scholarly journals Optical and Galvanomagnetic Properties of Bi1-xSbx Thin Films in the Terahertz Frequency Range

2020 ◽  
Vol 10 (8) ◽  
pp. 2724 ◽  
Author(s):  
Anton D. Zaitsev ◽  
Petr S. Demchenko ◽  
Dmitry V. Zykov ◽  
Ekaterina A. Korotina ◽  
Elena S. Makarova ◽  
...  
Keyword(s):  
Thin Films ◽  
Film Thickness ◽  
Time Domain ◽  
Hall Coefficient ◽  
Transport Coefficients ◽  
Thz Radiation ◽  
Frequency Range ◽  
Terahertz Time Domain Spectroscopy ◽  
Time Domain Spectroscopy ◽  
Mobility Of Charge Carriers

We report results of galvanomagnetic and terahertz time-domain spectroscopy measurements on thin films of Bi 1 − x Sb x on polyimide and mica substrates with various antimony concentrations (x from 0 to 15 %) and film thickness (70, 150 nm). The resistivity, Hall coefficient and magnetoresistivity of the films were measured experimentally in the magnetic field of 0.65 T at room temperature. Mobility and concentration of electrons and holes in the film plane were calculated using the transport coefficients. The terahertz time-domain spectroscopy is used to measure the complex conductivity and permittivity of Bi 1 − x Sb x thin films on the dielectric substrates in the frequency range from 0.2 to 1 THz. The plasma frequency, relaxation time, DC conductivity and effective carrier mass were extracted from these data and evaluated as functions of the Sb concentration for different film thickness and substrate. We observed that the film magnetoresistivity decreases with increasing the Sb concentration and for most of the films the Hall coefficient is negative and depends on the external factors insignificantly. We show that the mobility of charge carriers weakly depends on Sb concentration, which confirms the assertion about the scattering of carriers on themselves and not on defects in the structure. It was revealed that film static and dynamic resistivity (conductivity) as well as dielectric permittivity depend on Sb content and the film thickness. The results may be used for development of various thermoelectric, electronic and optical devices, such as THz detectors or components which can control the properties of THz radiation.

scholarly journals Terahertz Time-Domain Spectroscopy of Graphene Nanoflakes Embedded in Polymer Matrix

2019 ◽  
Vol 9 (3) ◽  
pp. 391 ◽  
Author(s):  
Anton Koroliov ◽  
Genyu Chen ◽  
Kenneth M. Goodfellow ◽  
A. Nick Vamivakas ◽  
Zygmunt Staniszewski ◽  
...  
Keyword(s):  
Polymer Matrix ◽  
Time Domain ◽  
Thz Radiation ◽  
Complex Conductivity ◽  
Frequency Range ◽  
Terahertz Time Domain Spectroscopy ◽  
Time Domain Spectroscopy ◽  
Graphene Nanocomposites ◽  
Graphene Nanoflakes ◽  
Exfoliated Graphene

The terahertz time-domain spectroscopy (THz-TDS) technique has been used to obtain transmission THz-radiation spectra of polymer nanocomposites containing a controlled amount of exfoliated graphene. Graphene nanocomposites (1 wt%) that were used in this work were based on poly(ethylene terephthalate-ethylene dilinoleate) (PET-DLA) matrix and were prepared via a kilo-scale (suitable for research and development, and prototyping) in-situ polymerization. This was followed by compression molding into 0.3-mm-thick and 0.9-mm-thick foils. Transmission electron microscopy (TEM) and Raman studies were used to confirm that the graphene nanoflakes dispersed in a polymer matrix consisted of a few-layer graphene. The THz-radiation transients were generated and detected using a low-temperature–grown GaAs photoconductive emitter and detector, both excited by 100-fs-wide, 800-nm-wavelength optical pulses, generated at a 76-MHz repetition rate by a Ti:Sapphire laser. Time-domain signals transmitted through the nitrogen, neat polymer reference, and 1-wt% graphene-polymer nanocomposite samples were recorded and subsequently converted into the spectral domain by means of a fast Fourier transformation. The spectral range of our spectrometer was up to 4 THz, and measurements were taken at room temperature in a dry nitrogen environment. We collected a family of spectra and, based on Fresnel equations, performed a numerical analysis, that allowed us to extract the THz-frequency-range refractive index and absorption coefficient and their dependences on the sample composition and graphene content. Using the Clausius-Mossotti relation, we also managed to estimate the graphene effective dielectric constant to be equal to ~7 ± 2. Finally, we extracted from our experimental data complex conductivity spectra of graphene nanocomposites and successfully fitted them to the Drude-Smith model, demonstrating that our graphene nanoflakes were isolated in their polymer matrix and exhibited highly localized electron backscattering with a femtosecond relaxation time. Our results shed new light on how the incorporation of exfoliated graphene nanoflakes modifies polymer electrical properties in the THz-frequency range. Importantly, they demonstrate that the complex conductivity analysis is a very efficient, macroscopic and non-destructive (contrary to TEM) tool for the characterization of the dispersion of a graphene nanofiller within a copolyester matrix.

