RESUMO
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.
RESUMO
Al-free and Al-doped V2O5 nanostructures were synthesized by a thermal-chemical vapor deposition (CVD) process on Si(100) at 850 °C under 1.2 × 10-1 Torr via a vapor-solid (V-S) mechanism. X-ray diffraction (XRD), Raman, and high-resolution transmission electron microscopy (HRTEM) confirmed a typical orthorhombic V2O5 with the growth direction along [110]-direction of both nanostructures. Metallic Al, rather than Al3+-ion, was detected by X-ray photoelectron spectroscopy (XPS), affected the V2O5 crystallinity. The photoluminescence intensity of V2O5 nanostructure at 1.77 and 1.94 eV decreased with the increasing Al-dopant by about 61.6% and 59.9%, attributing to the metallic Al intercalated between the V2O5-layers and/or filled in the oxygen vacancies, which behaved as electron sinks. Thus the Al-doped V2O5 nanostructure shows the potential applications in smart windows and the electrodic material in a Li-ion battery.
RESUMO
Substantial silver-embedded aluminum/silica nanospheres with uniform diameter and morphology were successfully synthesized by sol-gel technique. After various annealing temperatures, the surface mechanisms of each sample were analyzed using scanning electron microscope, transmission electron microscope, and X-ray photoelectron spectroscopy. The chemical durability examinations and antibacterial tests of each sample were also carried out for the confirmation of its practical usage. Based on the result of the above analyses, the silver-embedded aluminum/silica nanospheres are eligible for fabricating antibacterial utensils.
RESUMO
High density Sb-doped SnO2 nanobelts and beak-like nanorods were synthesized on alumina substrates using thermal evaporation. X-ray diffraction (XRD) pattern shows that both the nanobelts and beak-like nanorods are single crystals with the tetragonal rutile structure. Transmission electron microscopy (TEM) images show that the nanobelts grow along the [110] direction, but the nanorods grow with an abrupt change from the [101] direction to the [301] direction. X-ray photoelectron spectroscopy (XPS) analysis shows that the Sb 3d 3/2 peak of not fully oxidized beak-like nanorods shifts from 540.5 eV to 535.4 eV, and the Sn 3d 3/2 peak also shifts from 496.3 eV to 492.8 eV. Room temperature cathodoluminescence (CL) measurements show that both the nanobelts and beak-like nanorods exhibit blue and orange emissions that are related to the interstitial defects and oxygen deficiencies. The comparative study of CL measurements between nanobelts and beak-like nanorods demonstrate that the optical properties can be modified by altering the oxygen deficiencies.
