Supplementary Figure S1. Concentration dependency of the diameter of printed

Transcription

1 Counts (%) Average Diameter, D (nm) a 2.93 wt% wt% wt% 4.72 wt% 5.71 wt% b D r d Slope, d ~ Diameter (nm) PVK Concentration (wt%) c 84.9 nm Supplementary Figure S1. Concentration dependency of the diameter of printed nanowires. a, Histograms of the diameter of printed PVK nanowire array with various PVK solution concentrations of 2.93, 3.96, 4.72, 5.71, or 6.19 wt %. b, Average diameter (D) versus concentration (r) of PVK solution, which follows the scaling relationship (D ~ r 1.68 ). Such a scaling relationship in ONP is consistent with the relationship established in the conventional electrospinning method 32,33 as d D r. Scaling exponent d differs greatly among polymers and solution systems. c, SEM image of printed P3HT:PEO nanowire with D = 84.9 nm.

2 a b Supplementary Figure S2. Local spiraling of printed nanowire. a, Optical microscope and b, fluorescence microscope images of self-entanglement, called local spiraling 34,35, observed when the collector was stationary. The circular cross-section of the NW and local spiraling confirm that the solution jet from the nozzle tip solidifies completely before reaching the collector. If the solution jet does not solidify until after it reaches the collector, the wires have non-circular cross-sections, junctions between wires merge, or liquid drops form on the collector. When a single strand of entangled wire was pulled, it separated easily without breaking.

3 a b Supplementary Figure S3. ONP on insulating substrates. ONWs can be successfully printed by ONP on the insulating substrates because a high electric field between the nozzle tip and the grounded collector can tunnel through the thin insulating layer. We successfully printed the P3HT:PEO-blend (70:30, w/w) nanowires on a, an insulating SiO 2 layer (300 nm) and even on b, thick paper (108 m, Double A Public Co., Ltd) substrate. Scale bar, 50 m.

4 V th (V) I D (-A) (cm 2 V -1 s -1 ) I D (-A) I D (-A) a b V D = -50 V wires V 10-8 D = -30 V 3 wires c (Bottom-gated) P3HT NW Au Au SiO 2 (100 nm) Highly-doped Si 275 nm V G (V) 10-6 V D = -30 V 0 h h 70 wires V G (V) d I on/off (Top-gated) PMMA P3HT NW Au Au Au Substrate V G (V) Time (hr) Supplementary Figure S4. P3HT:PEO-blend nanowire s. Transfer characteristics ( I D -V ) of a, bottom-gated and b, top-gated P3HT:PEO-blend (70:30, w/w) nanowire s G with the field effect mobility of cm 2 V -1 s -1 and cm 2 V -1 s -1, respectively. c, Transfer characteristics and d, mobility, on/off ratio, and threshold voltage shift versus time plots of bottom-gated P3HT:PEO-blend nanowire s with bias stress condition of V = - G 20 V.

5 I D (A) 10-8 V D = 40 V (Bottom-gated) N2200 NW Au Au Highly-doped Si V G (V) SiO 2 (100 nm) Supplementary Figure S5. N2200:PVK-blend nanowire s. Transfer characteristics ( I D -V ) of bottom-gated N2200:PVK-blend (80:20, w/w) nanowire s with the G of 0.03 cm 2 V -1 s -1.

6 Intensity (a.u.) a b C S O c Carbon Sulfur Oxygen Length (nm) Supplementary Figure S6. Morphology of printed P3HT:PEO nanowire. a, TEM image of printed P3HT:PEO-blend (70:30, w/w) nanowire; circle: anomalous patch of PEO-rich phase in the P3HT core. b, Electron energy-loss spectroscopy mapping. c, Energy-dispersive X-ray spectroscopy graph of carbon, sulfur, and oxygen atoms along the red arrow in (a).

7 Supplementary Figure S7. X-ray analysis of P3HT:PEO nanowire. 2D grazing-incidence X-ray diffraction (GIXRD) patterns of a, homo-p3ht, b, P3HT:PEO-blend (70:30, w/w) spun-cast films and c, aligned P3HT:PEO-blend nanowires on Si substrates. d, 1D out-ofplane X-ray profiles extracted from (a-c). (The inset in (c) shows the GIXRD set-up used in this paper. The crystal refractions for PEO were indexed by Ref. 36) e, Schematic illustration of the microstructure of P3HT chains in a printed blend nanowire.

