Palladium thiolate bonding of carbon nanotubes

Abstract

Carbon nanotube (CNT) arrays are attractive thermal interface materials with high compliance and conductance that can remain effective over a wide temperature range. Disclosed herein are CNT interface structures in which free CNT ends are bonded using palladium hexadecanethiolate Pd(SC 16 H 35 ) 2 to an opposing substrate (one-sided interface) or opposing CNT array (two-sided interface) to enhance contact conductance while maintaining a compliant joint. The palladium weld is mechanically stable at high temperatures. A transient photoacoustic (PA) method is used to measure the thermal resistance of the palladium bonded CNT interfaces. The interfaces were bonded at moderate pressures and then tested at 34 kPa using the PA technique. At an interface temperature of approximately 250° C., one-sided and two-sided palladium bonded interfaces achieved thermal resistances near 10 mm 2 K/W and 5 mm 2 K/W, respectively.

1 .- 38 . (canceled) 
     
     
         39 . A method for fabricating a thermal interface, comprising:
 providing a growth substrate;   growing carbon nanotubes from the growth substrate, each nanotube being anchored at one end to the growth substrate;   aligning the nanotubes in a direction generally perpendicular to the growth substrate;   increasing the number of defect sites in the CNTs by growing carbon nanotubes by microwave plasma enhanced chemical vapor deposition; and   altering the density of states of an energy carrier in the nanotubes;   wherein said increasing occurs prior to said altering.   
     
     
         40 . The method of  claim 39  wherein the energy carriers are electrons or phonons. 
     
     
         41 . The method of  claim 39  wherein said altering is at the interface of the nanotube and the substrate. 
     
     
         42 . The method of  claim 39  wherein said altering is by exposing the carbon nanotubes to an electron-donating material. 
     
     
         43 . The method of  claim 42  wherein the electron-donating material includes one of tetracyanoquinodimethane, tetramethyltetrathiafulvalene, tetramethylselenafulvalenes, or dimethylanthracene. 
     
     
         44 . The method of  claim 39  wherein said altering is by exposing the carbon nanotubes to an electron-withdrawing material. 
     
     
         45 . The method of  claim 44  wherein the electron-withdrawing material includes one of tricyanomethane, tetracyanoethylene, tetracyanoquinodimethanide, nitrobenzene, 1,3,6,8-pyrenetetrasulfonic acid tetra sodium salt hydrate, or 9,10-dibromoanthracene. 
     
     
         46 . The method of  claim 39  wherein said altering is by exposing the carbon nanotubes to one of phenylamine, o-toluidine, 2,4,6-trimethylaniline, anisidine, or 3-trifluoromethylaniline. 
     
     
         47 . The method of  claim 39  wherein said altering is by exposing the carbon nanotubes to one of tetrathiafulvalene, tetracyanoquinodimethane, tetramethyltetrathiafulvalene, tetramethylselenafulvalenes, or dimethylanthracene. 
     
     
         48 . The method of  claim 39  wherein said altering is by exposing the carbon nanotubes to one of tetracyanoethylene, tricyanomethane, tetracyanoethylene, tetracyanoquinodimethanide, nitrobenzene, 1,3,6,8-pyrenetetrasulfonic acid tetra sodium salt hydrate, or 9,10-dibromoanthracene. 
     
     
         49 . The method of  claim 39  wherein said altering is by exposing the carbon nanotubes to an aromatic amine. 
     
     
         50 . The method of  claim 39  wherein said altering is by exposing the carbon nanotubes to an organosulfur compound. 
     
     
         51 . The method of  claim 39  wherein the substrate includes a layer of at least one of Ti or Cr to promote adhesion of the carbon nanotubes. 
     
     
         52 . The method of  claim 39  wherein the substrate includes material chosen from the group of aluminum, platinum, gold, nickel, iron, tin, lead, silver, titanium, indium, or copper. 
     
     
         53 . The method of  claim 39  wherein said growing is by microwave plasma chemical vapor deposition. 
     
     
         54 . The method of  claim 39  wherein said growing is a density of nanotubes greater than about 10 7  nanotubes per square millimeter. 
     
     
         55 . The method of  claim 39  wherein said growing is a density of nanotubes less than about 10 9  nanotubes per square millimeter. 
     
     
         56 . The method of  claim 39  wherein said carbon nanotubes are multi-walled. 
     
     
         57 . The method of  claim 39  further comprising:
 providing a contact substrate; 
 contacting carbon nanotubes to the contact substrate; and 
 increasing the density of states of the energy carrier by creation of metallic-like bonds between the nanotubes and the contact substrate. 
 
     
     
         58 . The method of  claim 57 , wherein the contact substrate includes a metal. 
     
     
         59 . The method of  claim 57 , wherein the contact substrate includes silver. 
     
     
         60 . The method of  claim 57 , wherein the metallic-like bonds are created by thermal treatment of a metal ethiolate. 
     
     
         61 . The method of  claim 57 , wherein the metallic-like bonds are created from metal nanoparticles. 
     
     
         62 . The method of  claim 57 , wherein the metallic-like bonds are created from palladium nanoparticles. 
     
     
         63 . A method for fabricating a thermal interface, comprising:
 providing a first growth substrate and a second growth substrate;   growing a first plurality of carbon nanotubes from a first surface of the first growth substrate, each nanotube of the first plurality being anchored at one end to the first surface;   growing a second plurality of carbon nanotubes from a second surface of the second growth substrate, each nanotube of the second plurality being anchored at one end to the second surface;   placing the first plurality of nanotubes in contact with the second plurality of nanotubes with the first surface being opposite of the second surface;   increasing the number of defect sites in the CNTs by growing carbon nanotubes by microwave plasma enhanced chemical vapor deposition; and   altering the density of states of an energy carrier in the contacting nanotubes;   wherein said increasing occurs prior to said altering.   
     
     
         64 . The method of  claim 63  which further comprises pressing the first surface against the second surface before said altering. 
     
     
         65 . The method of  claim 63  wherein altering the density of states includes increasing the density of states. 
     
     
         66 . The method of  claim 63  wherein increasing the density of states includes creation of metallic-like bonds between free ends of the first plurality of nanotubes and the second plurality of nanotubes.