Surface passivation of c-Si by Atomic Layer Deposition TiO2 thin films deposited at low temperature

For the silicon surface passivation, we investigate titanium dioxide (TiO2) deposited on p-type FZ silicon wafer by Atomic Layer Deposition (ALD) technique at low temperature as 200°. In the repost, four kinds of film thickness: 8 nm, 15 nm, 35 nm and 66 nm were proposed, and we found amorphous TiO2 thin film with thickness 8 nm have very good surface passivation properties on Si, and its surface recombination velocity can be lowered to 44.24 cm/s, which is good for the applications in crystalline silicon solar cells. However, we find the surface passivation properties decline as increasing the thickness of TiO2 films. From the characterization of Scanning Electron Microscopy (SEM), Grazing Incidence X-Ray (GIXRD), Transmission Electron Microscopy (TEM), Atomic Force Microscopy (AFM) and stress measurements of thin film, TiO2 anatase phase forms due to the stress inducing phase transformation, and surface roughness increases a lot for thicker TiO2 films. The phase transformation and surface roughening make the defects formation at the interface of Si and TiO2, which increase surface recombination velocity.