8 PL Intensity (a.u.) Absorbance (a.u.) Absorbance (a.u.) PL Intensity (a.u.) a c VVV exc det l l = nm Wavelength (nm) VVH exc det VHV exc det P3HT:PEO Film P3HT:PEO NW VHH exc det Wavelength (nm) VVV VHV VVH VHH b d nm 663 nm 0.2 P3HT:PEO Film 0.0 P3HT:PEO NWs Wavelength (nm) 0.06 VOV VOV VOH exc det 0.05 VOH exc det Wavelength (nm) Supplementary Figure S8. UV-vis absorbance and photoluminescence of P3HT:PEO nanowire. a, UV-vis absorption and b, photoluminescence (PL) spectra of P3HT:PEO-blend (70:30, w/w) spin-cast films and aligned P3HT:PEO-blend nanowires. c, Polarized PL spectra of aligned P3HT:PEO-blend nanowires with different polarization directions: i) exciting light and detection polarized parallel to the wire axis (VVV), ii) exciting light polarized perpendicular to the wire axis, and detection polarized parallel to the wire axis (VHV), iii) exciting light polarized parallel to the wire axis, and detection polarized perpendicular to the wire axis (VVH), and iv) exciting light and detection polarized perpendicular to the wire axis (VHH). d, Polarized UV absorption spectra of aligned P3HT:PEO-blend nanowires with unpolarized exciting light; detection is polarized parallel (VOV) and perpendicular (VOH) to the wire axis.

9 a b 50 m 350 nm Supplementary Figure S9. Organic nanowire lithography to fabricate grid-structured nano-gap metal pattern on large-area substrate. To fabricate grid-structured nano-gap patterns on large area, PVK NWs were printed perpendicularly on an 8-inch wafer. a, After metal deposition and b, NW removal process, a grid-structured gold nano-gap was successfully obtained. The size of the nano-gap was ~300 nm; gap was uniform over the entire substrate.

10 a 50 m b 100 m c d 350 nm Supplementary Figure S10. Organic nanowire lithography to fabricate organic nanogap patterns. ONWL can be used to fabricate not only metal nano-patterns, but also organic patterns. Nano-gap pattern of aluminum tris (8-hydroxyquinoline) (Alq 3 ) was obtained using PVK NW as a shadow mask. a, b, Fluorescence microscope and c, d, SEM images show that Alq 3 does not exist at the gap region. ONWL is a very useful patterning technique because it can form a nano-sized gap at a desired position without any thermal or chemical damages to the pattern material.

11 a b c 378 nm 200 m Supplementary Figure S11. Organic nanowire lithography on flexible PAR substrate. a, Nano-sized electrode gap patterns on flexible polyarylate (PAR) substrate. b, Optical microscope and c, SEM images of metal gap region with a gap width of 378 nm.

12 I D (- A) I D (-A) a 800 V G = -3.0V b 10-3 V D = -1V -2.8V V V -2.2V V V D (V) V G (V) Supplementary Figure S12. P3HT:PEO-blend nanowire and nano-channel based on polyelectrolyte gate dielectric. a, Output characteristics ( I - D V ) and b, transfer D characteristic ( I D -V ) of the best device among the P3HT:PEO-blend (70:30, w/w) nanowire G and nano-channel s based on the polyelectrolyte gate dielectric.

13 I D (-A) R total (M ) R C W ( cm) a b c nm 317 nm 391 nm 515 nm 615 nm V G (V) V G = -1.9 V -2.0 V -2.1 V -2.3 V -2.5 V Channel length (nm) V G (V) Supplementary Figure S13. Contact Resistance in ion-gel gated P3HT:PEO-blend nanowire s. a, Transfer characteristics ( I D -V ) of ion-gel gated P3HT:PEO-blend G nanowire s with different channel lengths. b, c, Total resistance (R total ) and contact resistance (R C W) of the device.

14 P3HT:PEO NW (core) (shell) I D (-A) I D 1/2 (A 1/2 ) a b c Gate Electrons Ion-gel Gate Direct gate Displaced gate V D = -1V Substrate Holes Substrate : Cations : Anions V G (V) Supplementary Figure S14. Operation of ion-gel-gated P3HT:PEO-blend nanowire s with different gate electrode positions. Schematic illustration of ion-gel gated P3HT:PEO-blend nanowire s with a, a direct gate electrode and b, a displaced gate electrode. c, Transfer characteristics of ion-gel gated NW s in (a, b).

