【作者】 王玉泉；

【导师】 张政军；

【作者基本信息】 清华大学 ， 核科学与技术， 2008， 博士

【摘要】 本文旨在研究以真空热蒸发法制备具有不同光电特性的氧化钒薄膜,实验中以纯金属钒片为原料、采用真空蒸发法制备VOx薄膜,并对制备的薄膜进行了一系列不同条件的热处理。在所制备纳米结构的基础上,采用现代测试手段对低维钒氧化物纳米材料的合成、结构和性能进行了深入研究,探讨了组织、结构和性能的相关性,分析了结构形成和性能优化的机理和规律,并且通过各种实验和计算的方式来从机理上进一步解释了这些关系。主要的研究内容和成果如下:(1)体心立方结构二氧化钒新相的发现:通过真空热蒸发的方式在硅片上制备了准直阵列排布的氧化钒(准)纳米棒,经过细致的选区电子衍射分析,我们证明了这些纳米棒的结构为体心立方结构,在结合RBS,XPS以及EELS等实验方法的基础上,我们分析了这些纳米棒的化学组成,并测试了纳米棒薄膜的场发射和光催化等性质。(2)五氧化二钒纳米棒的制备:将220 oC真空热蒸发的三氧化二钒薄膜在空气中进行退火,在500 oC得到了五氧化二钒的纳米棒,对五氧化二钒纳米棒的性能测试可以发现,纳米棒有很强的光致发光现象;同时观察到纳米棒稳定的氧气的敏感性,可以用来作为探测氧气浓度的传感器。(3)五氧化二钒薄膜光学性能的增强:将180 oC真空热蒸发的三氧化二钒薄膜在空气中进行退火,发现通过改变热处理工艺可以改变薄膜中的缺陷浓度,从而进一步控制氧化钒薄膜的光学性能。对于五氧化二钒光学性能的分析我们分别在室温、低温和变温条件下进行了研究,揭示了缺陷工程中通过改变氧缺陷的浓度来调控薄膜的光学性能的作用。(4)强磁场下氧化钒纳米材料的生长和性能变化:磁场下对于薄膜的热处理过程进行了磁场影响的研究,研究结果发现,在磁场的作用下,样品的生长和光致发光性能都受到了影响。实验中我们发现,受磁场的影响越大时,纳米棒的生长越不容易,同时,热处理之后样品的光致发光强度也越低。更多还原

【Abstract】 Vanadium oxides have attracted tremendous interest due to their excellent properties and applications in a wide range of fields. For example, vanadium pentoxide （V2O5） exhibits properties such as chemical sensing, photochromism and catalysis, and is a candidate material for applications in electronic information displays, electrochromic devices, optical-electrical switch and color memory devices, etc., Since materials having reduced dimensions may possess interesting properties that are very different from their bulk states, efforts have been directed recently to the synthesis of nanostructures of vanadium oxides and to the study of their structure-property relationships.In this dissertation, the low-dimensioned Vanadium Oxide nanomaterials were chosen as the objects. Some modern methods were used to study the preparation, structure and properties of low-dimensioned Vanadium Oxide nanomaterials. The main results are as follows:（1） VO₂ of a BCC structure: a new phase in the vanadium oxides systemFilms of aligned rods of vanadium oxides were deposited by heating a sheet of vanadium in a rough vacuum. Careful identification indicates that the rods are VO₂ with a body-centered-cubic structure. Due to the cone shape, they exhibited good field emission property. Upon heating in air at 400oC, the VO₂ rods were oxidized into V₂O₅, which induced intense visible light emission.（2） Synthesis and optical properties of V2O5 nanorodsTwo-step method was proposed to synthesize V2O5 nanorods on planar substrates. The V₂O₅ nanorods are single crystalline and could emit intense visible light at room temperature. This study provides a simple and low-substrate temperature route to fabricate V2O5 nanorods on planar substrates, which might be also applicable to other metal oxides.（3） Optical properties adjustment of V2O5 films by“Defect Engineering”The effect of optical properties with different heat-treatment of V₂O₅ films has been investigated. The relationship of the heat-treatment process on the red PL has been studied in detail. We find the photoluminescence property can be modified by different heat-treatment process. Meantime, the photosensitivity property is also changed. By calculation of the ab initio simulation and positron annihilation method, the PL property can be concluded caused by the Oxygen vacancies.（4） The influence of the strong magnetic fieldThe heat-treatment in strong magnetic field has been investigated. The result shows that the crystallization and PL property will both be modified by magnetic field. Stronger the magnetic field, harder could the nanorods grow, and weaker could the PL intensity be.更多还原