Study of the Anatase to Rutile/Brookite phase transition and its dependence with film strain

Anatase(001) films grown by PLD show heteroepitaxial strain along their growth direction. The strain is dependent on the film growth temperature and/or heat treatment (annealing) processes. The strain tends to disappear with increasing growth temperature and/or subsequent annealing (film relaxation). The gradual effect of relaxation of the film with temperature occurs through a progressive expansion of the cell parameter c. Complete relaxation of the film occurs at a temperature of 950ºC. The relaxed state of the film enables the initiation of the anatase to rutile phase transition if the temperature of the film continues to increase. There are indications that during the transition not only the rutile phase is formed but also the brookite. The objective is to study the structural phase transition of anatase to rutile and brookite using anatase films grown at 600ºC by PLD. The effects of structural strain and oxygen vacancies on the phase transition will be investigated.