Atomic scale mapping of structural and chemical surface properties by tip-enhanced Raman spectroscopy

十多年来，尖端增强光谱技术，包括尖端增强拉曼光谱（TERS），在化学和结构研究方面取得了突破性进展，直至单轨道水平。虽然通过传统拉曼光谱获得的丰富的化学和结构信息受限于光的衍射极限，但由于原子力显微镜和扫描隧道显微镜等化学不敏感的扫描探针技术具有高空间分辨率，因此TERS受益。*我们的团队已经在纳米电子器件上实现了小于5纳米的出色光学分辨率。为此，在激光的同时照射下，将贵金属尖端带到样品表面附近，以共振激发尖端表面的电子，从而产生近场增强。结果，局部激光场被放大和限制了几个数量级。*虽然这项技术取得了巨大的成功，但由于制造合适的贵金属尖端的复杂性，许多研究人员已经放弃了他们的活动。因此，我们研究计划的一个支柱是系统地优化我们现有的TERS技巧，并由硕士生测试替代过程。第二个支柱是系统地研究决定约束和增强的尖端附近的近场效应。这意味着通过拉曼光谱直接测量近场温度，以及对入射光和出射光之间耦合的偏振依赖研究。第三个支柱将是将该技术应用于纳米电子系统中物理和材料科学中尚未解决的挑战：例如，沿着铁电畴壁或位错的应变的直接测量以及电阻开关二元和三元氧化物中扩展缺陷的化学鉴定。* TERS对于HQP训练的优势在于其实验的复杂性。尖端的近场增强是扫描探针显微镜、光谱学和近场光学共同作用产生的附加值。我们的HQP正在并将在所有这些领域接受培训。所有这些能力都是从行业中寻找的，我们可以通过各种合作研发项目来确认。*该计划的主要影响将是通过HQP在这些领域的培训，其次是通过将这些高度复杂的实验技术部署到加拿大学术界和工业界的研究社区，这将允许对化学，局部结构甚至应变进行非破坏性的调查，例如疲劳后的纳米级分辨率。

Since little more than a decade, tip-enhanced spectroscopy techniques, including tip-enhanced Raman spectroscopy (TERS) provide groundbreaking progress in chemical and structural investigations down to the level of single orbitals. While the wealth of chemical and structural information through conventional Raman spectroscopy is limited to microscopic structures by the diffraction limit of light, TERS benefits from the high spatial resolution of otherwise chemically insensitive scanning probe techniques like atomic force microscopy and scanning tunneling microscopy.*Our group already achieved an outstanding optical resolution of less than five nanometers on nanoelectronic devices. For this purpose, a noble metal tip is brought into proximity of the sample surface under simultaneous illumination of a laser to resonantly excite the tip's surface electrons that will create a near-field enhancement. As a result, the local laser field is amplified and confined by several orders of magnitude. *While this technique has seen tremendous success, many researchers have abandoned their activities due to the complications in the fabrication of suitable noble metal tips. One pillar of our research program is therefore the systematic optimization of our existing TERS tips and the testing of alternative processes by a Master student. The second pillar is the systematic investigation of the near field effects in the proximity of the tip that determine the confinement and the enhancement. This implies direct measurements of the temperature in the near-field by Raman spectroscopy as well as polarization-dependent studies on the coupling between incoming and outgoing light. The third pillar will be the application of this technique to unsolved challenges in physics and material science on nanoelectronic systems: e.g. the direct measurement of strain along ferroelectric domain walls or dislocations and the chemical identification of extended defects in resistively switching binary and ternary oxides.*The strength of TERS for the training of HQP lies in its experimental complexity. The near-field enhancement at the tip apex is an additional value generated by the concerted action of scanning probe microscopy, optical spectroscopy, and near field optics. Our HQP is and will be trained in all these domains. All these competences are searched for from industry as we can confirm through various collaborative R&D projects.*The primary impact of this program will be through the training of HQP in these domains and secondly through the deployment of these highly sophisticated experimental techniques to the Canadian research community in academia and industry which will allow for non-destructive investigations of the chemistry, the local structure and even strain e.g. after fatigue with unrivalled nanoscale resolution.