Structure-Dependent Optical Properties of Self-Organized Bi₂Se₃ Nanostructures: From Nanocrystals to Nanoflakes

Abstract

Bismuth selenide (BiSe), with a wide bulk band gap and single massless Dirac cone at the surface, is a promising three-dimensional topological insulator. BiSe possesses gapless surface states and an insulator-like bulk band gap as a new type of quantum matter. Different BiSe nanostructures were prepared using electron beam evaporation with high production efficiency. Structural investigations by energy-dispersive X-ray analysis, scanning electron microscopy, and X-ray diffraction revealed the sample stoichiometries and the structural transition mechanism from nanocrystals to nanoflakes. The optical properties systematically probed and analyzed by spectroscopic ellipsometry showed strong dependence on the nanostructures and were also predicted to have structure-modifiable technological prospects. The optical parameters, plasma frequencies, scattering rates of the free electrons, and optical band gaps were related to the topological properties of the BiSe nanostructures via light-matter interactions, offering new opportunities and approaches for studies on topological insulators and spintronics. The high-quality BiSe nanostructures provide advantages in exploring novel physics and exploiting prospective applications.

Low Deposition Temperature Amorphous ALD-Ga2O3 Thin Films and Decoration with MoS2 Multilayers toward Flexible Solar-Blind Photodetectors

“…Similarly, E g can also be evaluated by linear extrapolation. Here, α depends on λ (incident wavelength) and k (extinction coefficient) and is given by 36,37 We found that E g decreases from 5.08 to 4.89 eV with the thickness increasing, which is consistent with the spectral analysis above. Meanwhile, an absorption coefficient α of about 10 4 cm −1 order of magnitude can also be obtained using the transmittance or extinction coefficient at the 254 nm wavelength.…”

“…Similarly, E g can also be evaluated by linear extrapolation. Here, α depends on λ (incident wavelength) and k (extinction coefficient) and is given by , …”

Surface-Induced Enhanced Band Gap in the (0001) Surface of Bi2Se3 Nanocrystals: Impacts on the Topological Effect

“…Several techniques have been used to measure E g of Bi 2 Se 3 . The reported range of E g of Bi 2 Se 3 single crystals is between 0.22 and 0.33 eV, , and that of the thin films varies between 0.1 and 2.0 eV. − The disparity of E g of Bi 2 Se 3 is widely explained by its thickness dependence. , The direct E g (0.332 ± 0.055 eV) type of Bi 2 Se 3 single crystals is evident from angle-resolved photoemission spectroscopy (ARPES) through a 3D band mapping in a large fraction of the Brillouin zone . A relatively lower value of E g (0.22 eV) has been established for the single crystal Bi 2 Se 3 from the combined magnetotransport, photoluminescence, and IR transmission experiments …”

Near infrared light activatable PEI-wrapped bismuth selenide nanocomposites for photothermal/photodynamic therapy induced bacterial inactivation and dye degradation

“…In recent times, among various transition metal chalcogenides bismuth selenide (Bi 2 Se 3 ) NMs 28,29 have been explored in biomedical applications such as bioimaging, 30 radiation therapy, 31 and PTT 32 of cancer. However, the photothermal bacterial killing ability of Bi 2 Se 3 NMs has not been explored yet.…”