基于正交LA-LIBS和LIF联用的亚微米尺度空间分辨高灵敏元素微区分析研究

Elemental microanalysis of sample with high spatial resolution and high sensitivity has a very important scientific significance for understanding the physical, chemical properties and performances of sample. In order to realize super-diffraction-limited high spatial resolution and high sensitivity elemental microanalysis in solid samples, orthogonal laser ablation (LA) LIBS combined with laser induced fluorescence (LIF) technique will be studied. Short wavelength laser pulse with low energy is used to ablated samples to achieve super-diffraction-limited submicron spatial resolution under ideal focusing and near-threshold laser-ablation conditions; 1064nm laser pulse based on the same Nd:YAG laser is used to excite the ablated sample from the direction which is perpendicular to the propagation direction of ablation laser beam. By irradiating the plasma from the other direction which is perpendicular to the propagation direction of ablation laser beam with a wavelength tunable laser, the ground state atoms of the target element can be stimulated to an excited state by the wavelength-tunable laser tuned to one characteristic line of the element, resulting in a great increase in transition lines from the excited state. Then the analysis sensitivity can be greatly enhanced. The aim of this proposal is to establish a high spatial resolution and high sensitivity elemental microanalysis system. With this technique we can realize microanalysis for different samples, especially for special samples such as special alloy, etc. The spatial resolution can be reached to 200nm and even less than 200nm, the limits of detection of common metal elements can be reached to 50ppm. The technical results can be broadly applied in physical scinece, material science and environmental science, etc.

高空间分辨高灵敏的样品元素微区分析技术对于了解样品的物理、化学特征及其性能有着非常重要的科学意义。为了实现固体样品中的高空间分辨高灵敏的元素微区分析，本项目拟开展基于正交LA-LIBS和LIF联用的样品微区元素分析研究。采用短波长、低能量激光作为剥离激光，在理想的聚焦条件和近阈值剥离条件下获得超光学衍射限亚微米尺度的高空间分辨本领；采用同一纳秒Nd:YAG激光器的1064nm激光从垂直方向二次激发被剥离的样品并利用特定波长的激光激发等离子体中待测元素原子发出荧光来提高光谱分析的灵敏度。该项目可系统建立起一套高空间分辨高灵敏度的元素微区分析系统，并利用所建立的技术开展特种合金等代表性样品的元素微区分析。空间分辨本领达到～200nm甚至更好的水平，常见金属元素检出限达到50ppm。该项目的技术成果可以广泛应用于物理、材料、环境等学科，具有良好的应用前景。

为了实现固体样品中的高空间分辨高灵敏的元素微区分析，本项目提出并研究了正交激光剥离激光诱导击穿和激光诱导荧光联用（LA-LIBS-LIF)技术。项目首先在近剥离阈值的条件下研究了产生强共振激发光谱的条件，建立了一套基于正交LA-LIBS和LIF联用的高分辨高灵敏元素微区分析系统并实现了铜合金中痕量铅元素的高空间分辨检测，空间分辨本领达到～200nm的水平。其次，基于优化的系统实现了不同样品的痕量重金属高灵敏微区分析。在定量分析方面，采用自由定标和一种改进的单点校准的无标样定量检测方法，有效地提高了样品元素定量分析的准确度并扩展了LIBS，LIBS-LIF和LA-SIBS技术在高灵敏检测领域的应用范围。我们还提出了一种可用于正交双脉冲LIBS以及LA-LIBS-LIF的信号增强方法，可以有效解决再加热激光能量利用率低、信号增强效果不理想的问题，显著提升信号强度。该方法有利于减少样品的损耗，可以在微烧蚀的前提下开展高灵敏的元素分析，从而更好的服务于艺术、考古和生物医学等领域的元素分析。项目研究共发表14篇SCI收录的论文，2篇EI收录的论文和1篇中文核心期刊收录的论文；参加3次国际国内学术会议交流；培养了3名博士研究生和5名硕士研究生。本项目的技术成果可以弥补传统LIBS技术以及基于电子或者 X-射线的样品元素微区分析技术的不足，在材料科学、生命科学、微电子、文物鉴定等领域具有较大的应用价值。