Enhanced diamond nucleation on copper substrates by employing an electrostatic self-assembly seeding process with modified nanodiamond particles

Nanodiamond seeding is a well-established approach to enhancing the nucleation density in chemical vapor deposition (CVD) diamond growth. However, the effects of nanodiamond seeding are highly dependent upon the dispersion properties of nanodiamond particles, the solvent and the interaction between nanoparticles and substrate surfaces. Surface modification and fractionalization were employed to improve the dispersion of nanodiamond particles and separate those particles into a more narrow range of particle size. Mono-dispersed nanodiamonds with a ζ-potential and average particle size of −41.5 mV and ∼25.3 nm, respectively, were then obtained. They can be charged on copper substrate without any contaminations. Two-dimensional self-assemblies of nanodiamond seeding were actualized. The density and homogeneity of nanodiamond particles which act as pre-existing sp3 seeds shorten the incubation time of diamond nucleation to less than 30 min. High quality of 750 nm thick continuous diamond film was deposited on copper substrate in 60 min. Furthermore, we calculated electrostatic interaction energy between nanodiamond particle and copper substrate by using the nonlinear Poisson–Boltzmann theory, and discussed interaction energy of nanodiamond-Cu substrate and nanodiamond–nanodiamond in the seeding process.

Graphical abstractBy adopting the nonlinear Poisson–Boltzmann theory, the electrostatic energy in the seeding process was calculated, where a2 = 25.3 nm, and the measured zeta potentials of ξ1 = −41.5 mV, ξ2 = 70.7 mV for nanodiamond particles and copper substrate, respectively, at pH 6.7, are used in the analysis. As the curve shown, when the distance between nanodiamond particles and copper substrate decreases, the value of the electrostatic energy exponentially increases.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Surface modification and fractionalization prepared a nanodiamond colloid. ► Two-dimensional self-assemblies of nanodiamond seeding without any contaminations. ► The seeding process was revealed from the nonlinear Poisson–Boltzmann theory. ► The interaction energies between ND particle and Cu substrate were calculated. ► High quality of 800 nm thick continuous diamond film was deposited in 60 min.