The Ultrasmoothness of Diamond-like Carbon Surfaces

Abstract

The ultrasmoothness of diamond-like carbon coatings is explained by an atomistic/continuum multiscale model. At the atomic scale, carbon ion impacts induce downhill currents in the top layer of a growing film. At the continuum scale, these currents cause a rapid smoothing of initially rough substrates by erosion of hills into neighboring hollows. The predicted surface evolution is in excellent agreement with atomic force microscopy measurements. This mechanism is general, as shown by similar simulations for amorphous silicon. It explains the recently reported smoothing of multilayers and amorphous transition metal oxide films and underlines the general importance of impact-induced downhill currents for ion deposition, polishing, and nanopattering.

Molecular dynamics of single-particle impacts predicts phase diagrams for large scale pattern formation

“…Third, moments are readily obtainable directly by MD simulation, and converge with far fewer trials than do descriptions of the entire crater function used in previous works. Last, although atomistic methods have been used in the past to obtain the amplitude of a single term in a PDE obtained by phenomenological modelling 17,[25][26][27] , we believe this is the first derivation of an entire PDE from MD results. A crucial component of our approach is that the crater function ∆h-and hence the moments M (i) -contains the contributions of both erosion and mass redistribution.…”

“…Displaced atoms that reach the surface with enough kinetic energy to leave are permanently sputtered away; all other displaced atoms come to rest within the solid or on the surface after phonon emission times of ~10 − 12 s. These processes contribute prompt erosive 14,15 and prompt redistributive 11,16,17 components of morphology evolution and are collectively denoted P [x].…”

“…The prompt regime may be characterized using molecular dynamics (MD) simulations 17,19 or experimental methods 20 . Given data from many impact events, we may obtain the 'crater function' ∆h(x − x′,θ) describing the average change in local surface height at a point x resulting from a single-ion impact at x′, with incidence angle θ (a potential dependence on the surface shape, which is very difficult to capture with MD, is left for future work).…”

Ion energy distribution measurements in rf and pulsed dc plasma discharges

“…Such a wide energy distribution of impinging ions is essential for obtaining ultra-smooth films according to the atomistic impact-induced downhill flow model [40] and the experimental validation [41]. Accordingly, the time-resolved IEDF with a nanosecond time resolution provides critical information for the design of pulse waveform in p-dc power sources in terms of IED optimization for the control of films microstructure and properties.…”

Influence of test methodology and probe geometry on nanoscale fatigue failure of diamond-like carbon film

“…Hydrogen free diamond-like-carbon (DLC) thin films are frequently used as protective coatings on magnetic and optical storage disks, solar panels, optical windows, medical implants and micro/nano-electromechanical (MEMS/NEMS) devices [1]. As these applications exhibit tribological aspects, there is a growing interest on advancing the understanding of the nanomechanical behaviour of these films.…”