Nano letters ■ ASSOCIATED CONTENT (23)Gudlksen, M. S. Lauhon, L J; Wang, J; Smith, D. C; Lieber, S Supporting Information C.M. Nature2002,4l5,617-620. Additional information and figures. This material is available 2002, 420, 57-61 4)Lauhon, L.J; Gudlksen, M. S; Wang, D ;Lieber,C.M.Nature freeofchargeviatheInternetathttp://pubs.acs.org )Kinked silicon nanowires synthesized by chemical on( CVD)through a nanoparticle-catalyzed vapo ■ AUTHOR| NFORMATION Corresponding Author 00 nm diameter gold nano (Ted Pella) were dispersed on Si growth substrates with 600 nm SiO, layer(Nova Electronic Materials) was first carried out by Author Contributions owth of heavily boron-doped p-type SThese authors contributed equally to this work. eding SiH,(1 sccm), 60 sccm)into the system for 15 min at a total pressure of 40 Torr and Note temperature of 450C. The growth was then paused for 15 s by The authors declare no competing financial interest. rapidly evacuating the chamber to lowest pressure and shutting off the gas lines. SiH, ( scam,1000 Ppm in H2), and H2 ■ ACKNOWLEDGMENTS (60 sccm)were then flown into the system at the same total pressure C. M.L. acknowledges support of this research from a nIH the p-n junction. A second evaculation or bype section for 30 s, forming Director's Pioneer Award(1DP1OD003900) heavily doped n-type arm was allowed to finish in additional 15 min (26)Two pairs of metal electrodes(1.5 nm Cr/120 nm Pd/60 nn REFERENCES Cr, spacing between electrodes 1.5 pm)were fabricated on each of the (1)Timko, B P; Cohen-Kami, T; Qing, Q; Tian, B Lieber, C.M.IEEE P- and n-type arms of a kinked nanowire device. The diameter of the Trans. Nanotechnol. 2009, DOI: DOL: 10.1109/TNANO 2009.2031807 nanowire was 100 nm. The doping levels of the arms were estimated (2)Tian, B. Cohen-Karni, T. Qing, Q; Duan, X; Xie, P; Lieber, using N=a/qu, where N is the doping level, a is the conductivity C.M. Science2010,329,830-834. alculated from the slope of the I-V trace in Supporting Information (3)Tian, B. Zheng X; Kempa, T. J; Fang, Y; Yu, N Yu, G Figure S2, q is the charge of an electron, and u is the mobility. Here we Huang, J; Lieber, C. M. Nature 2007, 449, 885-890 (4)Kempa, T. J Tian, B. Kim, D. R; Hu, J; Zheng, X. Lieber C.M. Nano Lett.2008,8,3456-3460. L. 2003, 3. 149-152. Wang. Da; Wang, w. U, Lieber, C. M. Nano (S)Tian, B; Xie, P. Kempa, T J; Bell,D.C.Lieber,CM.Nat (28)Rusu, A Bulucea, C. Proc. Rom. Acad. 2009, 10, 285-290. Nanotechnol. 2009, 4, 824-829. (29)Wilson, N R; Cobden, D H Nano Left. 2008, 8, 2161-216S (6)Xu, S; Qin, Y. Xu, C; Wei, Y; Yang, R; Wang, Z.L.Nat. (30)The device chip was mounted on a Bio Scope MultiMode SPM stage(Digital Instrument). A constant current of 250-700 nA was (7)Yan, H; Choe, H. S. Nam, S. W; Hu, Y; Das, S. Klemic, ]. F; injected into the kinked p-n device, resulting in a forward bias of Ellenbogen, J. C. Lieber, C. M. Nature 2011, 470, 240-244 ( 8)Dick, KA; Deppert, K; Larsson, M W; Martensson, T; Seifert, differential preamplifier(SRS60, Stanford Research Systems).A W; Wallenberg, L. R; Samuelson, L. Nat. Mater. 2004, 3, 380-384 onductive AFM tip(ARROW-CONTPT-10, Nano World) vibrating at a resonance frequency of 90 kHz was used as a local gate and L: Lieber. c.m. proc. natl. acad. sci u... 2011. 108. 