skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Metallic line defect in wide-bandgap transparent perovskite BaSnO 3
A line defect with metallic characteristics has been found in optically transparent BaSnO 3 perovskite thin films. The distinct atomic structure of the defect core, composed of Sn and O atoms, was visualized by atomic-resolution scanning transmission electron microscopy (STEM). When doped with La, dopants that replace Ba atoms preferentially segregate to specific crystallographic sites adjacent to the line defect. The electronic structure of the line defect probed in STEM with electron energy-loss spectroscopy was supported by ab initio theory, which indicates the presence of Fermi level–crossing electronic bands that originate from defect core atoms. These metallic line defects also act as electron sinks attracting additional negative charges in these wide-bandgap BaSnO 3 films.  more » « less
Award ID(s):
2011401 1420013 1741801
PAR ID:
10217871
Author(s) / Creator(s):
; ; ; ; ; ;
Date Published:
Journal Name:
Science Advances
Volume:
7
Issue:
3
ISSN:
2375-2548
Page Range / eLocation ID:
eabd4449
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; ; ; (, Communications Physics)
    Abstract Materials that blend physical properties that are usually mutually exclusive could facilitate devices with novel functionalities. For example, the doped perovskite alkaline earth stannates BaSnO 3 and SrSnO 3 show the intriguing combination of high light transparency and high electrical conductivity. Understanding such emergent physics requires deep insight into the materials’ electronic structures. Moreover, the band structure at the surfaces of those materials can deviate significantly from their bulk counterparts, thereby unlocking novel physical phenomena. Employing angle-resolved photoemission spectroscopy and ab initio calculations, we reveal the existence of a 2-dimensional metallic state at the SnO 2 -terminated surface of 1% La-doped BaSnO 3 thin films. The observed surface state is characterized by a distinct carrier density and a lower effective mass compared to the bulk conduction band, of about 0.12 m e . These particular surface state properties place BaSnO 3 among the materials suitable for engineering highly conductive transition metal oxide heterostructures. 
    more » « less
  2. ; ; (, 2D Materials)
    Abstract The structural properties of co-deposited ultrathin PtSe 2 films grown at low temperatures by molecular beam epitaxy on c-plane Al 2 O 3 are studied. By simultaneously supplying a Se flux from a Knudsen cell and Pt atoms from an electron-beam evaporator, crystalline (001)-oriented PtSe 2 films were formed between 200 °C and 300 °C. The long separation between substrate and electron beam evaporator of about 60 cm ensured minimal thermal load. At optimum deposition temperatures, a ten times or even higher supply rate of Se compared to Pt ensured that the pronounced volatility of the Se was compensated and the PtSe 2 phase was formed and stabilized at the growth front. Postgrowth anneals under a Se flux was found to dramatically improve the crystalline quality of the films. Even before the postgrowth anneal in Se, the crystallinity of PtSe 2 films grown with the co-deposition method was superior to films realized by thermal assisted conversion. Postgrowth annealed films showed Raman modes with narrower peaks and more than twice the intensity. Transmission electron microscopy investigations revealed that the deposited material transitioned to a two-dimensional layered structure only after the postgrowth anneal. PtSe 2 growth was found to start as single layer islands that preferentially nucleated at atomic steps of the substrate and progressed in a layer-by-layer like fashion. A close to ideal wetting behavior resulted in coalesced PtSe 2 films after depositing about 1.5 PtSe 2 layers. Detailed Raman investigation of the observed PtSe 2 layer breathing modes of films grown under optimized co-deposition conditions revealed an interlayer coupling force constant of 5.0–5.6 × 10 19 N m −3 . 
    more » « less
  3. ; ; ; ; ; ; (, APL Materials)
    The molecule-based ferrimagnetic semiconductor vanadium tetracyanoethylene (V[TCNE]x, x ≈ 2) has garnered interest from the quantum information community due to its excellent coherent magnonic properties and ease of on-chip integration. Despite these attractive properties, a detailed understanding of the electronic structure and mechanism for long-range magnetic ordering have remained elusive due to a lack of detailed atomic and electronic structural information. Previous studies via x-ray absorption near edge spectroscopy and the extended x-ray absorption fine structure have led to various proposed structures, and in general, V[TCNE]x is believed to be a three-dimensional network of octahedrally coordinated V2+, each bonded to six TCNE molecules. Here, we elucidate the electronic structure, structural ordering, and degradation pathways of V[TCNE]x films by correlating calculations of density functional theory (DFT) with scanning transmission electron microscopy and electron energy-loss spectroscopy (EELS) of V[TCNE]x films. Low-loss EELS measurements reveal a bandgap and an excited state structure that agree quantitatively with DFT modeling, including an energy splitting between apical and equatorial TCNE ligands within the structure, providing experimental results directly backed by theoretical descriptions of the electronic structure driving the robust magnetic ordering in these films. Core-loss EELS confirms the presence of octahedrally coordinated V+2 atoms. Upon oxidation, changes in the C1s-π* peak indicate that C=C of TCNE is preferentially attacked. Furthermore, we identify a relaxation of the structural ordering as the films age. These results lay the foundation for a more comprehensive and fundamental understanding of magnetic ordering and dynamics in these classes of metal–ligand compounds. 
    more » « less
  4. ; ; ; ; ; ; ; ; ; ; et al (, ChemPhysChem)
    ChemPhysChem (Ed.)
    Abstract Molecular clusters can function as nanoscale atoms/superatoms, assembling into superatomic solids, a new class of solid‐state materials with designable properties through modifications on superatoms. To explore possibilities on diversifying building blocks, here we thoroughly studied one representative superatom, Co6Se8(PEt3)6. We probed its structural, electronic, and magnetic properties and revealed its detailed electronic structure as valence electrons delocalize over inorganic [Co6Se8] core while ligands function as an insulated shell.59Co SSNMR measurements on the core and31P,13C on the ligands show that the neutral Co6Se8(PEt3)6is diamagnetic and symmetric, with all ligands magnetically equivalent. Quantum computations cross‐validate NMR results and reveal degenerate delocalized HOMO orbitals, indicating aromaticity. Ligand substitution keeps the inorganic core nearly intact. After losing one electron, the unpaired electron in [Co6Se8(PEt3)6]+1is delocalized, causing paramagnetism and a delocalized electron spin. Notably, this feature of electron/spin delocalization over a large cluster is attractive for special single‐electron devices. 
    more » « less
  5. ; ; ; ; ; (, Advanced Functional Materials)
    Abstract Edges and point defects in layered dichalcogenides are important for tuning their electronic and magnetic properties. By combining scanning tunneling microscopy (STM) with density functional theory (DFT), the electronic structure of edges and point defects in 2D‐PtSe2are investigated where the 1.8 eV bandgap of monolayer PtSe2facilitates the detailed characterization of defect‐induced gap states by STM. The stoichiometric zigzag edge terminations are found to be energetically favored. STM and DFT show that these edges exhibit metallic 1D states with spin polarized bands. Various native point defects in PtSe2are also characterized by STM. A comparison of the experiment with simulated images enables identification of Se‐vacancies, Pt‐vacancies, and Se‐antisites as the dominant defects in PtSe2. In contrast to Se‐ or Pt‐vacancies, the Se‐antisites are almost devoid of gap states. Pt‐vacancies exhibit defect induced states that are spin polarized, emphasizing their importance for inducing magnetism in PtSe2. The atomic‐scale insights into defect‐induced electronic states in monolayer PtSe2provide the fundamental underpinning for defect engineering of PtSe2‐monolayers and the newly identified spin‐polarized edge states offer prospects for engineering magnetic properties in PtSe2nanoribbons. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email