Forming nanowires

Abstract

A method of forming nanowires, including the forming on a metal region of a layer having through openings, and the forming in the through openings of portions deposited in a chemical bath, forming all or part of the nanowires and extending from the metal region.

1 . Method of forming nanowires, comprising:
 the forming on a metal region of a layer having through openings;   the forming in the through openings of portions deposited in a first chemical bath, forming first portions of the nanowires and extending from the metal region; and   the deposition in a second chemical bath, of a composition different from that of the first chemical bath, of second portions of the nanowires extending from the first portions.   
     
     
         2 . Method according to  claim 1 , wherein the first chemical bath for forming said portions comprises, in solution:
 a first compound defining a source of metal cations; and   a second compound comprising a source of hydroxide, sulfide, or selenide ions,   the concentrations of the first and second compounds and/or their ratio being lower than a concentration threshold of said first chemical bath, said threshold being such that, when the concentrations are lower than said threshold, a growth of said portions parallel to said layer is favored over a growth of said portions in a thickness direction of said layer, said threshold being preferably in the order of 10 mM; and/or   the first chemical bath comprising one or a plurality of additives adapted to favoring a growth of said portions parallel to said layer over a growth of said portions in the thickness direction of said layer, preferably citrate or chloride ions; and/or   the first compound being in a superstoichiometric concentration with respect to the second compound.   
     
     
         3 . Method according to  claim 2 , wherein:
 said metal cations are cations of at least one metal from the group formed of Zn, Cd, Ni, Ag, and Cu; and/or   the first compound comprises at least one component from the group formed of nitrates, acetates, chlorides, and sulfates; and/or   the second compound comprises at least one component from the group formed of HTMA, of ammonia, of sodium hydroxide, of thiourea, of selenourea, and of sodium selenite.   
     
     
         4 . Method according to any of  claim 1 , wherein the second chemical bath for forming the second portions comprises, in solution:
 a first compound defining a source of metal cations; and   a second compound comprising a source of hydroxide, sulfide, or selenide ions,   the concentrations of the first and second compounds and/or their ratio being greater than a concentration threshold of the second chemical bath for forming the second portions, the concentration threshold of the second chemical bath for forming the second portions being such that, when the concentrations are greater than this threshold, a growth of the second portions orthogonally to said layer is favored over a growth of the second portions parallel to said layer, the concentration threshold of the second chemical bath for forming the second portions being preferably in the order of 20 mM; and/or   the second chemical bath for forming the second portions comprising one or a plurality of additives adapted to favoring a growth of the second portions orthogonally to said layer over a growth of the second portions parallel to said layer, preferably polyethylene imide or ethylene diamine; and/or   the first compound being in a substoichiometric concentration with respect to the second compound.   
     
     
         5 . Method according to  claim 4 , wherein:
 said metal cations of the second chemical bath for forming the second portions are cations of at least one metal from the group formed of Zn, Cd, Ni, Ag, and Cu; and/or   the first compound of the second chemical bath for forming the second portions comprises at least one component from the group formed of nitrates, acetates, chlorides, and sulfates; and/or   the second compound of the second chemical bath for forming the second portions comprises at least one component from the group formed of HTMA, of ammonia, of sodium hydroxide, of thiourea, of selenourea, and of sodium selenite.   
     
     
         6 . Method according to  claim 1 , comprising the forming, at one end of the nanowires opposite to said metal region, of an electrically-conductive region in contact with the nanowires. 
     
     
         7 . Method according to  claim 1 , comprising the forming of a polymer matrix between the nanowires. 
     
     
         8 . Method according to  claim 1 , comprising the removal of said layer. 
     
     
         9 . Method according to  claim 1 , wherein the metal region comprises at least one of the materials from the group formed of gold, of nickel, of copper, of palladium, and of platinum. 
     
     
         10 . Method according to  claim 1 , wherein the metal region has a thickness greater than 100 nm. 
     
     
         11 . Method according to  claim 1 , wherein said layer is obtained by lithography from a layer comprising a block copolymer or from a layer sensitive to electrons or to ultraviolet radiations. 
     
     
         12 . Method according to  claim 1 , wherein said layer is defined by a DNA origami. 
     
     
         13 . Method according to  claim 1 , wherein:
 the nanowires have a transverse dimension smaller than 300 nm, preferably smaller than 50 nm;   the nanowires have a length greater than 500 nm, preferably greater than 1 μm; and/or   said layer has a thickness smaller than 100 nm, preferably smaller than 50 nm.