15 P3HT:PEO NW (core) (shell) I D (-A) a 6 5 b Ion-gel Au P3HT Au SiO 2 (100 nm) Highly doped Si Ion-gel PEO Au P3HT Au SiO 2 (100 nm) Highly doped Si Ion-gel PCL Au P3HT Au SiO 2 (100 nm) Highly doped Si (cm 2 /V s) c Homo-P3HT NW P3HT:PCL NW P3HT:PEO NW P3HT:PEO NW Gate Reverse P3HT P3HT/PEO P3HT/PCL V Ref (V) Gate Forward Electrons Ion-gel Ion Gel Substrate Holes : Cations : Anions Supplementary Figure S15. Operation mechanism of ion-gel gated P3HT:PEO-blend nanowire s. a, Mobilities of ion-gel gated s based on electrospun homo-p3ht nanowires, electrospun P3HT:PCL-blend (70:30, w/w) nanowires, and printed P3HT:PEOblend (70:30, w/w) nanowires. b, Device structures (top) and channel current ( I D ) vs. reference electrode potential ( V ) characteristics (bottom) of spin-cast homo-p3ht film Ref without an overlayer and with a PEO and PCL overlayer. c, Operation mechanism of ion-gel gated P3HT:PEO-blend nanowire s.

16 Inensity (a.u.) a b C S O c Length (nm) Carbon Sulfur Oxygen Supplementary Figure S16. Morphology of electrospun P3HT:PCL-blend nanowire. a, TEM image of electrospun P3HT:PCL-blend (70:30, w/w) nanowire. b, Electron energy-loss spectroscopy mapping. c, Energy-dispersive X-ray spectroscopy graph of carbon, sulfur, and oxygen atoms along red arrow in (a).

17 No. of Devices No. of Devices a 30 b Max I on (-ma) V th (V) Supplementary Figure S17. Large-area single P3HT:PEO-blend nanowire array with nano-scale channel length. Histogram and fitted curve of the a, maximum on-current and b, threshold voltage for large-area P3HT:PEO-blend NW array with average current of ± 0.13 ma at V = -3.5 V, G V = -1 V and average threshold voltage of -1.5 ± 0.4 V. D

18 Voltage (V) 30 Input Output Time (ms) Supplementary Figure S18. Dynamic response characteristics of organic nanowire complementary inverter. Dynamic output characteristics of nanowire complementary inverter [P3HT:PEO-blend NW (70:30, w/w):n2200:peo-blend NW (70:30, w/w)].

19 Supplementary Table S1. Comparison of our results with those in previous studies based on P3HT. Year Mobility (cm 2 V -1 s -1 ) 1 [a] 2 [b] On/off ratio Device Structure [c] Dielectric Material Channel Notes Ref BG, BC SiO 2 Thin film BG, TC SiO 2 Thin film BG, BC SiO 2 Thin film Surface-treated BG, BC SiO 2 Thin film TG CYTOP Thin film BG, TC SiO 2 Thin film Surface-treated BG, BC SiO 2 Thin film BG, BC SiO 2 Thin film Surface-treated BG, BC SiO 2 Thin film Dip-coating TG, BC [BMIM][PF 6 ] /PS-PEO-PS Thin film TG, TC PEO/LiClO 4 Thin film TG, BC [EMIM][TFSI] /PS-PEO-PS Thin film BG, BC SiO 2 Nanowire Self-organized [d] [e] BG, BC SiO 2 Nanowire Electrospinning [e] BG, BC SiO 2 Nanowire Electrospinning, BG, BC SiO 2 Nanowire Self-organized [d] TG, BC [EMIM][TFSI] /PEGDA Nanowire Electrospinning [e] BG, TC SiO 2 Nanowire Electrospinning, Surface-treated, 51 Annealed at [e] BG, TC SiO 2 Nanowire ONP, 20wt% PEO Our work [e] TG, BC PMMA Nanowire ONP, 30wt% PEO Our work [f] 3.8 [f] [f] [EMIM][TFSI] ONP, (66.5 [g] ) (9.7 [g] ) ( [g] TG, BC Nanowire ) /PS-PMMA-PS 30wt% PEO Our work [a] Mobility is calculated using thin film model. [b] Mobility is calculated using gate-displacement current. [c] BG: bottom gate, TG: top gate, BC: bottom contact, TC: top contact [d] The nanowires are obtained by self-organization. [e] Mobility is calculated using cylinder-on-plate model. [f] Average value and [g] Maximum value of devices in large-area P3HT:PEO-blend nanowire array.

