Nanomechanical, structural, and transport properties of Bi3Se2Te thin films

• Effects of helium gas pressure on the properties of nanocrystalline Bi3Se2Te films were studied.
• Hardness and Young's modulus of the Bi3Se2Te films enhanced with increasing helium gas pressure.
• Bi3Se2Te films exhibited 2D weak antilocalization for B ±1 T and linear magnetoresistance for B ≥ 4 T.
• The new phase of Bi3Se2Se likely exist the topological insulator surface state.

New ternary phase of Bi3Se2Te thin films were successfully grown through pulsed laser deposition with a single Bi2Se2Te crystal as the target. Bi-rich and Se- and Te-deficient compositions deposited at a substrate temperature (Ts) of 250 °C and helium gas pressures (PHe) ranging from 2.0 × 10−5 to 6.5 × 10−1 Torr aided the formation of the dominant Bi-rich phase: Bi3Se2Te. The films were grown epitaxially on Al2O3 (001) substrates with Bi3Se2Te [001]//Al2O3 [001] and Bi3Se2Te [110]//Al2O3 [210]. An increase in PHe remarkably enhanced the hardness and Young's modulus of the films, primarily because of the decrease in nanograin size, following the Hall–Petch relationship. Moreover, the Bi3Se2Te films present linear magnetoresistance under a high perpendicular magnetic field (B ≥ 4 T) and two-dimensional weak antilocalization effect under a low B (±1 T) which may be attributed to topological insulator surface state (TSS). Clearly, further theoretical calculations and experiments are needed to confirm the suggested interpretation.

Figure optionsDownload as PowerPoint slide