Electron spin resonance study of single‐walled carbon nanotubes

Abstract

Studies of electron spin resonance (ESR) are reported on several types of single-walled carbon nanotubes (SWCNTs) synthesized by different methods. We work both with the obtained samples, which contained randomly distributed semiconducting and metallic SWCNTs, and with selected 99% semiconducting or metallic SWCNTs. Our aim is to use ESR spectroscopy in order to assess the quality of carbon nanotubes. We analyze the temperature dependence of ESR spectra in the range 4-300 K and report the temperature dependence of the linewidth, the intensity and the asymmetry factor (I þ /I À ) of the ESR lines. The ESR response from the arc discharge SWCNTs produced using non-magnetic Pt/Rh catalyst and from the selected semiconducting tubes exhibits an asymmetric line with an intensity that remains almost constant with decreasing temperature, showing a constant linewidth of about 2.9 mT. For selected bucky paper (BP) metallic or semiconducting carbon nanotubes, we also study the ESR signal according to the BP parallel or perpendicular orientation to the magnetic field. The g-factor and the asymmetry factor show a clear anisotropy.

Ultralong spin decoherence times in graphene quantum dots with a small number of nuclear spins

“…However, a controlled localization of the donor impurities is still a challenging task and electrostatically confined Si QDs often involve nanostructures with other materials like Ge, which potentially introduce addi-tional nuclear spins 23 . Carbon based QDs can be realized by confining an electron spin in carbon nanotubes [24][25][26][27][28][29][30][31] (CNT) via electrical gates allowing for a good control in the few electron regime. However, the curvature of the CNTs gives rise to a sizable spin-orbit coupling, yet another intrinsic source of decoherence to the electron spin.…”

Влияние Скин-Эффекта И Активных Потерь На Интенсивность Линий ЭПР В Полупроводящих Веществах

“…В качестве наполнителей, используемых для обеспечения электропроводящих свойств таких композитов чаще всего используется технический углерод и углеродные нанотрубки [3][4][5]. Присутствие последних в составе полимерного композита обуславливает не только электропроводность, но и достаточно интенсивный сигнал ЭПР, что свидетельствует о наличии неспаренных электронов в структуре частиц технического углерода и углеродных нанотрубок [6][7][8][9]. Это может быть использовано для исследования электронного состояния, механизмов проводимости и, например, определения концентраций технического углерода или углеродных нанотрубок в составе композита.…”