FRG: Materials Physics and Chemistry of Light-Ion-Exfoliation of Single-Crystal Ferroelectric Films

寻求通过深度注入轻离子(He和H)以及随后的选择性化学腐蚀来剥离铁电薄膜的新知识和更多的基础知识。剥离过程产生了铁电材料的单晶膜，如铌酸锂、锆酸铅和钛酸锶，但对该过程的基础材料科学知识缺乏。该项目寻求关于高能离子工艺如何改变单晶复合氧化物中狭窄空间区域的基本信息，以及工艺问题的确定，如垂直和横向图案化分辨率和晶体质量。这里研究的剥离过程不同于半导体中的剥离过程，因为剥离是通过对大量注入区域进行高度选择性的湿法刻蚀来进行的。关于这一过程需要解决的研究问题包括：什么物理机制调节了刻蚀过程的高选择性？在He或H注入铁电晶体后，注入区域的固态化学变化是什么？间质介导的应力在种植区的作用是什么？氢离子注入的硅中是否形成了纳米空穴？在剥离过程之后，表面的化学计量比发生了多大程度的变化？这种方法是研究深度、大量注入的铁电晶体的基本材料化学和物理，以及随后从这种材料上剥离。特别是，该项目将涉及1)铁电晶体中晶格的变化，即缺陷、纳米空穴、间隙浓度；2)晶体化学的变化，即挥发性间隙物种的组成和形成以及植入区域中局部应力诱导的化学溶解反应；以及3)在铁电晶体中大量注入轻离子后，剥落的复杂氧化物表面的成分变化和恢复。%该项目致力于具有高度技术相关性的材料科学主题领域的基础研究问题。这项研究将在基础水平上贡献基本材料科学知识，促进对电子/光子学的新理解和能力，并促进研究和教育的融合。该项目是跨学科的，涉及电气工程、应用物理、化学和材料科学，本科生和研究生共同合作，在新材料、材料加工技术和设备方面进行基础和应用研究。该项目是高度协作的，使PI/合作PI和学生能够通过与主要的国家实验室布鲁克海文以及两所纽约州大学哥伦比亚大学和纽约州立大学奥尔巴尼分校进行长期访问和较短的旅行进行合作，这两所大学都提供独特的设施和体验。与其他内部和外部研究小组的合作研究互动也是预期的，例如哥伦比亚大学的MRSEC和罗格斯大学的那些小组。***

New knowledge and greater fundamental understanding of exfoliation of ferroelectric thin films by deep implantation of light ions (He and H), followed by selective chemical etching are sought. The exfoliation process yields single-crystal films of ferroelectric materials, such as lithium niobate, lead zirconate, and strontium titanate, but fundamental materials science knowledge of the process is lacking. This project seeks basic information about how high-energy ion-based processes alter narrow spatial regions in single-crystal complex oxides, as well as determination of process issues such as vertical and lateral patterning resolution and crystal quality. The exfoliation process being studied here differs from that seen in semiconductors since lift-off proceeds by highly selective wet etching of the heavily implanted region. Research questions to be addressed regarding this process include: What physical mechanism mediates the high selectivity of the etching process? What are the solid-state chemical changes in the implantation region following He or H implantation of ferroelectrics crystals? What is the role of interstitial-mediated stress in the implantation region? Are nanocavities formed as in H-implanted Si? To what extent is the chemical stoichiometry of the surface changed following the exfoliation process? The approach is to investigate basic materials chemistry and physics of deeply, heavily implanted ferroelectric crystals and subsequent exfoliation from this material. In particular, the project will involve examination of 1) changes in crystal lattice, i.e. defects, nanocavities, interstitial concentration, in ferroelectric crystals; 2) changes in crystal chemistry, i.e. the composition and formation of volatile interstitial species and local-stress-induced chemical dissolution reactions in the implant region; and 3) compositional changes in, and recovery of, the exfoliated complex-oxide surface-following heavy implantation of light ions in ferroelectric crystals. %%%The project addresses basic research issues in a topical area of materials science having high technological relevance. The research will contribute basic materials science knowledge at a fundamental level to new understanding and capabilities in electronics/photonics and promotes the integration of research and education. The project is interdisciplinary spanning aspects of electrical engineering, applied physics, chemistry and materials science with undergraduate and graduate students working together to conduct both fundamental and applied research in new materials, materials processing techniques, and devices. The project is highly collaborative enabling PI/co-PIs and students to collaborate via extended visits and shorter trips with a major National Laboratory, Brookhaven, and across two New York State universities, Columbia and SUNY Albany, each of which offers unique facilities and experiences. Collaborative research interactions with other internal and external research groups, such as those at Columbia's MRSEC and Rutgers, are also anticipated. ***