Study on Nanoinstability of Nanowire as Athermally Induced by Electron Beam Irradiation and Related Physics Issues

当今纳米科学技术的研究背景要求我们不仅要从纳米空间尺度（极小空间限制），而且还要从纳、皮、飞秒时间尺度（超快时间限制）去揭示材料的结构和性能。在现有文献中，已经有了关于电子束辐照下晶态Si纳米线、ZnO纳米线、金属纳米线的结构转变和彼此间焊接等交互作用，以及电子束辐照辅助下，通过外部作用力实现SiO2、Li2O、Si纳米线的塑性伸长或弯曲变形等零散、不系统的文献报道。尽管如此，它们并没有从非平衡、极度局域和超快角度对高能电子束辐照下纳米线的结构不稳定性转变和相关物理问题进行系统性研究。因此，对纳米线结构不稳定性转变起关键作用的纳尺寸效应（或表面纳米曲率效应）以及电子束超快过程效应（或电子束非热...With the rapid development of nanoscience and nanotechnology, we areincreasingly motivated to reveal structure and property of materials not only at nanometer scale (or under extremely small space limitation) but also at nano-, pisco-, or femto-second scale (or under extremely short time limitation). In current literature, there are some scattered and unsystematic reports on structure changes of a...学位：理学博士院系专业：物理科学与技术学院_凝聚态物理学号：1982013015423

电子束辐照下两种不同构型非晶SiO_x纳米线的不稳定性比较

室温下利用高分辨透射电子显微镜对比观察了两端固定和一端固定、另一端自由的非晶SiO_x纳米线在电子束辐照下的结构不稳定性。实验发现,在相同辐照条件下,两端固定的非晶SiO_x纳米线径向持续均匀收缩;一端固定、另一端自由的非晶SiO_x纳米线轴向长度持续快速收缩,而径向无明显变化。利用我们最近提出的非晶SiO_x纳米线表面纳米曲率效应和电子束诱导非热激活效应基础上发展的原子'融蒸'和'扩散'机制,对上述电子束辐照下非晶SiO_x纳米线结构不稳定现象进行了全新、合理的解释

Controllable surface modification of nanowires by focused-electron-beam-induced deposition of carbon

作为一种典型的准一维纳米材料,纳米线具有纳米材料所特有的小尺寸效应或纳米曲率效应,经表面修饰的纳米线一般具有不同于普通纳米线的特殊性质.利用实验室发展成熟的透射电子显微镜原位辐照技术,以透射电子显微镜中残留的有机气体分子为前驱体,成功地在纳米线表面可控沉积了非晶碳纳米颗粒和碳纳米棒,以及局域凸起的非晶碳膜并形成局域肿大的同轴结构.实验结果表明,该方法能够方便地通过控制聚焦电子束的束斑尺寸、辐照方式、辐照时间以及辐照位置等参数,在纳米线表面精确可控地沉积各种非晶碳纳米结构,从而实现纳米线的表面可控修饰.对聚焦电子束辐照下基于纳米线的各种碳纳米结构的可能沉积机理作了进一步地探索,并针对透射电子显微镜中如何减少因电子束辐照诱导非晶碳沉积造成的样品污染提出了几点建议.Surface-modified nanowires generally own some additional properties,and thus in this paper,the authors particularly studied the surface modification of nanowires via irradiation of focused electron beam in a Tecnai F-30 field emission transmission electron microscope (TEM).It was observed that controllable deposition of all kinds of amorphous carbon nanostructures,such as carbon particles,carbon rods and carbon films with local bulging,could be got on the surface of nanowires after intentional irradiation.In details,the controllable deposition of carbon nanostructures could be easily and precisely controlled by changing of some irradiation parameters such as beam spot diameter,irradiation manner,irradiation time and irradiation position.The possible deposition mechanisms of carbon nanostructures on the wire surface as induced by irradiation of focused electron beam in TEM were further discussed.In addition,some suggestions were also proposed on reducing of specimen pollution caused by undesired deposition of amorphous carbon materials during the irradiation.国家科技计划国际科技合作与交流专项(编号:2008DFA51230);国家重点基础研究发展计划(编号:2007CB936603);国家自然科学基金(批准号:90401022;60776007);中澳科技合作特别基金(编号:20050222);教育部科技研究重点项目(编号:105099)资

