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

非技术描述：2010年诺贝尔物理学奖认可的石墨烯的发现，开启了单层材料研发的时代，通常被称为二维(2D)材料，在高速光电子、太阳能转换和化学传感器方面具有潜在的应用。该项目主要关注一类新的2D材料，包括GES、SNS、SnSe和Gese。这些材料环境稳定，由地球上丰富的元素组成，预计将显示出独特的特性，如高电导率和自发电极化，或铁电性。铁电性使其在下一代太阳能电池中的应用特别有吸引力，因为固有电场有助于将吸收的光转化为电流。这个项目研究这些材料吸收光线时发生的过程。了解这些过程对于为新的光伏和光电子器件奠定基础是必要的。该项目的研究活动与教育和外联活动相结合，旨在激励弱势背景的妇女和学生从事科学和技术职业，并为他们提供指导和研究机会。为了实现这一目标，首席调查员团队与伍斯特女孩公司(Wocester Girls，Inc.)合作，这是一个针对高中女孩的项目，并主办年度研究论坛，将来自伍斯特理工学院、沃切塞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：该项目主要研究一类新出现的二维范德华纳米材料--IV族单醇化合物中的光激电荷载流子的动力学。这些材料被预测具有非凡的性质，如强室温铁电性和强各向异性的电子和光学性质，可以由外场控制。首席研究员团队研究亚皮秒到纳秒时间尺度上的载流子动力学，旨在揭示2D第四族单硫化物纳米结构中结构和光电性能之间的关系。该项目的一个关键目标是开发新的方法，通过光学和强烈的太赫兹脉冲来快速、全光学地控制这些材料的光学性质和铁电偏振。为了实现这些目标，研究团队应用了全光超快技术，包括太赫兹发射光谱和时间分辨太赫兹光谱、时间分辨显微光致发光和强烈太赫兹的非线性激发，以研究2D第四类纳米结构。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.