Study of the properties of two-dimensional МоS$_{2}$ and WS$_{2}$ films synthesized by chemical-vapor deposition

Molybdenum- and tungsten-disulfide films are synthesized by chemical-vapor deposition. The set of optimal synthesis parameters (temperature, time, and amount and ratio of precursors) is established at which МоS$_{2}$ domains with maximum lateral sizes of up to 250 $\mu$m on sapphire and МоS$_{2}$ and WS$_{2}$ domains up to 80 $\mu$m in size on SiO$_2$ can be grown. Domain intergrowth leads to the formation of homogeneous single-layer МоS$_{2}$ films. The Raman spectra of the synthesized films contain two characteristic peaks corresponding to the atomic vibrations in МоS$_{2}$ and WS$_{2}$. Photoluminescence of the single-layer and bilayer МоS$_{2}$ films with a maximum intensity of 670 $\pm$ 2 nm and of the single-layer WS$_2$ films with a maximum intensity of 630 $\pm$ 2 nm is detected. The photoluminescence spectral maps (the dependences of the photoluminescence intensity on the luminescence and excitation-light wavelengths) are measured. According to the measured data, the photoluminescence excitation spectrum of МоS$_{2}$ has a maximum at 350 $\pm$ 5 nm and the photoluminescence excitation spectrum of WS$_{2}$ has a maximum at 330 $\pm$ 5 nm. The I – V characteristics of the synthesized films are photosensitive in the visible spectral range.