Abstract
Pristine, and In-, Sn-, and (In, Sn)-doped Bi2Se3 nanoplatelets synthesized on Al2O3(100) substrate by a vapor–solid mechanism in thermal CVD process via at 600 °C under 2 × 10−2 Torr. XRD and HRTEM reveal that In or Sn dopants had no effect on the crystal structure of the synthesized rhombohedral-Bi2Se3. FPA–FTIR reveals that the optical bandgap of doped Bi2Se3 was 26.3%, 34.1%, and 43.7% lower than pristine Bi2Se3. XRD, FESEM–EDS, Raman spectroscopy, and XPS confirm defects (), (), (), (), and (). Photocurrent that was generated in (In,Sn)-doped Bi2Se3 under UV(8 W) and red (5 W) light revealed stable photocurrents of 5.20 × 10−10 and 0.35 × 10−10 A and high Iphoto/Idark ratios of 30.7 and 52.2. The rise and fall times of the photocurrent under UV light were 4.1 × 10−2 and 6.6 × 10−2 s. Under UV light, (In,Sn)-dopedBi2Se3 had 15.3% longer photocurrent decay time and 22.6% shorter rise time than pristine Bi2Se3, indicating that (In,Sn)-doped Bi2Se3 exhibited good surface conduction and greater photosensitivity. These results suggest that In, Sn, or both dopants enhance photodetection of pristine Bi2Se3 under UV and red light. The findings also suggest that type of defect is a more important factor than optical bandgap in determining photo-detection sensitivity. (In,Sn)-doped Bi2Se3 has greater potential than undoped Bi2Se3 for use in UV and red-light photodetectors.
Highlights
The crystalline Bi2 Se3 is composed of layered structures; each layer consists of five stacked monoatomic layers, as in Se-Bi-Se’-Bi-Se, and is known as a quintuple layer (QL) [3]
The decreases in a are attributed to the substitution of Bi rather than Se by the In or Sn
These results suggest that the dopants, and especially the co-dopants In and Sn, in Bi2 Se3 nanoplatelets, have various favorable effects, which are (1) extending the electron lifetime, (2) increasing the electron concentration, (3)
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. A TI has an insulating bulk state and a topologically protected gapless surface state in three dimensions and an edge state in two dimensions, owing to spin-orbital coupling (SOC) and time-reversal symmetry (TRS) [6,7] Both SOC and TRS suppress backscattering and reduce the sensitivity to surface impurities or defects when electrons are transported on the surface of a TI. As required for use in photodetectors, topological insulating Bi2 Se3 is a potential material and has fascinating optoelectronic properties, such as a tunable surface bandgap, a polarization-sensitive photocurrent, and thicknessdependent optical absorption [35]. Alemi et al synthesized Bi2 Se3 nanoplatelets, which had a bandgap of 2.95 eV, by a hydrothermal process [41] These results reveal that the absorption range of Bi2 Se3 can be narrowed, affecting its photodetective efficiency. The photosensitivities were systematically obtained by measuring the photocurrents under UV and red light
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
