On the influence of conductor, semiconductor and insulating substrate on the structure of atomic layer deposited titanium dioxide thin films

Abstract

Titanium dioxide (TiO( 2 ) thin films were deposited on conductive (titanium and fluorine tin oxide glass), insulant (mica, cover glass and thermal SiO( 2 thin film on silicon) and semiconductive (silicon (100) and 4H-SiC) substrates by atomic layer deposition (ALD) technique. The metal and ligand precursors used were titanium tetrachloride and water, respectively. Grazing incidence x-ray diffraction (GIXRD) analysis was performed to investigate the dependence of crystalline phase of the as-deposited thin films on different substrates for process temperatures ranging from $150-450 ^{\circ}\mathrm{C}$. Results indicate that the ALD TiO( 2 crystalline phase is dependent on the substrate nature which modifies the required temperature for phase change, i.e. from amorphous to anatase to rutile. For example, for conductive substrates the temperature for formation of rutile phase is around $350 ^{\circ}\mathrm{C}$ while for semiconductor substrates it was observed only from $400 ^{\circ}\mathrm{C}$. By other hand, when the substrate has an amorphous structure there is not a common rule, i.e. for mica and thermal SiO( 2 thin film on silicon only anatase phase was formed in all temperature range investigated while, for cover glass, it was possible to observe all stages of TiO( 2 phase change, highlighting the formation of brookite phase for temperatures between 300 and $350 ^{\circ}\mathrm{C}$. Moreover, it is shown that rutile phase can be obtained, in pure phase, at temperatures higher than $400 ^{\circ}\mathrm{C}$, however only for glass and titanium substrates. These results allow us to infer that less expensive Ti thin film could act as a good seed layer for growth of good quality rutile TiO( 2 phase, by using ALD process on Si substrate and using precursors such as TiCl 4 and H 2 O.