Combinatorial Atmospheric Pressure CVD of a Composite TiO2/SnO2 Thin Film


  • The authors thank Dr. Felicity Sartain for useful discussions and Mr. Kevin Reeves for assistance with SEM imaging. They also thank Pilkington for the glass substrates. The project was funded by the Deanship of Scientific Research (DSR), King Abdulaziz University, Jeddah under grant No. D-5/432. The authors, therefore, acknowledge DSR with thanks for their technical and financial support.


Combinatorial atmospheric pressure (cAP)CVD is used to deposit a film of graded composition from mainly TiO2 to TiO2/SnO2 to mainly SnO2. This is the first cAPCVD study of a TiO2/SnO2 system. The thin film is characterized using a range of techniques such as X-ray diffraction (XRD), wavelength dispersive X-ray (WDX) spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and ultra violet-visible (UV-vis) spectroscopy. It is found that, at various positions on the film, there are intimate compositions of TiO2 and SnO2. The photocatalytic activity is examined via the degradation of a Resazurin-based ‘intelligent ink’ under 365 nm wavelength irradiation. The change in the concentration of the dye can be monitored by digital imaging alone. The results show how TiO2-rich regions are photocatalytically active, producing a maximum formal quantum yield of 3.32 × 10−4 molecules per absorbed photon. The sheet resistance is determined using a four-point probe via the van der Pauw method. The conductivity is highest in the SnO2-rich and thicker regions of the film, however some of the intimate composite regions of TiO2/SnO2 show both conductivity and photocatalytic activity.