Long poly-diacetylene chains are excellent candidates for planar, on-surface synthesized molecular electronic wires. Since hexagonal-Boron Nitride (h-BN) was identified as the best available atomically flat insulator for the deposition of poly-diacetylene precursors, we demonstrate the polymerization patterns and rate on it under UV-light irradiation, with subsequent polymer identification by atomic force microscopy. The results on h-BN indicate self-sensitization which yields blocks comprised of several polymers, unlike on the well-studied graphite/diacetylene system, where the polymers are always isolated. In addition, the photo-polymerization proceeds at least 170 times faster on h-BN, where it also results in longer polymers. Both effects are explained by the h-BN bandgap, which is larger than the diacetylene electronic excitation energy, thus allowing the transfer of excess energy absorbed by polymerized wires to adjacent monomers, triggering their polymerization. This work sets the stage for conductance measurements of single molecular poly-diacetylene wires on h-BN.

Single crystal sapphire and diamond surfaces are used as planar, atomically flat insulating surfaces, for the deposition of the diacetylene compound 10,12-nonacosadiynoic acid. The surface assembly is compared with results on hexagonal boron nitride (h-BN), highly oriented pyrolytic graphite (HOPG) and MoS₂ surfaces. A perfectly flat-lying monolayer of 10,12-nonacosadiynoic acid self-assembles on h-BN like on HOPG and MoS₂. On sapphire and oxidized diamond surfaces, we observed assemblies of standing-up molecular layers. Surface assembly is driven by surface electrostatic dipoles. Surface polarity is partially controlled using a hydrogenated diamond surface or totally screened by the deposition of a graphene layer on the sapphire surface. This results in a perfectly flat and organized SAM on graphene, which is ready for on-surface polymerization of long and isolated molecular wires under ambient conditions.

Vanadium dioxide (VO₂) is a well-known phase-changing material that goes from a semiconducting state to a metallic one at a critical temperature of 68 °C, which is the closest to room temperature (25 °C). The electrical transition is also accompanied by structural and optical changes. The optical transition upon heating-also known as thermochromism-makes VO₂ a possible coating for “intelligent” windows. In this work, the relationship between the thermochromic performance of VO₂ films and the surface morphology was investigated using Temperature-dependent Atomic Force Microscopy (T-AFM) in conjunction with the X-ray Diffraction technique and Scanning Electron Microscopy. In particular, VO₂ films were deposited using the rf sputtering technique on Silicon and glass substrates at a substrate temperature of 300 °C, which is one of the lowest for this technique to grow the thermochromic monoclinic phase of VO₂. It was found that upon heating (25–100 °C), there was a decrease in RMS roughness for all films independent from the substrate; the value of RMS roughness, however, varied depending on the substrate. Finally, the thermochromic parameters of the VO₂ films were correlated with the surface morphology and appeared to be dependent on the kind of substrate used.

A He ⁺ ion beam is used to induce electronic localization, on a single graphene layer exfoliated on an ultra-flat sapphire substrate, based on crystalline defects and with a lateral irradiation precision of 1 nm. Inducing a 1% carbon defect density by step by step irradiation of a 100-nm-wide band on the supported graphene increases its electrical resistance from 0.90 to 133 kΩ. The resistance build-up was monitored in situ and in real time by measuring the I ( t ) current intensity through the graphene monolayer flake during its irradiation. The whole process takes place on an ultra-polished sapphire surface used to retain the planarity of the graphene. We propose that local heating of the graphene by irradiation promotes the migration of the created atomic carbon defects to the edge of the flake. This inherently moderates the increase of resistance with time during He ⁺ irradiation due to the gradual re-opening of low-voltage graphene ballistic channels.