Local investigation of electronically-driven non-thermalsurface restructuring

电子驱动非热表面重组的局部研究

• 批准号: 436994487
• 负责人: Professorin Dr. Karina Morgenstern
• 金额: --
• 依托单位: Lehrstuhl für Physikalische Chemie I
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/436994487?language=en
• 关键词: Local; investigation; electronically; driven; non

Intense short laser pulses are an intriguing tool for tailoring surface properties by producing nanoscale structural changes in the surface layer of an irradiated target to the needs of practical applications. Short-pulse laser irradiation has the ability to bring material into a highly non-equilibrium state. It thus provides insight into material behaviour under extreme conditions. Ultra-short radiation of semi-conductor surfaces below the thermal melting threshold was found to destroy the crystal order on the sub-picosecond time-scale. This has been explained theoretically by a softening of the phonon modes due to electron depletion in the near surface region. Under the same conditions, theory predicts a hardening of the phonon modes for noble metals. The corresponding multiplication of their melting temperature would imply no non-thermal melting for this class of materials. In contrast, we recently discovered that fs-laser irradiation creates surface vacancies and adatoms, at odds with the theoretical prediction. The goal of this project is to use our unique set-up that allows to couple a fs-laser beam directly into the tunneling junction of a low-temperature scanning tunneling microscope to investigate this phenomenon systematically for surfaces of different materials and orientation to eventually understand the phenomenon of non-thermal melting of metals based on microscopic information. Our results will give microscopic insight into the response of metal surfaces to ultra-short laser irradiation.

强短激光脉冲是一种有趣的工具，可以通过在被照射目标的表面层中产生纳米级结构变化来定制表面特性，以满足实际应用的需要。短脉冲激光辐照具有使材料进入高度非平衡状态的能力。因此，它提供了在极端条件下的材料行为的洞察力。在亚皮秒时间尺度上，半导体表面低于热熔化阈值的超短辐射会破坏晶体的有序性。这已经在理论上解释了由于在近表面区域的电子耗尽的声子模式的软化。在相同的条件下，理论预测了贵金属的声子模式的硬化。它们的熔化温度的相应倍增将意味着这类材料没有非热熔化。相反，我们最近发现飞秒激光照射会产生表面空位和吸附原子，这与理论预测不符。该项目的目标是使用我们独特的设置，允许将fs激光束直接耦合到低温扫描隧道显微镜的隧道结中，以系统地研究不同材料和方向的表面的这种现象，最终了解基于微观信息的金属非热熔化现象。我们的研究结果将提供微观洞察金属表面的响应超短激光照射。