176 | Nature | Vol 581 | 14 May 2020
Article
found to be intercalated into the atomic network of the pristine FeTe
matrix as interstitials, because telluride-based TMDs offer the largest
spacing between the host atoms^43. Upon intercalation, the FexTey phase
reveals new symmetries, as confirmed by the emergence of superspots
in the FFT pattern (Fig. 4h). A similar complex intercalation network
was also observed in VxTey (Supplementary Fig. 28).
We have developed a robust method to engineer the composi-
tion of a broad class of TMDs, by means of self-intercalation with
native metal atoms during growth. Because the main principle is the
application of high chemical potential of metal atoms to provide
the driving force for intercalation during growth, this technique
should be compatible with most growth methods. The metal inter-
calants occupy octahedral vacant sites in the vdW gap, and distinct
stoichiometric phases are produced depending on the levels of
intercalation. High-throughput DFT simulations—supported by
growth experiments—show that the self-intercalation method is
applicable to a large class of 2D layered materials, thus enabling
a library of materials with potentially new properties to be cre-
ated from existing layered materials. Owing to the versatility with
which the composition can be controlled, it is possible to tune—in
one class of materials—properties such as ferromagnetism and the
formation of spin-frustrated Kagome lattices. The implication of
this work is that bilayer (or thicker) TMDs can be transformed into
ultrathin, covalently bonded 3D materials, with stoichiometry that
can be tuned over a broad range by varying the concentration of
the intercalants.abcfdgV 11 S 16ehIn 11 Se 16 FexTey1T-Co 7 X 12
X = S, Se X = S, Se, Te2Hc-Mo 7 X 12
X = S, Se, Te2Ha-Nb 7 X 12
X = S, Se, Te1T-Ti 8 X 12S
Se
Te33.3%S
Se33.3%
S
Se
Te33.3%S
Se
Te66.7%
S
Se
Te33.3%2 a2 a2 a2 a3.95 PB, 5.27 PB 1.11–1.19 PB 0.88–0.90 PB 2.01–7.03 PBa2 aa2 a26 27 28IIIB22 22IVB23VB24VIB25VIIB VIII29IB30IIBVIA163452VIIA173539 40 41 42 43 44 45 46 47 48 5357 72 73 74 75 76 77 78 79 8031IIIA4981IIA12203832IVA5082Sc Ti VCrMnCFe Co Ni uZn
S
Se
Te
Cl
Br
YZrNbMoTcRuRhPdAgCd I
La Hf Ta WReOsIrPtAuHg
Ga
In
Tl
Mg
Ca
Sr
Ge
Sn
Pb
Fig. 4 | A library of ic-2D crystals. a, Periodic table showing metal (blue) and
chalcogen (red) combinations that form ic-2D crystals according to our DFT
calculations; the list is not exhaustive. Blue triangles indicate that
self-intercalation can be experimentally realized, whereas grey triangles
indicate that intercalation was not successful under our experimental
conditions. MX 2 structures with intrinsic ferromagnetism are highlighted with
orange triangles. b, Atomic models, obtained from DFT calculations, of ic-2D
crystals that exhibit ferromagnetism. c–e, STEM–ADF images of V-intercalated
V 11 S 16 (c), In-intercalated In 11 Se 16 (d) and Fe-intercalated FexTey (e). f–h, Left,
enlarged STEM images of c–e, respectively; right, the corresponding FFT
patterns. Scale bars: c–e, 2 nm; f–h, 0.5 nm; FFT patterns in f–h, 5 nm−1.