Supporting Information I. The detailed process to determine the chirality of a CNT The electron diffraction pattern of a SWCNT

The electron diffraction pattern of a SWCNT has an equatorial line L0 and several layer lines L1, L2, L2, etc.. The distance between the layer lines and the equatorial line can be written as d1, d2, d3, etc.. The relationship between the chiral angle of a CNT and d1, d2, and d3 in its electron diffraction pattern has been given as formula (2) in Reference 27. We take SWCNT1 in S1 and SWCNT2 in S2 for instance. From the diffraction patterns shown in the insets of Figures 2 (a) and 2 (b), the chiral angles are obtained to be 22.6 degree for SWCNT1 and 28.2 degree for SWCNT2, respectively. From the HRTEM images in the insets of Figures 2 (a) and 2 (b), the diameters of SWCNT1 and SWCNT2 are measured to be 2.1 nm and 2.5 nm, respectively. Therefore, the chirality of SWCNT1 is (19, 12) and the chirality of SWCNT2 is (19, 17). For DWCNTs and TWCNTs, we first identify the layer lines corresponding to each wall of the multi-layered CNT in the electron diffraction pattern and then obtain the chiral angle of each wall using formula (2) in Reference 27. Coupled with the diameter of the wall measured from the HRTEM image, the chirality of each wall can be determined. We determine separately the chirality of the same CNT at both the left side and the right side of the segments of the CNT in the device and we obtain the same result. Therefore, we are confident that the chirality we determine by TEM is the chirality of the CNT in the measured device, because we believe that the nanotube’s chirality preserves during its growth in a small scale.