20 Supplementary Notes 1. Bias stress stability of P3HT:PEO-blend nanowire s. To observe the stability of P3HT:PEO-blend NW, we applied the bias stress of V = G -20 V to the bottom-gated device with 70 wires. Transfer characteristics and threshold voltage ( V ) shift versus time plots showed that th V was rapidly shifted and then saturated within 1 th h while, was kept nearly identical over time (Supplementary Figs. S4c,d). The initial abrupt shift of V is possibly due to strong charge trapping in the localized states at the th SiO 2 /PEO and PEO/P3HT interfaces that shields the gate bias 52. It is noted that after initial electrical bias stress for 1 h, all the electrical performance parameters did not change significantly for 11 h.

21 Supplementary Note 2. Morphology of printed P3HT:PEO-blend nanowire. To identify the structure of the printed P3HT:PEO-blend (70:30, w/w) NW, TEM analysis and elemental analysis using electron energy-loss spectroscopy (EELS) and energy-dispersive X-ray spectroscopy (EDS) were conducted for sulfur atoms in the P3HT chain and for oxygen atoms in the PEO chain. The TEM image (Supplementary Fig. S6a) revealed that the NW consists of two different phases: a dark interior (core) region and a bright exterior (shell) region, although patches of PEO-rich phase may occur in the P3HT core (red circles in Supplementary Figs. S6a,b). This contrast implies that the chemical compositions of the interior and exterior regions are different from each other. Each composition can be identified using the EELS mapping image of sulfur and oxygen (Supplementary Fig. S6b). In the carbon EELS mapping image (Supplementary Fig. S6b), carbons were uniformly distributed throughout the NW. However, sulfur had a relatively narrow distribution, with a width that agreed well with the core region shown in Supplementary Figure S6a. In contrast, the oxygen EELS mapping image showed a higher intensity in the shell than in the core. These results indicate that the NW core consists mainly of P3HT with small scattered PEO domains, whereas the NW shell is PEO. This structure was also confirmed by EDS line mapping (Supplementary Fig. S6c). The sulfur distribution was narrower than that of carbon, and the oxygen intensity was higher in the shell region than in the core region. Therefore, we concluded that the NWs consist of a P3HT core with small scattered PEO domains and a PEO shell.

22 Supplementary Note 3. X-ray analysis of P3HT:PEO nanowire. Based on grazing-incidence X-ray diffraction (GIXRD) analysis for the OSNWs aligned on a native SiO 2 /Si substrate, P3HT rich cores had less ordered crystal structure, in comparison to P3HT and P3HT:PEO-blend (70:30, w/w) films spin-cast from CB (Supplementary Fig. S7); the 2D GIXRD pattern for these aligned NWs showed weak Debye ring X-ray refraction of (100) crystal planes, suggesting that the NWs had less crystalline structure, in comparison to spin-cast films, which had mostly edge-on P3HTs containing intermolecular -overlap parallel to the substrates 43. However, it was found that the aligned NWs had long-range ordered nano-domains along the wire axis, as determined by intense X- ray scattering peaks with Q = Å -1 along the Q z. This value corresponded to a periodic distance of 4.65 nm (originating from the approximately 2-3 side-chain interdigitation of P3HT) 53. This was mainly related to the directed self-assembly between the -conjugated backbone chains extended along the wire axis by a strong tip-to-collector electric field during printing (Supplementary Fig. S7e). It was difficult for the extended P3HTs to form a highly crystalline structure owing to the rapid solvent evaporation. In contrast, it was also found that the extended P3HTs had strong intermolecular - overlap, as determined by UV-vis analysis (refer to following Supplementary Figs. S8a,b). These results strongly support that interdigitated P3HTs could be laterally stacked with the nearest neighbors and form highly - conjugated nano-domains extended along the NW axis, as illustrated in Supplementary Figure S7e. This chain morphology facilitates charge transport in the NW-based field-effect transistors.

