Facile Preparation of Porous Diamond Films via Microwave Plasma Based on Metal Particles Heterogeneous Catalysis Etching

The porous diamond film was fabricated via a self-developed microwave plasma chemical vapor deposition (MPCVD) system in H-2/Ar plasma by utilizing micrometer-sized diamond films coated with nickel as starting material. SEM and Raman spectroscopy were used to evaluate the evolution of the morphology and sp(3) phase of porous diamond with changes in the surface treatment process parameters, including the etching temperature and time. The results indicate that once the etching temperature exceeds 700 degrees C, the pitting etching phenomenon can be observed on the surface of diamond film. In a certain range, increasing the etching time increases the depth of surface holes on diamond film, whereas the microporous density exhibits an inverted parabolic change pattern. The porous diamond films with uniform pores structure can be obtained by adopting optimal etching process parameter when the H-2/Ar plasma temperature is determined at 900 degrees C for 30 min. The porous formation mechanism of diamond film is attributed to the nickel particles' heterogeneous catalysis behavior, which promotes the transition route from diamond phase to graphite phase, followed by the preferential etching of graphite phase by H-2/Ar plasma.