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Electrically induced ambipolar spin vanishments in carbon nanotubes.

Matsumoto D, Yanagi K, Takenobu T, Okada S, Marumoto K - Sci Rep (2015)

Bottom Line: Carbon nanotubes (CNTs) exhibit various excellent properties, such as ballistic transport.The field-induced ESR technique is suitable for microscopic investigation because it can directly observe spins in the CNTs.We observed a clear correlation between the ESR decrease and the current increase under high charge density conditions, which directly demonstrated electrically induced ambipolar spin vanishments in the CNTs.

View Article: PubMed Central - PubMed

Affiliation: Division of Materials Science, University of Tsukuba, Tsukuba, Ibaraki 305-8573, Japan.

ABSTRACT
Carbon nanotubes (CNTs) exhibit various excellent properties, such as ballistic transport. However, their electrically induced charge carriers and the relation between their spin states and the ballistic transport have not yet been microscopically investigated because of experimental difficulties. Here we show an electron spin resonance (ESR) study of semiconducting single-walled CNT thin films to investigate their spin states and electrically induced charge carriers using transistor structures under device operation. The field-induced ESR technique is suitable for microscopic investigation because it can directly observe spins in the CNTs. We observed a clear correlation between the ESR decrease and the current increase under high charge density conditions, which directly demonstrated electrically induced ambipolar spin vanishments in the CNTs. The result provides a first clear evidence of antimagnetic interactions between spins of electrically induced charge carriers and vacancies in the CNTs. The ambipolar spin vanishments would contribute the improvement of transport properties of CNTs because of greatly reduced carrier scatterings.

No MeSH data available.


Related in: MedlinePlus

ESR study of a SWCNT thin film.(a) ESR signals of the SWCNT thin film at H⊥. The solid lines show the data measured at 15 K (upper), 60 K (center), and 290 K (bottom). The symbols of circles (upper), triangles (center), and squares (bottom) show the least-squares fits with a Lorentzian lineshape to the observed ESR signals. (b) Temperature dependence of the spin susceptibility χ (main panel) and the inverse spin susceptibility 1/χ (inset) of the ESR signal of the SWCNT thin film at H⊥. The solid lines show the least-squares fits with the Curie law to the data. (c) Temperature dependence of the full width at half maximum, ΔH1/2, of the ESR signal of the SWCNT thin film at H⊥.
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f3: ESR study of a SWCNT thin film.(a) ESR signals of the SWCNT thin film at H⊥. The solid lines show the data measured at 15 K (upper), 60 K (center), and 290 K (bottom). The symbols of circles (upper), triangles (center), and squares (bottom) show the least-squares fits with a Lorentzian lineshape to the observed ESR signals. (b) Temperature dependence of the spin susceptibility χ (main panel) and the inverse spin susceptibility 1/χ (inset) of the ESR signal of the SWCNT thin film at H⊥. The solid lines show the least-squares fits with the Curie law to the data. (c) Temperature dependence of the full width at half maximum, ΔH1/2, of the ESR signal of the SWCNT thin film at H⊥.

Mentions: In the following, we present further detailed microscopic properties of atomic vacancies, such as spin concentration, spin-lattice relaxation time, motion of vacancies, and anisotropy of spin-orbit interaction. We present the ESR results of SWCNT thin films with 300 nm thickness because the signal-to-noise (SN) ratio of the ESR signal of the thin films is better than that of the SWCNT transistor in the absence of dielectric loss due to wirings and electrodes. The solid lines in Fig. 3a show the ESR signal of the SWCNT thin film at 15, 60, and 290 K. At each temperature, the g value was found to be 2.0029 ± 0.00002. The ΔHpp values were found to be 0.36 ± 0.03 mT at 15 K, 0.33 ± 0.03 mT at 60 K, and 0.50 ± 0.05 mT at 290 K. The open symbols in Fig. 3a show the least-squares fits with a Lorentzian lineshape for the observed ESR signals. The fitting data with a single Lorentzian component explain the experimental results very well at all measured temperatures. In previous ESR studies, a complicated Dysonian lineshape was observed because of the skin effects of microwave absorption due to bulk or thick-film samples3334384142. In contrast to these previous studies, the use of thin films in the present study makes it possible to avoid such skin effects and to perform a precise ESR analysis using a simple Lorentzian lineshape, as described below.


