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.

FABRICATION AND CHARACTERIZATION OF BROADBAND TERAHERTZ WIRE-GRID POLARIZER

2010 ◽  
Vol 19 (04) ◽  
pp. 827-833 ◽  
Author(s):  
Z. C. CHEN ◽  
M. H. HONG ◽  
T. C. CHONG
Keyword(s):  
Time Domain ◽  
Quartz Substrate ◽  
Terahertz Wave ◽  
Mean Value ◽  
Frequency Range ◽  
Terahertz Time Domain Spectroscopy ◽  
Free Standing ◽  
Wire Grid ◽  
The Wire ◽  
Wire Grid Polarizer

A wire-grid terahertz polarizer fabricated on quartz substrate working in broadband is demonstrated. The transmission spectra of the fabricated wire-grid polarizer are characterized by terahertz time domain spectroscopy, showing the good performance of this polarizer in the terahertz frequency range up to 3.5 THz. The transmission of the peak in the time domain is 80% when the incident terahertz wave polarization is perpendicular to the wire-grid. The transmission of the peak is lower than 10% when the incident polarization is parallel to the wire-grid. The polarization factor ranges from 0.92–0.99 with the mean value of 0.97 in the frequency range from 0.1 to 3.5 THz, which is better than that of the free-standing wire-grid polarizer.

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.

Research of Landmine Detection Using Terahertz Technology

2014 ◽  
Vol 644-650 ◽  
pp. 1313-1316 ◽  
Author(s):  
Qing Miao ◽  
Gao Wang ◽  
Yang Jun Li
Keyword(s):  
Time Domain ◽  
Major Part ◽  
Terahertz Wave ◽  
Landmine Detection ◽  
Terahertz Range ◽  
Terahertz Time Domain Spectroscopy ◽  
Time Domain Spectroscopy ◽  
Characteristic Spectrum ◽  
Terahertz Technology

The detection of landmines has become a hard task to deal with because of the diversity of landmines and the complexity of minefield. The development of terahertz technologies has provided a feasible way to detect the buried landmines. Landmines’ shell is usually made of ceramics, plastics, even wood and so on, which terahertz wave could penetrate them easily. The explosives are the major part of landmines. Many types of explosives have the characteristic spectrum in terahertz range, so it would be an effective method to detect landmines by measuring the spectrum of explosives with terahertz time-domain spectroscopy.

Structurally Sensitive Changes in Absorption THz Spectra of Corticosteroids

2010 ◽  
Vol 5 (4) ◽  
pp. 162-167
Author(s):  
Irina N. Smirnova ◽  
Elena V. Fedulova ◽  
Maxim M. Nazarov ◽  
Оlga P. Cherkasova
Keyword(s):  
Steroid Hormones ◽  
Absorption Spectra ◽  
Time Domain ◽  
Spectral Response ◽  
Frequency Range ◽  
Terahertz Time Domain Spectroscopy ◽  
Characteristic Lines ◽  
Pure Substances ◽  
Thz Absorption ◽  
The Given

The series of steroid hormones, such as progesterone, 17α-hydroxyprogesterone, cortisol and other was measured by terahertz time-domain spectroscopy (THz TDS). It was obtained that THz absorption spectra of steroid hormones have characteristic lines of absorption in the frequency range 0.1-3.0 THz. We investigate the relation between the position of side functional groups and THz spectral response. Besides pellets of polycrystalline pure substances, steroids solution in methanol was analyzed. The given method can be applied for express diagnostics of different classes of steroid

Terahertz Time-Domain Spectroscopy Technology and its Application in the Field of Pesticide

2013 ◽  
Vol 561 ◽  
pp. 640-645
Author(s):  
Yi Hu Huang ◽  
Man Hu ◽  
Gui Hua He ◽  
Wen Long Liu
Keyword(s):  
Time Domain ◽  
Information Science ◽  
Far Infrared ◽  
Terahertz Wave ◽  
Electromagnetic Spectrum ◽  
Terahertz Time Domain Spectroscopy ◽  
Time Domain Spectroscopy

Terahertz wave lies between far-infrared and microwave in electromagnetic spectrum with frequency form 0.1 THz to10 THz. Terahertz is believed to be the master technology of electronics and information science, and to be the bridge between micro electronics and macro wavelength. THz has formed a worldwide research climax. This paper introduces the main characters of Terahertz wave, Terahertz time-domain spectroscopy technology and its application researches, especially detailed the researches in pesticide spectra.

