Hello Sritiama,

Appended is some links that you might find useful.

In the first, the authors report a breakdown voltage of 2.7 MV/cm for synthesised TiO2 thin films.

In the second, the authors use a dip-coating method and report a value of 21 MV/m.

http://adsabs.harvard.edu/abs/1998JAP....83.3311S

http://iopscience.iop.org/article/10.1088/0953-2048/28/3/035010/meta

Sritiama, 

As requested, here are the full texts.