Tin phosphide coatings from the atmospheric pressure chemical vapour deposition of SnX4 (X=Cl or Br) and PRxH3−x (R=Cychex or phenyl)

Atmospheric pressure chemical vapour deposition (APCVD) of tin phosphide thin films was achieved on glass substrates from the reaction of SnCl4 or SnBr4 with RxPH3−x (R=Cychex or phenyl) at 500–600°C. These coatings show good uniformity and surface coverage. They are reasonably adherent, passing the Scotch tape test. The films were largely opaque in appearance with regions of birefringence. The films were X-ray amorphous. Scanning electron microscopy (SEM) showed surface morphologies consistent with an island growth mechanism. X-ray photoelectron spectroscopy (XPS) binding energy shifts for SnP1.00 were 487.2 eV for Sn 3d5/2 and 133.6 eV for P 2p3/2. Energy dispersive X-ray analysis (EDXA) and electron probe studies gave elemental ratios that were in agreement indicating slightly tin rich and stoichiometric films, with negligible chlorine or bromine incorporation (SnP1.33–SnP0.40). No Raman scattering was observed. Sheet resistance measurements indicated the films were insulating. Optically the films showed very poor reflectance (approximately 2%) and 5–20% total transmissions from 300 to 800 nm. Contact angle measurements were in the range 70–80°, and showed little change after 60-min irradiation at 254 nm.