Engineering Electronic Structure of 2D Semiconductors with Non-Equilibrium Processing

技术描述：该项目的研究目标是通过极不平衡的材料加工来调整二维(2D)半导体的电子结构。为此，2D半导体合金是通过混合原本不相容的2D半导体和动力学控制的方法来稳定非平衡相而形成的，其中电子和结构属性是根据命令进行设计的。由此产生的2D半导体合金有望为实现现有材料无法实现的各种潜在技术提供一个新的平台。研究的具体目标是：i)在任意成分的二维极限下合金化层状半导体。这是使用脉冲激光合金化方法实现的，并通过结构和物理表征工具对产品进行评估；以及ii)通过设计合适的成分和异质结构来设计2D合金的电子结构。对它们的带隙、能带、有效质量和载流子掺杂率进行了设计和计算，并与密度泛函理论和格林函数计算进行了比较，以期对其有全面的了解。非技术描述：量子极限的层状半导体正在成为创新信息和能量转换技术的一类重要材料。与现有的大量块状半导体不同，这些2D半导体的全部潜力受到现有成员数量较少的限制：主要是过渡金属硫化物。该项目旨在通过创建2D半导体合金库来消除这一限制，其中电子结构经过设计并不断调整以满足特定需求。与研究工作相结合，该项目还包括一系列教育活动，刺激和准备大学预科学生在材料科学和工程领域的职业生涯。在这个项目中：i)与Techbridge Girls项目合作，为中学生制作了一系列动手展览和实验；ii)与校园教育小组合作，为未被充分代表的高中生开发了“纳米材料科学与工程”暑期课程系列。

Technical Description: The research objective of this project is to tune the electronic structure of two-dimensional (2D) semiconductors by extremely off-equilibrium materials processing. For this purpose, 2D semiconductor alloys are formed by mixing the otherwise immiscible 2D semiconductors with kinetically controlled means to stabilize non-equilibrium phases, in which the electronic and structural properties are engineered on command. The resultant 2D semiconductor alloys are expected to offer a new platform for implementation of a wide variety of potential technologies that are not possible with existing materials. The specific aims of the research are to: i) alloy layered semiconductors in the 2D limit at arbitrary compositions. This is achieved using the pulsed laser alloying method, and the products are evaluated by structural and physical characterization tools; and ii) engineer electronic structure of 2D alloys by designing proper compositions and heterostructures. Their bandgap, band offsets, effective mass, and carrier dopability are designed and evaluated, and compared to density-functional theory and Green's function calculations for a comprehensive understanding. Non-technical Description: Layered semiconductors at the quantum limit are emerging as an important class of materials for innovative information and energy conversion technologies. Unlike the large number of existing bulk semiconductors, the full potential of these 2D semiconductors is limited by the small number of members currently available: mostly being transition metal chalcogenides. This project seeks to remove this limit by creating a library of 2D semiconductor alloys where the electronic structure is designed and continuously tuned to fit specific needs. Integrated with the research efforts, the project also includes a set of educational activities that stimulates and prepares pre-college students for careers in materials science and engineering. Within this project the PI: i) creates a series of hands-on exhibits and experiments for middle-high school students in partnership with the Techbridge Girls project; and ii) teams up with a campus education group to develop a summer class series in "Nanoscale Materials Science and Engineering" for underrepresented high-school students.