Microbelts: Electrospinning Preparation and Luminescent Properties

One-dimensional X-1-Y2SiO5:Ce3+ and -Tb3+ nanofibers and quasi-one-dimensional X-1-Y2SiO5:Ce3+ and -Tb3+ microbelts have been prepared by a simple and cost-effective electrospinning process. X-ray powder diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry, transmission electron microscopy, high-resolution transmission electron microscopy, photoluminescence (PL), and cathodoluminescence spectra were used to characterize the samples. SEM results indicate that the as-prepared fibers and belts are smooth and uniform with a length of several tens to hundreds of micrometers, whose diameters decrease after being annealed at 1000 degrees C for 3 h. Under ultraviolet excitation and low-voltage electron beam excitation, the doped rare earth ions show their characteristic emission, that is, Ce3+ 5d-4f and Tb3+ D-5(4)-F-7(J) (J = 6, 5 4, 3) transitions, respectively.

Preparation and Luminescence Properties of Gd2MoO6:Eu3+ Nanofibers and Nanobelts by Electrospinning

Gd2MoO6:Eu3+ nanofibers and nanobelts have been prepared by a combination method of the sol-gel process and electrospinning. X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy, photoluminescence, and low voltage cathodoluminescence as well as kinetic decays were used to characterize the resulting samples. The results of XRD and FTIR indicate that the Gd2MoO6:Eu3+ samples have crystallized at 600 degrees C with the monoclinic (alpha) structure. The SEM and TEM results indicate that the as-formed precursor fibers and belts are uniform and that the as-prepared nanofibers and nanobelts consist of nanoparticles. Gd2MoO6:Eu3+ phosphors show their strong characteristic emission under UV excitation (353 nm) and low voltage electron-beam excitation (3 kV), making the materials have potential applications in fluorescent lamps and field-emission displays.

Preparation and luminescence properties of Ce3+ and/or Tb3+ doped LaPO4 nanofibers and microbelts by electrospinning

Ce3+ and/or Tb3+ doped LaPO4 nanofibers and microbelts have been prepared by a combination method of sol-gel process and electrospinning. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL), low voltage cathodoluminescence (CL) and time-resolved emission spectra as well as kinetic decays were used to characterize the resulting samples. SEM and TEM results indicate the as-formed precursor fibers and belts are smooth. and the as-prepared nanofibers and microbelts consist of nanoparticles. The doped rare-earth ions show their characteristic emission under ultraviolet excitation, i.e. Ce3+ 5d-4f and Tb3+ D-5(4)-F-7(j) (J = 6-3) transitions, respectively. The energy transfer process from Ce3+ to Tb3+ in LaPO4:Ce3+, Tb3+ nanofibers was further studied by the time-resolved emission spectra.

Preparation and luminescence properties of Mn2+-doped ZnGa2O4 nanofibers via electrospinning process

One-dimensional Mn2+-doped ZnGa2O4 nanofibers were prepared by a simple and cost-effective electrospinning process. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), scanning electron microscopy (SEM), energy-dispersive X-ray spectrum (EDS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL) and cathodoluminescence (CL) spectra as well as kinetic decays were used to characterize the samples. SEM results indicated that the as-formed precursor fibers and those annealed at 700 degrees C are uniform with length of several tens to hundred micrometers, and the diameters of the fibers decrease greatly after being heated at 700 degrees C. Under ultraviolet excitation (246 nm) and low-voltage electron beams (1-3 kV) excitation, the ZnGa2O4:Mn2+ nanofibers presents the blue emission band of the ZnGa2O4 host lattice and the strong green emission with a peak at 505 nm corresponding to the T-4(1)-(6)A(1) transition of Mn2+ ion.