ABSTRACT
Ion implantation into insulators at high fluence is one of important ways to synthesize compounds involved nanoparticles(NPs).These nano-compounds have potential application in various fields,such as opto-electronic devices,biosensors, optical switches,etc.In this dissertation,we performed the modifications of the size distribution and optical properties of Ag nanoparticles embedded in SiO2by post heavy ion irradiation.The main contents and results are given as follows.
(1)Ag NPs embedded into SiO2were fabricated by implantation of45keV Ag ions at a fluence of5×1016ions/cm2,and their structures and optical absorption properties were characterized in detail.The formation of Ag NPs into SiO2gives rise to a surface plasma resonance absorption peak at about400nm.Results from XTEM show that Ag ion implantation induces formation of Ag nanoparticles in the shallow surface,which mainly have(111)and(200)orientations.The Ag NPs show a bimodal distribution in their sizes.Large Ag NPs are mainly distributed in the region close to the surface,while small ones are located around the end of the Ag ion range. Moreover,HRTEM observations of Ag NPs also indicate that most of the NPs are spherical and have good crystalline structure.
(2)The synthesized Ag NPs were then subjected to irradiation of Ar and Xe ions at the same energy of50
0keV and same fluence of1×1016ions/cm2,respectively.By using techniques of XTEM,UV-vis and GXRD,modifications in structures and optical properties of Ag NPs were investigated.Our results clearly show that post Xe ion irradiation could induce intensity increase in the Ag SPR absorption companying with remarkable decrease in its full width at half maximum of the SPR absorption peak.XTEM results demonstrate that post Xe ion irradiation promotes growth of small Ag NPs around the Ag ion range into larger NPs,which leads to quantity increase of the large NPs.Moreover,results from HRTEM observations also indicate that post Xe ion irradiation gives rise to formation of Ag NPs with various damaged structures.Comparing with Ar ion irradiation at the same conditions,Xe ion irradiation is more effective to modulate the SPR absorption of Ag NPs together with their structures.
(3)By using Xe ion irradiation of the synthesized Ag NPs at the same energy but at different fluences,the effects of Xe irradiation on structures and optical properties of NPs have been studied.Our results clearly show that increasing fluence could give rise to decrease in intensity of Ag SPR absorption accompanying with significant increase in the530nm shoulder absorption peak.In such case,most of the Ag NPs are heavily damaged.Therefore,NPs with special structures,such as octahedron,“star-like”decahedron and so on,were created.Based on our experimental results,we propose that the occurrence of shoulder absorption peak at large wavelength could be related to the fo
rmation of damaged Ag NPs due to post Xe ion irradiation.Moreover, the possible mechanisms for heavy ion irradiation induced modifications in structure and size distribution of Ag NPs have also been discussed and presented.
Our findings may present experimental and theoretical basis for modulation of structure and optical properties of NPs embedded in insulators.
