Intra- and Intergranular Fracture of Diamond Thin Films

Abstract

Diamond thin films have been synthesized at low pressures by chemical vapor deposition (CVD) and, recently, at ambient atmosphere with an oxygen-acetylene welding torch. By the application of appropriate thermal or mechanical stresses to the substrate, the diamond films can be delaminated. The delaminated films which are only a few microns thick have been fractured by manual bending. Scanning electron microscopy (SEM) examination of fractured CVD diamond films shows the presence of primarily intragra-nular fracture attesting to the inherent strength of the films. Using transmission electron microscopy (TEM), twinning and stacking faults are seen within the crystallites of the films along the fracture surfaces. By combining SEM and TEM examination, the relative degree of intragranular fracture found in films synthesized by both CVD and oxygen-acetylene torch has been investigated. Possible mechanisms for the intragranular fracture and the relative strength of such films are discussed.