On-Site Synthesis and Characterizations of Atomically-Thin Nickel Tellurides with Versatile Stoichiometric Phases through Self-Intercalation

Abstract

Self-intercalation of native metal atoms in two-dimensional (2D) transition metal dichalcogenides has received rapidly increasing interest, due to the generation of intriguing structures and exotic physical properties, however, only reported in limited materials systems. An emerging type-II Dirac semimetal, NiTe2, has inspired great attention at the 2D thickness region, but has been rarely achieved so far. Herein, we report the direct synthesis of mono- to few-layer Ni-tellurides including 1T-NiTe2 and Ni-rich stoichiometric phases on graphene/SiC(0001) substrates under ultra-high-vacuum conditions. Differing from previous chemical vapor deposition growth accompanied with transmission electron microscopy imaging, this work combines precisely tailored synthesis with on-site atomic-scale scanning tunneling microscopy observations, offering us visual information about the phase modulations of Ni-tellurides from 1T-phase NiTe2 to self-intercalated Ni3Te4 and Ni5Te6. The synthesis of Ni self-intercalated Ni x Te y compounds is explained to be mediated by the high metal chemical potential under Ni-rich conditions, according to density functional theory calculations. More intriguingly, the emergence of superconductivity in bilayer NiTe2 intercalated with 50% Ni is also predicted, arising from the enhanced electron–phonon coupling strength after the self-intercalation. This work provides insight into the direct synthesis and stoichiometric phase modulation of 2D layered materials, enriching the family of self-intercalated materials and propelling their property explorations.

Realization of Multiple Charge-Density Waves in NbTe2 at the Monolayer Limit

“…The evolution of those superstructures upon postannealing confirms the instability of the 4 × 4, 4 × 1, and 28 × 28 phases, which was further verified by another postannealing process on the sample grown at 300 °C (see Figure S3 for details). In Supporting Note 1, we show that the Te-deficiency-induced structural changes − and the interfacial intercalation are not readily observed and unlikely to exist.…”

Research progress of transition-metal dichalcogenides for the hydrogen evolution reaction

“…Interestingly, Ni x Te y compounds in the other ratios of Ni and Te also appeared in this process, which indicated that self-intercalation occurred in these finished products. 73 In the CVD process, the key to achieving uniform large nanosheets lies in the lattice matching between the synthesized 2D material and the substrate. This is depicted in Fig.…”

Advanced Strategies in Synthesis of Two‐Dimensional Materials with Different Compositions and Phases

“…[ 85 ] Particularly, the structures of M 3 Te 4 were also observed in Cr‐ and V‐ tellurides. [ 86 ] Differing from the Cr‐ and V‐based intercalated crystals, Ni‐based intercalated crystals Ni 3 Te 4 and Ni 5 Te 6 are formed due to the high metal chemical potential under Ni‐rich conditions, [ 87 ] as shown in Figure 5f,g. According to the intercalation concentration, 2/3 layer (≈66.7%) of Ni intercalation endows a Ni 5 Te 6 phase, while 1/2 layer (≈50%) of Ni intercalation results in Ni 3 Te 4 .…”

“…Panels (f) and (g) reproduced with permission. [ 87 ] Copyright 2022, American Chemical Society. h) Schematic illustration of pristine TaS 2 and self‐intercalated Ta 7 S 12 by MBE under a low and a high Ta‐flux environment, respectively.…”

“…g) Calculated formation energy as a function of the chemical potential of Te (µTe) for monolayer 1T-NiTe 2 and self-intercalated Ni x Te y phases with different intercalation concentrations on graphene substrates. Panels (f) and (g) reproduced with permission [87]. Copyright 2022, American Chemical Society.…”