Charge transport in Cu₂S nanocrystals arrays: Effects of crystallite size and ligand length

Quantum confinement effects are observed in transport measurements of Cu₂S nanocrystal based devices. Two nanocrystals sizes are studied, 3nm being in the quantum-confinement regime, and 14nm, lacking confinement. The effect of ligand length on the charge transport mechanism is studied via conductance temperature dependence measurements. While in the 14nm nanocrystal based devices unique non-monotonic temperature dependence is observed, the 3nm based devices show only thermally activated transport for all ligands. The difference is attributed to a cross-over from inter-particle hopping to intra-particle dominated transport as the ligand length increases. In the 3nm devices the effect of ligand length on the charge-hopping activation energy is also discussed.