Optical constants of CuO and ZnO particles in the terahertz frequency range

 Calvo-de la Rosa, Jaume, Alexandre Locquet, Denis Bouscaud, Sophie Berveiller, and D. S. Citrin. "Optical constants of CuO and ZnO particles in the terahertz frequency range." Ceramics International (2020).

Abstract

The optical constants (complex dielectric function) of CuO and ZnO particles in polyethylene pellets are measured by terahertz time-domain spectroscopy. The determination of the dielectric properties of these materials is of interest for energy-storage applications, for instance. Maxwell-Garnett theory is used to extract the contribution to the frequency-dependent optical constants of the oxide powders. The validity of the assumptions of Maxwell-Garnett theory are experimentally verified and self-consistency of the results of the model confirmed. On this basis, experimental complex permittivity values for isotropic CuO and ZnO oxide powders are reported in the 100 GHz-3 THz range.

for full paper see https://www.sciencedirect.com/science/article/pii/S0272884220318502

"THz transmission data through the pellets were obtained using a TeraView TPS Spectra 3000 in transmission mode. The experimental bandwidth (power spectrum of "

Quantification of residual crystallinity of ball-milled, commercially available, anhydrous β-lactose by differential scanning calorimetry and terahertz spectroscopy

Geoff Smith, Amjad Hussain, Nadeem Irfan Bukhari, Irina Ermolina

Abstract

The quantification of crystallinity is necessary in order to be able to control the milling process. In this study, the changes in the amount of residual crystallinity of ball-milled anhydrous β-lactose (β-LA), for periods up to 60 min, were evaluated by differential scanning calorimetry (DSC) and by terahertz pulsed spectroscopy. The percentage of residual crystallinity using DSC was estimated by two methods: The first method was based on the measurement of the melting of the crystalline part, while the second was based on the measurement of the devitrification of the amorphous part. Peaks in THz spectra, related to the residual crystalline material were analyzed by two methods: (1) area under peak and (2) partial least square. The milled samples of β-LA show a monotonic decrease in crystallinity with milling time, although the quantitative analysis performed by different techniques reveals very different results. THz technique gives significantly lower estimates for % crystallinity (in the early time period) than that calculated from the DSC data, possibly because of the recrystallization of amorphous form during sample preparation. The comparison of residual crystallinity of β-LA with its hydrated counterpart [i.e., α-lactose monohydrate (α-LMH)] has shown that the amount of amorphous material produced from the α-LMH is 20–30 % greater than from β-LA at extended milling times (i.e. 60 min).

This study was performed using TeraView's Spectra 3000 system. (TeraView, Cambridge, UK)

Full Article: http://link.springer.com/article/10.1007%2Fs10973-015-4469-4

Terahertz and optical study of monolayer graphene processed by plasma oxidation

Appl. Phys. Lett. 102, 131901 (2013); http://dx.doi.org/10.1063/1.4795526
(Received 7 February 2013; accepted 26 February 2013; published online 1 April 2013)

Authors: Kyujin Choi¹, Juhwan Lim², J. R. Rani², Hyong Seo Yoon², Juyeong Oh², Taeyoon Hong¹, Taewoo Ha¹, Byung Cheol Park¹, Kyung Ik Sim¹, Seong Chan Jun², and Jae Hoon Kim^1
1 Department of Physics and Institute of Physics and Applied Physics, +Yonsei University, Seoul 120-749, Republic of Korea 
² Department of Mechanical Engineering, +Yonsei University, Seoul 120-749, Republic of Korea 

Abstract

We report on our terahertz and optical study of monolayer graphene grown by chemical vapor deposition and processed by plasma oxidation. The plasma oxidation induces oxygen-related defects, and the resulting disorder increases the sheet resistance of graphene as measured via terahertz spectroscopy. The excitonic absorption peak weakens considerably and blue shifts upon plasma oxidation, resulting in higher transmittance in both the visible and ultraviolet regions. Our oxygen plasma-treated graphene also exhibits a free-carrier doping effect as confirmed by the blue shift of the Raman G band.

... Raman spectroscopy was performed with WITEC ALPHA300M Raman System (excitation at 532 nm, 2.33 eV). The VUV spectrophotometry was carried out with a Cary 5G spectrophotometer and THz-TDS with TeraView TPS Spectra 3000 ... 

More details at: http://apl.aip.org/resource/1/applab/v102/i13/p131901_s1?isAuthorized=no

More about terahertz equipment: http://www.teraview.com/products/index.html