Electrical Characterization of a Large-Area Single-Layer Cu3BHT 2D Conjugated Coordination Polymer

Abstract

Understanding charge transport properties of large-area single-layer 2D materials is crucial for the future development of novel optoelectronic devices. In this work, the synthesis and electrical characterization of large-area single-layers of Cu₃BHT 2D conjugated coordination polymers are reported. The Cu₃BHT are synthesized on the water surface by the Langmuir-Blodgett method and then transferred to SiO₂/Si substrates with pre-patterned electrical contacts. Electrical measurements revealed ohmic responses across areas up to ≈1 cm², with a mean resistance of approximately 53 ± 3 kΩ at a probe separation of 50 µm. Cooling and heating cycles show hysteresis in the electrical response, suggesting different current pathways are formed as the samples underwent structural-chemical changes during temperature sweeps. This hysteresis vanished after several cycles and the conductivity shows a stable exponential behavior as a function of temperature, suggesting that a temperature-dependent tunneling process is governing the conduction mechanism in the analyzed polycrystalline single-layer Cu₃BHT samples. These results, together with density functional theory calculations and valence band X-ray photoelectron spectroscopy data suggest that the single-layer samples exhibit a semiconducting rather than a metallic behavior.