Optically-pumped NMR Enhancements Enable Studies of Semiconductor Interfaces

所有现代电子产品的基础都依赖于由半导体组成的多层材料。在这里，研究人员正在开发仪器来确定不同半导体层相互接触的界面区域中的特殊化学结构和三维形式。这些方法将联合收割机激光激发与核磁共振检测相结合，以提供对改善这些现代电子设备的性能至关重要的原子级信息。该项目包括与国家高磁场实验室的合作，将影响半导体器件制造行业。研究创新与华盛顿大学提供的多学科课程相结合，用于教育和培训学生。合作还为团队成员提供了新的研究网络，加强了学生和博士后研究人员的专业发展。通过学校伙伴关系研究所为高中教师提供非正式的科学教育活动。技术说明：本研究通过使用传导电子的光泵浦产生的增强信号来询问半导体界面的结构。光泵浦核磁共振（OPNMR）中的光泵浦将检测信号定位到界面区域，并大大提高了灵敏度，将NMR从体相技术转变为表面技术。与国家高磁场实验室合作，通过利用基于高温超导体的新线圈设计来提高激光接入和NMR灵敏度，该线圈允许无阻碍的激光接入和比传统超导体更高的性能。这样的光谱学可以通过揭示界面的底层构成，并检查由缺陷、晶格失配和掺杂剂引起的应变来实现器件的工程化。探讨了GaAs表面淀积金属氧化物薄膜（如氧化铝和二氧化铪）的模型结构。OPNMR的发展，以适应这些方法研究其他金属氧化物半导体器件，以检查在这个接口的费米能级钉扎缺陷的作用。这些信息对于提高金属氧化物半导体器件的性能至关重要。利用获得的高极化来测量磁光穿透深度，并最终测量核极化。迄今为止，这些值只是估计，但对于理解观察到的自旋和光学泵浦的有效性至关重要，明确使用核自旋温度。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

Non-Technical Description: The basis of all modern electronics relies on multilayered materials composed of semiconductors. Here, the investigators are developing instrumentation to determine the specialized chemical structures and the 3-dimensional forms in interface regions where different semiconductor layers are in contact with one another. These methods combine laser excitation with nuclear magnetic resonance detection to provide atomic-level information critical to improving the performance of these modern electronic devices. This project includes collaboration with the National High Magnetic Field Lab and will impact semiconductor device fabrication industries. The research innovations are integrated with multidisciplinary courses offered at Washington University for educating and training students. The collaboration also provides new research networks for team members, enhancing the professional development of students and postdoctoral researchers. Informal science education activities for high school teachers are offered through the Institute for School Partnership.Technical Description: This research interrogates the structure of semiconductor interfaces by using enhanced signals that are created through optical pumping of conduction electrons. Optical pumping in the optically pumped nuclear magnetic resonance (OPNMR) localizes the detected signal to interfacial regions and greatly enhances the sensitivity, transforming NMR from a bulk to a surface technique. In collaboration with the National High Magnetic Field Lab, laser access and NMR sensitivity are improved by utilizing a new coil design based on high-temperature superconductors that permits unimpeded laser access and higher performance than conventional solenoids. Such spectroscopy can enable engineering of devices by revealing the underlying makeup of the interface, and examining strain induced by defects, lattice mismatch, and dopants. Model structures of GaAs coated with deposited metal oxide thin films, such as alumina and hafnium dioxide are probed. The OPNMR is developed to adapt these methods for studying other metal-oxide semiconductor devices to examine the role of defects in Fermi-level pinning at this interface. This information is critical to improving performance of metal-oxide semiconductor devices. The high polarization achieved is utilized to measure the magneto-optical penetration depth and ultimately the nuclear polarization. To date, these values have only been estimates but are crucial for understanding the observed spins and the effectiveness of the optical pumping, explicitly using nuclear spin temperature.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.