Affiliation:
1. Center for Physical Sciences and Technology, Saulėtekio al. 3, LT-10257 Vilnius, Lithuania
Abstract
Thin bismuth films of various thicknesses between 5 and 32 nm grown by molecular beam epitaxy on Si (111) substrates were investigated. The samples were characterized by the x-ray diffraction method, which allowed us to identify two types of Bi crystallographic structures—[Formula: see text] and [Formula: see text] bismuth. Terahertz radiation pulses emitted from the samples after their illumination by femtosecond optical pulses with different wavelengths were characterized. The main THz emission features were similar for both types of Bi layers. Due to 2D confinement, the electron energy band structure depends on the thickness. With the terahertz excitation spectroscopy method, direct bandgaps were determined to be in the range from 0.25 to 0.5 eV—much greater than the indirect bandgaps of the layers. A simple model was used to describe the nature of THz emission from these films, which is the cause of uncompensated lateral photocurrents occurring because of the diffusive electron scattering at the Bi/Si interface.
Funder
European Social Fundand Hellenic Resources
Development of Competences of Scientists, other Researchers and Students through Practical Research Activities
Subject
General Physics and Astronomy
Cited by
1 articles.
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