CAREER: Ultrafast Carrier Dynamics in 2D Group-IV Monochalcogenides

非技术描述：石墨烯的发现，获得了2010年诺贝尔物理学奖的认可，开启了单层（通常称为二维（2D）材料）研究和开发的时代，在高速光电子学，太阳能转换和化学传感器方面具有潜在的应用。该项目重点研究一类新的二维材料，包括GeS、SnS、SnSe和GeSe。这些材料是环境稳定的，由丰富的地球元素组成，预计将表现出独特的特性，如高导电性和自发电极化，或铁电性。铁电性使它们在下一代太阳能电池中的应用特别有吸引力，因为内在电场有助于将吸收的光转化为电流。这个项目研究了当这些材料吸收光时发生的过程。了解这些过程是必要的，为新的光伏和光电子器件奠定基础。该项目的研究活动与教育和外联活动相结合，目的是鼓励来自不利背景的妇女和学生从事科学和技术事业，并向他们提供指导和研究机会。为了实现这一目标，首席研究员的团队与伍斯特女孩公司合作，这是一个针对高中女生的项目，并举办年度研究论坛，将伍斯特理工学院、伍斯特山社区学院和马萨诸塞州中部其他社区学院的本科生聚集在一起。技术描述：本项目重点研究一类新兴的二维（2D）范德华纳米材料（iv族单硫族）的光激发载流子动力学。据预测，这些材料具有非凡的性能，如强大的室温铁电性和强各向异性的电子和光学性能，可以由外场控制。首席研究员的团队在亚皮秒到纳秒的时间尺度上研究载流子动力学，旨在揭示二维iv族单硫族纳米结构中结构与光电特性之间的关系。该项目的一个关键目标是开发新的方法，通过光学和强太赫兹脉冲来快速、全光地控制这些材料的光学特性和铁电极化。为了实现这些目标，研究小组应用全光超快技术，包括太赫兹发射光谱和时间分辨太赫兹光谱，时间分辨微观光致发光和强太赫兹非线性激发来研究二维iv族纳米结构。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Non-technical Description: Discovery of graphene, recognized by the 2010 Nobel Prize in Physics, ushered an era of research and development of single layer, often called two-dimensional (2D) materials, with potential applications in high-speed optoelectronics, solar energy conversion, and chemical sensors. This project focuses on a new class of 2D materials that includes GeS, SnS, SnSe and GeSe. These materials are environmentally stable, composed of earth abundant elements, and predicted to exhibit unique characteristics such as a high electric conductivity and a spontaneous electric polarization, or ferroelectricity. Ferroelectricity makes them particularly attractive for applications in next generation solar cells as intrinsic electric field facilitates conversion of absorbed light into electric current. This project investigates processes that occur in these materials when they absorb light. Understanding these processes is necessary to lay the foundation to new photovoltaic and optoelectronic devices. The research activities in this project are integrated with educational and outreach activities aimed at inspiring women and students from disadvantaged backgrounds to pursue careers in science and technology and providing them with mentorship and research opportunities. To achieve this goal, the Principal Investigator's team works with Worcester Girls, Inc., a program for high school girls, and hosts annual research forums that bring together undergraduate students from Worcester Polytechnic Institute, Mount Wachusett Community College and other community colleges in Central Massachusetts. Technical Description: This project focuses on dynamics of photoexcited charge carriers in an emergent class of the two-dimensional (2D) van der Waals nanomaterials, group-IV monochalcogenides. These materials have been predicted to possess extraordinary properties such as robust room temperature ferroelectricity and strongly anisotropic electronic and optical properties that can be controlled by external fields. The Principal Investigator's team studies the carrier dynamics over sub-picosecond to nanosecond time scales and aims to uncover the relationship between structure and optoelectronic properties in 2D group-IV monochalcogenide nanostructures. A key objective of this project is development of novel approaches to fast, all-optical control over optical properties and ferroelectric polarization in these materials by means of optical and intense THz pulses. To achieve these objectives, the research team applies all-optical ultrafast techniques including terahertz emission spectroscopy and time-resolved terahertz spectroscopy, time-resolved microscopic photoluminescence and nonlinear excitation with intense terahertz to investigate 2D group-IV nanostructures.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.