Exploration of Non-Equilibrium Interfacial Phenomena in Spin Forbidden Oxidation

现代计算机芯片是由半导体（如硅）制成的，表面涂有一层极薄的氧化硅。为了制造可靠的电子元件，必须精确控制氧化层的厚度，随着器件变得越来越小，这提出了重大挑战。目前制造氧化硅薄膜的方法需要在高温下加热半导体。这一过程导致了不均匀的氧化层。在这个由化学部门化学结构、动力学和机理a （CSDM-A）项目资助的项目中，麻省理工学院的Sylvia T. Ceyer教授和她的学生正在使用复杂的分子束技术来研究氧化物的形成过程。他们的发现可能会改进使用较低温度的方法，这将具有重大的社会和经济效益。这项研究还为从事化学工业的学生提供了科学解决问题的基础广泛的教育。Ceyer教授利用MIT？“夏季研究计划”（MSRP）旨在招募代表性不足的本科生进行夏季研究，让他们参与科学发现的兴奋。Ceyer教授还在YouTube上撰写和讲述引人入胜的普通化学讲座，作为教育和推广活动的一部分，旨在使所有人都能理解和了解科学。这项工作提出了一种新的方法，利用（O2）2二聚体在其第一电子激发单重态下容易合成O2，目的是绕过限制半导体氧化活性的自旋禁止反应。这个想法可能会导致对设备中越来越薄的氧化层的精确控制。实验确定的O2与（O2）2相互作用动力学之间的比较，为这种自旋禁止反应的低但非零概率的起源提供了见解。本研究项目还探索了一种非平衡现象，包括由于入射O2的初始碰撞引起的晶格电子激发，以寻求理解O2的非零反应性。最后，这些实验验证了一个假设，即解离化学吸附的另一种机制，即不需要自旋禁止跃迁的原子抽象，可能通过亚稳态、非平衡前体态或与瞬态势能最大值相关的直接原子抽象来实现。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Modern computer chips are made from semiconductors, such as silicon, coated with an extremely thin layer of silicon-oxide. To fabricate reliable electronic components, the thickness of this oxide layer must be precisely controlled, which presents significant challenges as devices become smaller and smaller. Present methods of creating the silicon-oxide film require heating the semiconductor at high temperature. This process leads to a non-uniform oxide layer. In this project, funded by the Chemical Structure, Dynamics, and Mechanisms-A (CSDM-A) program of the Chemistry Division, Professor Sylvia T. Ceyer of the Massachusetts Institute of Technology and her students are using sophisticated molecular beam techniques to study the oxide formation process. Their discoveries could lead to improved methods using lower temperatures, which would have significant societal and economic benefit. This research is also providing a broad-based education in scientific problem solving for students embarking on careers in chemical industry. Professor Ceyer leverages MIT?s Summer Research Program (MSRP) to recruit underrepresented undergraduate students for summer research engaging them in the excitement of scientific discovery. Professor Ceyer also authors and narrates compelling general chemistry lectures on YouTube as a part of educational and outreach activities designed to make science understandable and accessible for all. This work proposes a novel method using (O2)2 dimer to easily synthesize O2 in its first electronically excited singlet state with the aim of bypassing a spin-forbidden reaction that limits oxidation activity of semiconductors. This idea may lead to precise control of ever-thinner oxide layers in devices. The comparison between the experimentally-determined interaction dynamics of O2 versus (O2)2 are providing insights into the origin of the low, but non-zero probability of this spin forbidden reaction. This research program also explores a non-equilibrium phenomenon involving lattice electronic excitations due to the initial collision of the incident O2 in the quest for understanding the non-zero O2 reactivity. Finally, these experiments test a hypothesis that an alternate mechanism for dissociative chemisorption, atom abstraction, which does not require a spin forbidden transition, may be operative via a metastable, non-equilibrium precursor state or a direct atom abstraction associated with a transient potential energy maximum.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.