12212-12216 scanned over the device to map the conductance image in "Lift Mode (10)Qing, Q. Pal,.K Tian, B Duan, X; Timko, B. P Cohen. Specifically, first for each scan line zero potential was applied to the tip, Karni, T. Murthy, V. N Lieber, C. M. Proc. Natl Acad. Sci. U.S.A. and a topographic image was acquired in Tapping Mode with feedback 2010,107,1882-1887 nabled. The tip was then lifted up 30 nm, and a tip potential of +5 Vwas (11)Cohen-Karni, T; Timbo, B P. Weiss, L E; Lieber, C.M. Proc. applied. The tip was scanned across the same line again following the Natl. Acad.sai.U.SA.2009,106,7309-7313 captured topologica with feedback turned off, when the change of (12)Cohen-Karni, T. Qing, Q; Li,Q; Fang,Y; Lieber,C.MNano oltage across the device was recorded with a lock-in amplifie Let2010,10,1098-1102 Stanford Research Systems) using the tip oscillation as the reference (13)Heller, I; Smaal, W TT; Lemay, S G Dekker, C. Small 2009, frequency. In order to remove the drift error during the imaging, we scanned in opposite directions for V. (14)Kotov, N. A; Winter, JO; Clements, I P Jan, E, Timk ,B. 2i0 nm as the corrected length of the sensitive region for our device. Vup =-5 V(fwhm 300 nm) images and obtained the average of P. Campidelli, S. Pathak, S. Mazzatenta, A- Lieber, C M. Prato, M j Bellamkonda, R V; Silva, G A; Kam, N. W.S. Patolsky, F; Ballerini, (31)Weber, L Gmelin, E. ApPL. Phys. A 1991,53, 136-140 LAdv. 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A confocal fluorescent microscope(FV1000, Olymp Small2009,S,208-212. was used to image the motion of the fluorescent nanobeads and the (20)Eschermann, J. F; Stockmann, R; Hueske, M; Vu, X. T; kinked probes in real time while the conductance was recorded. Real brandt, S. Offenhausser, A. AppL. Phys. Lett. 2009, 95, 083703-1 time fluorescent images of unction area were captured at a 083703-3. te of 2 hz a 559 nm laser to excite the nanobeads. Two (21)Stern, E; Klemic, J. F; Routenberg, D. A; Wyrembak, P.N hannels with filters of 490-540 nm and 575-675 nm were recorded Turner-Evans, D. B; Hamilton, A. D. LaVan, D. A Fahmy, T. M; together to rule out noise signals and unambiguously identify the Reed,M. A. Nature2007,445,519-522 anobeads. Images were then superimposed over the device image (22)Sze, S. M. Semiconductor devices, physics and technology: wiley: recorded with a 535-565 nm filter to mark the relative position of the apore, 2002; Pp nanobeads and the p-n junction. 1715 dxdoloro/0.1021/l300256 rINgno Lett.2012,12,1711-1716■ ASSOCIATED CONTENT *S Supporting Information Additional information and figures. This material is available free of charge via the Internet at http://pubs.acs.org. ■ AUTHOR INFORMATION Corresponding Author *E-mail: cml@cmliris.harvard.edu. Author Contributions § These authors contributed equally to this work. Notes The authors declare no competing financial interest. ■ ACKNOWLEDGMENTS C.M.L. acknowledges support of this research from a NIH Director’s Pioneer Award (1DP1OD003900). ■ REFERENCES (1) Timko, B. P.; Cohen-Karni, T.; Qing, Q.; Tian, B.; Lieber, C. M. IEEE Trans. Nanotechnol. 2009, DOI: DOI:10.1109/TNANO.2009.2031807. (2) Tian, B.; Cohen-Karni, T.; Qing, Q.; Duan, X.; Xie, P.; Lieber, C. M. Science 2010, 329, 830−834. (3) Tian, B.; Zheng, X.; Kempa, T. J.; Fang, Y.; Yu, N.; Yu, G.; Huang, J.; Lieber, C. M. Nature 2007, 449, 885−890. (4) Kempa, T. J.; Tian, B.; Kim, D. R.; Hu, J.; Zheng, X.; Lieber, C. M. Nano Lett. 2008, 8, 3456−3460. (5) Tian, B.; Xie, P.; Kempa, T. J.; Bell, D. C.; Lieber, C. M. Nat. Nanotechnol. 