Two Distinct Stages of Structural Modification of ZIF-L MOF under Electron-Beam Irradiation

Metal-organic frameworks (MOFs) are gaining more prominence as low-dielectric materials for applications in electronic devices and sensors using top-down electron-beam patterning. Using a combination of electron diffraction and electron energy-loss spectroscopy (EELS) in a transmission electron microscope, the details of structural modification of ZIF-L MOF under electron-beam irradiation were identified. It was found that the modification of ZIF-L under the electron beam happens in two distinct stages. In addition to the collapse of the original ZIF-L porous framework and loss of crystallinity occurring at the initial low-dose stage, it was observed that the disordered ZIF-L then undergoes a second stage of changes, where the molecular structure of the linker starts to breakdown. Further, it was observed that the degradation of the linker molecules in the second stage of the ZIF-L modification has a considerable impact on its dielectric function, shifting energies of the electronic transitions.