Thermal interfaces and methods include an array of carbon nanotubes aligned substantively perpendicularly from a substrate. One method includes arranging metal catalyst particles with a particular ligand on a fluid surface of a Langmuir-Blodgett trough. This forms uniformly spaced particles with spacing based on the particular ligand. The uniformly spaced metal catalyst particles are deposited on a substrate and carbon nanotubes are grown on the particles using chemical vapor deposition. A thermal interface can be produced with a carbon nanotube packing ratio greater than fifty percent and used in a thermal switch or other device. In some methods, commercially available nanotubes are condensed on a substrate using carbon nanotubes with terminal carboxylic acids in solution and an amine monolayer on the substrate. Pretreatment of the nanotubes in a switch by applying heavy pressure between two surfaces results in good thermal conductivity between those surfaces at smaller operating pressures.