Growth of NiSe ₂ , NiTe ₂ and alloy NiSe _{2− x} Te _x nanosheets with tunable shape evolution and chemical composition

Abstract The nano-devices based on atomic layers of nickel dichalcogenides, including NiS ₂ , NiSe ₂ and NiTe ₂ , are rarely studied due to synthetic problems. Recently, ultrathin NiTe ₂ nanosheets are reported to be grown on SiO ₂ /Si substrate through chemical vapour deposition (CVD). However, the CVD synthesis of other nickel dichalcogenides is still unknown. Here we report the synthesis of NiSe ₂ , NiTe ₂ and alloy NiSe _{2− x} Te _x (0 < x < 2) nanosheets through a similar CVD method. We found that the growth temperature has great influences on the shape, size and thickness of as-grown nanosheets. When the growth temperature is about 650 °C, the as-grown NiSe ₂ and NiTe ₂ nanosheets are as thin as 2.7 nm and 3.1 nm, respectively, which is equal to three layers of crystal unit. Combining the transmission electron microscopy and high-angle annular dark field scanning transmission electron microscope characterizations, the atomic structures of NiSe ₂ , NiTe ₂ and alloy NiSe _{2− x} Te _x are proved to be hexagonal with little differences in the lattice parameters. The energy dispersive spectrometer and Raman spectra demonstrate a wide range of the x in NiSe _{2− x} Te _x from nearly 0 to almost 2, which proves that the chemical composition can be readily tunable.