Structural, optical, and electrical properties of TiO2 thin films deposited by ALD: Impact of the substrate, the deposited thickness and the deposition temperature

TiO 2 films were deposited by ALD on Si and glass substrates. FTIR analysis reveals an incomplete process for deposition temperatures below 160 °C. The transition from the amorphous to the crystallized anatase phase is observed during the variation of the deposition temperature. Films were uniform and homogeneous, with a crystallization threshold temperature depending on the substrate’s nature. This delay in crystallization temperature was highlighted by many characterization techniques and found higher by about 50 °C on glass compared to Si substrate. We have also identified the determining role of the deposition temperature and the thickness in the crystallization process and we propose a growth model, independently of the substrate’s nature, using different structural analyses. TiO 2 refractive index (n) and extinction coefficient (k) were studied at various deposition temperature. The evolution of the TiO 2 polarizability ( α opt ) with material density was determined from n values, showing a large variation of polarizability as a function of material density, in agreement and complementary with other studies. The investigation of the dielectric properties at low frequency shows that the losses and relaxation in TiO 2 decrease with deposition temperature, reaching at 300 °C a high and frequency-independent dielectric constant, close to the one reported for polycrystalline anatase.