A tri-layer approach to controlling nanopore formation in oxide supports
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A novel tri-layer approach for immobilizing metal nanoparticles in SiO2 supports is presented. In this work, we show that under rapid heating to temperatures of approximately 1,000 °C, metal nanoparticles less than 15 nm in size will entrench in the SiO2 layer on a silicon wafer to create pores as deep as 250 nm. We studied and characterized this entrenching behavior and subsequent nanopore formation for a wide variety of metal nanoparticles, including Au, Ag, Pt, Pd, and Cu. We also demonstrate that an Al2O3 layer acts as a barrier to such pore formation. Thus, by creating a tri-layer architecture consisting of SiO2 on Al2O3 on silicon wafers, we can control the depth to which nanoparticles entrench between 3–5 nm. This small range allows one to entrench particles for the purpose of immobilization but still present them above the surface. The two advances of moving into the sub-15 nm size regime and of controlled particle immobilization through entrenchment have important implications in studying site-isolated and stabilized metal nanoparticles for applications in sensing, separations, and catalysis.
Keywordsnanopore formation nanoparticle entrenchment nanoparticle stabilization atomic force microscopy Au nanoparticles
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This material is based upon work supported by the Sherman Fairchild Foundation, Inc. and the Air Force Office of Scientific Research under Award number FA9550-16-1-0150. J. L. H. was supported by the Department of Defense (DoD) through the National Defense Science & Engineering Graduate Fellowship (NDSEG). P. C. C. acknowledges support from the Cabell Terminal Year Fellowship from Northwestern University. This work made use of the EPIC and SPID facilities of Northwestern University’s NUANCE Center, which has received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205); the MRSEC program (NSF DMR-1121262) at the Materials Research Center; the International Institute for Nanotechnology (IIN); the Keck Foundation; and the State of Illinois, through the IIN. This work utilized Northwestern University Micro/Nano Fabrication Facility (NUFAB), which is partially supported by Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205), the Materials Research Science and Engineering Center (DMR-1720139), the State of Illinois, and Northwestern University.
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