Electrically induced ambipolar spin vanishments in carbon nanotubes.

Matsumoto D, Yanagi K, Takenobu T, Okada S, Marumoto K - Sci Rep (2015)

ESR study of a SWCNT thin film.(a) ESR signals of the SWCNT thin film at H⊥. The solid lines show the data measured at 15 K (upper), 60 K (center), and 290 K (bottom). The symbols of circles (upper), triangles (center), and squares (bottom) show the least-squares fits with a Lorentzian lineshape to the observed ESR signals. (b) Temperature dependence of the spin susceptibility χ (main panel) and the inverse spin susceptibility 1/χ (inset) of the ESR signal of the SWCNT thin film at H⊥. The solid lines show the least-squares fits with the Curie law to the data. (c) Temperature dependence of the full width at half maximum, ΔH1/2, of the ESR signal of the SWCNT thin film at H⊥.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493558&req=5

f3: ESR study of a SWCNT thin film.(a) ESR signals of the SWCNT thin film at H⊥. The solid lines show the data measured at 15 K (upper), 60 K (center), and 290 K (bottom). The symbols of circles (upper), triangles (center), and squares (bottom) show the least-squares fits with a Lorentzian lineshape to the observed ESR signals. (b) Temperature dependence of the spin susceptibility χ (main panel) and the inverse spin susceptibility 1/χ (inset) of the ESR signal of the SWCNT thin film at H⊥. The solid lines show the least-squares fits with the Curie law to the data. (c) Temperature dependence of the full width at half maximum, ΔH1/2, of the ESR signal of the SWCNT thin film at H⊥.
Mentions: In the following, we present further detailed microscopic properties of atomic vacancies, such as spin concentration, spin-lattice relaxation time, motion of vacancies, and anisotropy of spin-orbit interaction. We present the ESR results of SWCNT thin films with 300 nm thickness because the signal-to-noise (SN) ratio of the ESR signal of the thin films is better than that of the SWCNT transistor in the absence of dielectric loss due to wirings and electrodes. The solid lines in Fig. 3a show the ESR signal of the SWCNT thin film at 15, 60, and 290 K. At each temperature, the g value was found to be 2.0029 ± 0.00002. The ΔHpp values were found to be 0.36 ± 0.03 mT at 15 K, 0.33 ± 0.03 mT at 60 K, and 0.50 ± 0.05 mT at 290 K. The open symbols in Fig. 3a show the least-squares fits with a Lorentzian lineshape for the observed ESR signals. The fitting data with a single Lorentzian component explain the experimental results very well at all measured temperatures. In previous ESR studies, a complicated Dysonian lineshape was observed because of the skin effects of microwave absorption due to bulk or thick-film samples3334384142. In contrast to these previous studies, the use of thin films in the present study makes it possible to avoid such skin effects and to perform a precise ESR analysis using a simple Lorentzian lineshape, as described below.

Bottom Line: Carbon nanotubes (CNTs) exhibit various excellent properties, such as ballistic transport.The field-induced ESR technique is suitable for microscopic investigation because it can directly observe spins in the CNTs.We observed a clear correlation between the ESR decrease and the current increase under high charge density conditions, which directly demonstrated electrically induced ambipolar spin vanishments in the CNTs.

View Article: PubMed Central - PubMed

Affiliation: Division of Materials Science, University of Tsukuba, Tsukuba, Ibaraki 305-8573, Japan.

ABSTRACT
Carbon nanotubes (CNTs) exhibit various excellent properties, such as ballistic transport. However, their electrically induced charge carriers and the relation between their spin states and the ballistic transport have not yet been microscopically investigated because of experimental difficulties. Here we show an electron spin resonance (ESR) study of semiconducting single-walled CNT thin films to investigate their spin states and electrically induced charge carriers using transistor structures under device operation. The field-induced ESR technique is suitable for microscopic investigation because it can directly observe spins in the CNTs. We observed a clear correlation between the ESR decrease and the current increase under high charge density conditions, which directly demonstrated electrically induced ambipolar spin vanishments in the CNTs. The result provides a first clear evidence of antimagnetic interactions between spins of electrically induced charge carriers and vacancies in the CNTs. The ambipolar spin vanishments would contribute the improvement of transport properties of CNTs because of greatly reduced carrier scatterings.

No MeSH data available.


Related in: MedlinePlus