Method for selective electroless attachment of contacts to electrochemically-active molecules

Abstract

A solution-based method for attaching metal contacts to molecular films is described. The metal contacts are attached to functional groups on individual molecules in the molecular film. The chemical state of the functional group is controlled to induce electroless metal deposition preferentially at the functional group site. The functionalized molecules may also be patterned on a surface to give spatial control over the location of the metal contacts in a more complex structure. Spatial control is limited only by the ability to pattern the molecular film. To demonstrate the feasibility of this concept, self-assembled monolayers of model, molecular-electronic compounds have been prepared on gold surfaces, and these surfaces were subsequently exposed to electroless deposition plating baths. These samples exhibited selective metal contact attachment, even on patterned surfaces.

1 . A process of making a solid-state device comprising: 
 forming a self-assembled monolayer on a metal substrate; and,    placing said metal substrate and said self-assembled monolayer in an electroless plating bath to form a metallic layer on said self-assembled monolayer.    
     
     
         2 . The process of  claim 1  wherein said step of placing said metal substrate and said self-assembled monolayer in an electroless plating bath comprises placing said metal substrate and said self-assembled monolayer in an electroless plating bath comprising: water, formaldehyde, copper sulfate, and sodium hydrogen tartrate.  
     
     
         3 . The process of  claim 1  wherein said step of placing said metal substrate and said self-assembled monolayer in an electroless plating bath comprises placing said metal substrate and said self-assembled monolayer in an electroless plating bath wherein the pH of said electroless plating bath is adjusted to approximately 12.8.  
     
     
         4 . A process of making a solid-state device comprising: 
 forming a self-assembled monolayer on a metal substrate; and    placing said metal substrate and said self-assembled monolayer in an electroless plating bath consisting of water, formaldehyde, copper sulfate, and sodium hydrogen tartrate and adjusted to a pH of approximately 12.8 to form a metallic layer on said self-assembled monolayer.    
     
     
         5 . A process of making a solid-state device comprising: 
 forming patterned areas of multiple self-assembled monolayers on a metal substrate; and    placing said metal substrate and said patterned areas of said multiple self-assembled monolayers in an electroless plating bath to form a metallic layer on said patterned areas of said self-assembled monolayers.    
     
     
         6 . The process of  claim 5  wherein said step of placing said metal substrate and said patterned areas of said multiple self-assembled monolayers in an electroless plating bath comprises placing said metal substrate and said patterned areas of said multiple self-assembled monolayers in an electroless plating bath comprising: water, formaldehyde, copper sulfate, and sodium hydrogen tartrate.  
     
     
         7 . The process of  claim 5  wherein said step of placing said metal substrate and said patterned areas of said multiple self-assembled monolayers in an electroless plating bath comprises placing said metal substrate and said patterned areas of said multiple self-assembled monolayers in an electroless plating bath wherein the pH of said electroless plating bath is adjusted to approximately 12.8.  
     
     
         8 . A process of making a solid-state device comprising: 
 forming patterned areas of multiple self-assembled monolayers on a metal substrate; and    placing said metal substrate and said patterned areas of said multiple self-assembled monolayers in an electroless plating bath consisting of water, formaldehyde, copper sulfate, and sodium hydrogen tartrate and adjusted to a pH of approximately 12.8 to form a metallic layer on said patterned areas of said self-assembled monolayers.    
     
     
         9 . A process of making a solid-state device comprising: 
 depositing a self-assembled monolayer on a metal substrate, said self-assembled monolayer having a functional group that provides increased interaction with metal ions in an electroless plating bath, said self-assembled monolayer being selectively deposited on predetermined areas of said metal substrate; and    placing said self-assembled monolayer, that is deposited on said metal substrate, together with said functional group, in an electroless plating bath so that metal ions in solution in said electroless plating bath are reduced on said self-assembled monolayer through interaction with said functional group to form a metallic contact layer such that said metallic contact layer does not penetrate said self-assembled monolayer and does not form a short circuit to said metal substrate.    
     
