Germanium phosphide coatings from the atmospheric pressure chemical vapour deposition of GeX4 (X = Cl or Br) and PCychexH2

Atmospheric pressure chemical vapour deposition of germanium phosphide thin films was achieved on glass substrates from the reaction of GeCl4 or GeBr4 with pCyc(hex)H(2) at 600degreesC. These coatings show good uniformity and surface coverage. They are reasonably adherent, passing the Scotch tape test. The films were translucent in appearance with regions of birefringence. The films were X-ray amorphous. Scanning electron microscopy showed surface morphologies consistent with an island growth mechanism. X-ray photoelectron spectroscopy binding energy shifts for GeP1.00 were 1218.2 eV for Ge 2P(3) and 131.5 eV for P 2P(3/2). Energy dispersive X-ray analysis and electron probe studies gave elemental ratios that were in agreement indicating films which varied from being germanium rich (Ge3P) to phosphorus rich (GeP2), with negligible chlorine or bromine incorporation dependent on deposition conditions. No Raman scattering was observed. Sheet resistance measurements indicated the films were poor conductors. Optically the films showed poor reflectance (5-10%) and 60-80% total transmission from 400 to 1000 run. UV-Vis spectroscopy indicated an indirect band gap of 1.1 eV. Contact angle measurements were in the range 60degrees-80degrees and showed no significant change after 60 min irradiation with 254 nm UV light. (C) 2003 Elsevier Science Ltd. All rights reserved.