Growth of NiSe2, NiTe2 and alloy NiSe2− x Te x nanosheets with tunable shape evolution and chemical composition

The nano-devices based on atomic layers of nickel dichalcogenides, including NiS2, NiSe2 and NiTe2, are rarely studied due to synthetic problems. Recently, ultrathin NiTe2 nanosheets are reported to be grown on SiO2/Si substrate through chemical vapour deposition (CVD). However, the CVD synthesis of other nickel dichalcogenides is still unknown. Here we report the synthesis of NiSe2, NiTe2 and alloy NiSe2−xTex (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 NiSe2 and NiTe2 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 NiSe2, NiTe2 and alloy NiSe2−xTex 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 NiSe2−xTex from nearly 0 to almost 2, which proves that the chemical composition can be readily tunable.