Evolution of TiOx-SiOx nano-composite during annealing of ultrathin titanium oxide films on Si substrate

This paper discusses the formation of the TiOx-SiOx nano-composite phase during annealing of ultrathin titanium oxide films (~27 nm). The amorphous titanium oxide films are deposited on silicon substrates by sputtering. These films are important for high-k dielectrics and sensing applications. Annealing of these films at 750 °C in the O2 environment (for 15–60 min) resulted in the polycrystalline rutile phase. The films exhibit Raman peaks at 150 cm−1 (B1g), 435 cm−1 (Eg), and 615 cm−1 (A1g) confirming the rutile phase. The signature TO (1078 cm−1) and LO (1259 cm−1) infrared active vibrational modes of Si–O–Si bond confirms the presence of silicon-oxide. The X-ray photoelectron spectra of the TiOx films show multiple peaks corresponding to Ti metal (453.8 eV); Ti4+ state (458.3 eV (Ti 2p3/2) and 464 eV (Ti 2p1/2)); and Ti3+ state (456.4 eV (Ti 2p3/2) and 460.8 eV (Ti 2p1/2)). The O1s XPS spectra peaks at 530–533 eV can be attributed to Ti–O and Si–O bonds of the TiOx-SiOx nano-composite phase in the annealed films. The depth profiling XPS study shows that the top surface of the annealed film is mainly TiOx and the amount of SiOx increases with the depth.