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

通过深注入光离子（He和H），然后进行选择性化学蚀刻，寻求铁电薄膜剥离的新知识和更大的基本理解。剥落过程产生铁电材料的单晶薄膜，如铌酸锂、锆酸铅和钛酸锶，但缺乏基本的材料科学知识。该项目寻求关于高能离子基工艺如何改变单晶复合氧化物中的狭窄空间区域的基本信息，以及确定工艺问题，如垂直和横向图案分辨率和晶体质量。这里研究的剥离过程不同于在半导体中看到的剥离过程，因为剥离过程是通过高度选择性的湿法蚀刻重植入区域进行的。关于这一过程需要解决的研究问题包括：什么物理机制介导了蚀刻过程的高选择性？铁电晶体He或H注入后，在注入区有什么固态化学变化？间质性应激在植入区有何作用？是否形成了像h注入硅一样的纳米空腔？在剥离过程中，表面的化学计量学发生了多大程度的变化？该方法是研究深植入铁电晶体的基本材料化学和物理以及随后从该材料剥离。特别是，该项目将涉及检查1)晶体晶格的变化，即铁电晶体中的缺陷，纳米空腔，间隙浓度；2)晶体化学的变化，即植入区挥发性间隙物质的组成和形成以及局部应力诱导的化学溶解反应；3)在铁电晶体中重注入轻离子后，脱落的配合物-氧化物表面的成分变化和恢复。该项目涉及具有高技术相关性的材料科学主题领域的基础研究问题。该研究将为电子/光子学的新理解和新能力提供基础材料科学知识，并促进研究和教育的整合。该项目是电气工程、应用物理、化学和材料科学的跨学科项目，本科生和研究生共同开展新材料、材料加工技术和器件的基础和应用研究。该项目是高度协作的，使PI/共同PI和学生能够通过延长访问和短途旅行与布鲁克海文的主要国家实验室以及两所纽约州立大学，哥伦比亚大学和纽约州立大学奥尔巴尼分校进行协作，每一所大学都提供独特的设施和体验。预计还将与其他内部和外部研究小组（如哥伦比亚大学MRSEC和罗格斯大学的研究小组）进行合作研究。＊＊＊

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. ***