Low temperature Au induced crystallization of titanium dioxide thin films for resistive switching applications

Abstract

Metal induced decrease of crystallization temperature of sol-gel derived titanium dioxide (TiO 2 ) thin films is reported. It is shown that the Au induced onset of crystallization occurs at a temperature of 250 C as compared to 400 C when it is deposited directly on the same substrate. The crystallization process is probed using X-ray diffraction and confirmed by Raman spectroscopy. The onset of crystallization is evidenced by the appearance of the diffraction peak from the (101) plane of anatase TiO 2 and the peak due to A 1g + B 1g Raman mode at 515 cm À1 . Polarized optical microscopy and Raman imaging indicated that the spatial spread of crystallization across the surface of the film increases with the increase in temperature. Unipolar resistive switching is demonstrated by fabricating an Au/TiO 2 /Au stack, which shows formation at 9 V, set voltage of 0.5 V and reset voltage of 3.3 V. The maximum set-reset resistance ratio achieved was 10 5 . The mechanism of resistive switching is established by a correlation with photoluminescence spectra which indicates the presence of defects that aid in the switching process.

Microwave-Assisted and Metal-Induced Crystallization: A Rapid and Low Temperature Combination

“…Another well-known method to decrease the temperature of crystallization is metal-induced crystallization, 18−21 which was applied to titania materials by Sangani et al in 2015. 22 This report showed a reduction of the crystallization temperature from 400 to 300 °C through the diffusion of gold species through a vitreous titania film. To our knowledge, no one has yet reported coupling metal-induced crystallization with microwave-assisted crystallization.…”

“…This burst of crystallization differs from what has been observed in TiO 2 films via convective heating metal-induced crystallization. In this report by Sangani et al, crystallization centers appeared in a mass of amorphous titania. The difference in mechanism may be explained by the inhomogeneous distribution of Au in the TiO 2 film.…”

“…Other similar examples can be referred to in refs – . Another well-known method to decrease the temperature of crystallization is metal-induced crystallization, − which was applied to titania materials by Sangani et al in 2015 . This report showed a reduction of the crystallization temperature from 400 to 300 °C through the diffusion of gold species through a vitreous titania film.…”

Metal-Induced Crystallization in Metal Oxides

“…The mechanism of crystallization of thin films using a gold layer was studied via Raman imaging and showed that very small and sparse crystallites appear at 250 °C. 27 The density of crystallites increases with annealing temperature; it seems that the crystallites do not grow in size, but rather, more small crystallites nucleate within the film. Yang et al 27 found that, when TiO 2 was deposited on a thin contact film, Ni and Cu participated in the MIC to a higher degree than Au and NiO contact films.…”

Crystallized TiO2 Nanosurfaces in Biomedical Applications

“…The relative amount of anatase formation in the final material is higher for the samples anodized with a higher voltage compared to the TiO 2 nanotubes anodized at a lower voltage [ 38 ]. Sangani et al [ 39 ] demonstrated that the addition of metals, such as Au, to the sol–gel derived TiO 2 thin films also decreases the crystallization temperatures. Elevated temperatures are, however, responsible for the atoms’ rearrangements in a TiO 2 lattice.…”