Fracture toughness estimation of thin chemical vapor deposition diamond films based on the spontaneous fracture behavior on quartz glass substrates

This article is on the experimental estimation of the fracture toughness of thin diamond film deposited by the microwave plasma chemical vapor deposition method on a quartz glass substrate. Because of their differences in the coefficient of thermal expansion, diamond films on a quartz glass substrate suffer tensile stress at room temperature and show various kinds of spontaneous fracture behavior, reflecting the mechanical properties of the films. On the basis of detailed observation of cracking patterns and also measuring the residual stress with the aid of Raman spectroscopy, the fracture toughness of the film having thickness of around 1 mu m has been estimated here satisfactorily without the help of any difficult microscopic experiment. The fracture toughness of the film of thickness 0.35 mu m is found to be around half of that obtained with much thicker films. (C) 1997 American Institute of Physics.