Polarizability of Aspirin at Terahertz Frequencies Using Terahertz Time Domain Spectroscopy (THz-TDS)

2018 ◽  
Vol 73 (3) ◽  
pp. 253-260 ◽  
Author(s):  
Tianyao Zhang ◽  
Zhaohui Zhang ◽  
Mark A. Arnold
Keyword(s):  
Time Domain ◽  
Low Frequency ◽  
Field Vector ◽  
Organic Crystals ◽  
Frequency Range ◽  
Terahertz Time Domain Spectroscopy ◽  
Time Domain Spectroscopy ◽  
Time Domain Signal ◽  
Pulse Experiment ◽  
Measured Time

A novel application of terahertz time-domain spectroscopy (THz-TDS) is described for the determination of permittivity and polarizability of organic crystals, as exemplified by measurements with the polymorph I form of crystalline aspirin (acetylsalicylic acid). The coherent nature of the THz pulse experiment, coupled with gated-detection, permits direct measure of differences in the phase angle of the electric field vector after passing through a pellet composed of the aspirin crystals embedded within an inert polymer matrix. An effective media model is used to extract dielectric information for the crystals from the measured time-domain signal that is representative of the entire pellet composition. Polarizability is then obtained for these organic crystals by using the Clausius–Mossotti relationship. Dielectric spectra and polarizability spectra are presented over the 0.3–3 THz frequency range (10–100 cm−1). The average polarizability values measured over the low frequency range (10–20 cm−1) are 22.4 ± 0.3 and 22.4 ± 0.5 Å3 for aspirin crystals embedded within matrixes of polytetrafluoroethylene (PTFE) and polyethylene (PE), respectively.

scholarly journals Enhanced Measurement of Paper Basis Weight Using Phase Shift in Terahertz Time-Domain Spectroscopy

2017 ◽  
Vol 2017 ◽  
pp. 1-14 ◽  
Author(s):  
Mengbao Fan ◽  
Binghua Cao ◽  
Guiyun Tian
Keyword(s):  
Phase Shift ◽  
Time Domain ◽  
Delay Time ◽  
Mathematical Formulation ◽  
Peak Amplitude ◽  
Noise Robustness ◽  
Multiple Reflections ◽  
Terahertz Time Domain Spectroscopy ◽  
Physical Relationship ◽  
Time Domain Spectroscopy

THz time-domain spectroscopy has evolved as a noncontact, safe, and efficient technique for paper characterization. Our previous work adopted peak amplitude and delay time as features to determine paper basis weight using terahertz time-domain spectroscopy. However, peak amplitude and delay time tend to suffer from noises, resulting in degradation of accuracy and robustness. This paper proposes a noise-robust phase-shift based method to enhance measurements of paper basis weight. Based on Fresnel Formulae, the physical relationship between phase shift and paper basis weight is formulated theoretically neglecting multiple reflections in the case of normal incidence. The established formulation indicates that phase shift correlates linearly with paper basis weight intrinsically. Subsequently, paper sheets were stacked to fabricate the samples with different basis weights, and experimental results verified the developed mathematical formulation. Moreover, a comparison was made between phase shift, peak amplitude, and delay time with respect to linearity, accuracy, and noise robustness. The results show that phase shift is superior to the others.

scholarly journals Complex Refractive Index of Strontium Titanate in the Terahertz Frequency Range

2019 ◽  
Vol 7 (4) ◽  
pp. 71-80 ◽  
Author(s):  
V. R. Bilyk ◽  
K. A. Grishunin
Keyword(s):  
Dielectric Constant ◽  
Refractive Index ◽  
Strontium Titanate ◽  
Time Domain ◽  
Complex Refractive Index ◽  
Complex Dielectric Constant ◽  
Terahertz Frequency ◽  
Frequency Range ◽  
Terahertz Time Domain Spectroscopy ◽  
Terahertz Frequency Range

The recent progress in terahertz time-domain spectroscopy enables the accurate and reliable measurements of dielectric properties in comparison with the traditional far-infrared spectroscopy using an incoherent light source. The broadband THz-TDS is a powerful tool to determine the real and imaginary parts of a complex dielectric constant by the transmission which allows to detect the parameters of the soft modes in ferroelectrics. In this work, the terahertz time-domain spectroscopy was used to investigate the dependence of the complex refractive index of a single-crystal quantum paraelectric strontium titanate in the terahertz frequency range from 0.3 to 2 THz. It was shown that the low-frequency terahertz response of the material is determined by the soft phonon mode TO1. The measured experimental dependences showed a good agreement with the theoretical curves obtained from the analysis of the Lorentz oscillator model for the complex dielectric constant of strontium titanate. The obtained results are necessary for understanding the principle of possibility to manipulate the order parameter in ferroelectric materials and can be used to create energy-efficient memory devices with a speed of recording information close to the theoretical limit.

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