3. Results and discussion
First, we characterized the surface morphology of bismuth-tellurium films, as-deposited and annealed at various temperatures, using SEM. The film surface for the as-deposited sample, overall, appears smooth and only a careful observation of the image reveals some minor surface roughness, as shown in Fig. 1(a) For the sample annealed at 100°C, the surface became somewhat rougher with a few protrusions. As the annealing temperature increases higher, such protrusions appear more pronounced and shape into roughly a hexagonally-faceted morphology (shown in Fig. 1(c) and (d). which signals a possible surface reconstruction.
Next, we checked the microstructure of the films using XRD, as shown in Fig. 2. The as-deposited sample displays several small peaks, the positions of which match with those of (0 15) and (1 0 10) planes of the BizTe phase, respectively. After annealing at elevated temperatures, the XRD graph displays the emergence of some new peaks. For the sample annealed at 100 oc for 8 h, three small peaks appear around 17.5. 44.5 and 54.1 the peak positions corresponding to (006) (0015) and (0018) planes of BizTe3. It is interesting to note that these peaks a all from atomic planes perpendicular to the c-axis of the crystal structure.