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 (In3+Bi3+), (In3+V0), (Sn4+Bi3+), (V0Bi3+), and (Sn2+Bi3+). 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.
Keywords: Bi2Se3; defects; nanoplatelets; optical bandgap; photocurrent.