Anharmonicity Study of Semiconductors and Metallic Nanotubes by Inelastic Spectroscopy

Abstract

In this work, we have studied the temperature dependence from 83 to 1300 K in the change of position of Raman modes in single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs). The effects of synthesis on the quality and quantity of carbon nanotubes (CNTs) were analyzed with high-resolution scanning electron microscopy (SEM) and micro-Raman spectroscopy. The behavior of the modes G for CNTs with the application of temperatures was studied, and we find that the (G)-peak position shifts to low frequency with increasing temperature. When reducing the ambient temperature to 83 K, there is displacement of the G-mode but not many changes were observed in the other modes. At high temperatures, there are changes in the position and intensity of the different modes. This behavior cannot be understood by purely thermal effects, it may also be due to uniaxial tension. The analysis of the experimental data showed the temperature dependencies of frequencies (w) and linewidths (FWHM). As a result of FWHM and the thermal expansion theoretical data, we calculated the Grüneisen parameter and the phonon decay rate, which are well described, taking into account the contributions from thermal expansion and anharmonicity.

Keywords::

• nanotubes
• single-walled
• multi-walled
• Raman
• anharmonicity
• temperature

Acknowledgment

The authors are thankful to Dra Elaine Paris (Embrapa-Sao Carlos) for the SEM measurements.

Additional information

Funding

The authors wish to express their thanks to CNPq (Brazil) and Colciencias (Colombia) for financial support provided to this work.