Effect of different annealing temperatures and SiO₂/Si(100) substrate on the properties of nickel containing titania thin sol–gel films

Abstract

Nickel containing titania thin films have been prepared on SiO 2 / Si(100) substrate by using the sol-gel deposition and annealing in the air at 450-1150 8C. Several experimental techniques [atomic force microscopy (AFM), X-ray diffraction (XRD), X-ray reflection (XRR), Raman spectroscopy, energy dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), UV-Vis spectroscopy and hydrophilicity measurements] have been applied to characterize these films. Further, the results of this study were compared to previously investigated nickel containing titania on HF-etched Si(100) (i.e. without oxide layer). The morphological and structural properties of nickel containing titania were found to be dependent on the kind of the substrate on which the films were prepared. The thin films deposited on SiO 2 /Si(100) substrate, compared to similar films on HF-etched Si(100) substrate, were more uniform, did not contain large pores and had smaller RMS roughness, especially when annealed below 650 8C. Also films on SiO 2 /Si(100) substrate were more crystalline and anatase transformation to rutile phase occurred at 150 8C lower temperature. Nickel in the films appeared to be in the 2þ oxidation state. When films were annealed above 650 8C, nickel was found mainly in the NiTiO 3 crystallites. Nickel compounds segregated to the surface of the film, forming islands. Nickel addition red-shifted the titania fundamental absorption edge further into the visible range. Films on both substrates demonstrated couple of tens of nanometers thick interlayer formation (between films and substrates) after annealing at 850 and 900 8C. We demonstrated that a well-crystallined anatase was crucial for obtaining a good light-induced hydrophilic nickel containing titania surface.

Heat treatment and substrate dependant properties of titania thin films with high copper loading

“…Contrary to Ni‐ and Co‐doped titania , where nickel‐ and cobalt‐containing compounds segregated to the surface of the films during annealing, further annealing of copper‐doped titania films to 900 °C leads to disappearance of the dopant from the surface region (Fig. ).…”

“…The procedure was repeated until the last sample was removed from the furnace after a 1‐h annealing at 900 °C. A similar sol–gel method and annealing procedure has been utilized previously by us to prepare undoped and cobalt‐doped titania films on SiO 2 /Si(100) and nickel‐doped titania on HF‐etched Si(100) and SiO 2 /Si(100) substrate .…”

“…It is proposed that initial Cu 2+ is reduced by photogenerated electrons or OH radicals in the precursor . Another interesting question is whether copper segregates during annealing out of the titania matrix as observed previously in case of nickel and cobalt . Photocatalytic reactions occur on the surface and therefore the behaviour of copper atoms on the surface is especially important.…”

Photocatalytic antibacterial activity of nano-TiO2 (anatase)-based thin films: Effects on Escherichia coli cells and fatty acids

“…Antibacterial applications of TiO 2 often use thin film coatings that can be deposited by various methods including sputtering [17], chemical solution deposition [18], pulsed laser deposition [19] or sol-gel method [20][21][22][23].…”

Influence of some system parameters on silica surface patterns by sol-gel phase separation method

“…In addition to the possibility of preparing different pure [5], doped [6,7], mixed oxides [8] and hybrids [8,9] at relatively low temperatures, sol-gel also enables in-situ control over the nano-and microstructure of prepared materials during transition from sol to gel [10]. Micro-and nanostructure of surfaces has a critical role in the design of superhydrophobic coatings [11] and solgel has been applied in phase separation based strategies [12,13] to achieve suitable micro-and nanoroughness.…”