Resistive Switching in Titanium dioxide: Comparison of thermally oxidized and magnetron sputtered films

Resistive RAM devices based on TiO2 are promising candidates for the next generation memory storage devices.
We compared TiO2 thin films from two different preparation methods with respect to crystallinity and resistive switching behavior.
While thermal oxidation of 100nm Ti on Pt/Ti/SiO2/Si substrates leads to polycrystalline rutile TiO2 layers, dc-magnetron sputter deposition of films on Nb:STO substrates leads to epitaxial anatase TiO2 structure.
In case of the rutile films, unipolar switching occurred, which points to a filamentary mechanism based on the formation of Magnéli phases [1]. The epitaxial anatase films, however, showed bipolar switching, which we correlated with the modification of the metal/oxide interface due to the drift of oxygen vacancies in the applied electric field [2].

The project is funded by the Initiative and Networking Fund of the Helmholtz Association (VI MEMRIOX, VH-VI-422).

[1] Deok-Hwang Kwon et al., “Atomic structure of conducting nanofilaments in TiO2 resistive switching memory”, Nature Nanotechnology 5, 148 – 153 (2010)

[2] J. Joshua Yang et al., “Memristive switching mechanism for metal/oxide/metal nanodevices”, Nature Nanotechnology 3, 429 – 433 (2008)