Coverage-dependent structures and thermodynamic stability of intercalated Gd layers beneath buffer-layer graphene on SiC(0001)

Journal Article · Thu Feb 13 00:00:00 EST 2025 · Applied Surface Science

DOI:https://doi.org/10.1016/j.apsusc.2025.162625· OSTI ID:2521988

Han, Yong ^[1]; Chen, Shen ^[1]; Kolmer, Marek ^[2]; Wang, Lin-Lin ^[1]; Evans, James W. ^[1]; Tringides, Michael C. ^[1]

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1. Ames Laboratory (AMES), Ames, IA (United States); Iowa State University, Ames, IA (United States)
2. Ames Laboratory (AMES), Ames, IA (United States)

Electronic properties of two-dimensional (2D) materials are strongly influenced by their atomic arrangements, making the theoretically-aided characterization of experimentally-synthesized 2D structures crucial. Using first-principles density functional theory, we analyze nearly 200 configurations of intercalated Gd layers beneath buffer-layer graphene on SiC(0001) over a Gd coverage range of 0.01 < θ < 1.2. By fully relaxing selectively-constructed configurations at each coverage within a large, low-strain supercell, we determine the coverage dependence of the chemical potential for intercalated Gd structures. Thermodynamically-preferred configurations below θ ≈ 0.8 form single-atom-thick monolayers, while 3D-like or multilayer structures emerge beyond θ ≈ 0.9. Most structures are amorphous-like, including the configuration at the chemical potential minimum around θ ≈ 0.4. In contrast, a strongly stretched Gd(0001)-like monolayer at θ = 1/3 and a nearly perfect Gd(0001) monolayer at θ = 1 are significantly less favorable with 0.16 eV and 0.82 eV higher chemical potentials above the minimum, respectively. Furthermore, the graphene layer decoupled by intercalated Gd near the chemical potential minimum is significantly flatter compared to its morphology above intercalated 3D structures at higher coverages and nearly isolated Gd atoms in the lowest coverage region. In conclusion, these findings align with our experimental results and underscore the need for further research on this unique intercalated system, which holds significant potential for diverse applications.

• Research Organization: Ames Laboratory (AMES), Ames, IA (United States); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences & Biosciences Division (CSGB); USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities (SUF)
• Grant/Contract Number: AC02-05CH11231; AC02-07CH11358
• OSTI ID: 2521988
• Alternate ID(s): OSTI ID: 2516787
• Report Number(s): AL-J--730
• Journal Information: Applied Surface Science, Journal Name: Applied Surface Science Vol. 691; ISSN 0169-4332
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
First-principles DFT calculations
Gd coverage dependence
Gd intercalation
Graphene on SiC(0001) substrate
Scanning tunneling microscopy
Thermodynamic stability