Effect of growth characteristics on fracture strength of free-standing diamond films

Free-standing diamond films were synthesized by 100 kW DC arc plasma jet chemical vapor deposition using a CH4/Ar/H2gas mixture. The effect of growth characteristics on fracture strength of the free-standing diamond films was investigated. The deposited films were characterized by scanning electron microscopy, Raman spectroscopy and X-ray diffraction. The fracture strength of diamond films was tested by three point bending method. The results show that the fracture strength decreases with I(111)/I(220)increasing. The pileup of small grains by second nucleation among columnar grain covers grain boundaries and forms joining bridge , and thus the fracture strength of free-standing diamond films is increased, however, non-diamond phase in the free-standing diamond films decreases its fracture strength.