We use in situ scanning tunneling microscopy (STM) to investigate intercalation of the ferromagnetic 3d metals Ni and Fe underneath a graphene monolayer on Rh(111). Upon thermal annealing of graphene/Rh(111) with the deposited metal on top, we observe the formation of epitaxial monatomic nanoislands grown pseudomorphically on Rh(111) and covered by graphene. The size and shape of intercalated nanoislands is strongly influenced by the local spatial variation of the graphene-Rh bonding strength. In particular, the side length of the intercalated nanoislands shows maxima around discrete values imposed by the periodicity of the graphene moiré. Intercalation can be performed efficiently and without any visible damage of the graphene overlayer in the studied temperature range between 670 and 870 K. We identify the main intercalation path to be via diffusion through pre-existing lattice defects in graphene, accompanied by the second mechanism which is based on the material diffusion via metal-generated defects followed by the defect healing of the graphene lattice. We deem these graphene-capped and sharply confined ferromagnetic nanoislands interesting in the fields of spintronics and nanomagnetism.
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Nat Commun
January 2025
Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA.
Applying long wavelength periodic potentials on quantum materials has recently been demonstrated to be a promising pathway for engineering novel quantum phases of matter. Here, we utilize twisted bilayer boron nitride (BN) as a moiré substrate for band structure engineering. Small-angle-twisted bilayer BN is endowed with periodically arranged up and down polar domains, which imprints a periodic electrostatic potential on a target two-dimensional (2D) material placed on top.
View Article and Find Full Text PDFACS Appl Mater Interfaces
November 2024
Laboratory for Physical Sciences, College Park, Maryland 20740, United States.
Intercalation is a promising technique to modify the structural and electronic properties of 2D materials on the wafer scale for future electronic device applications. Yet, few reports to date demonstrate 2D intercalation as a viable technique on this scale. Spurred by recent demonstrations of mm-scale sensors, we use hydrogen intercalated quasi-freestanding bilayer graphene (hQBG) grown on 6H-SiC(0001), to understand the electronic properties of a large-area (16 mm) device.
View Article and Find Full Text PDFNano Lett
October 2024
Department of Mechanical Engineering, University of California Merced, Merced, California 95343, United States.
Using atomic force microscopy experiments and molecular dynamics simulations of gold nanoislands on graphite, we investigate why ultralow friction commonly associated with structural lubricity can be observed even under ambient conditions. Measurements conducted within a few days after sample synthesis reveal previously undiscovered phenomena in structurally lubric systems: , a drop in kinetic friction of an order of magnitude shortly after the onset of sliding; , a significant increase in kinetic friction forces after a rest period of 30 min or more; and , spontaneous jumps between distinct friction branches. These three effects are drastically suppressed a few weeks later.
View Article and Find Full Text PDFACS Nano
August 2024
Department of Materials Science and Engineering, The Pennsylvania State University, University Park,Pennsylvania 16802, United States.
A scalable platform to synthesize ultrathin heavy metals may enable high-efficiency charge-to-spin conversion for next-generation spintronics. Here, we report the synthesis of air-stable, epitaxially registered monolayer Pb underneath graphene on SiC (0001) by confinement heteroepitaxy (CHet). Diffraction, spectroscopy, and microscopy reveal that CHet-based Pb intercalation predominantly exhibits a mottled hexagonal superstructure due to an ordered network of Frenkel-Kontorova-like domain walls.
View Article and Find Full Text PDFACS Nano
July 2024
nanotech@surfaces Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology, Dübendorf 8600, Switzerland.
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