Nanoindentation of TiO₂thin films with different microstructures

Abstract

A series of nanoindentation tests has been carried out with TiO2 films produced by physical vapour deposition (PVD) under different conditions. Films with different microstructures and crystallographic structures have been prepared by changing experimental parameters such as the temperature of the substrate, the deposition angle (by the so-called glancing angle physical vapour deposition, GAPVD) or by exposing the growing film to a beam of accelerated ions. The obtained results of hardness and Young's modulus depict interesting correlations with the microstructure and structure of the films providing a general picture for the relationships between these characteristics and their mechanical properties. Different models have been used to extract Young's modulus and hardness parameters from the experimental nanoindentation curves. The obtained results are critically discussed to ascertain the ranges of validity of each procedure according to the type of sample investigated.

Nanoindentation and scratch resistance of multilayered TiO2-SiO2coatings with different nanocolumnar structures deposited by PV-OAD

“…These data are also presented in Figure 3a and b, in order to better compare the different values of hardness and elastic modulus, respectively. This figure clearly shows that hardness and elastic modulus depend on the deposition angle, a result that agrees with previous results for TiO 2 PV-OAD coatings [19,21]. Common features of PV-OAD thin films, including the TiO 2 -SiO 2 multilayers studied here, are that both the tilting angle of nanocolumns and the void space increase with the deposition angle (c.f., Figure 1) [2,3,6,7].…”

“…However, mechanical properties such as hardness, elastic modulus or interfacial cohesion of this type of nanostructured multilayer TiO 2 -SiO 2 coatings have not been reported so far. In previous works, the mechanical properties of TiO 2 nanocolumnar coatings made by PV-OAD were investigated as a function of the zenithal angle of deposition [19,21], finding a strong dependence between the mechanical response and the deposition angle. The objective of the present work is to characterize the mechanical response of multilayer coatings formed by a different number layers of TiO 2 and SiO 2 stacked in the form of distinct microarchitectures where the tilted nanocolumns in successive layers present slanted, zigzag or chiral configurations.…”

Bending Induced Self-Organized Switchable Gratings on Polymeric Substrates

“…This deposition technique produces anisotropic porous thin films characterized by a tilted columnars microstructure resulting from shadowing effects during the growth process [16][17][18] . The nanocolumns tilting angle and porosity of these films increase gradually with the deposition angle while, simultaneously, the number of nanocolumns per unit area decreases 19,20 . In some materials like SiO2 the tilted nanocolumns tend to aggregate in the form of parallel nanochannels arranged perpendicular to the direction of the incoming flux.…”

“…Similar experiments carried out with G-TiO2/PDMS foils showed a similar decreasing trend, although in this system no significant differences were found by bending along the x or y axis (see S5). This different behavior can be linked with the low tendency of the TiO2-GLAD films to develop bundles of nanocolumns 19,20 and stresses the importance of the film nanostructure for the control of the micropatterning processes. Another interesting feature of the G-SiO2/PDMS system is that the average crack spacing is independent of the thin film thickness.…”

Investigation of the Young's modulus and thermal expansion of amorphous titania-doped tantala films

“…The opposite trend is seen with the 55% titaniadoped samples (black, upward triangles); again, with the exception of the 400°C sample. This is most likely due to the abundance of titania, which is known to have a low crystallization temperature and a high Young's modulus [36,37]. The two titania-doped samples heat-treated at 400°C were produced at the same time; they were most likely heat-treated together and may not have been fully heat-treated.…”