Atmospheric pressure chemical vapor deposition of WSe2 thin films on glass - highly hydrophobic sticky surfaces

Atmospheric pressure chemical vapour deposition (APCVD) of tungsten selenide films on glass substrates was achieved by reaction of diethyl selenide with WCl6 at 500-650 degrees C. X-Ray diffraction showed that the WSe2 films were crystalline with cell constants close to those expected-some preferred orientation was noted at higher deposition temperature. Energy-dispersive analysis by X-rays (EDAX) gave a W : Se ratio close to 1 : 2 for all the films formed at 550 degrees C. The films were matt black in appearance, were adhesive, passed the Scotch tape test but could be scratched with a steel scalpel. SEM showed that the films were composed of either plate or needle like crystals which become longer and thicker with increasing deposition temperature. The films were highly hydrophobic with contact angles for water droplets in the range of 135-145 degrees. Furthermore these surfaces were highly adherent for water droplets-that did not roll or slide even at a tilt angle of 90 degrees.