Self-assembly of patterned copper films by small incident angle deposition

利用新发展的小入射角沉积(SIAd)技术在玻璃衬底上自组装制备了图案化金属铜膜.利用金相显微镜(MM)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)/选区电子衍射(SAEd)/能量弥散X射线光谱仪(EdX)以及X射线衍射仪(Xrd)等技术对所制备的图案化金属铜膜进行了表征.通过分析对比SIAd和垂直入射沉积(nId)铜沉积物的形貌和结构差异,揭示了图案化金属铜膜的形成机理.In this paper, the small incident angle deposition (SIAD) technique to fabricate patterned copper films is developed.The fabricated patterned copper films are characterized by metallurgical microscopy, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction.Analysis of morphological and structural differences between copper deposits formed by SIAD and normal incidence deposition reveals the formation mechanisms of the patterned copper films.常州大学自然科学基金(ZMF02020042); 国家科技计划国际科技合作与交流专项(2008DFA51230)资

Structural instabilities of single-walled carbon nanotubes under electron beam irradiation

利用透射电镜(TEM)原位观察了一端固定一端自由和两端固定的单壁碳纳米管(SWNT(s))在电子束辐照下的结构不稳定性。研究发现,一端固定一端自由的SWNT优先轴向和径向收缩后颈缩,最后形成一个个碳笼紧密相连的收缩结构("碳笼-碳笼"结构);两端固定的SWNT仅径向收缩后颈缩,最后形成许多碳笼相连的类似结构。此外,后者在电子束辐照下断开后又会重新粘合起来,表现出很强的表面塑性流变或湿润效应。这些电子束辐照诱导SWNTs非热激活结构不稳定性现象可以用我们最近提出的表面纳米曲率效应和能量束超快诱导软模和点阵失稳进行全新、全面、正确的解释。Structural instabilities of single-walled carbon nanotubes(SWNTs) of two typical settings,which are respectively fixed at only one end and at both ends,were investigated under electron beam irradiation by our developed in-situ transmission electron microscopy observation technique.It was observed that the tube fixed only at one end preferentially shrunk in axis direction first,then shrunk and necked in diameter,and finally formed a carbon cagelike strand structure at the tube free end whereas the tube fixed at both ends merely shrunk and necked in diameter with the similar formation of carbon cage-like strand structure.It is especially intriguing that the necked carbon cage-like strand structure in the latter case was able to re-fuse after breaking and thus demonstrated a strong wetting ability and an amazing athermal plastic flow on the surface of the SWNT fixed at both ends under the electron beam irradiation at room temperature.The above athermal structural instabilities of SWNTs as induced by electron beam irradiation can be well accounted for by the completely new concepts of the surface nanocurvature and ultrafast energetic beam-induced soft mode and lattice instability as we recently proposed.国家自然科学基金资助项目(No.90401022No.90406024);; 国家教育部科技重点资助项目(No.105099);; 中澳科技合作特别基金资助项目(No.20050222);; 福建省科技项目(No.2005HZ1019);; 厦门市科技局资助项目(No.3502Z20055010

Fractal growth of deposited carbon on the unirradiated surface of SiO_x nanowires induced by focused electron beam

电子束诱导沉积技术已被证实可以实现各种材料的分形生长,但是目前尚未发现聚焦电子束辐照下低维纳米结构表面未受辐照位置的分形生长现象,造成了聚焦电子束诱导分形生长机理研究的空白与片面性.以透射电子显微镜中残留的有机气体分子为前驱体,室温下利用高能聚焦电子束辐照,研究了一维非晶SIOX纳米线表面未受辐照位置碳沉积的分形生长.利用高分辨透射电子显微镜对SIOX纳米线表面非晶碳的沉积过程进行原位观察,发现了SIOX纳米线表面未受辐照位置非晶碳的不均匀沉积及分形生长,并捕捉到了碳沉积分形生长过程的细节.同时对聚焦电子束诱导SIOX纳米线表面未受辐照位置非晶碳的不均匀沉积及分形生长机理进行了深入的探索.It has been proven that electron beam induced deposition technique can lead to fractal growth of some materials,while there is no report on the fractal growth on the unirradiated surface of low dimensional nanostructures as induced by focused electron beam irradiation.In this paper,the fractal growth on the unirradiated surface of amorphous SiOx nanowire was designedly investigated via focused electron beam irradiation at room temperature,and the deposition details of amorphous carbon on the surface of SiOx nanowire was in-situ observed by a high resolution transmission electron microscope.It was found that a series of intriguing phenomena such as nonuniform deposition and fractal growth of amorphous carbon occured on the unirradiated surface of SiOx nanowire.More importantly,details of the fractal growth process of deposited carbon were also in-situ observed.Furthermore,the nonuniform deposition and fractal growth mechanisms of amorphous carbon occurred on the unirradiated surface of SiOx nanowire under focused electron beam irradiation were proposed and discussed.国家科技计划国际科技合作与交流专项(2008DFA51230);国家重点基础研究发展计划(2007CB936603);国家自然科学基金(90401022;60776007);中澳科技合作特别基金(20050222);教育部科技研究重点项目(105099)资

