【作者】 王卉；

【导师】 刘冰冰；

【作者基本信息】 吉林大学 ， 凝聚态物理学， 2004， 硕士

【摘要】 材料的性质和材料的尺寸大小及形状密切相关。材料的尺寸小到纳米量级时，由于量子限域效应和表面效应的存在,形状和尺寸的改变将直接影响材料的电子结构，从而影响材料的光学、电学等物理性质。球壳状的纳米材料具有特殊的形状，其电子在径向上受到束缚，在切向是自由的，但由于球壳是曲面，所以电子在切向方向的自由度低于电子在平面内的自由度，使其物理性质不仅与体材料也与纳米颗粒相比存在许多差异。因此，研究结构、尺寸和形状各异的纳米材料，改变材料的物理性质，是目前纳米材料研究中的重要课题也是极具挑战性的课题，球壳状纳米材料是目前研究的新热点。硫化锌作为典型的宽禁带半导体材料，其体材料和纳米材料的结构和发光性质的研究一直是倍受关注的课题。具有球壳结构的纳米硫化锌的研究在国际上刚刚开始，其结构、基本性质还没有全面开展。其研究存在很多机会与挑战。利用高压手段为我们深入认识材料的结构、性质以及它们之间的关系提供了十分有效的手段。高压不仅可以改变纳米材料的晶体结构，还能够通过对纳米材料尺寸和形貌的改变调节其电子结构，进而改变其物理性质。高压下体材料、纳米颗粒硫化锌的结构变化已经有较为系统的研究，但是高压下纳米球壳结构硫化锌的研究还未见报道。研究高压下纳米球壳结构硫化锌的结构变化规律，探讨压力对其发光性质的影响，揭示晶体结构、形貌和<WP=71>尺寸变化和光学性质之间的联系，为深入认识具有特殊结构的纳米材料的物理本质，探索具有优异性能的新材料提供了有效途径，该研究具有重要的科学意义和潜在的应用前景。本论文首次利用高压金刚石对顶砧技术和同步辐射X光技术，原位研究了高压下新近合成的纳米球壳结构硫化锌的结构变化规律；研究了准静水压和非静水压不同的压力作用下纳米球壳结构硫化锌的形貌变化，以及不同压力对其光致发光特性的影响，并建立了形貌和发光性质变化之间的联系。利用同步辐射高压原位X光能量色散衍射方法研究了在33.3 GPa准静水压压力范围内纳米ZnS空心球的结构变化，实验发现，纳米ZnS空心球经历了由闪锌矿和纤锌矿共存结构，到纯的闪锌矿相，再到岩盐矿相的相变历程。且该相变过程是可逆的，与体结构、纳米颗粒相变过程一致。首次发现了在高于17.5GPa直到33.3GPa压力范围内存在未知结构。卸压后仍保持原来的结构。研究了准静水压和非静水压不同压力处理后的纳米ZnS空心球的形貌变化和光致发光性质。研究发现，纳米ZnS空心球经33.3GPa准静水压处理后，仍呈空心球状结果，纳米颗粒较为分散；经30.0GPa非静水压处理后，不再呈现中空球状，而是长方形条晶，且有晶化趋势，与原样品相比晶体结构都没发生变化。纳米ZnS空心球的发光与体材料不同，呈一宽化的发光带，这是由纳米尺寸效应和表面效应共同作用的结果。经准静水压处<WP=72>理的纳米ZnS空心球的发光在短波段呈现是对称的发光峰，峰宽明显变窄，发光中心蓝移，同时长波段发光峰消失，这是由于静水压处理后纳米ZnS空心球中的纳米粒子间相互作用减弱，表面态增多，导致发光峰淬灭所致。非静水压处理后的样品呈现两个发光峰，与体材料相比峰形相似，但峰位整体蓝移，这是由于非静水压处理后有晶化趋势，表面和界面效应大大减弱。更多还原

【Abstract】 Comparing with the bulk semiconductor, nanometer scale semiconductors especially some different shaped nanometer scale semiconductors show many good properties which normal materials don’t have. Those properties have attracted many scientists’ interest. ZnS is the wide band gap semiconductor. It has perfect luminescent property. There are thousands of literatures about it in past ten years. ZnS hollow sphere has been synthesized by many methods recently. But the properties of luminescent and under high pressure have not been studied. By using diamond anvil cell and synchrotron radiation source the in situ energy dispersive X-ray diffraction(EDXD) measurements on nano ZnS hollow sphere have been carried out. The luminescent properties of nano ZnS hollow sphere which were treated with hydrostatic pressure and un-hydrostatic pressureIn situ EDXD measurements on nano ZnS hollow sphere have been carried out by using diamond anvil cell with synchrotron radiation. The EDXD pattern of nano ZnS hollow sphere under atmospheric pressure shows that there are two structures of ZnS in the nano ZnS hollow sphere. They are wurtzite and zinc blende ZnS. In high pressure processing, the wurtzite structure ZnS transform to zinc blende structure ZnS as the pressure is up to 11.2 GPa. And, there is a phase transition from zinc blende structure to rocksalt structure when the pressure is up to 16.0 GPa. This phase transition pressure is the same as the normal nanocrystalline zinc sulfide which was reported in <WP=74>many literatures before. An unknown diffraction peak appeared at about 18.3 KeV as the pressure reach 26.8 GPa. This peak can not be found in the same studies of other groups. There are three probabilities of the appear of this unknown peak in our analysis. Firstly, there are two structures of ZnS in the sample at the same time as the pressure reach 26.8 GPa, zinc blende structure and rocksalt structure, there must be some interface between these two structures, and the distance of this interface shoud be constant, this pead may be the diffraction pead of the interface distance. Secondly, the cinnabar structure of ZnS was concluded by many theory calculations, but this structure has not been found in experimental study, and the theory studies did not give the crystal constant, there is probability that the peak is one of the diffraction peaks of the cinnabar structure of ZnS. Lastly, the peak may be the sudden noise of the equipment system.The photo luminescence (PL) spectrum was measured by JOBIN YVON HORIBAC Raman spectrograph excitated by the laser of He-Cd that weavelength is 325nm. Three samples were measured, the raw nano ZnS hollow sphere, the ZnS that had been treat with 33.6 GPa hydrostatic pressure and 30.0GPa un-hydrostatic pressure respectively. There many difference among the three photo luminescence spectrums. The PL of raw nano ZnS hollow sphere become broaden but has not shift Compare to the PL spectrum of normal bulk ZnS. However, the second sample’s PL spectrum become broaden and has a shift to high frequency, but the peak of low frequence vanished. Further more, the third sample’s PL spectrum has <WP=75>two peaks and a shift to high frequency at the same time. With comparing the TEM photos of the same three samples, we find the fact that cause the differences of the PL spectrum of the samples. Nanometer scale is the importan fact which lead to the broadening of the PL spectrum. And it can also cause the shift of the PL spectrum to high frequence band. But the interface effec cause the PL spectrum shift to low frequency band. The shift of the luminescence spectrum is decided by the two facts at the same time. Further more, the appearance of the surface effect can lead the low frequency peak of the PL spectrum of ZnS vanish away or to be weaken. In a summary, our investigations of the structure phase transition of nano ZnS hollow sphere and PL spectrum of the sample after being treated with different high pressure are basal research. It make us know the structure and PL characters clear更多还原