23 Supplementary Note 4. UV-vis absorbance and photoluminescence of P3HT:PEO nanowire. Ultraviolet-visible (UV-vis) absorption and photoluminescence (PL) spectra of aligned P3HT:PEO-blend (70:30, w/w) NWs were red-shifted in comparison to spectra of blend spincast films (Supplementary Figs. S8a,b); this indicates that NWs have longer effective - conjugation length than do films. To verify the chain orientation of aligned NWs, we performed polarized PL and UV-vis absorption spectroscopy experiments. Two polarizers in front of the exciting light and detector were rotated to vertical (V) and horizontal (H) positions keeping the aligned NWs at the V position. The peak intensity with detection polarized parallel to the wire axis is higher than that when detection polarization is perpendicular to the wire axis (I VVV, I VHV > I VVH, I VHH ). Also, when the exciting light was polarized parallel to the wire axis, the emission intensity was stronger with the same detection polarization direction (I VVV > I VHV, I VVH > I VHH ) (Supplementary Fig. S8c), indicating that the exciting light polarized parallel to the wire axis was preferentially absorbed by aligned NWs. This result was also confirmed using polarized UV-vis spectra (Supplementary Fig. S8d). From these results, we concluded that the long chain of P3HT had an orientation with a direction parallel to the wire axis, resulting from the extended chain conformation of the polymers due to the strong electric field between the nozzle tip and the collector. Such results are consistent with those previously reported literature 54 and with our GIXRD results (Supplementary Fig. S7).

24 Supplementary Note 5. Contact Resistance in ion-gel gated P3HT:PEO-blend nanowire s. To analyze the contact resistance (R C W) of ion-gel gated P3HT:PEO-blend NW s, the transfer length method was used for several devices with different channel lengths. Channel length of device was controlled using diameter of mask NWs in the ONWL process. As the channel length decreased, the maximum on-current increased (Supplementary Fig. S13a), and the total resistance (R total ) decreased (Supplementary Fig. S13b). Extrapolated R C W at V = G -1.9 V was 5.53 cm, which is extremely low 55. Our finding that the source and drain electrodes in ion-gel gated P3HT:PEO-blend NW s form very low contact resistance even in nano-scale channels can explain the origin of the high value of and the on-current level of the ion-gel gated device with a nano-channel.

25 Supplementary Note 6. Derivation of mobility of ion-gel gated P3HT:PEO-blend nanowire s. To calculate the of ion-gel-gated P3HT:PEO-blend NW s, we considered two models, the thin film model and the gate-displacement current model. The thin film model has been used for s with thin film semiconductors. With the thin film model, is calculated as: 56,57 2 1/ 2 2L d( I D ) ( G ) (S1) W C d V where L is the channel length, W is the channel width, and C is the capacitance. This equation is derived under several assumptions: i) no current through the gate dielectric, and ii) a gradual channel approximation: the electric charge density related to variation of the electric field along the channel is much smaller than that related to variation across the channel 56,57. However, these assumptions are not satisfied in the geometry of ion-gel gated NW s, which showed gate displacement current through the ion-gel dielectric and had short channel length (~250 nm). The calculated using thin film model was unacceptably high (average : ~31.00 cm 2 V -1 s -1 ). In ion-gel gated s, as the gate bias increases, a large number of charge carriers are induced and the gate current also increases accordingly. Therefore, instead of the thin film model, we used the gate-displacement current model which is derived according to the gate-displacement current ( I I is gate current before turnon) and induced carrier density ( P i ), 28,29 Disp IG I Background, where Background L I D (S2) W VD epi P i I dv Disp G / ( dvg / dt) ea (S3)

26 where e is the elementary charge, and A is the area of the gate. For the calculation, W was defined as the circumference of a single P3HT:PEO-blend NW (250 nm) because of the high polarizability of the ion-gel dielectric. When the gate electrode was not positioned directly on the P3HT:PEO-blend NW, the device showed similar transfer characteristics (Supplementary Figs. S14,S15); this suggests that an electrical double layer is formed around the NW-ionic electrolyte interface, regardless of location. This result is consistent with previously reported results on ion-gel s with non-aligned gate electrode 25.

