CAREER: Raman Spectroscopy of Interlayer Phonons in van der Waals Heterostructures

职业：范德华异质结构中层间声子的拉曼光谱

• 批准号: 1552482
• 负责人: Rui He
• 金额: $ 51.79万
• 依托单位: University of Northern Iowa
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-02-01 至 2017-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1552482&HistoricalAwards=false
• 关键词: CAREER; Raman; Spectroscopy; Interlayer; Phonons

Non-technical abstract:Van der Waals heterostructures are a new class of materials that could lead to new novel electronic and optoelectronic devices. These materials are formed by vertically stacking atomic layers such as graphene, hexagonal boron nitride, and transition metal dichalcogenide (e.g. molybdenum disulfide) layers. The forces between these layers are relatively weak. However, they can dramatically change the properties of the system and induce phenomena that are absent in individual layers. By stacking or epitaxially growing different atomic layers on one another, one may design and fabricate artificial materials with unprecedented optical, electronic, and vibrational properties that cannot be achieved in natural crystals. Raman spectroscopy, which is a direct, noninvasive, and sensitive optical probe, is used to explore the interlayer coupling, the interface effect, and the interaction between vibrations and charge carriers in these heterostructures. This research provides crucial guidance in designing novel electronic and optoelectronic devices using stacked atomic layers. The research activities have a powerful impact on the undergraduate students at the University of Northern Iowa. The principal investigator integrates the research topics into two existing courses. Undergraduates at all levels, including freshman students, are encouraged to participate. The principal investigator also uses departmental contacts with area high schools and collaborates with Physics Education faculty colleagues and the director of the Classic Upward Bound program to involve teachers and students at regional high schools. Engaging high school students and undergraduates in research is very important in advancing STEM (Science, Technology, Engineering, and Mathematics) education in young people.Technical abstract:This research explores fundamental physical properties of various van der Waals heterostructures using Raman spectroscopy of interlayer phonons (typically at low frequencies) and photoluminescence. The research projects include: (i) Develop an interlayer-phonon-based Raman technique to characterize the rotational angle and Moire wavelength of heterostructure superlattices. This study offers a simple method of characterizing Moire pattern features without using scanning tunneling microscopy; (ii) Explore the electronic, optical, and vibrational properties of complex multilayer van der Waals heterostructures and the indirect-direct gap transition in MoS2 bilayers intercalated with different middle layer materials. This research provides crucial guidance in designing novel electronic and optoelectronic devices using stacked van der Waals multilayers; (iii) Study van der Waals heterostructures that involve Dirac materials. In particular, the research team investigates the change in the electronic band structure of twisted bilayer graphene after it is placed or sandwiched between hexagonal boron nitride. This study probes the change in the electronic and vibrational properties of graphene at the hetero-interface; (iv) Probe the interaction between carriers and interlayer phonons in twisted bilayer graphene devices with a dual-gate. This study explores the Coulomb interaction between two charged graphene layers and the interlayer potential formed upon gating. The techniques and methods established in these research activities can be applied to heterostructures formed from any two-dimensional crystals stacked in any desired sequence.

非技术摘要：范德华异质结构是一类新的材料，可以导致新的新型电子和光电设备。 这些材料是通过垂直堆叠的原子层（例如石墨烯，六边形硼硼）和过渡金属二北核化元素（例如二硫化钼）层形成的。这些层之间的力相对较弱。 但是，它们可以显着改变系统的特性，并诱导单个层中不存在的现象。通过在彼此之间堆叠或外延生长不同的原子层，可以设计和制造具有前所未有的光学，电子和振动特性的人造物质，这些特性在天然晶体中无法实现。拉曼光谱是一种直接的，无创和灵敏的光学探针，用于探索这些异质结构中振动与振动载体之间的层间耦合，界面效应以及相互作用。这项研究为使用堆叠的原子层设计新型的电子和光电设备提供了至关重要的指导。研究活动对爱荷华大学北部大学的本科生产生了强大的影响。首席研究人员将研究主题纳入了两个现有课程。鼓励包括新生在内的各个级别的大学生参加。首席调查员还使用与地区高中的部门联系，并与物理教育教职员工和经典的向上界计划的主任合作，让教师和学生参与区域高中。吸引高中生和本科生在研究中对年轻人的STEM（科学，技术，工程和数学）教育非常重要。技术摘要：这项研究探讨了使用互层互音声子（通常在低频频率下）和光照明的各种范德尔·沃尔斯异构结构的基本物理特性。研究项目包括：（i）开发一种基于层次的拉曼技术，以表征异质结构超级晶格的旋转角度和摩尔波长。这项研究提供了一种表征Moire模式特征的简单方法，而无需使用扫描隧道显微镜； （ii）探索复杂多层范德华异质结构的电子，光学和振动特性以及与不同中层材料插入的MOS2双层中的间接差距跃迁。这项研究为使用堆叠的Van der Waals多层设计设计新型电子和光电设备提供了至关重要的指导。 （iii）研究涉及狄拉克材料的范德华异质结构。特别是，研究小组研究了扭曲双层石墨烯的电子带结构的变化，将其放置或夹在六角形硝化硼之间。这项研究探究了杂烯在异质接口处电子和振动特性的变化。 （iv）探测带有双门的扭曲的双层石墨烯设备中载体和层中音子之间的相互作用。这项研究探讨了两个带电的石墨烯层与门控时形成的层间电势之间的库仑相互作用。这些研究活动中建立的技术和方法可以应用于由堆叠在任何所需序列中的任何二维晶体形成的异质结构。