2009, 4, 824−829. (6) Xu, S.; Qin, Y.; Xu, C.; Wei, Y.; Yang, R.; Wang, Z. L. Nat. Nanotechnol. 2010, 5, 366−373. (7) Yan, H.; Choe, H. S.; Nam, S. W.; Hu, Y.; Das, S.; Klemic, J. F.; Ellenbogen, J. C.; Lieber, C. M. Nature 2011, 470, 240−244. (8) Dick, K. A.; Deppert, K.; Larsson, M. W.; Martensson, T.; Seifert, W.; Wallenberg, L. R.; Samuelson, L. Nat. Mater. 2004, 3, 380−384. (9) Jiang, X.; Tian, B.; Xiang, J.; Qian, F.; Zheng, G.; Wang, H.; Mai, L.; Lieber, C. M. Proc. Natl. Acad. Sci. U.S.A. 2011, 108, 12212−12216. (10) Qing, Q.; Pal, S. K.; Tian, B.; Duan, X.; Timko, B. P.; Cohen￾Karni, T.; Murthy, V. N.; Lieber, C. M. Proc. Natl. Acad. Sci. U.S.A. 2010, 107, 1882−1887. (11) Cohen-Karni, T.; Timbo, B. P.; Weiss, L. E.; Lieber, C. M. Proc. Natl. Acad. Sci. U.S.A. 2009, 106, 7309−7313. (12) Cohen-Karni, T.; Qing, Q.; Li, Q.; Fang, Y.; Lieber, C. M. Nano Lett. 2010, 10, 1098−1102. (13) Heller, I.; Smaal, W. T. T.; Lemay, S. G.; Dekker, C. Small 2009, 5, 2528−2532. (14) Kotov, N. A.; Winter, J. O.; Clements, I. P.; Jan, E.; Timko, B. P.; Campidelli, S.; Pathak, S.; Mazzatenta, A.; Lieber, C. M.; Prato, M.; Bellamkonda, R. V.; Silva, G. A.; Kam, N. W. S.; Patolsky, F.; Ballerini, L. Adv. Mater. 2009, 21, 3970−4004. (15) Patolsky, F.; Timko, B. P.; Yu, G.; Fang, Y.; Greytak, A. B.; Zheng, G.; Lieber, C. M. Science 2006, 313, 1100−1104. (16) Lieber, C. M. MRS Bull. 2011, 36, 1052−1063. (17) Patolsky, F.; Timko, B. P.; Zheng, G. F.; Lieber, C. M. MRS Bull. 2007, 32, 142−149. (18) Timko, B. P.; Cohen-Karni, T.; Yu, G.; Qing, Q.; Tian, B.; Lieber, C. M. Nano Lett. 2009, 9, 914−918. (19) Pui, T. S.; Agarwal, A.; Ye, F.; Balasubramanian, N.; Chen, P. Small 2009, 5, 208−212. (20) Eschermann, J. F.; Stockmann, R.; Hueske, M.; Vu, X. T.; Ingebrandt, S.; Offenhausser, A. ̈ Appl. Phys. Lett. 2009, 95, 083703−1− 083703−3. (21) Stern, E.; Klemic, J. F.; Routenberg, D. A.; Wyrembak, P. N.; Turner-Evans, D. B.; Hamilton, A. D.; LaVan, D. A.; Fahmy, T. M.; Reed, M. A. Nature 2007, 445, 519−522. (22) Sze, S. M. Semiconductor devices, physics and technology; Wiley: Singapore, 2002; pp 84−130. (23) Gudlksen, M. S.; Lauhon, L. J.; Wang, J.; Smith, D. C.; Lieber, C. M. Nature 2002, 415, 617−620. (24) Lauhon, L. J.; Gudlksen, M. S.; Wang, D.; Lieber, C. M. Nature 2002, 420, 57−61. (25) Kinked p−n silicon nanowires were synthesized by chemical vapor deposition (CVD) through a nanoparticle-catalyzed vapor− liquid−solid (VLS) process as described previously.5 Specifically, 100 nm diameter gold nanoparticles (Ted Pella) were dispersed on Si growth substrates with 600 nm SiO2 layer (Nova Electronic Materials). Growth of heavily boron-doped p-type arm was first carried out by feeding SiH4 (1 sccm), B2H6 (10 sccm, 100 ppm in H2), and H2 (60 sccm) into the system for 15 min at a total pressure of 40 Torr and temperature of 450 °C. The growth was then paused for 15 s by rapidly evacuating the chamber to lowest pressure and shutting off the gas lines. SiH4 (1 sccm), PH3 (4 sccm, 1000 ppm in H2), and H2 (60 sccm) were then flown into the system at the same total pressure and temperature to grow a heavily doped n-type section for 30 s, forming the p−n junction. A second evaculation of 15 s followed, and finally the heavily