27 Supplementary Note 7. Operation mechanism of ion-gel gated P3HT:PEO-blend nanowire s. To verify the origin of the higher value of of NW s, despite the addition of 30 wt% of PEO, than that of previous P3HT s based on polyelectrolyte gate dielectrics, we compared the of ion-gel gated s based on electrospun homo-p3ht NWs, electrospun P3HT:poly( -caprolactone) (PCL)-blend (70:30, w/w) NWs, and printed P3HT:PEO-blend (70:30, w/w) NWs with identical device structure in Fig. 4d. We found that the of homo-p3ht NW s and P3HT:PEO-blend NW s were almost the same, while the of P3HT:PCL-blend NW was lower (Supplementary Fig. S15a). To explain the similar of ion-gel-gated homo-p3ht and P3HT:PEO-blend NW s despite the addition of PEO to P3HT, we investigated the role of the PEO shell in P3HT:PEO blend NWs. We spin-coated a 30-nm-thick overlayer (PEO and PCL) on top of 50-nm-thick homo-p3ht films and then deposited an ion-gel gate dielectric by drop-casting. We compared the electrical characteristics of devices that had an overlayer with the electrical characteristics of devices that did not have an overlayer. We plotted I as a function of D reference electrode potential ( V Ref ), the potential difference between the reference electrode and the source electrode (Supplementary Fig. S15b). The homo-p3ht and P3HT/PEO film s showed hysteresis in the I - D V Ref plots. The hysteresis originated from ion motion at the semiconductor-ionic electrolyte interface because the contribution from the gate-ionic electrolyte interface to hysteresis can be removed in the I D -V Ref measurement 29. In other words, the hysteresis observed in the I D -V Ref plots of homo-p3ht and P3HT/PEO film s suggests that an electrochemical doping reaction at the semiconductor-ionic electrolyte interface occurred because the PEO layer can provide pathways for ion diffusion into the semiconducting polymer layer. In contrast, P3HT/PCL film s did not show hysteresis in

28 the I - D V Ref plot, indicating that the ions did not penetrate through the PCL layer. From the results of the above experiments, we concluded that the excellent electrical characteristics of P3HT:PEO-blend NW s with an ion-gel dielectric can be explained by (i) the formation of a core-shell structure of blend NWs that separates the P3HT active phase from the insulating PEO phase and (ii) the good ion permeability of the PEO shell (Supplementary Fig. S15c). The TEM analysis of P3HT:PEO-blend NWs showed a P3HT core-peo shell structure along the wire axis (Supplementary Fig. S6). When the ion-gel dielectric is formed on the P3HT:PEO-blend NWs, ions in the ion-gel can migrate through the PEO shell because PEO can provide pathways for ionic transport; ions finally reach the P3HT core phase. Therefore, when the gate voltage is applied, ions can be effectively doped into the P3HT phase, resulting in inducing a large number of hole carriers. This is the reason why the ion-gel gated P3HT:PEO-blend NW s showed excellent electrical characteristics even if the NWs contained 30 wt% of insulating PEO. Additionally, the extended chain orientation of P3HT along the wire axis is another reason for the high value of in ion- gel gated NW s (Supplementary Figs. S7,S8).

29 Supplementary Note 8. Morphology of electrospun P3HT:PCL-blend nanowire. To confirm the structure of electrospun P3HT:PCL-blend (70:30, w/w) NW, TEM analysis and elemental analysis using EELS and EDS were conducted for sulfur atoms in the P3HT chain and for oxygen atoms in the PCL chain. Unlike printed P3HT:PEO-blend NW (Supplementary Fig. S6), the P3HT:PCL-blend NW showed a uniform distribution of chemical composition (C, S, and O), indicating uniform phase morphology (Supplementary Fig. S16). Therefore, PCL domains may scatter the charge transport in the NW.

30 Supplementary Note 9. Dynamic response characteristics of organic nanowire complementary inverter. We measured the dynamic switching behavior of P3HT/N2200 NW complementary inverters (Supplementary Fig. S18), which depends on the device parasitic capacitances and resistances. The evaluated average propagation delays for the corresponding polymer NW inverter was ~1 ms and we expect the speed of the inverter will be improved by reducing overlap capacitance between the gate and the source and drain electrode through the gate patterning. Although our inverter device showed a counter-mirrored voltage characteristics by a source-measurement unit (Keithley 4200, Keithley Instruments Inc.), a mismatch between input and output voltages (Supplementary Fig. S18) was observed when we measured the dynamic behavior of the inverter by a digital oscilloscope (Model 54832B, Agilent Technologies Inc.). The mismatch can be ascribed to a higher impedance of the device than that of the oscilloscope (1 M ) due to a small channel width of NWs. Therefore, this voltage mismatch problem in the NW inverter can be resolved by reducing the channel impedance of the devices.

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