Segmented Nanowires Displaying Locally Controllable Properties

Abstract

Vapor-liquid-solid growth of nanowires is tailored to achieve complex one-dimensional material geometries using phase diagrams determined for nanoscale materials. Segmented one-dimensional nanowires having constant composition display locally variable electronic band structures that are determined by the diameter of the nanowires. The unique electrical and optical properties of the segmented nanowires are exploited to form electronic and optoelectronic devices. Using gold-germanium as a model system, in situ transmission electron microscopy establishes, for nanometer-sized Au—Ge alloy drops at the tips of Ge nanowires (NWs), the parts of the phase diagram that determine their temperature-dependent equilibrium composition. The nanoscale phase diagram is then used to determine the exchange of material between the NW and the drop. The phase diagram for the nanoscale drop deviates significantly from that of the bulk alloy.

1 . A nanowire comprising a first section and a second section adjacent to the first section wherein the nanowire diameter changes abruptly from the first section to the second section. 
     
     
         2 . The nanowire of  claim 1  wherein the change in diameter is abrupt on an atomic scale, occurring over a few lattice spacings along the growth direction. 
     
     
         3 . The nanowire of  claim 2  wherein the diameter of each section is between 1 and 100 nm and the diameter of the second section is larger than that of the first section. 
     
     
         4 . A nanowire according to  claim 1 , further comprising at least one additional section wherein the nanowire diameter changes between each section. 
     
     
         5 . A nanowire according to  claim 4 , wherein a concentration of a dopant in the nanowire changes abruptly between each section. 
     
     
         6 . An electronic device comprising a nanowire according to  claim 4 . 
     
     
         7 . An electronic device comprising a nanowire comprising a first section and a second section adjacent thereto wherein the nanowire diameter changes abruptly from the first section to the second section. 
     
     
         8 . A nanowire of uniform composition comprising a plurality of segments adjoining one another, each segment having an energy bandgap, wherein the bandgap differs between first and second adjacent segments of the plurality of segments. 
     
     
         9 . The nanowire of  claim 8 , wherein the bandgap difference between the first and second adjacent segments is abrupt on an atomic scale forming an interface between the first and second adjacent segments. 
     
     
         10 . The nanowire of  claim 9 , wherein a first electronic junction is co-located with the interface between the first and second adjacent segments. 
     
     
         11 . The nanowire of  claim 10 , further comprising a third nanowire segment adjacent to the second segment, the bandgap of the third nanowire segment differing from the bandgap of the second segment, the bandgap difference between the second and third segments abrupt on an atomic scale forming an interface between the second and third segments and wherein a second electronic junction is co-located with the interface between the second and third segments.