In this study the crystallization and defect analysis of $Ta_2O_5$ thin films on Si grown by plasma enhanced chemical vapor deposition have been investigated by transmission electron microscopy. The amorphous $Ta_2O_5$ films were annealed in dry $N_2$ by furnace. Annealing times were 4 min, 5 min, 10 min, 20 min, and 16h, at a temperature of 750℃, and annealing at 800℃ was carried out for 10 min.
When the $Ta_2O_5$ films were annealed for 20 min at a temperature of 750℃, the amorphous films were perfectly crystallized. The crystallized $Ta_2O_5$ thin films have δ phase with hexagonal structure. The average grain size of $Ta_2O_5$ films is 400-500 nm and the shape of grain is circular.
In grain, bend extinction contour is observed, and this contour is parallel to the particular plane. The rotation moire pattern with a spacing of 42 Å is observed. This moire pattern is appeared by twisting the (10$\bar{1}$0) plane with respect ot other (10$\bar{1}$0) plane by a small angle, and this moire pattern is approximately perpendicular to the (10$\bar{1}$0) plane. The crystal growth occurs by ledge mechanism, and the domain structure is observed in grain.
In [0001] zone, the dislocations with Burgers vector $\vec{b}$=[$\bar{1}$2$\bar{1}$0] are observed, and this dislocations dissociate into Shockley partial dislocation with $\vec{b}_1$=[$\bar{1}$100] and $vec{b}_2$=[01$\bar{1}$0]. In [1210] zone, dislocations with $\vec{b}$=[0001] and Frank partial dislocations with $\vec{b}$=1/2[0001] are observed.
The formation of $SiO_2$ layer at $Ta_2O_5$/Si interface is observed and the thickness of this layer is about 3 nm. The thickness of $Ta_2O_5$ layer is about 18.5 nm and the surface of this layer is rough.
