CAREER: Probing Crystallization of Atomic Layers Using In Situ Electron Diffraction

职业：利用原位电子衍射探测原子层的结晶

• 批准号: 1752956
• 负责人: Nick Strandwitz
• 金额: $ 59.98万
• 依托单位: Lehigh University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-07-01 至 2024-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1752956&HistoricalAwards=false
• 关键词: CAREER; Probing; Crystallization; Atomic; Layers

NON-TECHNICAL DESCRIPTION: Control of atomic scale structure in ultra-thin films on non-planar substrates is critical to next generation optical, electrical, biological, and magnetic materials and devices. In particular, nanoscale control of materials is essential to enable further decreases in the feature sizes and growth of materials in three dimensional architectures that are being developed for applications such as logic circuitry, memories, and photovoltaics. This research investigates the fundamental rearrangement of single atomic layers on surfaces during thin film growth, and provides important knowledge regarding the factors that influence transformation of disordered layers of atoms into ordered, crystalline arrangements. The primary experimental platform utilizes an electron beam to probe the structure of atomically-thick layers during growth and thermal processing. The research also uses atomically-resolved electron microscopy to probe the structure of these films. The knowledge generated from this research allows for an enhanced control and understanding of the formation of nanoscale crystalline materials that can be created on three dimensional (non-planar) surfaces and impacts a wide variety of fields in nanoelectronics, computing, photovoltaics, and nanoscale mechanical systems. This research activity is integrated with a university thin film course, a hands-on equipment laboratory, and an industrial outreach effort. Graduates typically find employment in national laboratory or industry. TECHNICAL DETAILS: This research elucidates the fundamental transformations that occur during atomic layer deposition and annealing by utilizing in situ reflection high energy electron diffraction (RHEED). Current atomic layer deposition (ALD) processes are often limited in terms of the structural control that is available due to precursor decomposition at high temperatures, which presents a significant barrier to precisely controlled three dimensional epitaxial architectures that are integral to next generation electronics. Therefore, this work separates the precursor chemisorption steps (ALD component) that result in amorphous layers from thermal processing that provides energy needed to induce crystallization in the model material system gallium oxide. Importantly, electron diffraction is probing in real time the structural transformations that occur to reveal the effect of ambient atmosphere, substrate structure, and orientation with adlayer thicknesses in the range of 0.5-10 nm. Analytical electron microscopy is providing precise structural and compositional details of the films and film-substrate interfaces including defect characteristics. This research captures a slow-motion picture of the structural changes that occur during many traditional thin film epitaxy techniques, and yields new relationships that control crystallization of ultra-thin layers and thus impacts the thin film/epitaxy communities. Undergraduate and graduate students are trained during the research. Industrial engagements are pursued with the Lehigh University Office of Economic Engagement. Mentorship and outreach are conducted with Lehigh University's Clare Booth Scholarship Program, Mountaintop Experience, and a local science center.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.

非技术描述：非平面底物上超薄膜中原子量表结构的控制对于下一代光学，电气，生物学和磁性材料和设备至关重要。尤其是，材料的纳米级控制对于能够在三维体系结构中进一步减少材料的特征大小和生长，这些材料的生长是针对逻辑电路，记忆和光伏的应用开发的。这项研究调查了薄膜生长期间单个原子层在表面上的基本重排，并提供了有关影响原子无序层转化为有序的结晶排列的重要因素。主要的实验平台利用电子束在生长和热处理过程中探测原子厚层的结构。该研究还使用原子分辨的电子显微镜来探测这些膜的结构。这项研究产生的知识可以增强和理解纳米级晶体材料的形成，这些材料可以在三维（非平面）表面上产生，并影响纳米电子，计算，光伏电脑和纳米级机械系统的各种领域。这项研究活动与大学薄膜课程，动手设备实验室和工业外展工作相结合。毕业生通常在国家实验室或工业中找到就业。 技术细节：这项研究阐明了原子层沉积过程中发生的基本转换和通过利用原位反射高能电子衍射（Rheed）进行退火。当前的原子层沉积（ALD）过程通常会受到高温下的前体分解而可用的结构控制，这在高温下呈现出明显的障碍，即精确控制的三维外延体系结构，这是下一代电子不可或缺的。因此，这项工作将前体化学吸附步骤（ALD成分）分开，从而导致无定形层的热处理，这些层提供了诱导氧化模型材料系统镀锌所需的能量。重要的是，电子衍射是实时探测的，这些结构变换揭示了环境大气，底物结构和方向的影响，而adlayer厚度在0.5-10 nm的范围内。分析电子显微镜提供了薄膜和薄膜基层界面的精确结构和组成细节，包括缺陷特征。这项研究捕获了许多传统薄膜外延技术中发生的结构变化的慢动作图，并产生了控制超薄层结晶的新关系，从而影响了薄膜/外交社区。在研究期间，对本科生和研究生接受了培训。 Lehigh University经济参与办公室进行了工业活动。 Lehigh University的Clare Booth奖学金计划，Mountaintop经验和当地科学中心进行了指导和外展活动。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的知识分子和更广泛影响的评估评估标准的评估值得支持的。