【作者】 彭智伟；

【导师】 邹炳锁；

【作者基本信息】 湖南大学 ， 材料物理与化学， 2010， 博士

【摘要】 纳米材料由于小尺寸效应、量子限域效应以及表面效应等引起一些新的物理、化学性质,受到广泛的关注和研究。ZnO、ZnSe、CdS是重要的II-VI族直接带隙化合物半导体材料,具有较大的禁带宽度和激子束缚能。它们在半导体激光器、太阳能电池、发光二极管、场效应晶体管、光电探测器件、气体传感器、光开关等光电子纳米器件方面有很大的应用前景。Gd2O3:Eu³⁺材料由于具有较高的发光量子效率和较好的光谱特性,是一种优质的红色荧光粉,可广泛用于高清晰度电视、投影电视、平板显示、绿色照明等领域,因此得到了广泛的关注。本论文利用热蒸发法制备出高质量ZnO、ZnSe、CdS纳米材料,并对ZnO、ZnSe、CdS纳米材料的晶体结构、形貌、生长机理和光学性质进行了研究。用燃烧合成法成功的制备了Gd2O3:Eu³⁺纳米晶,对其光学性质进行了研究。具体研究内容如下:（1）采用简单的热蒸发方法,成功的制备出ZnO四足和多足纳米结构。所制备的ZnO纳米结构纯度高,为六方纤锌矿结构。ZnO四足和多足纳米结构的足部沿[0001]方向生长。讨论了它们的生长过程。ZnO纳米结构的室温光致发光（PL）谱中出现一个较弱的紫外发射峰和一个较强的绿色发射峰,分别位于383nm和495nm处。其中紫外发射峰来源于近带边发射,绿色发射峰可能是表面缺陷和氧空位共同引起的。通过热蒸发方法,还制备出ZnO纳米棒和星状ZnO纳米结构,并对它们的光学性质进行了研究。（2）运用氢气辅助热蒸发方法制备出大量结晶良好的周期性孪晶结构的ZnSe纳米线。结构分析表明ZnSe纳米线为立方相结构并沿[111]方向生长。室温PL光谱中,在462nm处出现蓝色的近带边发射峰,在500至680nm间出现缺陷相关的发射带。在488nm激光激发下,首次观察到ZnSe纳米线的反斯托克斯（anti-Stokes）发光。用近场光学显微系统观察到ZnSe纳米线的Fabry–Pérot谐振现象。对ZnSe纳米线的光波导性质和表面光伏性质也进行了研究。（3）利用氢气辅助的一步热蒸发法,制备出大量的纤锌矿结构的CdS纳米带和纳米锯（nanosaw）。研究了沉积温度对CdS纳米结构形貌的影响。应用气–液–固（VLS）机理结合气–固（VS）生长机理来解释了CdS纳米结构的形成过程。CdS纳米结构在488nm激光的激发下,发射出波长为512nm的绿色发射峰,对应于CdS的带–带发射。研究了CdS纳米结构的光波导性质,其中CdS纳米带显示出很好的光波导性质。（4）用燃烧合成法成功的制备了Gd2O3:Eu³⁺纳米晶。在甘氨酸–硝酸盐体系中,通过调节甘氨酸与稀土离子的比例得到不同相结构的Gd2O3:Eu³⁺纳米晶,随着甘氨酸比例的增加,纳米晶逐渐从立方相向单斜相转变。研究了甘氨酸和退火温度对尺寸和发光性能的影响。在柠檬酸–硝酸盐体系中成功地制备出纯立方相的Gd2O3:Eu³⁺纳米晶。所制备的立方相Gd2O3:Eu³⁺纳米晶,主发射峰均出现在612nm处,对应于5D0→7F2跃迁。更多还原

【Abstract】 Due to small size effect, quantum confinement effect and surface effect, nanomaterials with unique physical and chemical properties have stimulated great interest and have been investigated extensively. ZnO, ZnSe and CdS, having wide band gap and large exciton binding energy, are important II–IV group direct band semiconductors. These semiconductors have been widely applied in many fields, including nanolasers, solar cell, light-emitting diodes, field-effect transistors, photodetectors, gas sensors, optical switches, etc. The gadolinium oxide doped with europium (Gd₂O₃:Eu³⁺) possess excellent luminescent characteristics and high thermal stability, which are useful in luminescent lighting and optoelectronic devices, including fluorescent lamps, high definition televisions, plasma display panels, flat panel displays, etc. In this dissertation, ZnO, ZnSe and CdS nanostructures have been achieved by the simple thermal evaporation methods. Their morphologies, structures, growth mechanism and optical properties have been investigated in detail. Nanocrystalline Gd₂O₃:Eu³⁺ have been synthesized by low temperature combustion method. The luminescent properties of the nanocrystals were studied. The main research results are shown as followed:（1） Novel ZnO tetrapod and multipod nanostructures were successfully synthesized in bulk quantity through thermal evaporation method. The ZnO nanostructures were of high purity, and were well-crystallized with wurtzite structure. The preferred growth direction of legs was found to be the [0001] direction. Possible growth mechanisms were proposed for the formation of the ZnO nanostructures. Room temperature photoluminescence spectra showed that the as-synthesized ZnO nanostructures had a strong green emission centered at 495 nm and a weak ultraviolet （UV） emission at 383 nm. The UV emission corresponds to the near band edge emission and the green emission probably originates from surface defects and oxygen vacancies. ZnO nanowires and star-like ZnO nanostructures were also synthesized in bulk quantity by thermal evaporation method. Optical properties of these ZnO nanostructures were studied.（2） ZnSe nanowires with zinc-blende structure were synthesized by a simple hydrogen assisted thermal evaporation method. Structure analysis indicated that the nanowires have periodically twinned structures and grown along the [111] direction. Photoluminescence spectra revealed that the nanowires have a near band edge emission at 462 nm and a broad defect-related deep level emission band extending from 500 to 680 nm. Anti-Stokes photoluminescence was observed for the first time in ZnSe nanowires excited by 488 nm laser. Optical waveguide behavior and surface photovoltage （SPV） of ZnSe nanowires was also investigated.（3） By using a simple one-step H2-assisted thermal evaporation method, high quality CdS nanostructures have been successfully fabricated in large scale. The as-synthesized CdS nanostructures consisted of nanobelts and nanosaws with a hexagonal wurtzite structure. The deposition temperature played an important role in defining the size and morphology of the CdS nanostructures. A vapor-liquid-solid （VLS） combined with vapor-solid （VS） growth mechanism was proposed to interpret the formation of CdS nanostructures. Room temperature photoluminescence measurements showed intense green emission centered at 512nm for both nanobelts and nanosaws, which is the band-to-band emission of CdS. The waveguide behavior of both types of CdS nanostructures was observed and discussed. CdS nanobelts exhibited excellent optical waveguide property.（4） Nanocrystalline Gd2O3 doped with europium was synthesized by the facile combustion method. In glycine-nitrate combustion reaction, the structure changed from cubic to monoclinic by varying the glycine-to-metal nitrate （G/M） molar ratio. The influences of glycine and annealing temperatures on the grain size, crystallinity and luminescent properties were clarified. Nanocrystalline Gd2O3:Eu3+ with cubic phase was also prepared by modified combustion synthesis using citric acid as the fuel. Nanocrystalline Gd2O3:Eu3+ with cubic structure showed a dominant emission peak at about 612 nm, being attributed to 5D0→7F2 transition.更多还原