title: Enhancing the mechanical properties of single-crystal CVD diamond.
abstract: Approaches for enhancing the strength and toughness of single-crystal diamond produced by chemical vapor deposition (CVD) at high growth rates are described. CVD processes used to grow single-crystal diamond in high density plasmas were modified to incorporate boron and nitrogen. Semi-quantitative studies of mechanical properties were carried out using Vickers indentation techniques. The introduction of boron in single-crystal CVD diamond can significantly enhance the fracture toughness of this material without sacrificing its high hardness (∼78 GPa). Growth conditions were varied to investigate its effect on boron incorporation and optical properties by means of photoluminescence, infrared, and ultraviolet-visible absorption spectroscopy. Boron can be readily incorporated into single-crystal diamond by the methods used, but with nitrogen addition, the incorporation of boron was hindered. The spectroscopic measurements indicate that nitrogen and boron coexist in the diamond structure, which helps explain the origin of the enhanced fracture toughness of this material. Further, low pressure/high temperature annealing can enhance the intrinsic hardness of single-crystal CVD diamond by a factor of two without appreciable loss in fracture toughness. This doping and post-growth treatment of diamond may lead to new technological applications that require enhanced mechanical properties of diamond.
authors.affiliation: Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Road NW, Washington, DC 20015, USA.
authors.forename: Qi
authors.initials: Q
authors.lastname: Liang
authors.forename: Chih-Shiue
authors.initials: CS
authors.lastname: Yan
authors.forename: Yufei
authors.initials: Y
authors.lastname: Meng
authors.forename: Joseph
authors.initials: J
authors.lastname: Lai
authors.forename: Szczesny
authors.initials: S
authors.lastname: Krasnicki
authors.forename: Ho-Kwang
authors.initials: HK
authors.lastname: Mao
authors.forename: Russell J
authors.initials: RJ
authors.lastname: Hemley