2 -30 -20 -10 0 10 20 30 V$_{G}$ (V) 10 -11 10 -10 10 -9 10 -8 10 -7 10 -6 10 -5 10 -4 |  I D |  (A) V$_{DS}$ = -14 V I$_{ON}$ = 15.9  ✁ A I$_{OFF}$ = 76.2 pA S$_{P}$ = 3.15 V/dec (a) 0 5 10 15 20 -V$_{DS}$ (V) 0 1 2 3 4 5 6 7 8 -I D  ( A) V$_{G}$ =-30 V -25 V -20 V -15 V (b) 0 1 2 3 4 5 6 R=Log$_{10}$(I$_{ON}$/I$_{OFF}$) 100 200 300 400 500 I ON  ( A) Sample M Sample S 3/3 1/10 3/10 5/10 (c) L=5 ☎ m W=400 ✆ m t$_{ox}$=500nm 0 5 10 15 20 25 G M =Transconductance ( S) FIG. 3: (Color online): (a) and (b) show the transfer charac- teristic of an FET device made by electrophoresis. (c) displays the AFM image of a s-SWNTs network. (d) shows I ON ( − ○ − ) and Transconductance ( − △ − ) versus Log 10 ( I ON /I OFF ). FIG. 2: (Color online): (a) and (b) display the transfer char- acteristic of an FET device made by spin-coating. (c) presents the histogram, I ON ( − ○ − ) and Transconductance ( − △ − ) versus Log 10 ( I ON /I OFF ) for sample S and M. Lines represent the linear fit and homogenized by sonication (1 hour using a water- bath and 5 minutes using a tip sonicators). Then, this mixture was centrifugated for 5 ∼ 120 minutes using ei- ther a desktop centrifuge (angle rotor type) or an ultra- centrifuge (swing rotor type). Next, the upper 80 % of the supernatant solution was collected. To recover only the SWNTs while washing out the PFO, the super- natant solution was filtered through 0.1 µ m Teflon filter and rinsed with toluene several time (until the charac- teristic optical absorption band of PFO at 385nm com- pletely disappears from the filtrate). Finally, this fil- ter was soaked in organic solvent (such as Toluene or N-Methyl-2-pyrrolidone (NMP)) and subjected to mild sonication. We shall focus on three types of SWNTs pro- cessable solutions centrifugated at 10000 g for 15 min (la- beled L), 250000 g for 30 min (labeled M) and 250000 g for 60 min (labeled S), with all the other processing pa- rameters identical. These samples were characterized by optical absorption, Raman and electrical measurements. To exclude residues of polymers and solvents, FET de- vices were annealed at 300-400 ◦ C for 1 hour in vacuum or nitrogen. Note that the transmission electron microscopy (TEM) reveals significant amount of catalytic particles in sample L but no detectable traces in sample M and S. Figure 1a displays the optical absorption spectra of L, M and S samples in toluene. Sharp peaks in the range 1100-1400 and 600-900 nm, labeled S$_{11}$ and S$_{22}$, corre- sponds to the first and to the second optical transitions in s-SWNTs, respectively. Whereas, less resolved peaks in the range 500-600 nm, labeled M$_{11}$, are assigned to op- tical transitions from m-SWNTs. The intensity of these features as well as the absorption background decrease in the following sequence L, M and S. It is worth notic- ing that the optical absorption spectrum of sample S is dominated by S$_{11}$ and S$_{22}$ features (s-SWNTs) without detectable traces of M$_{11}$ peaks (m-SWNTs). To ascertain this result, the Raman spectra were recorded at 514.5 nm, which resonantly probes m-SWNTs. We observed that the Radial Breathing Mode (RBM) around 270 cm $_{−}$1 (m- SWNTs) normalized to the RBM mode around 190 cm $_{−}$1 (s-SWNTs) decreases from L to M, and eventually van- ishes in sample S (Fig. 1b). It is essential to corroborated those results by electrical measurements. The electrical properties were investigated in field ef- fect configuration. A few droplets of SWNTs solutions were spin-coated on Si/SiO$_{2}$ wafer, with pre-patterned drain and source electrodes (Cr/Au) and Si as a back gate electrode. Figure 1c present the drain current I$_{D}$ ver- sus gate bias V$_{G}$ with drain-source bias V$_{DS}$ =-14 V. The sample S presents a sizable gate bias dependence char- acteristic of a p-type semiconductor behavior, whereas sample M exhibits a weaker gate effect and higher con- ductivity typical of metallic behavior. Similar results