Palladium thiolate bonding of carbon nanotubes
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. 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;
applying a solution containing a metal organic compound to the nanotube array, wherein the solution includes a metal alkanethiolate; and
thermally decomposing the solution around the nanotubes and the substrate.
2. The method of claim 1 which further comprises compressing the nanotubes during said decomposing.
3. The method of claim 1 wherein said decomposing is performed in air, nitrogen or high vacuum.
4. The method of claim 1 wherein said decomposing is performed in a heated environment.
5. The method of claim 1 which further comprises increasing the number of defect sites in the CNTs prior to said applying the solution to the aligned CNT array.
6. The method of claim 1 wherein the solution includes a metal butanethiolate.
7. The method of claim 1 wherein the solution includes one of palladium hexadecanethiolate or palladium butanethiolate.
8. The method of claim 1 wherein the solution includes a metal acetate, thiol and toluene.
9. The method of claim 1 wherein the solution is solvent based.
10. The method of claim 1 which further comprises removing the excess thiolate during said decomposing.
11. The method of claim 1 wherein the substrate includes a layer of at least one of Ti or Cr to promote adhesion of the carbon nanotubes.
12. The method of claim 1 wherein the substrate includes material chosen from the group of aluminum, platinum, gold, nickel, iron, tin, lead, silver, titanium, indium, or copper.
13. The method of claim 1 wherein said growing is by microwave plasma chemical vapor deposition.
14. The method of claim 1 wherein said carbon nanotubes are multi-walled.
15. The method of claim 1 which further comprises:
providing a contact substrate;
contacting carbon nanotubes to the contact substrate; and
thermally decomposing the solution around the nanotubes, the growth substrate and the contact substrate.
16. 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;
applying a solution containing a metal organic compound to the contacting nanotubes and to the first surface and the second surface, wherein the solution includes a metal alkanethiolate; and
thermally decomposing the solution around the contacting nanotubes and the first surface and the second surface.
17. The method of claim 16 which further comprises pressing the first surface against the second surface before said decomposing.