Graphene has shown great potential for terahertz (THz) applications in recent years. THz sheet conductivity of graphene is essential to assess the high performance of THz devices such as modulators based on graphene. In this work, THz sheet conductivity of graphene grown with different temperatures, along with the effects of chemical doping by HNO3, were studied in detail. Graphene films were synthesized on Cu surface by atmospheric pressure chemical vapor deposition with C2H2. Different samples with growth temperature from 850 to 1030 °C were characterized by Raman spectroscopy, transmission electron microscope, and UV–vis spectroscopy. THz time-domain spectroscopy was used to study the THz sheet conductivity of the samples before and after HNO3 doping. The results show that graphene grown at 1000 °C has the highest THz sheet conductivity. As compared to the sample grown at 850 °C, the value enhances 600%. In addition, after HNO3 doping, the THz sheet conductivity of the sample grown at 1000 °C becomes 2.42 mS, which enhances 44%. These indicate that both the optimization of the growth temperature and chemical doping can improve the THz sheet conductivity of graphene significantly. Combining with the characterization of the material, we have attributed the effect of the growth temperature to the influence of carrier momentum scattering time in graphene, and the chemical doping to the influence of the carrier concentration in graphene. This work advances the understanding of improving THz sheet conductivity by in situ growth and postgrowth and paves the way for efficient THz components with graphene.
Time-domain terahertz (THz) spectroscopy is employed to investigate the dielectric response of silicaencapsulated FePt core-shell colloid film in THz region. The absorption of the colloid film increases with the increasing of the frequency, while the refractive index is stable at about 1.85 in the range of 0.85-3.0 THz. The real and imaginary parts of the dielectric constant of the silica@FePt film are demonstrated to be broadband from 0.85-3.0 THz. Small dispersive features can be seen below the frequency of 0.85 THz, which is tentatively attributed to the scattering effect and the polarization relaxation under low frequency with a low dynamic range. A core-shell model combined with Maxwell-Garnett mixing rule has been used to describe the dielectric response of the colloid film, which is necessary for a reasonable explanation of the experimental data as few experiments have been done with the core-shell model employed. In the high-frequency region, the real part of the dielectric constant fits well; however, the imaginary part of the dielectric constant is lower than the experimental data. The difference between the theoretical analysis and the experimental data suggests that the interfacial effect should be paid attention for the core-shell structures as the diffusion of interfacial dipoles could influence the dielectric properties.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.