Synthesis of crack-free thick diamond wafer by step-down control of deposition temperature

Due to growth tensile stress, which evolves in diamond films during deposition, thick diamond films are easily cracked. In this study we successfully prevented growth cracks by introducing thermal compressive stress with step-down control of deposition temperatures during growth. Three deposition temperature drops of 10 °C each during deposition enabled us to successfully synthesize crack-free four-inch diamond wafers several hundred micrometers in thickness. This method is very simple and may be applicable to coating of films of various materials different from those of substrates.