A Pyrenylpropyl Phosphonic Acid Surface Modifier for Mitigating the Thermal Resistance of Carbon Nanotube Contacts

With the on-going increase in the power density of electronic devices, thermal management remains a central issue for upholding device performance and reliability. Thermal interface materials (TIMs), used to conduct heat across the multiple interfaces between the device and heat sink, with unprecedentedly low thermal resistance and a high degree of mechanical compliance to accommodate mismatches in thermal expansion are required. [ 1 ] Forests comprised of nominally vertically aligned carbon nanotubes (CNTs), with individual thermal conductivities on the order of 3000 W m −1 K −1 [ 2,3 ] and an in-plane elastic modulus as low as 8 MPa, [ 4 ] are excellent candidates for thermal interface materials (TIMs). [ 5–16 ] However, despite nearly a decade of research TIMs based on vertically aligned CNT (VACNT) forests have yet to harness effectively the high thermal conductivity of individual CNTs. One of the key obstacles that has limited the effectiveness of VACNT TIMs is the presence of high thermal contact resistances between the CNT free ends and the surfaces comprising the interface. [ 6–8,17 ] Previous approaches to mitigate the contact resistance have focused on methods for bonding the free ends of the CNTs to the interface. [ 6,9–14,16 ] A few of the more successful bonding methods that have been developed are summarized in Table 1 . While, many of the methods have produced TIMs with thermal resistances that are comparable to conventional metallic solder TIMs (5 mm 2 KW −1 ), [ 18 ]