负偏置沉积法可控制备CuO多孔纳米结构薄膜

由于具有低成本、无毒、铜源丰富等优点,以及在气敏传感器、太阳能电池、光催化等领域的潜在应用前景,CuO薄膜引起了人们的广泛关注.采用射频平衡磁控溅射镀膜系统,在薄膜沉积过程中通过施加不同衬底负偏压可控制备了CuO多孔纳米结构薄膜.研究发现,所得CuO薄膜具有灵活可调的孔隙度和纳米构筑单元形貌特征,并且它们与衬底负偏压的大小密切相关;薄膜沿衬底法线方向呈柱状生长且具有显著的（111）择优取向;禁带宽度在2.0.35 eV之间可调.很明显地,传统的溅射离子轰击、再溅射理论并不适合用来解释上述负偏压效应,因此在此基础上提出了一种负偏置沉积过程中材料原子或分子在薄膜表面选择性优先沉积机制.国家自然科学基金(51501018,11574255)；江苏省自然科学基金(BK20150267,BK20141169)；江西省教育厅科技项目(GJJ161197)；江西省自然科学基金(20132BAB212005)资助

Controllable fabrication of Cu_2O porous nanostructured films by negative bias deposition method

由于具有低成本、无毒、铜源丰富等优点,以及在气敏传感器、太阳能电池、光催化等领域的潜在应用前景,; Cu_2O薄膜引起了人们的广泛关注.采用射频平衡磁控溅射镀膜系统,在薄膜沉积过程中通过施加不同衬底负偏压可控制备了Cu_2O多孔纳米结构薄膜.研; 究发现,所得Cu_2O薄膜具有灵活可调的孔隙度和纳米构筑单元形貌特征,并且它们与衬底负偏压的大小密切相关;薄膜沿衬底法线方向呈柱状生长且具有显著; 的(111)择优取向;禁带宽度在2.0~2.35; eV之间可调.很明显地,传统的溅射离子轰击、再溅射理论并不适合用来解释上述负偏压效应,因此在此基础上提出了一种负偏置沉积过程中材料原子或分子在薄; 膜表面选择性优先沉积机制.As one of the most common two kinds of copper oxides, cuprous oxide; (Cu_2O) is an important p-type transition metal oxide semiconductor; material. Due to the advantages of low-cost, non-toxicity and abundant; copper sources and the potential applications in the fields of gas; sensors, solar cells and photocatalysts, thin films of Cu_2O have; attracted great interest of researchers. To enhance the performances of; the above Cu_2O-based surface-sensitive devices and materials, the; researchers tend to prepare Cu_2O thin films of porous or even; nanoporous structures. However, there is still no effective method; available for the controllable fabrication of Cu_2O porous; nanostructured films (or porous nanostructure-films, short for PNFs),; which owns not only the common features of porous thin films but also; the unique properties of nanosize building units. By using a; radiofrequency balanced magnetron sputtering (MS) deposition system, in; this paper, Cu_2O PNFs were prepared on clean glass slides by applying; different negative bias voltage during film deposition. After the; preparation, a field-emission scanning electron microscope (FESEM), a; grazing-incidence X-ray diffractometer (GIXRD) and an; ultraviolet-visible (UV-Vis) spectrophotometer were applied subsequently; for the detailed characterizations of surface morphology, texture and; optical property respectively. It was observed that the as-prepared; Cu_2O PNFs exhibited flexible porosities and nanosize building units,; which were greatly dependent on the substrate negative bias voltage. In; particular, when the substrate bias voltage was kept at -50 or -150 V,; the as-prepared Cu_2O PNFs both demonstrated intriguing triangular; pyramid-like nanostructures with distinct edges and corners on the; porous film surface. Further, the side view FESEM images and the; out-of-plane GIXRD spectra demonstrated a columnar growth of the Cu_2O; PNFs with a notable preferential orientation of (111). The optical; testing results showed that the band gap of the Cu_2O PNFs obtained at; different negative bias voltages was tunable between 2.0 and 2.35 eV,; which demonstrated a little red or blue shift relative to that of bulk; Cu_2O (2.17 eV). It is expected that the traditional ion bombardment and; re-sputtering theories are not suitable for the explanation of the above; bias voltage effects. This is because the traditional ion bombardment; and re-sputtering theories were proposed to account for the bias; deposition in an unbalanced magnetron sputtering (MS) system rather than; the present balanced MS system. Further, the experimentally observed; non-linearly changed density or porosity of the Cu_2O PNFs with the bias; voltage at relatively low values and the common even surface at; relatively high values confirmed this viewpoint. Based on the above; findings and analysis, a selectively preferential deposition of material; atoms or molecules on the film surface during the negative bias; deposition was proposed. That is, when the substrate is negatively; biased, the tipcharging effect of electrons would occur on the nanoscale; rough surface of the substrate or the depositing film. The resulting; electric field near the substrate or film surface is non-uniform and; could be regarded as an assembly of many electric fields of particle or; tip charges.国家自然科学基金; 江苏省自然科学基金; 江西省教育厅科技项目; 江西省自然科学基