doped n-type arm was allowed to finish in additional 15 min. (26) Two pairs of metal electrodes (1.5 nm Cr/120 nm Pd/60 nm Cr, spacing between electrodes 1.5 μm) were fabricated on each of the p- and n-type arms of a kinked nanowire device. The diameter of the nanowire was 100 nm. The doping levels of the arms were estimated using N = σ/qμ, where N is the doping level, σ is the conductivity calculated from the slope of the I−V trace in Supporting Information Figure S2, q is the charge of an electron, and μ is the mobility. Here we take μ as 14 cm2 /V·s.27 (27) Cui, Y.; Zhong, Z.; Wang, D.; Wang, W. U.; Lieber, C. M. Nano Lett. 2003, 3, 149−152. (28) Rusu, A.; Bulucea, C. Proc. Rom. Acad. 2009, 10, 285−290. (29) Wilson, N. R.; Cobden, D. H. Nano Lett. 2008, 8, 2161−2165. (30) The device chip was mounted on a BioScope MultiMode SPM stage (Digital Instrument). A constant current of 250−700 nA was injected into the kinked p−n device, resulting in a forward bias of ∼1 V. The voltage drop across the device was measured using a low-noise differential preamplifier (SR560, Stanford Research Systems). A conductive AFM tip (ARROW-CONTPT-10, NanoWorld) vibrating at a resonance frequency of 90 kHz was used as a local gate and scanned over the device to map the conductance image in “Lift Mode”. Specifically, first for each scan line zero potential was applied to the tip, and a topographic image was acquired in Tapping Mode with feedback enabled. The tip was then lifted up 30 nm, and a tip potential of ±5 V was applied. The tip was scanned across the same line again following the captured topological profile with feedback turned off, when the change of voltage across the device was recorded with a lock-in amplifier (SR830, Stanford Research Systems) using the tip oscillation as the reference frequency.29 In order to remove the drift error during the imaging, we scanned in opposite directions for Vtip = +5 V (fwhm = 120 nm) and Vtip = −5 V (fwhm = 300 nm) images and obtained the average of 210 nm as the corrected length of the sensitive region for our device. (31) Weber, L.; Gmelin, E. Appl. Phys. A 1991, 53, 136−140. (32) To control the solution flowing over the devices, a 1.7 mm thick polydimethylsiloxane (PDMS) sheet with a microfluidic channel 50 μm in height and 1 mm in width was put on the device chip. Fluorescent polystyrene nanobeads of 100 nm in diameter (initial concentration 24 nM in DI water, excitation wavelength 540 nm, emission wavelength 560 nm, from Phosphorex) were diluted in DI water (1:20) and introduced into the microfluidic channel at a flow rate of 0.02 mL/hour set by a syringe pump (PHD 2000, Harvard Apparatus). A confocal fluorescent microscope (FV1000, Olympus) was used to image the motion of the fluorescent nanobeads and the kinked probes in real time while the conductance was recorded. Real￾time fluorescent images of the p−n junction area were captured at a rate of 2 Hz using a 559 nm laser to excite the nanobeads. Two channels with filters of 490−540 nm and 575−675 nm were recorded together to rule out noise signals and unambiguously identify the nanobeads. Images were then superimposed over the device image recorded with a 535−565 nm filter to mark the relative position of the nanobeads and the p−n junction. Nano Letters Letter 1715 dx.doi.org/10.1021/nl300256r | Nano Lett. 2012, 12, 1711−1716