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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

Schematics of a SWCNT transistor and spin states in SWCNTs.(a) Schematic of the device structure of the SWCNT transistor used in this study. (b) Schematics of the cross section of the device structure with spin states in the transistor at VG = 0 V (left), for VG > 0 V (center), and for VG < 0 V (right). (c) Schematics of the energy diagram of conduction band (CB), valence band (VB), and non-bonding orbital (NBO) of the SWCNTs with spin states at VG = 0 V (left), for VG > 0 V (center), and for VG < 0 V (right).
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f1: Schematics of a SWCNT transistor and spin states in SWCNTs.(a) Schematic of the device structure of the SWCNT transistor used in this study. (b) Schematics of the cross section of the device structure with spin states in the transistor at VG = 0 V (left), for VG > 0 V (center), and for VG < 0 V (right). (c) Schematics of the energy diagram of conduction band (CB), valence band (VB), and non-bonding orbital (NBO) of the SWCNTs with spin states at VG = 0 V (left), for VG > 0 V (center), and for VG < 0 V (right).

Mentions: First, we present the ambipolar spin vanishments in the SWCNTs by applying gate voltage (VG). Figure 1a shows the device structure of the SWCNT transistor. Ion gels used in the structure are currently attracting considerable attention because they enable low voltage operation due to the formation of an electric double layer (EDL) at the semiconductor/insulator interfaces13141718192021222324. Details of the fabrication of the SWCNT thin films and their devices are described in the Methods. Figure 2a shows the ESR signals of the SWCNT transistor at VG values of 0, 0.6, and 3.2 V with a drain voltage VD = 0.2 V. The observed ESR signals show a Lorentzian ESR lineshape with the g value of 2.0029 ± 0.00002 and the peak-to-peak ESR linewidth ΔHpp of 0.6 ± 0.1 mT. These features do not depend on VG. The origin of the ESR signal is ascribed to atomic vacancies in the SWCNTs, as discussed later10. Notably, the ESR intensity decreased when VG increased from 0 to 3.2 V.


Electrically induced ambipolar spin vanishments in carbon nanotubes.

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

Schematics of a SWCNT transistor and spin states in SWCNTs.(a) Schematic of the device structure of the SWCNT transistor used in this study. (b) Schematics of the cross section of the device structure with spin states in the transistor at VG = 0 V (left), for VG > 0 V (center), and for VG < 0 V (right). (c) Schematics of the energy diagram of conduction band (CB), valence band (VB), and non-bonding orbital (NBO) of the SWCNTs with spin states at VG = 0 V (left), for VG > 0 V (center), and for VG < 0 V (right).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f1: Schematics of a SWCNT transistor and spin states in SWCNTs.(a) Schematic of the device structure of the SWCNT transistor used in this study. (b) Schematics of the cross section of the device structure with spin states in the transistor at VG = 0 V (left), for VG > 0 V (center), and for VG < 0 V (right). (c) Schematics of the energy diagram of conduction band (CB), valence band (VB), and non-bonding orbital (NBO) of the SWCNTs with spin states at VG = 0 V (left), for VG > 0 V (center), and for VG < 0 V (right).
Mentions: First, we present the ambipolar spin vanishments in the SWCNTs by applying gate voltage (VG). Figure 1a shows the device structure of the SWCNT transistor. Ion gels used in the structure are currently attracting considerable attention because they enable low voltage operation due to the formation of an electric double layer (EDL) at the semiconductor/insulator interfaces13141718192021222324. Details of the fabrication of the SWCNT thin films and their devices are described in the Methods. Figure 2a shows the ESR signals of the SWCNT transistor at VG values of 0, 0.6, and 3.2 V with a drain voltage VD = 0.2 V. The observed ESR signals show a Lorentzian ESR lineshape with the g value of 2.0029 ± 0.00002 and the peak-to-peak ESR linewidth ΔHpp of 0.6 ± 0.1 mT. These features do not depend on VG. The origin of the ESR signal is ascribed to atomic vacancies in the SWCNTs, as discussed later10. Notably, the ESR intensity decreased when VG increased from 0 to 3.2 V.

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