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.