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

Abstract Combinatorial atmospheric pressure (cAP)CVD is used to deposit a film of graded composition from mainly TiO 2 to TiO 2 /SnO 2 to mainly SnO 2 . This is the first cAPCVD study of a TiO 2 /SnO 2 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 TiO 2 and SnO 2 . 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 TiO 2 ‐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 SnO 2 ‐rich and thicker regions of the film, however some of the intimate composite regions of TiO 2 /SnO 2 show both conductivity and photocatalytic activity.