single - crystalline kinked nanowires were synthesized by the nanocluster - catalyzed vls method described previously18,19 in quartz tube connected to gas manifold and vacuum pump and heated by a temperature controlled tube furnace . monodisperse gold nanoparticles ( ted pella ) were dispersed on sio2/si or sapphire growth substrates ( au surface coverage : 0.010.1 particles/m ) , which were placed within the central region of the quartz tube reactor . the silicon ( si ) nanowires were synthesized at 450460 c using silane ( sih4 ) as the silicon reactant source , hydrogen ( h2 ) as the carrier gas , and phosphine ( ph3 , 1,000 p.p.m . in h2 ) and diborane ( b2h6,100 p.p.m . in h2 ) as the n- and p - type dopants . in a typical synthesis of uniform n - type , 80 nm kinked silicon nanowires , the flow rates of sih4 , ph3 and h2 were 12 , 210 and 60 standard cubic centimetres per minute , respectively , and the total pressure was 40 torr and purge duration was 15 s ; the minimum pressure during the purge cycle was ca . 3  10 torr . the dopant feed - in ratios ( silicon : boron / phosphorus ) in kinked p - n silicon nanowires were 500:1 for both p - and n - type segments . in n - kink - n - kink-(n - n ) dopant modulated silicon nanowires , the silicon - phosphorus feed - in ratios were 200:1 and 10000:1 for n- and n - type segments , respectively , and the n- segment was grown for 30 s. germanium nanowires were synthesized at 270290 c , 40 torr , with germane ( geh4 , 10 % in h2 ) and h2 as the reactant and carrier gas , respectively . cadmium sulphide nanowires were grown in a three - zone furnace by evaporating cds power at 650720 c , with nanowire growth by gold nanocluster catalyzed vls method at 550 - 500 c . the purge cycle used to form kinks in the germanium and cadmium sulphide nanowires was typically 15 s. zeiss ultra55/supra55vp field - emission sems and jeol 2010 field emission tem were used to carry out sem and tem analyses , respectively . for sample preparation , kinked nanowires were gently sonicated in isopropyl alcohol and dispersed onto heavily doped silicon substrates ( 100 nm oxide/200 nm nitride , 110 cm resistivity , nova electronic materials , carrollton , tx ) or lacey carbon grids ( ted pella ) . devices were fabricated on silicon substrates ( nova electronic materials , n - type 0.005 cm ) with 100 nm thermal oxide and 200 nm silicon nitride at the surface . devices were defined by electron - beam lithography followed by ti / pd ( 1.5 nm/100 nm ) contact deposition in a thermal evaporator . current - voltage ( i  v ) data were recorded using an agilent semiconductor parameter analyzer ( model 4156c ) with contacts to devices made using a probe station ( desert cryogenics , model ttp4 ) . electrostatic force microscopy and scanned gate microscopy measurements were carried out with a digital instruments nanoscope iiia multimode afm and metal coated tips ( nanosensors , ppp - nchpt ) . the electrostatic force microscopy surface potential maps and scanned gate microscopy conductance maps were acquired in lift mode with lift heights of 40 and 20 nm , respectively . in the surface potential measurements , the p - n diode was reverse - biased at 5 v and the tip voltage was modulated by 3v at the resonance frequency . in scanned gate measurements , the tip functions as a local gate vtip = 10 v , and the conductance versus position provides a measure of local accumulation or depletion of carriers in the device . single - crystalline kinked nanowires were synthesized by the nanocluster - catalyzed vls method described previously18,19 in quartz tube connected to gas manifold and vacuum pump and heated by a temperature controlled tube furnace . monodisperse gold nanoparticles ( ted pella ) were dispersed on sio2/si or sapphire growth substrates ( au surface coverage : 0.010.1 particles/m ) , which were placed within the central region of the quartz tube reactor . the silicon ( si ) nanowires were synthesized at 450460 c using silane ( sih4 ) as the silicon reactant source , hydrogen ( h2 ) as the carrier gas , and phosphine ( ph3 , 1,000 p.p.m . in h2 ) and diborane ( b2h6,100 p.p.m . in h2 ) as the n- and p - type dopants . in a typical synthesis of uniform n - type , 80 nm kinked silicon nanowires , the flow rates of sih4 , ph3 and h2 were 12 , 210 and 60 standard cubic centimetres per minute , respectively , and the total pressure was 40 torr and purge duration was 15 s ; the minimum pressure during the purge cycle was ca . 3  10 torr . the dopant feed - in ratios ( silicon : boron / phosphorus ) in kinked p - n silicon nanowires were 500:1 for both p - and n - type segments . in n - kink - n - kink-(n - n ) dopant modulated silicon nanowires , the silicon - phosphorus feed - in ratios were 200:1 and 10000:1 for n- and n - type segments , respectively , and the n- segment was grown for 30 s. germanium nanowires were synthesized at 270290 c , 40 torr , with germane ( geh4 , 10 % in h2 ) and h2 as the reactant and carrier gas , respectively . cadmium sulphide nanowires were grown in a three - zone furnace by evaporating cds power at 650720 c , with nanowire growth by gold nanocluster catalyzed vls method at 550 - 500 c . the purge cycle used to form kinks in the germanium and cadmium sulphide nanowires was typically 15 s. zeiss ultra55/supra55vp field - emission sems and jeol 2010 field emission tem were used to carry out sem and tem analyses , respectively . for sample preparation , kinked nanowires were gently sonicated in isopropyl alcohol and dispersed onto heavily doped silicon substrates ( 100 nm oxide/200 nm nitride , 110 cm resistivity , nova electronic materials , carrollton , tx ) or lacey carbon grids ( ted pella ) . devices were fabricated on silicon substrates ( nova electronic materials , n - type 0.005 cm ) with 100 nm thermal oxide and 200 nm silicon nitride at the surface . devices were defined by electron - beam lithography followed by ti / pd ( 1.5 nm/100 nm ) contact deposition in a thermal evaporator . current - voltage ( i  v ) data were recorded using an agilent semiconductor parameter analyzer ( model 4156c ) with contacts to devices made using a probe station ( desert cryogenics , model ttp4 ) . electrostatic force microscopy and scanned gate microscopy measurements were carried out with a digital instruments nanoscope iiia multimode afm and metal coated tips ( nanosensors , ppp - nchpt ) . the electrostatic force microscopy surface potential maps and scanned gate microscopy conductance maps were acquired in lift mode with lift heights of 40 and 20 nm , respectively . in the surface potential measurements , the p - n diode was reverse - biased at 5 v and the tip voltage was modulated by 3v at the resonance frequency . in scanned gate measurements , the tip functions as a local gate vtip = 10 v , and the conductance versus position provides a measure of local accumulation or depletion of carriers in the device .
the ability to control and modulate the composition14 , doping1,35 , crystal structure68 and morphology9,10 of semiconductor nanowires during the synthesis process has allowed researchers to explore various applications of nanowires1115 . however , despite advances in nanowire synthesis , progress towards the ab initio design and growth of hierarchical nanostructures has been limited . here 
 we demonstrate a 
 nanotectonic approach that provides iterative control over the nucleation and growth of nanowires and use it to grow kinked or zigzag nanowires in which the straight sections are separated by triangular joints . 
 moreover , the lengths of the straight sections can be controlled and the growth direction remains coherent along the nanowire . 
 we also grow dopant - modulated structures in which specific device functions , including p - n diodes and field - effect transistors , can be precisely localized at the kinked junctions in the nanowires .