Tuesday, 3 October 2017: 12:20
Chesapeake H (Gaylord National Resort and Convention Center)
Bismuth selenide (Bi2Se3) is a semiconductor presenting two distinct crystalline phases, one with rhombohedral structure (R-3M), and another, metastable, with orthorhombic phase (Pnma). Each phase has distinct band gap and interesting optical, thermoelectric and topological electronic properties. Thin films of thicknesses up to 1.5 μm were grown by electrodeposition under constant potential onto silicon (100) substrate. It is shown that under an optimum set of deposition parameters, simultaneous heating and electrolyte stirring, very smooth and thick films can be obtained. Morphological characterization evidences the formation of compact, uniform and smooth layers, attributed to the growth of very small grains of ~50 nm. Structural characterization of the samples indicates a majority of a metastable orthorhombic phase with traces of a rhombohedral phase. The films grow initially with a rhombohedral crystalline structure, which progressively changes to orthorhombic, likely due to the accumulation of internal stresses and successive stress relaxation. In addition, a full recrystallization to the rhombohedral structure can be achieved by using short time and low temperature thermal treatments. These results show the possibility to grow smooth samples and also to control the crystalline structure of Bi2Se3. This is of interest since both phases present different but complementary properties, and each one or the combination of the two may be successfully exploited to the construction of low cost, efficient novel devices based on thermoelectric, optical or topological insulator technologies.