Pierre Giovanni Mani Gonzalez

arXiv2019

Effect of Ion Bombardment on the Chemical Properties of Crystalline Tantalum Pentoxide Films

The effect of argon ion bombardment on the chemical properties of crystalline Ta$_2$O$_5$ films grown on Si(100) substrates by radio frequency magnetron sputtering was investigated by X-ray photoelectron spectroscopy. All samples were irradiated for several time intervals [(0.5, 3, 6, 9) min] and the Ta $4f$ and O $1s$ core levels were measured each time. Upon analysis at the surface of the films, we observe the Ta $4f$ spectrum characteristic of Ta$_2$O$_5$. Irradiated samples exhibit the formation of Ta suboxides with oxidation states Ta$^{1+}$, Ta$^{2+}$, Ta$^{3+}$, Ta$^{4+}$, and Ta$^{5+}$. Exposing the films, after ion bombardment, to ambient for some days stimulates the amorphous phase of Ta$_2$O$_5$ at the surface suggesting that the suboxides of Ta are unstable. Using a sputtering simulation we discuss that these suboxides are largely generated during ion bombardment that greatly reduces the oxygen to tantalum ratio as the irradiation time increases. The computer simulation indicates that this is due to the high sputtering yield of oxygen.

cond-mat.mtrl-sci↗

arXiv2018

Influence of post-deposition annealing on the chemical states of crystalline tantalum pentoxide films

We investigate the effect of post-deposition annealing (for temperatures from 848 K to 1273 K) on the chemical properties of crystalline Ta$_2$O$_5$ films grown on Si(100) substrates by radio frequency magnetron sputtering. The atomic arrangement, as determined by X-ray diffraction, is predominately hexagonal ($δ$-Ta$_2$O$_5$) for the films exposed to heat treatments at 948 K and 1048 K; orthorhombic ($β$-Ta$_2$O$_5$) for samples annealed at 1148 K and 1273 K; and amorphous for samples annealed at temperatures below 948 K. X-ray photoelectron spectroscopy for Ta $4f$ and O $1s$ core-levels were performed to evaluate the chemical properties of all films as a function of annealing temperature. Upon analysis, it is observed the Ta $4f$ spectrum characteristic of Ta in Ta$^{5+}$ and the formation of Ta-oxide phases with oxidation states Ta$^{1+}$, Ta$^{2+}$, Ta$^{3+}$, and Ta$^{4+}$. The study reveals that the increase in annealing temperature increases the percentage of the state Ta$^{5+}$ and the reduction of the others indicating that higher temperatures are more desirable to produce Ta$_2$O$_5$, however, there seems to be an optimal annealing temperature that maximizes the O\% to Ta\% ratio. We found that at 1273 K the ratio slightly reduces suggesting oxygen depletion.

cond-mat.mtrl-sci↗