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. ***
