Scanning-probe-microscopy studies of superlattice structures and density-wave structures in 2H-NbSe[sub 2], 2H-TaSe[sub 2], and 2H-TaS[sub 2] induced by Fe doping

Journal Article · Mon Nov 15 04:00:00 EST 1993 · Physical Review, B: Condensed Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.48.14543· OSTI ID:5725977

Dai, Z; Xue, Q; Gong, Y; Slough, C G; Coleman, R V ^[1]

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1. Physics Department, University of Virginia, Charlottesville, Virginia 22901 (United States)

The intercalation of Fe into the van der Waals gap in the 2H phase transition-metal dichalcogenides NbSe[sub 2], TaSe[sub 2], and TaS[sub 2] produces many interesting electronic, magnetic, and structural effects. The scanning tunneling microscope (STM) and atomic force microscope (AFM) prove to be very sensitive to these changes and we report a wide range of results as a function of Fe concentration. All three materials support similar 3[bold a][sub 0][times]3[bold a][sub 0] charge-density-wave (CDW) structures in the pure state at low temperatures. At low concentrations of Fe the CDW superlattice is still strong at 4.2 K and persists to high concentrations of Fe. At high concentrations, the Fe becomes ordered in the octahedral holes in the van der Waals gaps, and superlattices of the form 2[bold a][sub 0][times]2[bold a][sub 0] and [radical]3 [bold a][sub 0][times] [radical]3 [bold a][sub 0] are observed. These can be detected at both 300 and 4.2 K. STM spectroscopy at 4.2 K shows that in 2H-Fe[sub [ital x]]NbSe[sub 2] and 2H-Fe[sub [ital x]]TaSe[sub 2] the energy gap in the electronic spectrum is initially reduced, but stabilizes at higher Fe concentrations and remains well defined for the ordered 2[bold a][sub 0][times]2[bold a][sub 0] phase. A transition from a CDW to a mixed CDW and spin-density-wave state is indicated, since these high Fe concentration phases are antiferromagnetic. In 2H-Fe[sub [ital x]]TaS[sub 2] both 2[bold a][sub 0][times]2[bold a][sub 0] and [radical]3 [bold a][sub 0][times] [radical]3 [bold a][sub 0] superlattices are observed. The 2[bold a][sub 0][times]2[bold a][sub 0] regions show a large energy gap, while the [radical]3 [bold a][sub 0][times] [radical]3 [bold a][sub 0] do not. The latter phase is ferromagnetic and would not be expected to exhibit a gap.

• DOE Contract Number: FG05-84ER45072
• OSTI ID: 5725977
• Journal Information: Physical Review, B: Condensed Matter; (United States), Journal Name: Physical Review, B: Condensed Matter; (United States) Vol. 48:19; ISSN PRBMDO; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
ALLOYS
CHALCOGENIDES
CHARGE DENSITY
CRYSTAL STRUCTURE
ELECTRON SPECTRA
IRON ADDITIONS
IRON ALLOYS
NIOBIUM COMPOUNDS
NIOBIUM SELENIDES
REFRACTORY METAL COMPOUNDS
SELENIDES
SELENIUM COMPOUNDS
SPECTRA
SULFIDES
SULFUR COMPOUNDS
SUPERLATTICES
TANTALUM COMPOUNDS
TANTALUM SELENIDES
TANTALUM SULFIDES
TRANSITION ELEMENT COMPOUNDS