KEY WORDS：Ion Implantation,Ag nanoparticles,Heavy ion irradiation,Surface plasmon resonance
目录
注入第一章绪论 (1)
1.1研究背景 (1)
1.1.1金属纳米颗粒的基本效应及其特殊性能 (2)
1.1.2金属纳米颗粒的制备方法 (5)
1.1.3离子注入技术及原理 (6)
1.2离子注入合成金属纳米颗粒研究现状 (8)
1.3金属纳米颗粒相关理论知识 (10)
1.3.1表面等离子体共振(SPR) (10)
1.3.2Mie理论[23] (13)
1.3.3Maxwell-Garnett(M-G)有效媒质理论[40] (19)
1.4离子辐照引起的纳米颗粒改性研究 (21)
1.5本论文的选题意义和主要研究内容 (22)
第二章实验过程及测试方法 (23)
2.1样品的制备 (23)
2.1.1样品的离子注入条件及SRIM模拟 (23)
2.1.2样品的退火处理 (24)
2.2测试方法及其原理 (26)
2.2.1X射线衍射(XRD) (26)
2.2.2紫外-可见分光光度计(UV-vis) (27)
2.2.3透射电子显微镜(TEM) (28)
2.2.4光致发光(PL)谱 (29)
第三章Ag离子注入SiO2纳米颗粒的合成 (31)
3.1Ag纳米颗粒的表面等离子共振及其热演变规律 (31)
3.2Ag纳米颗粒的结构特性 (34)
3.2.1GXRD结果与分析 (34)
3.2.2TEM结果与分析 (35)
3.3本章小结 (37)
第四章重离子辐照对SiO2中Ag纳米颗粒光学性质及结构的影响 (38)
4.1Ar和Xe离子辐照对Ag纳米颗粒光学性质及结构的影响 (38)
4.1.1Ar离子辐照下Ag纳米颗粒表面等离子共振吸收及其热演变 (39)
4.1.2Xe离子辐照对Ag纳米颗粒光学性质及其结构的影响 (41)
4.2两种重离子辐照对Ag纳米颗粒等离子共振峰影响的机制研究 (49)
4.3较高剂量Xe离子辐照对Ag纳米颗粒的光学性质及其结构的影响 (50)
4.4Ag离子注入及后续重离子辐照SiO2样品的光致发光研究 (57)
4.5本章小结 (59)
第五章结论与展望 (61)
5.1本论文的主要结论 (61)
5.2展望 (62)
参考文献 (63)
发表论文和参加科研情况说明 (70)
致谢 (71)
第一章绪论
第一章绪论
1.1研究背景
纳米材料以其不同于块体材料的独特性质脱颖而出从而引起学术界的广泛兴趣。纳米材料是组成相或晶粒在任一维上尺寸小于100nm的材料，也叫超分子材料，是由粒径尺寸介于1～100nm之间的超细颗粒组成的固体材料。1984年德国Gleiter[1]教授等人首先采用惰性气体凝聚法制备了具有清洁表面的纳米粒子，然后在真空中原位加压制备了Pd、Cu、Fe等金属纳米块体材料，这在学术界引起了广泛的关注。1990年在美国召开了“第1届纳米科学和技术讨论会”，各国科学家积极参与到纳米材料的研究中，不断发现纳米材料的特殊性质，使纳米材料的开发、制备技术和实际应用得到了迅速发展。如今纳米材料种类较多，按其材质分有：纳米金属材料、纳米陶瓷材料、纳米半导体材料、纳米复合材料、纳米聚合材料等等。纳米材料是超微粒材料，被称为“21世纪新材料”，具有许多特异性能。许多物质一旦被制成纳米
材料后，它们的力、热、光、电、磁学、催化、和生物等性质就会发生巨大的变化，具有常规材料所不具备的奇异或反常的理化性质。例如用纳米级金属微粉烧结成的材料，强度和硬度均大大高于原来的金属，尤其是纳米金属如Au、Ag、Cu居然由导电体变成绝缘体。一般的陶瓷强度低并且很脆，但纳米级微粉烧结成的陶瓷不但强度高并且有良好的韧性。纳米材料的熔点会随超细粉的直径的减小而降低。例如金的熔点为1064℃，但10 nm的金粉熔点降低到940℃，6nm的金粉熔点降低到830℃，2nm降低到327℃，因而烧结温度可以大大降低。纳米陶瓷的烧结温度大大低于原来的陶瓷且在常温下韧性大大提高。纳米级的催化剂加入汽油中，可提高内燃机的效率。药物制成纳米微粉，可以注射到血管内顺利进入微血管等。
纳米颗粒的应用前景，除了光、电、磁、敏感和催化特性外，就是由5~50nm 的纳米颗粒在真空下原位压制纳米材料，或制作颗粒涂层，或根据纳米颗粒的特性设计紫外反射涂层、红外吸收涂层、微波隐身涂层，以及其他的纳米功能材料。如今，设计和制备具有特殊性能的金属纳米颗粒已成为最近几年材料科学研究领域内的一大热点。并且随着科技的发展，纳米材料将会受到人们越来越多的重视，纳米材料的应用领域将会不断拓展并且产生革命性的变革。
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