     
         10 . The process of  claim 9  wherein said functional group comprises carboxylic acid.  
     
     
         11 . The process of  claim 9  wherein said self-assembled monolayer comprises 4-mercaptobenzoic acid.  
     
     
         12 . A method of attaching metal contacts to molecular films to produce a solid-state device comprising: 
 attaching a functional molecular group to a metallic plate to form a self-assembled monolayer with a conductive bottom contact;    attaching a metal contact to said self-assembled monolayer by depositing a metallic layer on a non-metallic surface of said self-assembled monolayer with an electroless plating bath for metal deposition onto said surface;    removing said self-assembled monolayer from said electroless plating bath after a prescribed length of time; and    rinsing said self-assembled monolayer with water.    
     
     
         13 . A method of  claim 12  wherein said electroless plating bath comprises: 
 water, formaldehyde, copper sulfate, sodium hydrogen tartrate.    
     
     
         14 . A method of  claim 13  wherein the pH of said electroless plating bath is adjusted to approximately 12.8  
     
     
         15 . A method of attaching metal contacts to molecular films to produce a solid-state device comprising: 
 attaching a functional molecular group to a metallic plate to a to form a self-assembled monolayer with a conductive bottom contact;    placing a non-metallic surface of said self-assembled monolayer into an electroless plating bath for metal deposition onto said surface;    attaching a metal contact to said self-assembled monolayer to form a top contact by depositing a metallic layer on said non-metallic surface of said self-assembled monolayer with an electroless plating bath consisting of water, formaldehyde, copper sulfate, sodium hydrogen tartrate;    adjusting the pH of said electroless plating bath to approximately 12.8;    removing said self-assembled monolayer from said electroless plating bath after a prescribed length of time; and    rinsing said self-assembled monolayer with water.    
     
     
         16 . A method of attaching metal contacts to molecular films to produce a solid-state device comprising: 
 attaching a functional molecular group to selective portions of a metallic plate to form patterned areas of self-assembled monolayers on a conductive bottom contact;    placing patterned surfaces of said self-assembled monolayers into an electroless plating bath for selective metal deposition onto said surfaces; and    attaching metal contacts to said patterned portions of said self-assembled monolayers to form top contacts by depositing a metallic layer on said patterned surfaces of said self-assembled monolayers with said electroless plating bath.    
     
     
         17 . A method of  claim 16  wherein said attachment of a functional molecular group to selective portions of a metallic plate to form patterned areas of self-assembled monolayers on a conductive bottom contact further comprises: 
 controlling the chemical state of said functional molecular group by preferentially inducing said electroless metal deposition at a functional molecular group site.    
     
     
         18 . A method of  claim 16  wherein said attachment of a functional molecular group to selective portions of a metallic plate to form patterned areas of self-assembled monolayers on a conductive bottom contact further comprises: 
 patterning the functionalized molecules on a surface to give spatial control over the location of the metal contacts.    
     
     
         19 . A method of attaching metal contacts to functional groups on individual molecules in a molecular film to produce solid-state devices comprising: 
 attaching a functional molecular group to selective portions of a metallic plate to form patterned areas of self-assembled monolayers on a conductive bottom contact;    patterning the functionalized molecules on a surface to give spatial control over the location of the metal contacts;    placing patterned surfaces of said self-assembled monolayers into an electroless plating bath for selective metal deposition onto said surfaces;    controlling the chemical state of said functional molecular group by preferentially inducing said electroless metal deposition at a functional molecular group site;    attaching metal contacts to said patterned portions of said self-assembled monolayers to form top contacts by depositing a metallic layer on said patterned surfaces of said self-assembled monolayers with said electroless plating bath comprising water, formaldehyde, copper sulfate, sodium hydrogen tartrate;    adjusting the pH of said electroless plating bath to approximately 12.8;    removing said self-assembled monolayers from said electroless plating bath after a prescribed length of time; and    rinsing said self-assembled monolayers with water.