Selective amorphization and novel coaxial structure formation of a single crystal Si nanowire induced by focused electron beam irradiation

使用改进的原位透射电镜观察技术研究了室温下单晶SI纳米线在聚焦电子束辐照下的结构不稳定性。实验发现辐照区域内单晶SI纳米线外层会优先非晶化且局部径向膨胀,并随辐照剂量增加进一步形成新型3层包裹同轴结构等一系列有趣的变化。传统knOCk-On机制和电子束热效应并不能完全解释上述实验现象,然而利用最近提出的纳米曲率效应和电子束非热激活效应则能得到较好的解释。Structural instability of a single crystal Si nanowire at room temperature under focused electron beam irradiation was investigated by our developed in-situ transmission electron microscopy observation technique.It was observed that a series of intriguing changes such as preferential amorphization at the surface of Si nanowire,local bulging in the radial direction and formation of a novel three layers-packaged coaxial structure of Si nanowire with the increasing of electron doses during the irradiation.The possible mechanism for such phenomena was proposed and further discussed by completely new concepts of nanocurvature effect and energetic beaminduced athermal activation effect,while the current knock-on mechanism and electron beam heating effect seemed inadequate to explain these processes.国家自然科学基金资助项目(11074207); 国家重点基础研究发展计划(973计划)资助项目(2007CB936603); 教育部高等学校博士学科点专项科研基金资助项目(20100121110023); 国家科技计划国际科技合作与交流专项资助项目(2008DFA51230

聚焦电子束诱导碳沉积实现纳米线表面可控修饰

作为一种典型的准一维纳米材料,纳米线具有纳米材料所特有的小尺寸效应或纳米曲率效应,经表面修饰的纳米线一般具有不同于普通纳米线的特殊性质.利用实验室发展成熟的透射电子显微镜原位辐照技术,以透射电子显微镜中残留的有机气体分子为前驱体,成功地在纳米线表面可控沉积了非晶碳纳米颗粒和碳纳米棒,以及局域凸起的非晶碳膜并形成局域肿大的同轴结构.实验结果表明,该方法能够方便地通过控制聚焦电子束的束斑尺寸,辐照方式,辐照时间以及辐照位置等参数,在纳米线表面精确可控地沉积各种非晶碳纳米结构,从而实现纳米线的表面可控修饰.对聚焦电子束辐照下基于纳米线的各种碳纳米结构的可能沉积机理作了进一步地探索,并针对透射电子显微镜中如何减少因电子束辐照诱导非晶碳沉积造成的样品污染提出了几点建