MRI: Development of an Ultrafast Photoluminescence and Transient Absorption Microscope in Ultrahigh Vacuum for Studying Electronic Properties of 2-Dimensional Materials

控制硅等半导体的生长和掺杂的能力，使电子材料的发展成为数字时代现代社会的革命。二维材料，如过渡金属二硫属化物，是一类新的电子材料，有可能在类似规模上开启新的技术进步。近年来，二维材料的生长取得了重大进展。然而，仍然存在开发能够控制二维材料的电子性质的掺杂和加工化学的基本需求。该项目开发的仪器结合了超快光致发光和瞬态吸收显微镜，用于表征二维材料的电子特性，并具有控制掺杂化学的真空系统。它通过使用多种表征方法在样品中的相同位置进行相关测量，大大扩展了NSF材料创新平台用户的研究基础设施，重点关注二维材料。该仪器为宾夕法尼亚州立大学和更广泛的国家二维材料社区的研究人员提供用户基础。研究生和博士后学者使用该仪器获得重要的专业发展经验，促进研讨会和相关的培训模块，提供并通过材料研究所在宾夕法尼亚州州立大学和原子薄多功能涂层中心，这是一个行业大学合作研究中心的广告。超快光致发光和瞬态吸收显微镜在真空系统中的发展开启了在成像平台中以超快时间分辨率探测发射和非发射状态的能力。它还可以控制样品环境和掺杂化学，以表征二维材料的电子和传输特性。这些能力是至关重要的，因为二维材料是单层或几层结构，其电子特性受到表面相互作用的强烈影响。此外，二维材料中的电荷转移和传输所涉及的许多电子状态是弱发射或非发射的，其扩散性质和寿命敏感地取决于材料的外延对准和生长。该仪器的超快显微镜能力与一个真空样品转移系统和附加的制备室相结合，使激子和电荷载流子的动力学和运输能够在空间和时间上分辨，并与它们的生长和掺杂化学相关。可以使用扫描探针和电子显微镜测量以及光电发射研究来研究样品的相同区域的电子和输运性质，以用于完整的表征和设计规则的开发，该设计规则将指导两个-该奖项反映了NSF的法定使命，并通过利用基金会的知识价值和更广泛的影响进行评估，被认为值得支持审查标准。

The ability to control the growth and doping of semiconductors such as silicon enabled the development of electronic materials that revolutionized modern society in the digital age. Two-dimensional materials such as transition metal dichalcogenides are a new class of electronic materials that have the potential to open new technological advances on a similar scale. Major advances in the growth of two-dimensional materials have occurred in recent years. However, there remains a fundamental need to develop doping and processing chemistries that enable the control of the electronic properties of two-dimensional materials. The instrument developed in this project combines an ultrafast photoluminescence and transient absorption microscope, to characterize the electronic properties of two-dimensional materials, with an ultrahigh vacuum system that controls doping chemistries. It significantly expands the research infrastructure for users of the NSF Materials Innovation Platform focused on two-dimensional materials by enabling correlative measurements at the same locations in the samples using multiple characterization methods. The instrument serves a user-base of researchers both at Pennsylvania State University and in the broader national two-dimensional materials community. Graduate students and post-doctoral scholars using the instrument gain important professional development experience by facilitating workshops and associated training modules that are offered and advertised through the Materials Research Institute at Pennsylvania State University and the Center for Atomically Thin Multifunctional Coatings, which is an Industry-University Cooperative Research Center. The development of the ultrafast photoluminescence and transient absorption microscope in an ultrahigh vacuum system opens the ability to probe both emissive and non-emissive states with ultrafast time resolution in an imaging platform. It also enables the control of the sample environment and doping chemistry for characterization of the electronic and transport properties of two-dimensional materials. These capabilities are critical because two-dimensional materials are single- or few layer-structures with electronic properties that are strongly influenced by surface interactions. Furthermore, many of the electronic states involved in charge transfer and transport in two-dimensional materials are weakly- or non-emissive with diffusion properties and lifetimes that depend sensitively on the epitaxial alignment and growth of the materials. The ultrafast microscopy capability of the instrument combined with an ultrahigh vacuum sample transfer system and attached preparation chamber enables the dynamics and transport of excitons and charge carriers to be spatially and temporally resolved and correlated with their growth and doping chemistries. The electronic and transport properties of the same regions of the samples can be investigated using scanned probe and electron microscopy measurements and photoemission studies for complete characterization and development of design rules that will guide the development of two-dimensional materials and devices.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.