Energy band alignment at TiO2/Si interface with various interlayers

Anatase TiO(2) films are grown on Si (100) by atomic layer deposition. Three different interlayers (Si(3)N(4), Al(2)O(3), and Ti-rich SiO(x)) between the TiO(2) films and the Si substrate have been considered. The band alignment of the titanium oxide films with the silicon substrate is investigated by x-ray photoelectron spectroscopy (XPS), internal photoemission (IPE) spectroscopy, and optical absorption (OA) measurements. XPS analysis indicates that TiO(2)/Si heterojunctions with different interlayers (ILs) have different valence-band offsets (VBOs). A VBO value of 2.56 +/- 0.09 eV is obtained for the TiO(2)/Ti-rich SiO(x)/Si sample. Similarly, we obtain a VBO value of 2.44 +/- 0.09 and 2.73 +/- 0.10 eV for the TiO(2)/Si(3)N(4)/Si and TiO(2)/Al(2)O(3)/Si samples, respectively. According to IPE and OA measurements, the band gap of the as-grown TiO(2) films is 3.3 +/- 0.1 eV for all the samples. Combining the XPS and IPE data, the conduction band offset values at the TiO(2)/Si heterojunction are found to be -0.2 +/- 0.1, -0.4 +/- 0.1, and -0.5 +/- 0.1 eV for the TiO(2)/Si(3)N(4)/Si, TiO(2)/Ti-rich SiO(x)/Si, and TiO(2)/Al(2)O(3)/Si samples, respectively. According to our experimental results, the band alignment of a TiO(2) film with the underlying Si (100) substrate is clearly affected by the presence of an IL, suggesting the possibility to tune the band structure of a TiO(2)/Si heterojunction by selecting the proper IL. (c) 2008 American Institute of Physics.