High Conductivity Copper–Carbon Nanotube Hybrids via Site-Specific Chemical Vapor Deposition

Abstract

Site-selective copper nanometal seeding through chemical vapor deposition (CVD) is demonstrated as a viable method in concert with solution electrodeposition of bulk Cu to enhance the electrical conductivity of a porous, low-density (0.12 g/cm 3 , ∼9 mg/m) CNT roving. An electrical bias applied directly to the CNT roving promotes Joule heating, which provides the thermal energy necessary for the decomposition of a bis(tert-butylacetoacetato)copper (Cu-(tBAOAC) 2 ) precursor. Localized changes in the resistance within the bulk CNT conductor were used to selectively deposit the precursor at thermally active sites, which were evaluated through thermal imaging. The deposition varies from localized Cu deposits at currents producing average temperatures of ∼225 °C to a consistent deposition of 10−40 nm Cu particles at applied currents producing average temperatures >300 °C, far above the threshold for the decomposition of the Cu(tBAOAC) 2 precursor. Scanning electron microscopy of a cross section of the roving reveals Cu depositions on the interior of the roving, demonstrating the penetration of the vapor into the CNT network and subsequent decomposition within the roving. A commercial acid-based Cu electroplating solution was used to deposit bulk Cu onto as-prepared and CVD seeded CNT wires, followed by planar densification and H 2 /Ar annealing. The finished conductors with Cu loadings from ∼30 to 95% w/w which combine CVD Cu seeding and electrodeposition result in specific conductivity values 3−5 times higher than Cu-CNT conductors produced by electrodeposition alone. Ultimately, a CNT hybrid conductor with 94.2% w/w Cu achieved a specific conductivity of 5632 S m 2 /kg and electrical conductivity of 28.1 MS/mapproaching values previously only seen in metallic conductors. Overall, the present results demonstrate the potential of site-specific CVD toward both seeding metal prior to electroplating and as a possible method toward the enhanced nanometal interconnection of carbon conductors (NICCs).

Fabrication of Light‐Weight and Highly Conductive Copper–Carbon Nanotube Core–Shell Fibers Through Interface Design

“…[ 33–35 ] To eliminate tin usage, the outer surface of the CNT fibers was functionalized with thiol groups. As a result, the Pd catalyst could be directly seeded on the CNT fibers, similar to the works of Subramaniam et al [ 4 ] and Leggiero et al [ 17 ] Moreover, the thiol functional groups create a strong bonding between the CNT fiber core and Cu shell. [ 30 ] Consequently, dense and smooth coating of Cu were deposited on the Pd‐seeded fibers and light‐weight core–shell fibers with remarkable electrical conductivity of 3.6 × 10 7 S m −1 and tensile strength of 1 GPa were fabricated.…”

“…[ 6–8 ] Therefore, there has been a great interest to improve the electrical performance of these fibers by metallization. [ 4,5,14–19 ] Subramaniam et al [ 4 ] combined several fabrication approaches to produce high density CNT (45 vol%)‐Cu composite films with specific conductivity 26% greater than copper. Similarly, Leggiero et al [ 17 ] used a chemical vapor deposition method to seed Cu on CNT roving.…”

“…[ 4,5,14–19 ] Subramaniam et al [ 4 ] combined several fabrication approaches to produce high density CNT (45 vol%)‐Cu composite films with specific conductivity 26% greater than copper. Similarly, Leggiero et al [ 17 ] used a chemical vapor deposition method to seed Cu on CNT roving. After plating and densification, a dense and uniform CNT hybrid conductor with 94.2 wt.% of Cu was obtained that has an electric conductivity of 2.81 × 10 7 S m −1 , which is five times higher than the samples that were not seeded.…”

Critical challenges and advances in the carbon nanotube–metal interface for next-generation electronics

“…The effect of pre-seeding is highlighted in a work by Leggiero et al in which a chemical vapor deposition method was used to seed Cu on CNT roving before Cu plating. 160 As a result, a dense and uniform CNT/Cu hybrid conductor was fabricated with an electric conductivity of 2.81 × 10 7 S m -1 , which is five times higher than the samples that were not pre-seeded (Figure 6i). Another approach that is worth considering is nitrogen-doping of the CNT fibers.…”

Enhancement of the electrical conductivity of defective carbon nanotube sheets for organic hybrid thermoelectrics by deposition of Pd nanoparticles

“…There are reports about the supported metal NPs on the surface of carbon nanomaterials like CNTs and graphenes. [44][45][46][47][48] However, only a few reports described the applications of the supported metal NPs on the SWCNTs for the hybrid thermoelectric materials. [36][37][38][39][40] The support of metal NPs on CNTs generally requires chemical modification of the CNTs on the surface or at the edge.…”