Do you mean the surface resistance of Titanium dioxide films?
If so, the film thickness also affects the surface resistance. To reduce the resistance, you could introduce some dopants into TiO2. Again it very much depends on how you form the films. The methods can be different.
The area is far too big for Hall effect measurement. Ideally four contact electrode point should not be bigger than 1cm by 1cm. The film thickness should be thicker from over 50nm to 200nm.