Orientation Control of a Two-Dimensional Conductive Metal-Organic Framework Thin Film by a Pyridine Vapor-Assisted Dry Process.

Metal-organic frameworks (MOFs) are attractive materials with periodic pore structures constructed by coordinating metal ions and organic ligands. Recently, Cu(HHTP) (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene), a two-dimensional conductive MOF, has attracted attention as a promising device material. Owing to the anisotropy of Cu(HHTP) properties, oriented thin films of this MOF are desired for evaluating its physical properties and device integration. To date, wet processes have been used to fabricate Cu(HHTP) films, whereas dry processes are essential for high-quality devices. However, oriented Cu(HHTP) thin films have not yet been fabricated by using dry processes. In this study, we succeed in fabricating an orientation-controlled Cu(HHTP) film on AlO (001) by using a two-step dry process involving (1) the multilayer deposition of copper acetate and HHTP using a vapor deposition system and (2) pyridine vapor-assisted annealing. In-plane and out-of-plane X-ray diffraction patterns confirm the successful fabrication of the (001)-oriented Cu(HHTP) films. The conductivity evaluated by four-probe measurements is 2.6 × 10 S cm, comparable to that of films fabricated by wet processes. This study provides a novel guideline for the orientation control of two-dimensional conductive MOF thin films via a dry process.