Sub-Surface Structural Damages in Laser-assisted Surface Nanostructuring: Experimental Characterization and Atomistic Modeling

作为一种自上而下的纳米加工技术，激光辅助扫描隧道显微镜（STM）在表面纳米修复、纳米到微尺度集成纳米电子学和纳米光子学的制造和表征、纳米颗粒和纳米管/线的加工和对准等方面具有广泛的应用前景。激光辅助STM制备的表面纳米结构的纳米级残余应力/应变和结构损伤会显著改变表面纳米结构的局部力学、热、光学和电子特性，从而降低表面纳米结构的功能和可靠性。针对这一关键问题，该项目的目标是：(1)开发激光辅助STM表面纳米结构中亚表面纳米级结构损伤形成的基础物理知识基础；(2)探索和确定实验参数如何以及在多大程度上影响亚表面纳米级结构损伤的形成。通过扫描隧道光谱和高分辨率透射电子显微镜，我们将在分子/原子水平上对激光辅助STM纳米结构中的应变和结构损伤进行深入研究。这是在如此小的尺度上定量探索残余应变和结构损伤特征的早期尝试。这种大规模的分子动力学模拟将为激光辅助STM表面纳米结构中应力/应变和结构损伤的发展和传播/迁移提供基本和动态的理解。这些有策略地结合实验和数值研究将揭示残余应变和结构损伤之间的关系以及不同的实验参数。预期的结果有助于减少残余应力/应变和结构损伤，提高微/纳米级系统的功能/性能和可靠性。充分了解纳米结构损伤形成背后的机制和驱动力，将有助于建立成功开发激光辅助STM纳米结构技术并将其应用于工业所需的基本知识构建块。研究结果将通过在专业会议上的演讲、在高知名度期刊上的出版物、跨部门研讨会和一个专门的项目网站广泛传播。研究成果将整合到新课程“纳米尺度和超短时间域的热传递”和“纳米技术导论”中。广泛的本科生参与将通过暑期研究就业。将作出特别努力，从传统上在高等教育中人数不足的群体，特别是妇女和少数民族中招收研究生和本科生。将为K-12学生开发一个专门设计的教学功能网站。

As a top-down nanofabrication technique, the laser-assisted scanning tunneling microscope (STM) provides a wide variety of potential applications in surface nano-repair, fabrication and characterization of nano- to microscale integrated nanoelectronics and nanophotonics, and machining and aligning of nanoparticles and nanotubes/wires. The nanoscale residual stress/strain and structural damages in surface nanostructures fabricated using laser-assisted STM can significantly change the local mechanical, thermal, optical, and electronic characteristics, thereby degrading the functionality and reliability of surface nanostructures. Targeting this critical problem, the objectives of the project are to (1) develop the knowledge base about the underlying physics in the formation of sub-surface nanoscale structural damages in surface nanostructuring with laser-assisted STM, and (2) explore and identify how and to what extent the experimental parameters affect the formation of sub-surface nanoscale structural damages. Significant insights into strain and structural damages at molecular/atomic levels in nanostructuring by laser-assisted STM will be attained using both scanning tunneling spectroscopy and high-resolution transmission electron microscopy. This represents the early attempts to quantitatively explore the characteristics of the residual strain and structural damages at such a small scale. This large-scale molecular dynamics simulation will provide fundamental and dynamic understanding of the development and propagation/migration of both stress/strain and structural damages in surface nanostructuring with laser-assisted STM. These strategically combined experimental and numerical investigations will reveal the correlations between residual strain and structural damages and varied experimental parameters.The anticipated outcomes are instrumental for minimizing residual stress/strain and structural damages and improving the function/performance and dependability of micro/nanoscale systems. Sufficient insights into the mechanisms and driving forces behind the formation of nanoscale structural damages will lead to the establishment of basic knowledge building blocks required for successful development of the nanostructuring technology with laser-assisted STM and its implementation to industries. Results of the research will be broadly disseminated through presentations at professional conferences, publications in highly visible refereed journals, across-department seminars, and a dedicated project website. The research results will be integrated into new courses "Heat Transfer at Nanoscales and in Ultra-short Time Domain" and "Introduction to Nanotechnology." Extensive undergraduate participation will be involved via summer research employment. Special efforts will be taken to recruit graduate and undergraduate students from groups traditionally underrepresented in higher education, particularly women and minorities. A specially designed website will be developed for instructional functions for K-12 students.