Titanium oxide (TiO 2 ) films and TiO 2 /SiN x stacks have potential in surface passivation, anti-reflection coatings and carrier-selective contact layers for crystalline Si solar cells. A Si wafer, deposited with 8-nm-thick TiO 2 film by atomic layer deposition, has a surface recombination velocity as low as 14.93 cm/s at the injection level of 1.0 × 10 15 cm −3 . However, the performance of silicon surface passivation of the deposited TiO 2 film declines as its thickness increases, probably because of the stress effects, phase transformation, atomic hydrogen and thermal stability of amorphous TiO 2 films. For the characterization of 66-nm-thick TiO 2 film, the results of transmission electron microscopy show that the anatase TiO 2 crystallinity forms close to the surface of the Si. Secondary ion mass spectrometry shows the atomic hydrogen at the interface of TiO 2 and Si which serves for chemical passivation. The crystal size of anatase TiO 2 and the homogeneity of TiO 2 film can be deduced by the measurements of Raman spectroscopy and spectroscopic ellipsometry, respectively. For the passivating contacts of solar cells, in addition, a stack composed of 8-nm-thick TiO 2 film and a plasma-enhanced chemical-vapor-deposited 72-nm-thick SiN x layer has been investigated. From the results of the measurement of the reflectivity and effective carrier lifetime, TiO 2 /SiN x stacks on Si wafers perform with low reflectivity and some degree of surface passivation for the Si wafer.
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