Acoustoelectric current transport through single-walled carbon nanotubes

We have contacted single-walled carbon nanotubes after aligning the tubes by the use of surface acoustic waves. The acoustoelectric current has been measured at $4.2\mathrm{K}$, and a probing of the low-dimensional electronic states by the surface acoustic wave has been detected. By decreasing the acoustic wavelength resulting in an adjustment to the length of the defined carbon nanotube constriction, a quantization of the acoustoelectric current has been observed.

Figure 1

(a) AFM picture of two short SWNT’s aligned by the SAW at $\pm 45°$. (b) Schematic sample layout. (c) AFM picture of a contacted SWNT of sample A.

Figure 2

Sample A: acoustoelectric current oscillations by raising the applied rf power for two frequencies inside the passband of the IDT. Source-drain measurements for different temperatures are shown as an inset.

Figure 3

Sample B: acoustoelectric current as a function of applied rf frequency. The inset shows an enlargement of the current at the frequency of the third harmonic.

Figure 4

Quantized acoustoelectric current as a function of applied rf power for two different SAW frequencies (first and third harmonics of the IDT) at $4.2\mathrm{K}$. The upper graph shows the derivative of the current.

Figure 5

Statistical overview of the height of the first current plateaus as a function of frequency.

Figure 6

Schematic model of the transport mechanism. One by one an electron is cycled through the CNTC by the piezoelectric SAW potential (sketched as dashed lines).