Growth of single phase tetragonal structure iron tantalum oxide thin films grown by sol-gel spin coating technique

Abstract

For the first time, crack free, and dense tetragonalFe2Ta2O8 thin films have been prepared by sol-gel method using tantalum isopropoxide and iron oxalate. As the annealing temperature increased from 700 to 800 ◦C, we have observed the growth of rhombohedral phase of iron tantalum oxide along with Fe2Ta2O8 tetragonal phase. The complete and single phase of Fe2Ta2O8 tetragonal structure was formed on silicon (100) substrate at an annealing temperature of 900 ◦C for 5 h. Structural, morphological studies of these Fe2Ta2O8 thin films produced by sol-gel synthesis have been characterized by grazing incidence X-ray diffraction (GIXRD), and tapping mode atomic force microscopy. Iron based mixed-type oxides containing metals such as MTaO4 (M = W, Ti, Co, Cr) are well known as functional inorganic materials having a wide range of applications such as electrodes of solid oxide fuels (SOFCs) [1], metal-air barriers [2], gas sensors [3], and as high performance catalysts [4] for the complete oxidation of hydrocarbons or CO and NO2 reduction as well as magnetic oxides for recording medium. Many preparation processes with low cost and low processing temperatures, such as the malate route [5], citrate route [6], polymeric precursor route [7], propionic acid route [8] have been reported to synthesize nanocrystalline powders. These methods can easily synthesize fine powders: however, it is difficult to use them to prepare thin films, as most of these amorphous precursors used in the processes mainly consist of some organic compounds and metal nitrates which easily explode to form powders. So far, oxide thin films structure have only been prepared by dry processes such as sputtering [9] and laser ablation [10] and metal organic chemical vapor deposition [11] methods. The sol-gel technique has many advantages over other fabrication techniques, such as homogeneity, stoichiometry control, purity, ease of processing and controlling the composition and ability to coat large and complex area substrates [12]. The crystallization of sol-gel derived films has followed a development path that is similar to that which has been observed in simple metal oxides that were prepared using sol-gel technique [13]. In the present study, we have selected iron oxalate for iron source and tantalum isopropoxide for tantalum source as starting materials of a sol-gel process to synthesize iron tantalum oxide