Plasma-Enhanced Atomic Layer Deposition Of Al2O3 Thin Film On Tio2 Nanotubes

In this work plasma-enhanced atomic layer deposition (PEALD) using trimetylaluminum (TMA) and oxygen plasma was used to deposit aluminum oxide (Al
2
O
3
) thin film on anodic titanium dioxide (TiO
2
) nanotube array with mean internal diameter of 100 nm. The effect of plasma power was investigated in order to found a better condition of covering of TiO
2
nanotubes for water splitting application. The reactor geometry is an asymmetric capacitive coupled (CCP) radio frequency (13.56 MHz) discharge, and the pressure investigated was fixed at 1 mbar and the discharge power varied in the range of 10-200 W. The total reaction cycle number was fixed on 200 cycles and the process temperature at $100 ^{\circ}\mathrm {C}$. These are typical conditions for PEALD process
¹
. SEM measurements were performed for investigate the covering process. Moreover, Raman spectroscopy was performed for investigate the structure change of material. Results indicate that the increase of RF power increase the growth rate in up to 10%, characterizing a possibility of fine adjustment of the coating of the nanotubes. SEM micrographs show that the PEALD of Al
2
O
3
were very conformal for wide range of RF power investigated, allowing to obtain a good coverage of TiO
2
nanotubes. Finally, Raman spectroscopy evidence that the increase of RF power caused a change on TiO
2
phase from amorphous to anatase.