WSe 2 film deposition. The preparation conditions were reported in detail recently. The X-ray amorphous WSe 2+x thin films were prepared by DC reactive magnetron sputtering at a power of 55 W in Ar:H 2 Se (1:4) atmosphere at a pressure of 1.25 Pa onto quartz glass (QG) and TiN:O back contact substrates at room temperature. The thickness of the films was changed by varying the deposition time. Afterwards, the WSe 2+x amorphous films were crystallized at 550-600 °C for 10 minutes by the amorphous solid -liquid -crystalline solid (aSLcS) process with Pd promoter (10-20 nm) at an H 2 Se gas pressure of 10 Pa under static conditions (turbo pump valve closed).