Temperature-dependent photonic properties of porous-shaped metal-organic frameworks on porous silicon substrates

A novel technique is introduced in this research to increase the surface roughness of metal-organic frameworks (MOF) to enhance the light absorption effect. To this end, porous silicon (PS) was selected as a template and zeolitic imidazolate frameworks (ZIF), a subset of MOFs, were deposited on the porous skeleton using the solvothermal method. It was found that the synthesized ZIF layers followed the physical pattern of porous silicon and developed a porous-shaped MOF thin film. The X-ray diffraction analysis proved the formation of polycrystalline ZIF-67 structures on the PS substrate with a dominant crystal orientation of (011). The SEM results showed the homogeneous formation of ZIF-67 on the top of the PS walls. The porous substrate provided sufficient nuclei for facilitating the formation of a compact and continuous ZIF top layer. Moreover, the morphology and crystalline properties of the PS substrate remained intact after the deposition of ZIF structures. The porous-shaped ZIF-67/PS sample exhibited an intense and sharp photoluminescence peak, reflecting its capability to capture the incident photon and generate electron-hole pairs. Thus, it can be regarded as a suitable candidate for light detection applications. The optoelectrical properties of the synthesized samples were further explored by the metallization of the ZIF/PS structures to fabricate metal–semiconductor–metal photodetectors whose current–voltage curves were measured upon exposure to different wavelengths. The photocurrent was found to be temperature-dependent with outstanding photosensitivity to ultraviolet radiation at lower temperatures. Therefore, porous-shaped ZIF-67 nanostructures on PS substrates can be a promising candidate for ultra-fast and highly sensitive UV detectors at low temperatures.