Experimental and Theoretical Study of Strong Low-Terahertz Absorption of Thymine

Zhang, W-D., A. Bykhovski, J. A. Deibel, and E. R. Brown. "Experimental and Theoretical Study of Strong Low-Terahertz Absorption of Thymine." Journal of Infrared, Millimeter, and Terahertz Waves 38, no. 12 (2017): 1521-1529.

Abstract

The absorption coefficient of a nucleobase-thymine-in powder form was measured with terahertz spectroscopy in both frequency- and time-domain experiments. For frequencies below 3 THz, a strong signature was observed at 1.27 THz. Furthermore, molecular-dynamic simulations were conducted to reveal that the 1.27 THz absorption signature is related to a transverse optical phonon mode. The simulations also indicated that bound water molecules are vital to the vibrational mode.

... 3 Experimental Methods and Results: Time-Domain Spectroscopy. Next to verify the frequency-domain result, we measured thymine samples with a time-domain system (Teraview TPS Spectra 3000) operating from 0.1 to ∼4.0 THz, and having a dynamic range of ∼60 dB ...

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For full paper see https://link.springer.com/article/10.1007/s10762-017-0420-z

Terahertz non-destructive imaging of cracks and cracking in structures of cement-based materials

Fan, Shujie, Tongchun Li, Jun Zhou, Xiaoqing Liu, Xiaoming Liu, Huijun Qi, and Zhiyong Mu. "Terahertz non-destructive imaging of cracks and cracking in structures of cement-based materials." AIP Advances 7, no. 11 (2017): 115202.

ABSTRACT

Cracks and crack propagation in cement-based materials are key factors leading to failure of structures, affecting safety in construction engineering. This work investigated the application of terahertz (THz) non-destructive imaging to inspections on structures of cement-based materials, so as to explore the potential of THz imaging in crack detection. Two kinds of disk specimens made of plain cement mortar and UHMWPE fiber concrete were prepared respectively. A mechanical expansion load device was deployed to generate cracks and control the whole process of cracking. Experimental tests were carried out on cracked specimens by using a commercial THz time domain spectroscopy (THz-TDS) during loading. The results show that crack opening and propagation could be examined by THz clearly and the material factors influence the ability of crack resistance significantly. It was found that the THz imaging of crack initiation and propagation agrees with the practical phenomenon and supplies more information about damage of samples. It is demonstrated that the damage behavior of structures of cement-based materials can be successfully detected by THz imaging.

....The THz imaging is throughout the whole loading procedure in Section 3.2. All of the TPI experiments were conducted using the TeraView TPS 3000 THz spectrometer,27 the main machine of which is shown in FIG. 5. .....

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For full paper see http://aip.scitation.org/doi/full/10.1063/1.4996053

Nondestructive Imaging of Packaged Microelectronics using Pulsed Terahertz Technology

Tyler Bowman and Magda El-Shenawee (2017) Nondestructive Imaging of Packaged Microelectronics using Pulsed Terahertz Technology. International Symposium on Microelectronics: Fall 2017, Vol. 2017, No. 1, pp. 000709-000714. https://doi.org/10.4071/isom-2017-THP23_160 Abstract This work presents the use of terahertz reflection imaging for nondestructive evaluation of packaged microelectronics. Power MOSFETs and SRAM devices are placed in a pulsed terahertz imaging system in the reflection mode with an incident angle of 30°. From the received signal at each point on the sample under test, the internal structure of the device can be clearly seen. For transistors, terahertz nondestructive imaging has been successful in determining die size and location as well as the bond wire size, number, and connections. High-pass frequency filters are utilized to enhance the image quality for viewing the bond wires. In addition, the terahertz B-scans are used to determine additional information including the vertical position of the bond wires and the die inside the packaged device. For the SRAM, the terahertz nondestructive imaging shows similar effectiveness in defining the layout of the metal connections inside the package and the wire positions. Thus terahertz imaging is shown to have a strong potential for nondestructive evaluation of these devices. ... This work makes use of the TPS Spectra 3000 (Teraview, Ltd., UK) pulsed terahertz imaging and spectroscopy system at the University of Arkansas. The system diagram is shown in Fig. 1a. ... For more information about TeraView visit https://www.azom.com/suppliers.aspx?SupplierID=12145 for full paper see http://www.imapsource.org/doi/abs/10.4071/isom-2017-THP23_160?code=imap-site

Dielectric properties of semi-insulating Fe-doped InP in the terahertz spectral region

Alyabyeva, L. N., E. S. Zhukova, M. A. Belkin, and B. P. Gorshunov. "Dielectric properties of semi-insulating Fe-doped InP in the terahertz spectral region." Scientific Reports 7 (2017).

Abstact

We report the values and the spectral dependence of the real and imaginary parts of the dielectric permittivity of semi-insulating Fe-doped InP crystalline wafers in the 2–700 cm−1 (0.06–21 THz) spectral region at room temperature. The data shows a number of absorption bands that are assigned to one- and two-phonon and impurity-related absorption processes. Unlike the previous studies of undoped or low-doped InP material, our data unveil the dielectric properties of InP that are not screened by strong free-carrier absorption and will be useful for designing a wide variety of InP-based electronic and photonic devices operating in the terahertz spectral range.

......The measurements of the dielectric properties in the ν = 0.21–3.00 THz range (7–100 cm−1) were performed using a pulsed THz TeraView TPS-Spectra-3000 time-domain spectrometer....

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For full paper see

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5544691/

Preparation, characterization, and spectroscopy study on CdSe quantum dots linked to multi-walled carbon nanotubes

Abouelsayed, A., Badawi Anis, Aly Okasha, Ali M. Ali, W. Elhotaby, and Ahmed SG Khalil. "Preparation, characterization, and spectroscopy study on CdSe quantum dots linked to multi-walled carbon nanotubes." Materials Chemistry and Physics 203 (2018): 1-8.

Abstract

We present spectroscopy study on cadmium selenide (CdSe) quantum dots (QDs) with different particle sizes linked to multi-walled carbon nanotubes (MWCNTs), so-called (CdSe-QDs/MWCNTs), in the ultraviolet and visible frequency range. Drude-Lorentz (DL) model has been used for fitting the absorption spectra for the samples under investigations. Quantitative information about the different excitonic bands and the particle sizes of CdSe-QDs were obtained from the fitting curves and their components. Furthermore, noncontact terahertz time-domain spectroscopy technique was used to compare the optical properties of the MWCNTs and CdSe-QDs/MWCNTs. Using DL model, the optical conductivities have been estimated from the optical parameters obtained from the data extracted from the differential complex terahertz analysis in the frequency range of 0.06–3 THz. The results illustrate that the optical conductivity of MWCNTs is smaller compared to the CdSe-QDs/MWCNTs due to the increased number of free electrons transferred from CdSe QDs and the availability of mobile carriers.

... The absorption bands are deconvoluted and fitted by Lorentzian model. The transmission measurements have been performed in the terahertz frequency range using (TPS spectra 3000 system (Teraview Ltd. England) model under Nitrogen gas N 2 purging. ...

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For full paper see

http://www.sciencedirect.com/science/article/pii/S025405841730754X