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Topological insulators and their characteristics are among the most highly studied areas in condensed matter physics. Bi2Se3 nanocrystals were synthesized via chemical vapor deposition at different temperatures on a silicon substrate with a gold catalyst. The effects of temperature on the obtained Bi2Se3 nanocrystals were systematically investigated. The size and length of Bi2Se3 nanocrystals change when the temperature increases from 500 °C to 600 °C. We found that the crystallization quality of the Bi2Se3 nanocrystals synthesized at 560 °C is optimal. At this temperature, we can get the desired thickness and length of the nanocrystals, which is quite suitable for nanoscale fabrication.

Large unsaturated magnetoresistance (XMR) with magnitude ∼103% is observed in topological insulator candidate TaSe3 from our high field (up to 38 T) measurements. Two oscillation modes, associated with one hole pocket and two electron pockets in the bulk, respectively, are detected from our Shubnikov-de Hass measurements, consistent with our first-principles calculations. With the detailed Hall measurements performed, our two-band model analysis exhibits an imperfect density ratio nh/ne ≈ 0.9 at T < 20 K, which suggests that the carrier compensations account for the XMR in TaSe3.