Impact of border traps in ultrathin metal-organic framework Cu₃(BTC)₂ based capacitors

The synthesis of metal-organic frameworks (MOFs) as thin films allows their integration into different electronic devices. Particularly, their application in metal-insulating-semiconductor (MIS) capacitors provides a comprehensive study of the electrical transport mechanism and, therefore, of the effect of border traps. A low concentration of border traps guarantees a good performance of MIS capacitors. This paper is focused on the investigation of the charge components within the MOF and near the MOF/substrate interface in ultrathin Cu₃(BTC)₂ films grown directly on silicon wafers by an innovative spray-coating method. The layer thickness was easily handled by varying the number of spray cycles in the deposition process. The crystal structure and morphology of the films were characterized via X-ray diffraction and Raman spectroscopy. Afterwards, the film thickness was determined via confocal microscopy. The electrical characterization was performed via capacitance-voltage (C-V) measurements in forward and reverse direction at room temperature and at different frequencies. Our results provide evidence of the existence of positive fixed charges in the Cu₃(BTC)₂ dielectric layer as well as of the presence of border traps which causes hysteresis in the C-V response.