【作者】 张丹莉；

【导师】 吴萍；

【作者基本信息】 汕头大学 ， 材料物理与化学， 2009， 硕士

【摘要】 In₂O₃是一种重要的n型宽带隙半导体材料,具有较高的可见光透过率和红外反射率,主要应用于光电装置的透明导电薄膜。In₂O₃纳米结构材料以其不同于块体材料的微观形貌、光学电学等性质、以及在纳米光电器件中潜在的应用前景,引起人们极大的兴趣。本文以碳热还原法制备In₂O₃纳米材料,获得不同的颗粒形貌和线状形貌,对样品进行了表征和分析。通过对其紫外可见光吸收谱的测试和分析,研究其吸收特性,并确定In₂O₃颗粒的光学带隙。对颗粒和线形貌产物的室温和低温光致发光谱进行测试,研究其发光特性,并对其发光机理进行了探讨。实验制备得到的产物以颗粒形貌为主,这些颗粒的形貌不单一,有完美的正八面体,截角八面体等。颗粒的形貌,粒径大小与温度,保温时间等制备条件有关。随着制备温度的升高,保温时间的延长,颗粒尺寸增大。通过XRD表征,所得颗粒产物为立方晶系In₂O₃,体心立方结构。在制备过程中得到线状形貌产物,直径分布在0.5-1μm范围,长度达几十微米。通过分析其EDS,XPS谱可以认为它是In@In₂O₃/SiO₂芯壳结构,In₂O₃和SiO₂以非化学计量比存在。从我们获得的大量样品的紫外可见光吸收谱均主要表现为两类吸收谱,一类是本征吸收谱,在可见光区没有吸收峰,从400 nm开始吸收系数急剧上升,这类吸收谱中出现陡峭的吸收边,吸收边大致位于310-325 nm范围,具有直接带隙半导体结构,用Tauc作图法获得的光学带隙值在3.0-3.48 eV之间。另一类吸收谱在吸收峰出现在400-600 nm之间,不存在陡峭的吸收边。这类吸收谱我们认为是间接带隙吸收。由光致发光谱的分析可知,两种形貌均有较强的紫外发射。In₂O₃颗粒材料在360-400 nm之间存在较宽的发光带。线状形貌芯壳结构的带边发光峰主要位于365 nm波长附近,测试得到所有线状形貌的中心发光峰均位于360-370 nm之间,相对颗粒形貌,发光带较窄,这个波长范围的发光峰是近带边发光。555 nm和595 nm处均存在两个微弱的深能级缺陷态发光峰。由低温PL谱分析看到,随着温度的增加,发光强度增加,峰位略有蓝移。论文工作对In₂O₃纳米材料可控制备进行了有益的探索,阐述了温度和保温时间对合成材料形貌的影响,得到了有意义的结果。在发光特性方面,通过测试获得In₂O₃颗粒的紫外可见光透射谱,获得其光学带隙值。通过对吸收系数的研究来研究光致发光谱,验证In₂O₃纳米材料的360-400 nm的较宽的发光带是从导带到价带的带-带辐射复合发光以及近带边的缺陷态参与的复合发光,这与目前大多数的In₂O₃纳米材料的与氧空位有关的发光不同。更多还原

【Abstract】 In₂O₃ is a very important n-type wide band gap semiconductor material. It has been widely used as transparent conductive films in photoelectric devices because of its especial properties, such as high visible light transmittance, high infrared reflectivity. I2nO3 nanostructure material has attracted a lot of attentions due to its unique electricity, optics and chemistry properties, which are different from bulk material. It may have potential applications in photoelectronics. In this paper, In₂O₃ nanostructure has been synthesized by carbon thermal reduction method. The crystal structure and morphology of the as-grown product are characterized by X-ray diffraction and scanning electron microscopy. The UV-Vis absorption spectrum and photoluminescence spectrum are measured and analyzed. The optical energy gap and photoluminescence mechanism are discussed.The morphologies of our product are different particles, such as perfect octahedrons, octahedrons with defects. The morphology and size of particles are affected by the preparation conditions such as temperature and growth time. With the increase of temperature and growth time, particle size increases. XRD characterization shows that the crystal structure of the In₂O₃ particles is body-centered cubic. In₂O₃ nanowires are obtained too. The diameter of the In₂O₃ nanowires distributes in the range of 0.5-1μm and the length in tens of microns. The EDS and XPS analyses confirm that the nanowire product is of In@In₂O₃ / SiO₂ core-shell structure.From a large number of samples we have obtained two types of the UV-Vis absorptions spectrum. One of the absorption spectrums shows the feature of direct band-gap semiconductor. In the absorption spectrum there is no absorption peak in the visible light and the absorption obviously increases beginning from 400 nm with a steep absorption edge at 310-325 nm range. By Tauc plot the optical band gap values are obtained between 3.00-3.48 eV. The other absorption spectrum has absorption peak at 400-600 nm with no steep absorption edge. We believe that this type of absorption spectrum is indirect band-gap absorption.Photoluminescence spectrum analysis indicates that both the particles and nanowires have ultraviolet emission. The In₂O₃ particles have strong emission band between 360-400 nm. The nanowires have a broad emission peak centered at 365 nm, which is attributed to near band edge emission. There are two weak deep-level defects emission peak centered at 555 nm and 595 nm. Low-temperature PL spectrum analysis indicates that with the increase of temperature the peaks shift to high energy （blue shift） with the emission intensity increases.This paper has explored the controllable preparation of In₂O₃ nano-materials and some useful results are obtained. The optical band gap value of In₂O₃ particles is measured from the UV-Vis transmission spectrum and the photoluminescence spectrum is studied by fluorescence spectrometry. It is found that the broad 360-400 nm photoluminescence emission band is caused by the radiation emitting near the conduction band and valence band. This is different from the deep-level defects-related emission of In₂O₃ nanomaterials, which is usually attributed to the oxygen vacancy.更多还原