Ultrafast local structural and electronic dynamics in chiral thin films

手性薄膜中的超快局部结构和电子动力学

• 批准号: 525783257
• 负责人: Professor Dr. Thomas Lenzer
• 金额: --
• 依托单位: Arbeitsgruppe Physikalische Chemie II
• 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/525783257?language=en
• 关键词: Ultrafast; local; structural; electronic; dynamics

Ultrafast processes changing the chirality of thin-film materials have important applications in diverse fields, such as films of liquid crystal arrangements and thin layers for spintronics and optical data storage. Such chiral films frequently show substantial inhomogeneities in circular dichroism (CD) on a microscopic length scale and apparent CD signals with hidden contributions from linear dichroism (LD/LD'), circular birefringence (CB) and linear birefringence (LB/LB'). In addition, the locally favored structural order of the films has a strong impact on their chiral response. Understanding the dynamics of such chiral systems requires both ultrafast time resolution and high spatial resolution. In this proposal, we will therefore implement two new methods for chirality-sensitive time-resolved microscopy: ellipsometry-based ultrafast broadband transient circular dichroism microscopy and ultrafast transient circularly polarized luminescence microscopy, both with diffraction-limited spatial resolution. The thin-film characterization using steady-state Müller matrix microscopy will provide complete information regarding polarization changes in terms of the CD, LD/LD', CB and LB/LB' contributions. One of the main investigations in this proposal deals with the time-resolved CD spectroscopy of the structural dynamics in chiral organic thin films. These include the aggregate-induced heterogeneity of the ultrafast local response in chiral copolymer thin films and photoswitch-driven supramolecular rearrangements in pre-aligned cholesteric phases. Another part will address the spatially resolved chiral dynamics of inorganic and hybrid inorganic-organic systems, specifically chiral thin films of perovskite-inspired compounds as well as undoped and doped phase-change materials. Here we aim to understand the dynamics of spin depolarization, i.e. the local "chiral memory" of perovskite materials. The result is relevant to future applications in spintronics. We also investigate the spatial dynamics of low-dimensional perovskites, which are embedded in cholesteric liquid crystals, in order to enhance their chiral optical response. Furthermore, we will use circular polarization as an "added dimension" for ultrafast information storage in phase-change materials. Thin films showing strong "non-CD" contributions will be also characterized using ultrafast Müller matrix spectroscopy.

改变薄膜材料手性的超快过程在许多领域都有重要的应用，如液晶排列薄膜和自旋电子学和光数据存储的薄层。这种手性薄膜通常在微观长度尺度上表现出圆二色性（CD）和明显的CD信号的不均匀性，这些信号隐藏着线性二色性（LD/LD‘）、圆双折射（CB）和线性双折射（LB/LB’）的贡献。此外，薄膜的局部有利结构顺序对其手性反应有很强的影响。了解这种手性系统的动力学需要超快的时间分辨率和高的空间分辨率。因此，在本提案中，我们将实现两种新的手性敏感时间分辨显微镜：基于椭圆偏振的超快宽带瞬态圆二色显微镜和超快瞬态圆偏振发光显微镜，两者都具有衍射限制的空间分辨率。使用稳态<s:1>勒矩阵显微镜对薄膜进行表征将提供有关CD、LD/LD‘、CB和LB/LB’贡献的极化变化的完整信息。本文主要研究手性有机薄膜结构动力学的时间分辨CD谱。这些包括聚集诱导的手性共聚物薄膜中超快局部响应的非均质性和光开关驱动的预排列胆甾相中的超分子重排。另一部分将讨论无机和杂化无机-有机系统的空间分辨手性动力学，特别是钙钛矿激发化合物的手性薄膜以及未掺杂和掺杂的相变材料。在这里，我们的目的是了解自旋去极化的动力学，即钙钛矿材料的局部“手性记忆”。该结果与自旋电子学的未来应用有关。我们还研究了嵌入胆甾液晶中的低维钙钛矿的空间动力学，以增强其手性光学响应。此外，我们将使用圆偏振作为相变材料中超快信息存储的“附加维度”。具有强“非cd”贡献的薄膜也将使用超快<s:1>勒矩阵光谱来表征。