Properties of Bi and BiSb Nano-Dimensional Layers in Thz Frequency Range

2020 ◽  
Vol 312 ◽  
pp. 206-212
Author(s):  
Ivan L. Tkhorzhevskiy ◽  
Anton D. Zaitsev ◽  
Petr S. Demchenko ◽  
Dmitry V. Zykov ◽  
Aleksei V. Asach ◽  
...  
Keyword(s):  
Phase Shift ◽  
Time Domain ◽  
Terahertz Wave ◽  
Film Structure ◽  
Charge Carriers ◽  
Frequency Range ◽  
Terahertz Time Domain Spectroscopy ◽  
Antimony Content ◽  
Mobility Of Charge Carriers ◽  
Substrate Film

In the present paper we demonstrate and compare different properties of Bi and Bi1-xSbx thin films placed on polyimide (PI) substrate in frequency range from 0.2 to 1.0 THz. Bi films with a thickness of 40, 105 and 150 nm have been studied as well as 150 nm Bi1-xSbx solid solutions with Sb concentration of 5, 8, 12 and 15 %. An effective refractive index and permittivity of whole substrate/film structures have been derived by using terahertz time-domain spectroscopy (THz-TDS) method. These measurements have shown the positive phase shift in PI substrate with a thickness of 42 μm and revealed that it is barely transparent in studied frequency range, but the whole substrate/film structure provides the negative phase shift of terahertz wave. It was shown that the permittivity depends on mobility of charge carriers which is driven by film thickness and antimony content.

scholarly journals Terahertz Time-Domain Spectroscopy Based on Commercially Available 1550 nm Fabry–Perot Laser Diode and ErAs:In(Al)GaAs Photoconductors

2019 ◽  
Vol 9 (13) ◽  
pp. 2704 ◽  
Author(s):  
Kai-Henning Tybussek ◽  
Kevin Kolpatzeck ◽  
Fahd Faridi ◽  
Sascha Preu ◽  
Jan C. Balzer
Keyword(s):  
Laser Diode ◽  
Time Domain ◽  
Dynamic Range ◽  
Laser System ◽  
Industrial Applications ◽  
Thz Radiation ◽  
Full Potential ◽  
Terahertz Time Domain Spectroscopy ◽  
Time Domain Spectroscopy ◽  
Fabry Perot

THz time-domain spectroscopy (TDS) is a promising tool for quality control purposes in industrial applications, but the high cost and the relatively large laser sources still make it difficult to use the full potential of the technology for a decent price. In this work, a THz TDS system, which uses a commercially available Fabry–Perot laser diode emitting at 1550 nm, is presented. By dispersion compensation, pulses with a duration of 544 fs were generated, resulting in THz radiation with a bandwidth of 1.4 THz and a peak dynamic range of 56 dB with state-of-the-art ErAs:In(Al)GaAs photoconducting antennas. These results are compared with those of a conventional and expensive fiber laser system with a 90 fs pulse duration.

Measurement of Electrical Properties of GaN Thin Films Using Terahertz-Time Domain Spectroscopy

2005 ◽  
Vol 44 (2) ◽  
pp. 926-931 ◽  
Author(s):  
Takeshi Nagashima ◽  
Kazue Takata ◽  
Shigeki Nashima ◽  
Hiroshi Harima ◽  
Masanori Hangyo
Keyword(s):  
Thin Films ◽  
Electrical Properties ◽  
Time Domain ◽  
Terahertz Time Domain Spectroscopy ◽  
Time Domain Spectroscopy
Sign in / Sign up

Export Citation Format

Share Document